Mixing....a matter of acoustics?

[Nanto Warrior]

Hello everyone! Happy independence day if you're in America!

Out of interest, how many people are mixing their music on headphones, and/or what monitors do you all use for your work? Is there any advice that anyone can offer regarding the qualities to look for in active monitors? (i.e. Flat frequency response, etc) And what about those who would say they are in less favourable acoustics? (e.g. in bedroom/carpeted room/not a specifically designed room that costs thousands of dollars!) What are your experiences of mixing with your current monitors/headphones on your DAW? How necessary are the model/brand of your monitors/and or headphones when mixing, and have you had any horrendous experiences where your magnificent music did not sound as great on your client's setup, as it did on yours?

Cheers!

The Warrior! :mad:

[LEX]

Hello everyone! Happy independence day if you're in America!

Out of interest, how many people are mixing their music on headphones, and/or what monitors do you all use for your work? Is there any advice that anyone can offer regarding the qualities to look for in active monitors? (i.e. Flat frequency response, etc) And what about those who would say they are in less favourable acoustics? (e.g. in bedroom/carpeted room/not a specifically designed room that costs thousands of dollars!) What are your experiences of mixing with your current monitors/headphones on your DAW? How necessary are the model/brand of your monitors/and or headphones when mixing, and have you had any horrendous experiences where your magnificent music did not sound as great on your client's setup, as it did on yours?

Cheers!

The Warrior! :mad:
This is a whole other world of work. There is so much that can depend on HOW your room sounds.

1) Headphones. Good headphone you can trust to mix on are open ended and expensive.
Only 2. Sennheiser HD650's ($600) and Grado's which start around $600.

2) Acoustics. I could spend a week discussing room acoustics. The only way to get a "perfect" room (of which there is no such thing) is to build it from the ground up.
If you have the money, get Carl Yancher or Vincent Van Hoff to design your room.

Untill then. #1 Rule. Don't put your speakers parallel to a straight wall. The standing waves will kill you.
If you have to, you must diffuse the rear wall and the ceiling above you.
If at all possible, put you workstation at a corner. Look in the studio pics post. That is how I have it done.

Absorption. You need yo listen around the room, against walls and in corners for reflections and bass build up. You'll need to absorb the reflections and trap the bass.

Everything that comes back to you will make your mix sound bright and/or boomy in which you will end up rolling off those frequencies to make it sound right.
When you take it out it now sounds thin.

3) Monitors are rarely flat. Some have better frequency representation than others, or is more even over the frequency spectrum.
Monitors are a judgement call on the user. I use JBL LSR6328P's.

4) once your acoustics are done, and you have your speakers set and SPL'ed, you should tune your room.

By this I mean measuring your frequency response with an RTA (realtime analyzer). The mic is flat and the reading will show you your room response curve.

I put in a Behringer DEQ 2496, because it is digital and has a toslink so I can play CD's with the same EQ tune. It has a 31 band EQ.

My room had a dip in 60, and 80 so I flattened them out and a slight bump in the 1-2k range.
Once I had the whole range flat, I started at 20k and rolled if off (6-8bd)all the way down to 10k at (-1.5bd) and from 20-50 (around -6db to -2db)
This helps to retain natural brightness and warm lows. With a flat high, tendency will be ear fatique and rolling off of the highs creating a dull mix.
Rolling off the lows helps to control the lowend response and keep you from rolling out low frequencies making your mix thin.

I also had my mastering engineer come over to go though the tune to see what he heard. He made a few slight adjustements.

I have went through thousands of dollars on Monitors and thousands on headphones (only because my Grado's were stolen and I bought the S HD650's)

I can tell you all this work took along time, alot of money but I am confident in the room and it translates well.

Good Luck

LEX

[Nanto Warrior]

WOW! So much information, and SO HELPFUL! Thank you very much Lex!!!

Im yet to invest in an outstanding pair of monitors-Im working purely with samples, and wont be sweetening any of my cues for a while. Im using AKG K66 stereo headphones for my work-do you think using sample libraries with this setup has much of a detrimental effect on the outcome, as opposed to not using monitors when recording and mixing pop music? This has been an issue in the back of my mind for a while-whether I really need monitors or not...I know one should never rely on one or the other, but everything is sounding great! (I know how naive that sounds) and my current acoustic isn't great. :mad:

Feel free to contribute to the debate everyone!

Cheers!

The Warrior :mad:

[MaestroRage]

Now i'm a musician who isn't going to be doing high end work for a while. In fact I like to often use earphones that the average person uses.

I hate it, and I mean HATE it, if I use expensive headphones, and then build the bass and everything JUST right, and then come back with like 50 emails going "dude, yur bass r suck!" and of course I could always say "Go buy better earphones/speakers!" but really that is unrealistic.

So for where I am at right now, I use slightly higher then average end earphones to mix my tracks. In this sense i'm always hearing what they are. Since I never use speakers, I havn't had the need to alter my room in any way.

[nickysnd]

I use slightly higher then average end earphones to mix my tracks. In this sense i'm always hearing what they are.
No you don't. I have to put it like that, abruptly, for I think you are totally mistaken about that. Avoid fooling yourself. "Assumption is the mother of all screw-ups."

Since I never use speakers, I havn't had the need to alter my room in any way.
There is a huge difference between altering and acoustically improving. Most (if not all) rooms are acoustically bad, altered. So they all need to be acoustically improved. If you don't want to, it's up to you, but that hardly will work in your advantage. In this respect, LEX's post is invaluable, you better copy-paste it somewhere, as I did. (Thx again, LEX! :) )

As for not using speakers, I think that is an even bigger mistake, and, again - it's working against yourself. Keep in mind that your headphones are creating in your head a false, bi-dimensional "image" of the sound, like a soundscreen. Speakers are creating a normal, 3D soundscape instead, the one that our ears are built for. That's why a mix done exclusively with headphones will translate poorly on speakers. Don't overlook speakers, they are the standard, headphones are good for editing details, mostly, and for checking how your mix translates in 2D.

My sound recording teacher once told me, about speakers, something like this: buy the best monitors you can afford, use your ears and your brains, do great mixes, and hope for the best!

[LEX]

As for not using speakers, I think that is an even bigger mistake, and, again - it's working against yourself. Keep in mind that your headphones are creating in your head a false, bi-dimensional "image" of the sound, like a soundscreen. Speakers are creating a normal, 3D soundscape instead, the one that our ears are built for. That's why a mix done exclusively with headphones will translate poorly on speakers. Don't overlook speakers, they are the standard, headphones are good for editing details, mostly, and for checking how your mix translates in 2D.

My sound recording teacher once told me, about speakers, something like this: buy the best monitors you can afford, use your ears and your brains, do great mixes, and hope for the best!
Well put.

I should have said I finalize everything on the monitors.

The problem I have with most headphones is the fake bass response. That is why the Senn and Grado's work very well.

They do translate pretty well from headphone to speaker. Also, the open ended design doesn't make is sound like it is in a tunnel.

Good for late night work, minor tweaks and editing. But finalizing is always on the JBL's.

As far as "realworld" speakers I have my NS-10's.

LEX

[MaestroRage]

so what you're saying is i've been living a lie. Hmm... I suppose should I have lived this lie for several years, I may have felt the need to fall to my knees and weep bitterly into the night.

My budget has frankly become ridiculous with all the information i'm getting from this site. It is safe to assume that hardware is always priority over software then? Because i'm going to have to go get me a good set of speakers.

Quick question, surround sound will not give me any real benefit over normal stereo will it?

[Crossingsound]

A good set of monitors are invaluable. I definetaly suggest getting a decent pair. There are a few models that try to make up for room acoustics as well, though you should take your room into consideration and tidy it up so to speak. But in the end, in a great acoustic room, or poor, you have to learn your monitors and how they translate over to other playback mediums, for instance, how is the low end? Clear, boomy, too much or too little bass, when you mix on your headphones or monitors, are the drums louder then when you take it into your car stereo and home DVD setup, etc etc. These are things that over time you will learn to mix properly and better to fit over a wider range of playback systems.

Learning how your mixes translate is gonna help you become a great mixer on your system, of course better monitors will give you a much better picture of what is exactly going on. You don't get the full spacial effect with headphones normally.

Surround, I would only get a surround system if you need to start supplying mixes in this format, just my opinion. First get a good stereo set and master that realm, then move onto bigger better things later when needed, at least thats my 2 cents thus far. Of course if you need to supply that service, then by all means go for it

[LEX]

so what you're saying is i've been living a lie. Hmm... I suppose should I have lived this lie for several years, I may have felt the need to fall to my knees and weep bitterly into the night.

My budget has frankly become ridiculous with all the information i'm getting from this site. It is safe to assume that hardware is always priority over software then? Because i'm going to have to go get me a good set of speakers.

Quick question, surround sound will not give me any real benefit over normal stereo will it?

The biggest problem I have seen over the years is people will drop thousands on software, samples and computers.

But when it comes to monitoring, they only have a little bit to spend. And it is one of the most important pieces of your studio.
This is what I never get.

There is nothing wrong with taking a mix to your car or home stereo for a listen, but proper monitoring will reveal problem areas.

Then comes your D/A converter. IT goes on.

LEX

[Paul Woodlock]

Greetings LEX :)

Someone asked me about your post here so I regisered as I could reply...

This is a whole other world of work. There is so much that can depend on HOW your room sounds.

1) Headphones. Good headphone you can trust to mix on are open ended and expensive.
Only 2. Sennheiser HD650's ($600) and Grado's which start around $600.

2) Acoustics. I could spend a week discussing room acoustics. The only way to get a "perfect" room (of which there is no such thing) is to build it from the ground up.
If you have the money, get Carl Yancher or Vincent Van Hoff to design your room.

Untill then. #1 Rule. Don't put your speakers parallel to a straight wall. The standing waves will kill you.

Sorry mate, that isn't true.

1] Standing waves are resonances that are basicalyl a storage of sound energy in a room that's filled up by being excited from a sound source and emptied through absorption of the energy through imperfections in structure.

Which way the speaker is pointing really doesn't make that much difference to exciting a standing wave.

2] Standing waves don't need straight walls to occour. The body of stringed instruments and acoustic guitars ( especailly those curved back models ) are good examples of where (benficial ) standing waves occour in spaces that have curved 'walls' YO ucan have a standign wave in a sphere which ahs no straight walls :)


Note: The positioning of the speakers can determine the efficiency at which standing waves are excited however. Soffit mounted speakers for example, which lie on a wall boundary will excite all standing waves in that plane and lots of absorption on the back wall is required to compensate. Needless to say that positioning of a subwoofer is ciritical and experimention is required.



If you have to, you must diffuse the rear wall and the ceiling above you.

In typical home studios diffusion is probably the least priority type of acoustic treatment you will want to apply. Most small rooms don't build up a late sound field that warrants diffusing. Most relfections in a small room are <20ms which is percieved by the ear as part of the direct sound. ersult ... smear.

Diffusion is simply a scattering of sound in the same way that matt paint scatters light by diffraction around objects An irregular object will only diffuse a frequency if it's size is equal or larger to the wavelength. A skyline type diffuser for example and will only really effecitely diffuse frequencies above 6.5kHz if it's irregularities are around 2" x2"

It won't hurt to apply some diffusion though, as it might help help scatter some flutter echos


If at all possible, put you workstation at a corner. Look in the studio pics post. That is how I have it done.

The positive with this approach is that the 'side' walls will reflect the sound backwards instead of at yoru ears. The negative is that unless you have a perfectly square room the setup won't be symetrical


Absorption. You need yo listen around the room, against walls and in corners for reflections and bass build up. You'll need to absorb the reflections and trap the bass.

You can't listen for a refletion at a wall boundary. Becuase at the wall boundary you can nly hear the direct sound and not the relfection egressing from the wall at that point.

Abvoe around 100Hs sound acts like light in a room. The best way to find the absorption points is to use the Mirror trick. Sit in your mix position and get a friend to move a mirror around all the surfaces in the room. Wherever you can see a speaker si the position to put your absorber panels.

The aim is to absorb evenly across the freqeuncy spectrum. 2" absorber panels placed directly on the waqll will only absorb effectively above 1Khz, or maybe down to 500Hz if you're lucky. Use at laest 4" ( 100mm ) thick absorption panels. Also yo ucannot absorb sound directly at the wall boundary becuase the velocity of vibrating air in the room at the boundary is ZERO. Leave an air gap and then have absorption. 2" airgap and then 4" absorption will give you a good even absorption from aroudn 120Hz upwards. Even absorption across the freqeuncy range means an even RT 60




Everything that comes back to you will make your mix sound bright and/or boomy in which you will end up rolling off those frequencies to make it sound right.
When you take it out it now sounds thin.

Actually the effect of reflections is that they causes a comb filtered freqeuncy response. You will get cancellations where the relfected path legth is 1/2 a wavelength ( or multiple thereof ) longer than the direct sound path length.

Relfections also mess up you stereo image as a relfection can be considered a ghost sound source. imagine a room made of mirrors and your speakers are two lightbulbs. You will obviously see many other lightbulbs reflected in the mirrors. So unless you absorb early refelctions you will effectively have many more than just two speakers in your room. And dont' foget the ceiling when doign the mirror trick. :)


3) Monitors are rarely flat. Some have better frequency representation than others, or is more even over the frequency spectrum.
Monitors are a judgement call on the user. I use JBL LSR6328P's.

true, but they are a lot flatter than the room


4) once your acoustics are done, and you have your speakers set and SPL'ed, you should tune your room.

By this I mean measuring your frequency response with an RTA (realtime analyzer). The mic is flat and the reading will show you your room response curve.

I put in a Behringer DEQ 2496, because it is digital and has a toslink so I can play CD's with the same EQ tune. It has a 31 band EQ.

My room had a dip in 60, and 80 so I flattened them out and a slight bump in the 1-2k range.
Once I had the whole range flat, I started at 20k and rolled if off (6-8bd)all the way down to 10k at (-1.5bd) and from 20-50 (around -6db to -2db)
This helps to retain natural brightness and warm lows. With a flat high, tendency will be ear fatique and rolling off of the highs creating a dull mix.
Rolling off the lows helps to control the lowend response and keep you from rolling out low frequencies making your mix thin.

While final tweaks can be helpful you should always flatten freqeuncy response issues with absorption rather than EQing. Room aberations are time based and cause the freqeuncy response to be out of wack, btu out of wack differently at different positions in the room.

If you analyse your room and find you have, for example, a dip at 60 and 80 due to standing waves then this will only hold true for that particular mic position,. Even moving the mic slightly can result in a compeltely different response. The same will happen for relection based freq response anomolies too. So using EQ can narrow your mix position and make it worse in other parts of the room.

The other problem with boosting low end freqs in order to compensate for standing wave nulls is that you can eat up hge amounts of headroom in your monitor amps and drivers. This will of coruse also increase distortion


Although you said your room translates well, and that is great, I just needed to clarify some points for the peeps reading lest they get hold of misinofrmation. :) hope ya don't mind. :)

Cheers

Paul

[Nanto Warrior]

INFORMATION!! Glorious information!! Syste..m......over..lo..a...d.....!!

Si...lver.....Nanto Warrior Th...anks....you :cool:

[chest]

The aim is to absorb evenly across the freqeuncy spectrum....Use at laest 4" ( 100mm ) thick absorption panels. Also yo ucannot absorb sound directly at the wall boundary becuase the velocity of vibrating air in the room at the boundary is ZERO. Leave an air gap and then have absorption. 2" airgap and then 4" absorption will give you a good even absorption from aroudn 120Hz upwards...
So you shouldn't stick (for instance) Auralex 4" foam tiles straight on to the walls or ceiling? - Mount on a grid of wooden slats?

Someone recommended that I mount some tiles in a "checker-board" pattern (leaving alternate areas of wall and ceiling untreated) to get partial damping - the 2" gap is still needed? - And, if so, must the edges of the air gaps beneath the tiles be filled in?

If you analyse your room and find you have, for example, a dip at 60 and 80 due to standing waves then this will only hold true for that particular mic position,. Even moving the mic slightly can result in a compeltely different response.
Does "slightly" mean less than your head moves when you're sitting where you'd ordinarily listen?

----

Separately from applying treatment for dealing with sound from loudspeakers, if you want also to record acoustic instruments in the same space, are there any simple procedures like the "mirror trick" to guide the placement of absorbent tiles? If I understand correctly, you should try to reduce reflections between parallel walls and in corners, but beyond that (if you don't have fancy analysis equipment) does it come down to trial and error?

[LEX]

Greetings LEX :)

Someone asked me about your post here so I regisered as I could reply...



Sorry mate, that isn't true.

1] Standing waves are resonances that are basicalyl a storage of sound energy in a room that's filled up by being excited from a sound source and emptied through absorption of the energy through imperfections in structure.

Which way the speaker is pointing really doesn't make that much difference to exciting a standing wave.

2] Standing waves don't need straight walls to occour. The body of stringed instruments and acoustic guitars ( especailly those curved back models ) are good examples of where (benficial ) standing waves occour in spaces that have curved 'walls' YO ucan have a standign wave in a sphere which ahs no straight walls :)


Note: The positioning of the speakers can determine the efficiency at which standing waves are excited however. Soffit mounted speakers for example, which lie on a wall boundary will excite all standing waves in that plane and lots of absorption on the back wall is required to compensate. Needless to say that positioning of a subwoofer is ciritical and experimention is required.




In typical home studios diffusion is probably the least priority type of acoustic treatment you will want to apply. Most small rooms don't build up a late sound field that warrants diffusing. Most relfections in a small room are <20ms which is percieved by the ear as part of the direct sound. ersult ... smear.

Diffusion is simply a scattering of sound in the same way that matt paint scatters light by diffraction around objects An irregular object will only diffuse a frequency if it's size is equal or larger to the wavelength. A skyline type diffuser for example and will only really effecitely diffuse frequencies above 6.5kHz if it's irregularities are around 2" x2"

It won't hurt to apply some diffusion though, as it might help help scatter some flutter echos



The positive with this approach is that the 'side' walls will reflect the sound backwards instead of at yoru ears. The negative is that unless you have a perfectly square room the setup won't be symetrical



You can't listen for a refletion at a wall boundary. Becuase at the wall boundary you can nly hear the direct sound and not the relfection egressing from the wall at that point.

Abvoe around 100Hs sound acts like light in a room. The best way to find the absorption points is to use the Mirror trick. Sit in your mix position and get a friend to move a mirror around all the surfaces in the room. Wherever you can see a speaker si the position to put your absorber panels.

The aim is to absorb evenly across the freqeuncy spectrum. 2" absorber panels placed directly on the waqll will only absorb effectively above 1Khz, or maybe down to 500Hz if you're lucky. Use at laest 4" ( 100mm ) thick absorption panels. Also yo ucannot absorb sound directly at the wall boundary becuase the velocity of vibrating air in the room at the boundary is ZERO. Leave an air gap and then have absorption. 2" airgap and then 4" absorption will give you a good even absorption from aroudn 120Hz upwards. Even absorption across the freqeuncy range means an even RT 60





Actually the effect of reflections is that they causes a comb filtered freqeuncy response. You will get cancellations where the relfected path legth is 1/2 a wavelength ( or multiple thereof ) longer than the direct sound path length.

Relfections also mess up you stereo image as a relfection can be considered a ghost sound source. imagine a room made of mirrors and your speakers are two lightbulbs. You will obviously see many other lightbulbs reflected in the mirrors. So unless you absorb early refelctions you will effectively have many more than just two speakers in your room. And dont' foget the ceiling when doign the mirror trick. :)



true, but they are a lot flatter than the room



While final tweaks can be helpful you should always flatten freqeuncy response issues with absorption rather than EQing. Room aberations are time based and cause the freqeuncy response to be out of wack, btu out of wack differently at different positions in the room.

If you analyse your room and find you have, for example, a dip at 60 and 80 due to standing waves then this will only hold true for that particular mic position,. Even moving the mic slightly can result in a compeltely different response. The same will happen for relection based freq response anomolies too. So using EQ can narrow your mix position and make it worse in other parts of the room.

The other problem with boosting low end freqs in order to compensate for standing wave nulls is that you can eat up hge amounts of headroom in your monitor amps and drivers. This will of coruse also increase distortion


Although you said your room translates well, and that is great, I just needed to clarify some points for the peeps reading lest they get hold of misinofrmation. :) hope ya don't mind. :)

Cheers

Paul
Thanks Paul.

No worries. But, Ironically this is completely opposite of what several people told me.
This may of course be based on my room.

1 being Bobby Owsinski, a long time friend who said himself, "The imaging and sound in here is better than some of the million dollar rooms in town."

BTW, in the corner there are no side wall boundries. Only rear, at least in my room.
Same as it would be parallel.

I understand that standing waves can occur in any position, but you are likely to have more with a flat surface directly behind you.

Absorption is key, but depending on the room, and no setup can mimic another really, diffusion can work very well.

I'll have to pass your info on and see how they all comment on it.

LEX

[LEX]

Read this:

http://mixonline.com/mag/audio_speaker_setup_acoustic/index.html

Since we are dealing more with non traditional setups, this my help.

LEX

[nickysnd]

Bobby Owsinski, a long time friend who said himself, "The imaging and sound in here is better than some of the million dollar rooms in town."
His Mastering Engineer's Handbook is on my desk, a helluva great info there!

My bedroom studio is a small pentagon of approx. 9x8x8x6x14ft, and my desk is placed in a 90 degree corner (there are three of them, plus two corners of approx. 160 and 110 degrees). Although I didn't check my room scientifically, only judging by ear with pink noise signals, I didn't notice any major problems as loud standing waves and big dips. My biggest problem seems to be a noticeable boost at 125Hz coming from my monitors (KRK Rokit5), maybe a bit amplified by the room, but I control it through EQ. I have just bought a measurement microphone and I am waiting for my Behringer Ultracurve, and soon I will find out more scientific details about my room. Then I will decide about some absorption/diffusion material to place somewhere, for I will surely need some.

[LEX]

His Mastering Engineer's Handbook is on my desk, a helluva great info there!

My bedroom studio is a small pentagon of approx. 9x8x8x6x14ft, and my desk is placed in a 90 degree corner (there are three of them, plus two corners of approx. 160 and 110 degrees). Although I didn't check my room scientifically, only judging by ear with pink noise signals, I didn't notice any major problems as loud standing waves and big dips. My biggest problem seems to be a noticeable boost at 125Hz coming from my monitors (KRK Rokit5), maybe a bit amplified by the room, but I control it through EQ. I have just bought a measurement microphone and I am waiting for my Behringer Ultracurve, and soon I will find out more scientific details about my room. Then I will decide about some absorption/diffusion material to place somewhere, for I will surely need some.

Right. Finding the right placement is 1st key.

Here in lies the problem with acoustic discussion, and my own fault in what Paul is commenting on.

Rather than speak from an all room perspective, I spoke more from a "my room" perspective.

As Paul had mentioned the EQ'ing of a room, I should comment. Radical EQ'ing to correct a room is not proper. And Like he said, will often result in speaker distortion.
A little bump or dip here and there is okay. Every room can be tuned up. just like a car for the better.

But 1st, one should find the best placement that has the least amount of interference and start room correction though absorption and diffusion. I still think diffusion can have benefits even in a small room, or square room.
It is in how you use it that makes the difference. A little can go a long way.

It is alot of trial and error, and time.

Nick. The 125hz boost is common. I had the same thing. Try moving the speakers out a bit from the wall. There are alot of things people say, like the distance between the speakers should equal the distance from the wall. Though in professional setups, that is ideal, we all don't necessarily have the space to do that.

General rule 20".

Now because of this, I had to go back into my first acoustic book.
The New Stereo Soundbook by Everest and Striecher.

So in terms of parallel surfaces, I am going to quote a large section of this book. And I highly recommend those getting into this, buy and read this book.

Axial Mode Resonances
Any pair of opposite, parallel surfaces constitutes a resonant system. For example, 2 ends of a rectangular room are 20ft apart, they are resonant at a frequency of 1,130 divided by twice the distance (1,130/40 = 28.3hz). The 1,130 ft/sec is the speed of sound; the sound must make one complete round trip at the resonance frequency.
The 2 side walls spaced 15ft resonate at a frequency of 1,130/30 = 37.7hz, and the floor/ceiling surfaces spaced 8ft resonate at 1,130/16 = 70.6hz. In this way the rectangular room resonates simultaneously at 28.3, 37.7, and 70.6hz, called the axial mode of the room. If stopping here, life would be simple. Each set of plane, parallel surfaces also resonates at multiples of the same frequency. Thus the 2 end walls not only resonant at 28.3hz, but aslo at 2,3,4 ......ect. times 28.3Hz. In other words, these 2 surfaces are just as resonant when the sound makes a second, third or forth trip as they were for the first round trip (neglecting successive reflection losses. A series of resonance frequencies exsits for each pair of surfaces. Each series is terminated at about 300hz because few axial mode problems are found above that frequency.

Tangentail and oblique Modes
The spaceing of modal resonance frequencies could be greater than desired. Each mode is effective over a narrow frequency region of approximatelt 5 hz. It would be good for room response if all modes were close enough to overlap. Independent action of single or coincident modes well spaced from neighbors often leads to audible colorations of the sound. Guilford came to the conclusion that spacings greater than 25hz were especially prone to sound colorations.

Fortunately, many modal resonances exist other than the axial modes. Tangential modes invlove four surfaces for their round trip; oblique modes involve all six surfaces. Even thought they are less powerful than the axial modes, tangential and oblique modes help to smooth the low-frequency response of a room as the fill in between the axial modes. Therefore, the tangential and oblique modes help make the response of this room smoother.


Now as Paul's response has validity, it is also contradictory as this quote shows.

Tangential and oblique modes reduce the round trip of the wave, as opposed to the axial mode (or parallel wall) smoothing out the low end frequencies making them much easier to deal with.

LEX

[Nanto Warrior]

Holy mackerel.....and all this so we can mix appropriately to improve how our product is perceived on the other end....what about if the client plays your magnificent score on his crappiest pair of speakers?

(Controversial topic)
Without the necessary studio acoustic design implemented, would you say that most composers /producer types are pretty much screwed before they've written a single note/bounced their mix? (As their auditory perception would have been affected by a crappy acoustic enviroment/headphones. Thus everyone would need to invest in considerable acoustic design of their environment so their product is PERCEIVED AS WELL as it was produced?)

Cheers,
The Silver Nanto Warrior! :cool:

[nikolas]

(Controversial topic)
Without the necessary studio acoustic design implemented, would you say that most composers /producer types are pretty much screwed before they've written a single note/bounced their mix? (As their auditory perception would have been affected by a crappy acoustic enviroment/headphones. Thus everyone would need to invest in considerable acoustic design of their environment so their product is PERCEIVED AS WELL as it was produced?)

Yes and no, I'd say.

I know almost nothing about hardware or acoustics (Lex knows that), and I don't have monitors (everybody knows that by now. Nicky, Lex, etc... :p). I'm getting monitors though pretty pretty soon, and I feel excited like a little child.

so I've spent 2 years of my life with software and a computer, and the first thing I got, because I couldn't afford, nor place anywhere safe, studio monitors (not with 2 children bellow 2 year old) was great headphones, The sennheiser HD600 (previous models than the 650 that Lex mentions). Well they are simply amazing. Yes, everything is too... stereo, and yes I know that, but I do use them for detailed mixing, and do listen to my crapy 50$ hi-fi speakers as well, to get an idea of how on earth this things sounds elsewhere and not 1 inch of my ears...

I won't recomend it to anyone, and will support that monitors are crucial, as well as acoustic treatment of your room, etc. But I will comment that I've done it, and I'm not screwed (not exactly anyways). I will also comment that acousticly treating a room can take a lot, and means a waste of a room. If you live in a studio somewhere in the UK, it could mean that you would make a "proper" studio your kitchen/bedroom/hallway all in one. It simply can't be done.

It does depend on the circumstances, so if you have the money, but not the room, buy other equipment (but do get monitors), and save for when you get your own basement/garage/extra room to make it acoustically correct. At least that's what I'm doing (and btw, I'm also building back in Greece and 1 room belongs to me and my stuff :D! Patience is a virtue! Wife architect too :D!)




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comments on the thread:

Just one!

This thread is BOOKMARKED!

[nickysnd]

what about if the client plays your magnificent score on his crappiest pair of speakers?
It is likely that the client's other CDs are produced with great acoustic care. Therefore, on the client's "crappy" (hmmm...) speakers, music mixed with acoustical care will sound better than carelessly produced music. It would be a mistake to think that they will sound "equally crappy."

Without the necessary studio acoustic design implemented, would you say that most composers /producer types are pretty much screwed before they've written a single note/bounced their mix?
It's best to keep separate these steps: music composition / midi sequencing /audio mixing. We were talking audio mixing. Audio production has a lot to do with the environment you are producing it. If you are wearing multicolored glasses when you are painting, then your picture will look funny to your client.

Composing is like conceiving the picture in your head and making paper sketches, midi sequencing is like drawing the right lines on the canvas, audio mixing is like coloring it. You better keep your eyes open and clean while doing the latter.

(As their auditory perception would have been affected by a crappy acoustic enviroment/headphones. Thus everyone would need to invest in considerable acoustic design of their environment so their product is PERCEIVED AS WELL as it was produced?)
No matter where your product will be played, if it is originally produced without acoustical care, you can be sure that it will display serious acoustic issues on each and every system, good or bad. But if you carefully design it from acoustical pov, close to what pros do, then chances are that the difference between your product and the pros' products will be smaller.

You only have control over your mix. That's your last chance to make your piece sound good. Of course you have no control over the environment it will be played, no one has. So I think it would be suicidal to think: "I don't know how it will translate on another system, so it doesn't matter what's in my mix." I will repeat here a good advice that I once received: do great mixes, and hope for the best. Being careful or careless about the sound of your piece, that will show, that will be heard by your client, be sure of that.

[LEX]

Okay so I got some info from 1 of my guys, my mastering engineer.

1st thing. Not room is alike, neither my information or Pauls information means anything for anyone else.

You need to find your position in your room for what sounds best 1st. The parallel surface theory has changed a bit over the past years, but, for example in my room the longer though is better because of the size of the room.

Determining parallel's does, however, depend on the size of the room.
Based on the size of your room and the position of your speakers from the point of their speaker points to the nearest parallel can change the low end dramtically.

So if from where your speakers are to the rear wall is 5 feet, you are going to run into problems.
If you can move it to a corner with a longer throw, your bass response will smooth better.
Then at that point it is determining the distance from the nearest reflective surface you have to determine.

Sorry mate, that isn't true.

1] Standing waves are resonances that are basicalyl a storage of sound energy in a room that's filled up by being excited from a sound source and emptied through absorption of the energy through imperfections in structure.

A Standing wave is a room resonance in the LOW frequency region that results in the uneven distribution of sound energy in the room.

Again the key is the Low frequencies. Nicks 125HZ bump is due likely because the nearest surface is about 8 feet away. 128hz is 8.8feet in length.
80hz is 12.75 feet.

2] Standing waves don't need straight walls to occour.
Yes of course. But once again, the difference comes down to the low freq round trip and multiples there of.

A rear wall, bare, 6 feet away will have a greater build up than an angled difference with an 8 or 10 foot throw reflecting off 4 surfaces before returning to its origin.
Hense, a smoother response and less of a low end boost.

Placing a workstation in a corner, room dependent of course doesn't mean the speaker will have side boundries. Actually, it is hard to create side boundries in a corner.
Just look at my studio pics. The only boundry is behind the speaker.

Though not ideal, but even the lowend reflection still return to the speaker, another reflective surface.
Since in both cases of parallel and corner we are dealing with diffraction instead of reflection.
Diffraction is when a wave length is longer than the object it reaches, it goes around.

At least in my room, diffraction was a key element in placement. Unlike a parallel back plane where the low freq has no choice but to go around the speaker and the monitors, in the corner the diffraction is reduced by about 6db as the low end freq's traveling around the back are collected.

2] Standing waves don't need straight walls to occour. The body of stringed instruments and acoustic guitars ( especailly those curved back models ) are good examples of where (benficial ) standing waves occour in spaces that have curved 'walls' YO ucan have a standign wave in a sphere which ahs no straight walls

Right, but that is the reason the guitar isn't square. It has more surfaces to bounce off of and resonant. If it were better, then it would be square.

In typical home studios diffusion is probably the least priority type of acoustic treatment you will want to apply. Most small rooms don't build up a late sound field that warrants diffusing. Most relfections in a small room are <20ms which is percieved by the ear as part of the direct sound. ersult ... smear.

Diffusion is simply a scattering of sound in the same way that matt paint scatters light by diffraction around objects An irregular object will only diffuse a frequency if it's size is equal or larger to the wavelength. A skyline type diffuser for example and will only really effecitely diffuse frequencies above 6.5kHz if it's irregularities are around 2" x2"

Well there is actually 2 schools of thought on this, so neither is wrong. But diffusion happens in the low mid, mid high and appreciable low frequency absorption.

George Oshburger uses diffusion heavily with heavy bass trapping in the corners. 6.5k is why to high. Diffusion begins far before that, and depending on how you do it neither is wrong.

Some prefer heavy absorption over diffusion, but neither is wrong or misleading.

[LEX]

The positive with this approach is that the 'side' walls will reflect the sound backwards instead of at yoru ears. The negative is that unless you have a perfectly square room the setup won't be symetrical
There are no side walls, only rear walls.

You can't listen for a refletion at a wall boundary. Becuase at the wall boundary you can nly hear the direct sound and not the relfection egressing from the wall at that point.
You didn't read it right. I wasn't talking about listening behind the speaker. I was talking about listening to the reflective walls and corners.
You can hear buildups of bass in corners and reflections off the walls.

Sorry to say, until I told him that I think you misread it, he laughed. People listen to reflections all the time. It is no different than the mirror.

2" airgap and then 4" absorption will give you a good even absorption from aroudn 120Hz upwards.
Though this may work, he doesn't think it will be effective down to 120. You need 6" absorption for that to work.

What will work though, and much better is this. 1" framing covered by masonite (peg board), then covered my your fiberglass absorber. I forget the model #, but he even said the 1" in this config would work better.
Or, like in my case the Auraluz elite panels mounted on top of it.

Early reflections

You early reflections are likey to come from your workstation and ceiling. As well, reflections in a room 16x23x8ft go between 12ms all the way to 30ms.

Your ceiling reflection will likely reach you before your side wall reflections will.

If your reflections go beyond 40ms, then you have echo.

In the example of this room size, being 23ft long with an 8 ft ceilting, the direct signal will take 10ms, and the ceiling reflection will take 12ms, and the side wall reflection will take 14ms.

Depending on your listening position and distance, your workstation might reach first before the ceiling.

Even moving the mic slightly can result in a compeltely different response

Depends on what you are looking at on the RTA. Moving the mic 1 inch back is going to do little in its reading in the low frequency reading.

For example, my listening position is about 2 feet from the speakers. So the mic responds to frequencies that have a wave length less that 2 feet, roughly 600hz and above.
If I move the mic 2 foot 1 inch back, this only effects the frequencies with wavelengths that are shorter.
The low Frequencies like 80hz, with a length of 13.75 ft might change by .01 of a dB, but will not be hear by the ear.

If you analyse your room and find you have, for example, a dip at 60 and 80 due to standing waves then this will only hold true for that particular mic position,.

This is not true as I have stated above. This would only be true for a distance equal and greater than those wave lengths.

So using EQ can narrow your mix position and make it worse in other parts of the room.

EQ or no EQ, it will sound different in varies parts of the room. That is why they call it a "sweet spot". There is always and ideal position, but even without EQ it is going to sound different if you are 10 feet back.

Relfections also mess up you stereo image as a relfection can be considered a ghost sound source. imagine a room made of mirrors and your speakers are two lightbulbs. You will obviously see many other lightbulbs reflected in the mirrors. So unless you absorb early refelctions you will effectively have many more than just two speakers in your room.
We both felt this a bit of an over exaggeration. Once again, it all depends on the room.

When Miles asked about his big cathedral room and reflections, then it is true. But in a smaller room like most people here, they are unlikey to have ghosting images of more than 2 speakers.
The low frequency bounce will eliminate that right away. It also depends on the distance from their listening position to the speaker.
Even with console and ceiling reflection that will reduce the stereo imaging, but not create a "ghost speaker image".

Wavelengths less than 7 inches (1.8k and above), bounce off your head anyway creating intensity not ghosting.

With Low freq, time effects perception. With High freq, intensity effects preception.
While final tweaks can be helpful you should always flatten freqeuncy response issues with absorption rather than EQing.
That is what I was trying to say, but like I said, unless you are building the room from the ground up it is unlikely you will be able to achieve a flat response in a room.

The other problem with boosting low end freqs in order to compensate for standing wave nulls is that you can eat up hge amounts of headroom in your monitor amps and drivers. This will of coruse also increase distortion

There is nothing wrong with applying some room EQ to "even out" some things. The problem with it, which SHOULD be mentioned is, how much.

If you are boosting a dip at 80 by 10db, then you need to reevaluate your speaker position, absorption and diffusion.
But if you are correction a dip at 80Hz that is -3db, that is fine.

It is called, as Chuck said, "fine tuning".

Sofit mounting tends to lead to more issues and tends to need more tweaking than freestanding monitors. Pretty much any room with sofit mounted monitors need to be tuned for the room because they are in an enclosure.
And their tuning is far more critical because of that. Absorption alone will not correction the problems soffit mounting creates.
Also because of the distance, phase and time aligning is critical. Even 2 months, Carl would come to the studio and tune the sofit speakers in every room.
If I remember, they were BSS EQs. One room might have had white EQ's.

This being the case, pretty much everyone I know will listen to them, but will mix on the nearfields over the sofit.
Even in 5.1 mixing, 5.1 nearfield was preferred.
Only on the dub stage was the "bigs" preferred. And speaking of that, I have THX come tune my stages every 6 months.

I think in both our discussions, we were speaking from a "my room" perspective.

You have some good points, but were not speaking from the "all" factor when discussing.

So hopefully this clarifies some of the earlier points I made.
If not, I am open for more discussion.

Maybe you guys have a bit different way of doing things across the Atlantic.

No worries, Paul the Fabulous ****er! Burrrrrnt!

LEX

[nickysnd]

I asked a physics teacher (my mother, no kidding) about this problem of low standing waves, and the first thing that she said to me was this: are the musicians playing equally with all the frequencies? ... I was stupefied by the simplicity of this question, and by its implications. Also, she told me about my 125Hz boost something similar to your assumption, LEX - that its wavelength is about 9ft - which is the distance between two of my parallel walls. She added that the law is: the distances equal to wavelengths are doubling the amplitude of their corresponding frequencies. Also, the same theory suggests that, if you place your head at the half of a standing wave (half wavelength), then, at that precise point, that particular standing wave has the amplitude zero, which is to say that it is not heard. Funny stuff, acoustics...

Back to my 125Hz issue and to my mother's question. Now: considering that 125Hz is very close to the note B=123.5Hz, every time an instrument (bass, mostly) hits that note, it doubles its loudness. That is what litarally happens in my room - and that matches the wavelength theory. So, if I change the distance between the walls (say with a thick curtain) to a distance corresponding to the wavelength of a sound that is hardly ever played, like 127Hz (which is roughly between B and C) then that might solve my problem. From my calculations, I need to place a curtain at about 1" and 1/4 from my wall. I think I will try that. It can't do any damage, some absorption will take place anyways...

But how about that - frequencies that are often hit by instruments vs. frequencies that are less likely to be hit by instruments? That's an interesting approach, isn't it?

[LEX]

I asked a physics teacher (my mother, no kidding) about this problem of low standing waves, and the first thing that she said to me was this: are the musicians playing equally with all the frequencies? ... I was stupefied by the simplicity of this question, and by its implications. Also, she told me about my 125Hz boost something similar to your assumption, LEX - that its wavelength is about 9ft - which is the distance between two of my parallel walls. She added that the law is: the distances equal to wavelengths are doubling the amplitude of their corresponding frequencies. Also, the same theory suggests that, if you place your head at the half of a standing wave (half wavelength), then, at that precise point, that particular standing wave has the amplitude zero, which is to say that it is not heard. Funny stuff, acoustics...

Back to my 125Hz issue and to my mother's question. Now: considering that 125Hz is very close to the note B=123.5Hz, every time an instrument (bass, mostly) hits that note, it doubles its loudness. That is what litarally happens in my room - and that matches the wavelength theory. So, if I change the distance between the walls (say with a thick curtain) to a distance corresponding to the wavelength of a sound that is hardly ever played, like 127Hz (which is roughly between B and C) then that might solve my problem. From my calculations, I need to place a curtain at about 1" and 1/4 from my wall. I think I will try that. It can't do any damage, some absorption will take place anyways...

But how about that - frequencies that are often hit by instruments vs. frequencies that are less likely to be hit by instruments? That's an interesting approach, isn't it?

See I am not as wrong as it may seem.
You are probably hear 125 at plus 6dB or more is boost.

The curtain something to try, but might not work. The wavelengths are probably too powerful to be absorbed, but that depends on the materail.
You would really need to test the absorption coeffiecent of the curtain and you might find it will work, but probably at a greater distance than that you expected.
Probably to great for the size of the room.

You might try a wall absorption after the curtain.

This tends to be the standing problem with home style rooms. Usually the length of the rooms are usually around the frequency of 120-130, which is about 8-9 feet.

In general, you want a greater parallel depth in the room no less than 18 feet.
Which again, goes back to the corner theory in which if you can increase the distance of the nearest reflection your low end problem is a lower frequency and smoothed by the extra bounces it creates.

Hi frequency issues in a small room can be easily corrected with simple absorption and diffusion, though probably not always completely ideal.

Nick, you will need to get an RTA and test the differences of your material to see how it acts in your room.

LEX

[Javee]

It is kinda funny how far this thread went. Someone asks advice about what kind of monitors he should get, how do headphones compare, and is it worth it in an un-accoustically tweaked room, Paul and LEX get into a huge heated debate over who's right and who's wrong! funny haha.

I am new to all this, but i think what is most important is that you know how to write music and good with your sequencer.

I am more of a performance/studio experienced musician. And i can tell you that some of the best sounds i've ever had come out of the many bands i've played in, have in been in the worsed acoustic halls/rooms. I believe, if your tracks dont sound good from the original recording, or before you begin to master a mix of sampled isntruments, than it can only be tweaked so much.

I aprreciate a good quality recording, but if you are too picky, it will haunt you everytime you listen to a recording.

Just my 2 bits

Mitch

[nickysnd]

you will need to get an RTA and test the differences of your material to see how it acts in your room.
What is an RTA? Here is what my internet research has revealed so far:

Ready To Assemble
Rapid Thermal Annealing
Real Time Access
Referral Travel Agent
Road Traffic Accident
RAPID TURN AROUND
Rubidium Titanyl Arsenate
Raise Taxes Again!
:D

[LEX]

What is an RTA? Here is what my internet research has revealed so far:

Ready To Assemble
Rapid Thermal Annealing
Real Time Access
Referral Travel Agent
Road Traffic Accident
RAPID TURN AROUND
Rubidium Titanyl Arsenate
Raise Taxes Again!
:D

Real Time Analyzer.

Look up Goldline. there are also software based ones that are good as well.

LEX

[Paul Woodlock]

A lot to plough through and it's late - sorry for not getting back before now. :)

Okay so I got some info from 1 of my guys, my mastering engineer.

1st thing. Not room is alike, neither my information or Pauls information means anything for anyone else.

My information relies on physics and is appliccable to any room. Although I'm aiming it at SMALL ROOMS - Small room meaning the typical room at home people have a studio in.


You need to find your position in your room for what sounds best 1st. The parallel surface theory has changed a bit over the past years, but, for example in my room the longer though is better because of the size of the room.

Determining parallel's does, however, depend on the size of the room.
Based on the size of your room and the position of your speakers from the point of their speaker points to the nearest parallel can change the low end dramtically.

So if from where your speakers are to the rear wall is 5 feet, you are going to run into problems.
If you can move it to a corner with a longer throw, your bass response will smooth better.
Then at that point it is determining the distance from the nearest reflective surface you have to determine.

The above is nothing to do with standing waves, It is to do with energy that is emitted from the rear of the speaker ( speakers are omnidirectional at low frequencies ) being relfeted forward.



Sorry mate, that isn't true.

1] Standing waves are resonances that are basicalyl a storage of sound energy in a room that's filled up by being excited from a sound source and emptied through absorption of the energy through imperfections in structure.


A Standing wave is a room resonance in the LOW frequency region that results in the uneven distribution of sound energy in the room.

The room dimenions determine the freqeuncy of the standing waves and small rooms will also exhibit standing waves in the low mids, althugh they are more closely spaced in freqeuncy in this regions and are less troublesome.



Again the key is the Low frequencies. Nicks 125HZ bump is due likely because the nearest surface is about 8 feet away. 128hz is 8.8feet in length.
80hz is 12.75 feet.


Yes of course. But once again, the difference comes down to the low freq round trip and multiples there of.

A rear wall, bare, 6 feet away will have a greater build up than an angled difference with an 8 or 10 foot throw reflecting off 4 surfaces before returning to its origin.
Hense, a smoother response and less of a low end boost.

??? Standing waves don't work like that. LF Doesn't act like rays in a small room it acts alike a pressure wave. What so you say above doesn't make sense





Placing a workstation in a corner, room dependent of course doesn't mean the speaker will have side boundries. Actually, it is hard to create side boundries in a corner.
Just look at my studio pics. The only boundry is behind the speaker.

Though not ideal, but even the lowend reflection still return to the speaker, another reflective surface.
Since in both cases of parallel and corner we are dealing with diffraction instead of reflection.
Diffraction is when a wave length is longer than the object it reaches, it goes around.

At least in my room, diffraction was a key element in placement. Unlike a parallel back plane where the low freq has no choice but to go around the speaker and the monitors, in the corner the diffraction is reduced by about 6db as the low end freq's traveling around the back are collected.

Again that doesn't make sense. LF is omnidirectional in a room. Diffraction around your speaker cabinet will affect mid frequencies. Unless you have huge 10 foot speakers :)



2] Standing waves don't need straight walls to occour. The body of stringed instruments and acoustic guitars ( especailly those curved back models ) are good examples of where (benficial ) standing waves occour in spaces that have curved 'walls' YO ucan have a standign wave in a sphere which ahs no straight walls
Right, but that is the reason the guitar isn't square. It has more surfaces to bounce off of and resonant. If it were better, then it would be square.

Again that's not the reason at all. Youre not understanding room resonances. The reason for a non square guitar body is ro provide an even resonant response. A square, or worse a cubic guitar would resonate at 1 particular frequency ( and it's harmonics ), as the modes would be at the same freqeuncy. The same applies to rooms and why certain room ratios sound better than others. Square rooms and rooms of ratios of fixed integers...i.e 1:1 1:2, etc are not recommnded.




In typical home studios diffusion is probably the least priority type of acoustic treatment you will want to apply. Most small rooms don't build up a late sound field that warrants diffusing. Most relfections in a small room are <20ms which is percieved by the ear as part of the direct sound. ersult ... smear.

Diffusion is simply a scattering of sound in the same way that matt paint scatters light by diffraction around objects An irregular object will only diffuse a frequency if it's size is equal or larger to the wavelength. A skyline type diffuser for example and will only really effecitely diffuse frequencies above 6.5kHz if it's irregularities are around 2" x2"

Well there is actually 2 schools of thought on this, so neither is wrong. But diffusion happens in the low mid, mid high and appreciable low frequency absorption.

I ave no idea what you mean by the sentance in bold.

Diffusion can happen at any freqeuncy as long as the size of the diffusing objects lends itself to those freqeuncies.


George Oshburger uses diffusion heavily with heavy bass trapping in the corners. 6.5k is why to high. Diffusion begins far before that, and depending on how you do it neither is wrong.

Some prefer heavy absorption over diffusion, but neither is wrong or misleading.

It dedns upon the size of the room. In profesional sized control rooms and recording rooms diffusion makes a lot of sense. In SMALL rooms. absorption as a preference makes more sense. but sure this is open to debate.

[LEX]

Paul,

All my above statement came from several books on acoustics, sound and how sound acts in a room.

So are these books, wrong?

BTW, the Standing Wave definition is straight out of the book.

LEX

Again that doesn't make sense. LF is omnidirectional in a room. Diffraction around your speaker cabinet will affect mid frequencies. Unless you have huge 10 foot speakers
Well, we've tested a 5.1 system with the sub in different areas of the room.

And yes, it makes a difference where you place it.

If it were TRUELY omni directional, you could place it behind you and it wouldn't make a difference. Yet, when we tested it, it made a major difference where the sub was placed
.
A little left a little right, isn't going to make the difference.
But placing the sub in the left hand corner of the room, changes the way it sounds.

The analogy we used was, "think of a bucket of water. Now stand in the left of the room and dump the water. where does it go and where does it come from. Stand in the front and dump the water, the water spreads evenly in front of you."

My information relies on physics and is applivvable to any room. Although I'm aiming it at SMALL ROOMS - Small room meaning the typical room at home people have a studio in.
So mine hasn't? Yet I referred to texted material in my response. Are they not applying physics? Are they all high?

Again the key is the Low frequencies. Nicks 125HZ bump is due likely because the nearest surface is about 8 feet away. 128hz is 8.8feet in length.
80hz is 12.75 feet.

Yes of course. But once again, the difference comes down to the low freq round trip and multiples there of.

A rear wall, bare, 6 feet away will have a greater build up than an angled difference with an 8 or 10 foot throw reflecting off 4 surfaces before returning to its origin.
Hense, a smoother response and less of a low end boost.
Standing waves don't work like that. LF Doesn't act like rays in a small room it acts alike a pressure wave. What so you say above doesn't make sense

I Quote:

Two pair of opposite, parallel surfaces constitutes a resonant system.
At 20 feet apart, that frequency of 1,130 divided by twice the distance (1,130/40 = 28.3hz) 1,130ft/sec is the speed of sound.

Each set of plan, parallel surfaces also resonates at multiples of the same frequency. Thus the 2 end walls are resonant not only at 28.3Hz, but also at 2,3,4,....ect times 28.3Hz. In other words, these two surfaces are just as resonant when the sound makes a second, third, or fourth round trip as they were for the first round trip (neglecting successive reflection losses). A series of resonance frequencies exists for each pair of surfaces. Each series of is terminated at around 300hz because few axial mode problems are found above that frequency.

Let me define Axial Mode again.

Axial Modes:
Acoustical resonance effects between two spaced, parallel surfaces such as side walls of a room, end walls and floor and ceiling.

So lets review.

28.3 Hz reflects and multiples, and reflects. If it were not to reflect, then why does it build in multitudes.

P-Waves:
Sound, being a pressure and longitudinal wave in air.

Sound is pressure, and low frequency waves are long. SO if a LF wave reaches a boundry. What does it do? We'd love it to absorb. But no, it comes back.

Nicks room at 9 feet.

1130/18 =62hz (trip 1), 124(trip2) (the 2nd multiple of 62)

Square rooms and rooms of ratios of fixed integers...i.e 1:1 1:2, etc are not recommnded.

All the above commented, and further back are based on rectangular rooms.

The above is nothing to do with standing waves, It is to do with energy that is emitted from the rear of the speaker ( speakers are omnidirectional at low frequencies ) being relfeted forward.

I'll Quote again:

What should be done to an untreated room to guard against serious room resonance effects? First, a critical listening test should be made with a recording rich in bass to see if serious boominess exists at certain positions. If troublesome spots are found, a few calculations probably can identify the specific axial mode causing the problem.

Axial Modes:
Acoustical resonance effects between two spaced, parallel surfaces such as side walls of a room, end walls and floor and ceiling.

Tangentail and oblique Modes
The spaceing of modal resonance frequencies could be greater than desired. Each mode is effective over a narrow frequency region of approximatelt 5 hz. It would be good for room response if all modes were close enough to overlap. Independent action of single or coincident modes well spaced from neighbors often leads to audible colorations of the sound. Guilford came to the conclusion that spacings greater than 25hz were especially prone to sound colorations.

Fortunately, many modal resonances exist other than the axial modes. Tangential modes invlove four surfaces for their round trip; oblique modes involve all six surfaces. Even thought they are less powerful than the axial modes, tangential and oblique modes help to smooth the low-frequency response of a room as the fill in between the axial modes. Therefore, the tangential and oblique modes help make the response of this room smoother.
[/QUOTE]

Diffusion:

Diffusion can happen at any freqeuncy as long as the size of the diffusing objects lends itself to those freqeuncies.

Yes, that is my point. LF diffusion requires a massive diffuser, so most diffusion is mid to high frequencies.
For an object to diffuse sound, it must be considerably larger than the wavelength of sound. SO in a 9 foot room, that is a very large diffuser.

Like nick, he would have to build a 12' by 12' diffuser to diffuse the 125hz problem he has.
So I say once again, diffusion if primarily low mid and above.

George Oshburger uses diffusion heavily with heavy bass trapping in the corners. 6.5k is why to high. Diffusion begins far before that, and depending on how you do it neither is wrong.

Some prefer heavy absorption over diffusion, but neither is wrong or misleading.
It dedns upon the size of the room. In profesional sized control rooms and recording rooms diffusion makes a lot of sense. In SMALL rooms. absorption as a preference makes more sense. but sure this is open to debate.

Yes this is open to debate, and depends on the designer. But my mastering engineer has had both schools of thought in the same room.

I agree that absorption makes more sense, but again it is size dependent. Some diffusion might be better than pure absorption.

Right, but that is the reason the guitar isn't square. It has more surfaces to bounce off of and resonant. If it were better, then it would be square.
Again that's not the reason at all. Youre not understanding room resonances. The reason for a non square guitar body is ro provide an even resonant response. A square, or worse a cubic guitar would resonate at 1 particular frequency ( and it's harmonics ), as the modes would be at the same freqeuncy. The same applies to rooms and why certain room ratios sound better than others. Square rooms and rooms of ratios of fixed integers...i.e 1:1 1:2, etc are not recommnded.

Actually we are both wrong.

The guitar top, or soundboard, is a finely crafted and engineered element often made of tonewood like spruce, red cedar or mahogany. This thin (often 2 or 3 mm thick) piece of wood, strengthened by different types of internal bracing, is considered by many luthiers to be the most prominent factor in determining the sound quality of a guitar. The majority of the sound is caused by vibration of the guitar top as the energy of the vibrating strings is transferred to it. It is thought by some that the details of the way in which the guitar top vibrates (characterised by many different modes of vibration at different frequencies) is a key influence on the timbre of the radiated sound.

When the strings vibrate, the vibrations travel through the saddle to the bridge to the soundboard. The entire soundboard is now vibrating. The body of the guitar forms a hollow soundbox that amplifies the vibrations of the soundboard.

So, technically a square guitar would work just fine. The body amplifies the sound, and the top of the guitar is the sound board/resonator.

Okay, so now?

LEX

[Paul Woodlock]

The positive with this approach is that the 'side' walls will reflect the sound backwards instead of at yoru ears. The negative is that unless you have a perfectly square room the setup won't be symetrical

There are no side walls, only rear walls.

No, what I meant was , if you set up in a corner you are looking at 2 walls that meet in a corner directly in front of you/ these walls form a 45 degree reflective surface that will reflect soundbackwards intead of at your ears. This is of course desirable to cut down the early reflections. IN terms fo semantics I suppose they are both fromt wall and side walls combined


You can't listen for a refletion at a wall boundary. Becuase at the wall boundary you can nly hear the direct sound and not the relfection egressing from the wall at that point.
You didn't read it right. possibly :) I wasn't talking about listening behind the speaker. I was talking about listening to the reflective walls and corners.
You can hear buildups of bass in corners and reflections off the walls.

Although you do need to stand in a corner to hear the increase in bass. The reason you hear the increase in bass in a corner, and at wall bounaries is becuase the standing waves have their anti-nodes ( Poitns of highest pressure ) at the walls. Its alsio why corners are the best place to put bass traps



2" airgap and then 4" absorption will give you a good even absorption from aroudn 120Hz upwards.
Though this may work, he doesn't think it will be effective down to 120. You need 6" absorption for that to work.

The figure was off the top of my head. however the point is that 4"+ 2" air gap is pretty much as effective as 6" against the wall. The reason is there is no air movement at the wall boundary. This can cut your absoption bill down by 25% for effectively the same absoption



What will work though, and much better is this. 1" framing covered by masonite (peg board), then covered my your fiberglass absorber. I forget the model #, but he even said the 1" in this config would work better.

This is a differnt system, a tuned absorber. Semi-rigid fibreglass batts are a broadband absorption.



Early reflections
You early reflections are likey to come from your workstation and ceiling. As well, reflections in a room 16x23x8ft go between 12ms all the way to 30ms.

Your ceiling reflection will likely reach you before your side wall reflections will.


Well that depends on the dimenions of the room. If you have a low ceiling and walls far away then that is true. If your walls are closer than teh ceiling then it's not true,






Depends on what you are looking at on the RTA. Moving the mic 1 inch back is going to do little in its reading in the low frequency reading.

1" isnt' going to make much difference suire, but 4" can.

http://forum.studiotips.com/files/mix_pos_test_mic_variable_height_full_range_436.jp g

That's the result of moving the measuremnt mic only 4" ( 100mm) vertically up and down at the mix position . you can particularly see the difference in intensity of 1 particulr standing wave


For example, my listening position is about 2 feet from the speakers. So the mic responds to frequencies that have a wave length less that 2 feet, roughly 600hz and above.
If I move the mic 2 foot 1 inch back, this only effects the frequencies with wavelengths that are shorter.
The low Frequencies like 80hz, with a length of 13.75 ft might change by .01 of a dB, but will not be hear by the ear.


If you analyse your room and find you have, for example, a dip at 60 and 80 due to standing waves then this will only hold true for that particular mic position,.

This is not true as I have stated above. This would only be true for a distance equal and greater than those wave lengths.


Again I'm talkign abotu standing waves intensity, not reflective wavelgtnh paths.










So using EQ can narrow your mix position and make it worse in other parts of the room.
EQ or no EQ, it will sound different in varies parts of the room. That is why they call it a "sweet spot". There is always and ideal position, but even without EQ it is going to sound different if you are 10 feet back.

So? I didn't say it wouldn't. I'm saying EQing the direct sound to compensate for relfections and standing waves will narrow the sweet spot and incrase the errors in other parts of the room




Relfections also mess up you stereo image as a relfection can be considered a ghost sound source. imagine a room made of mirrors and your speakers are two lightbulbs. You will obviously see many other lightbulbs reflected in the mirrors. So unless you absorb early refelctions you will effectively have many more than just two speakers in your room.

We both felt this a bit of an over exaggeration. Once again, it all depends on the room.

It's not an exaggeration it's physics. You probably misread????



When Miles asked about his big cathedral room and reflections, then it is true. But in a smaller room like most people here, they are unlikey to have ghosting images of more than 2 speakers.

You will if you have relfecticve surfaces. It's simple physics.


Sorry about the rush to reply - it's 6:30 here and I need to goto bed. :)

[LEX]

1" isnt' going to make much difference suire, but 4" can.

You never stated up or down. Sure than makes sence.

Moving a mic closer and further will have little difference in the LF reading.
And little on the mids depending on how far you are from the speakers you are measuring.

You need the read the above.

LEX

[nickysnd]

When Miles asked about his big cathedral room and reflections, then it is true. But in a smaller room like most people here, they are unlikey to have ghosting images of more than 2 speakers.
You will if you have relfecticve surfaces. It's simple physics.
Which reminds me of a sound engineer I once knew who, when asked what sound is, he answered - "Sound is a ghost." Also, I have noticed that physics are often misleading, especially acoustics and optics. Waves' behavior is not always that clear to understand, they don't seem to care much for our theories...

I actually love my ghosting images continuously reflecting from my walls. If I didn't have them, I would surely have missed them. Imagine an an-echoic room - I have heard frightening things about it...

As about MY standing waves - I proudly announce that I have finally tested my room, and, besides the gross 125Hz boost, I have discovered three more, smaller: at 50Hz, 198Hz, and, curiously, at 12.5kHz. Also, there were two small dips, at 3.1kHz and 6.2kHz. All these, of course, measured from my sweet spot. They were not big, and pretty easy to control: I have made two EQ presets on my DP master track - one for "flat" response (so I can hear "everything"), and another one more humane - with smoother edges in lows and highs - so I won't keep those marginal areas too low in my mixes.

So my pentagon-room is now pretty much "calibrated," and I am quite happy with its sound. Ultimately, I think it all comes down to what our mixes sound like when compared to professional mixes. So, with a little bit of "aesthetic surgery" to reduce nasty standing waves in the sweet spot, I think that everything else is a matter of how well we are able to bring our mixes close to a pro level, by continuously comparing our results to professional mixes of similar music. I mean - all rooms inevitably (and thankfully, I'd say) have their acoustic color, but they have the SAME acoustic color for each and every piece of music. So we are listening to everything from within the same acoustic rainbow.

I guess what I am trying to say is that all rooms are good, providing that the exaggerated standing waves are reduced to a reasonable level in the sweet spot. Furthermore, the sound quality of one's mixes depends "entirely" of one's capacity to make his mixes sound close to pro mixes (by listening/comparing them from the same "sweet spot"). I keep repeating that... bad sign...

This is only my $0.02 worth. Please correct me where I am wrong.

[LEX]

Just a little more on Standing Waves:

A standing wave, also known as a stationary wave, is a wave that remains in a constant position. This phenomenon can occur because the medium is moving in the opposite direction to the wave, or it can arise in a stationary medium as a result of interference between two waves traveling in opposite directions. There is no net propagation of energy.



Standing waves don't work like that. LF Doesn't act like rays in a small room it acts alike a pressure wave.
Paul

Standing waves are also observed in physical media such as strings and columns of air. Any waves travelling along the medium will reflect back when they reach the end. This effect is most noticeable in musical instruments where, at various multiples of a string or air column's natural frequency, a standing wave is created, allowing harmonics to be identified. Nodes occur at fixed ends and antinodes at open ends. If fixed at only one end, only odd-numbered harmonics are available.

Although you do need to stand in a corner to hear the increase in bass. The reason you hear the increase in bass in a corner, and at wall bounaries is becuase the standing waves have their anti-nodes ( Poitns of highest pressure ) at the walls.

Which is why I said:

ou can hear buildups of bass in corners

Its alsio why corners are the best place to put bass traps
Right. Even the kid going to Guitar center will figure that out based on the Auralex design.

When Miles asked about his big cathedral room and reflections, then it is true. But in a smaller room like most people here, they are unlikey to have ghosting images of more than 2 speakers.
You will if you have relfecticve surfaces. It's simple physics.


Everyone has reflective surfaces in their room. We maybe speaking different languages here, but since you say LF material doesn't reflect, and the lowest mid is 4.4 feet at 250 cycles how far does the nearest reflective surface have to be to "ghost"

I have yet to hear a "ghost" image, unless you mean something else.

Still have one more.

And maybe it is speaker depended.

Why is the low frequency from the front of the speaker measure louder than it does from the rear of the speaker?
If it were truely omni directional, I should get the same SPL level from the front as I do the rear?

More testing a foot!

LEX

LEX

[LEX]

Imagine an an-echoic room - I have heard frightening things about it...

Shure mics have one. It is frightening.
It is hard to describe.

The complete absence of sound and ambience. You feel and hear yourself and your body.

It all depends on the person, but some people can't be in there long. Saying it feels like the walls are closing in and getting closer by the second.

I have to do it again.

Want to see if I can spend 1 hour in there.

LEX

[Paul Woodlock]

Paul,

All my above statement came from several books on acoustics, sound and how sound acts in a room.

So are these books, wrong?

BTW, the Standing Wave definition is straight out of the book.

LEX




If the book says that surfaces need to be parrallel for Axial mode standing waves to exist then it is wrong. You can have a room with no parrallel surface and you will still get axial mode standing waves.

for example - It is a myth that having non parrallel panes of glass between control room and trackign room eliminates standing waves between the panes - it doesn't.



So, technically a square guitar would work just fine. The body amplifies the sound, and the top of the guitar is the sound board/resonator.

Okay, so now?

LEX
Sorry but I wasn't wrong, you are talking about something different. I didn't say a square guitar wouldnt' work. I explained the differences in the spacing of the standing waves within the guitar, not how the guitar makes a good soundboard.

A sqaure enclisure , whether that is a square guitar or a sqaure room will have 2 axial modes at the same frequency. This is not desirable in a control room as the standign wave is higher intensity at 1 frequency ( and multiples ) and thus harder to eliminate.

[Paul Woodlock]

1" isnt' going to make much difference suire, but 4" can.

You never stated up or down. Sure than makes sence.


Actually it makes NO difference whether it's up or down, front to back or side to side. :)

[Paul Woodlock]

When Miles asked about his big cathedral room and reflections, then it is true. But in a smaller room like most people here, they are unlikey to have ghosting images of more than 2 speakers.


You will if you have relfecticve surfaces. It's simple physics.

Everyone has reflective surfaces in their room.

Of course

We maybe speaking different languages here, but since you say LF material doesn't reflect, and the lowest mid is 4.4 feet at 250 cycles how far does the nearest reflective surface have to be to "ghost"

I have yet to hear a "ghost" image, unless you mean something else.


I meant that LF material doesn't act like light rays in a small room as the wavelengths are too big. higher frequencies behave like rays in a room. Sound reflecting of a surface will show a mirror sound source image. imagine a mirrored room with light bulbs instead of speakers. This is the best way to imagine it


Why is the low frequency from the front of the speaker measure louder than it does from the rear of the speaker?
If it were truely omni directional, I should get the same SPL level from the front as I do the rear?


I didn't mean omnidirectional in that there would be eactly the same energy emiited from teh rear of the speaker as the front. but none the less a speaker is pretty mucih oimnidirectional in the bass end. That's why decent active speakers have bass roll off filters to compensate for half space and quarter space situations where the rear emmited energy is reflected towards the front.

:)

[nickysnd]

Sorry but I wasn't wrong, you are talking about something different.
Hey guys, watch the following string of letters:

You are right.

And also this one:

I was wrong.

Now, you will be amazed how easy it is to write them down. Just try and see. If it proves to be hard, well, then - I was wrong.

[LEX]

If the book says that surfaces need to be parrallel for Axial mode standing waves to exist then it is wrong. You can have a room with no parrallel surface and you will still get axial mode standing waves.



That is not what it says. I have stated to several times. Axial modes have a greater build up on standing waves.

Axial Mode Resonances
Any pair of opposite, parallel surfaces constitutes a resonant system. For example, 2 ends of a rectangular room are 20ft apart, they are resonant at a frequency of 1,130 divided by twice the distance (1,130/40 = 28.3hz). The 1,130 ft/sec is the speed of sound; the sound must make one complete round trip at the resonance frequency.
The 2 side walls spaced 15ft resonate at a frequency of 1,130/30 = 37.7hz, and the floor/ceiling surfaces spaced 8ft resonate at 1,130/16 = 70.6hz. In this way the rectangular room resonates simultaneously at 28.3, 37.7, and 70.6hz, called the axial mode of the room. If stopping here, life would be simple. Each set of plane, parallel surfaces also resonates at multiples of the same frequency. Thus the 2 end walls not only resonant at 28.3hz, but aslo at 2,3,4 ......ect. times 28.3Hz. In other words, these 2 surfaces are just as resonant when the sound makes a second, third or forth trip as they were for the first round trip (neglecting successive reflection losses. A series of resonance frequencies exsits for each pair of surfaces. Each series is terminated at about 300hz because few axial mode problems are found above that frequency.

Tangentail and oblique Modes
The spaceing of modal resonance frequencies could be greater than desired. Each mode is effective over a narrow frequency region of approximatelty 5 hz. It would be good for room response if all modes were close enough to overlap. Independent action of single or coincident modes well spaced from neighbors often leads to audible colorations of the sound. Guilford came to the conclusion that spacings greater than 25hz were especially prone to sound colorations.

Fortunately, many modal resonances exist other than the axial modes. Tangential modes invlove four surfaces for their round trip; oblique modes involve all six surfaces. Even thought they are less powerful than the axial modes, tangential and oblique modes help to smooth the low-frequency response of a room as the fill in between the axial modes. Therefore, the tangential and oblique modes help make the response of this room smoother.


Check it out.

LEX

[Paul Woodlock]

Hey guys, watch the following string of letters:

You are right.

And also this one:

I was wrong.

Now, you will be amazed how easy it is to write them down. Just try and see. If it proves to be hard, well, then - I was wrong.

Why would you say you were wrong if you were right though? it doesn't amke sense :)

[Paul Woodlock]

That is not what it says. I have stated to several times.

The book is correct about axial, tangential and oblique modes. however the book is misleading when it mentions parallel surfaces.

You do NOT need parallel surfaces for there to be standing waves.



Axial modes have a greater build up on standing waves.


? That doesn't makes sense. Axial modes ARE standing waves

[LEX]

The book is correct about axial, tangential and oblique modes. however the book is misleading when it mentions parallel surfaces.

You do NOT need parallel surfaces for there to be standing waves.




? That doesn't makes sense. Axial modes ARE standing waves

I understand that you don't need parallels for standing waves, I never said you need parallel surfaces for standing waves.
Maybe I stated that standing waves will kill you with a parallel surface, but that is because of the build up.

But, a greater build up is created when it reflects directly back to the on coming wave.

Giving the waves more to travel around, rather than directly back in the path they came from, the build up is less than it would be.
Which is why a Tangential/oblique modes in an untreated room will have less of that typical bass, LF build up because when it finally returns the intensity of the LF wave will be less.

And hense easier to deal with at this point in terms of absorption.

LEX

[ToddK]

my peepee is bigger than your peepee!!!!!! So there..

[LEX]

my peepee is bigger than your peepee!!!!!! So there..

I doubt it! LOL!

LEX

[nickysnd]

Blessed are they who can laugh at themselves, for they shall never cease to be amused.

[Erik Wietzel]

I wish composing for the movies was all about composing:p