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Old 10-18-2017, 11:27 PM
Guitar Slim II Guitar Slim II is offline
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Default Bass Traps and Foam: Seeking advice

I've been sprucing up my basement room recently, trying to make it a more pleasant space for teaching and shooting videos. Although the goal is mostly cosmetic, I figure it's a good opportunity to do some sound treatment as well, since this is also the room I record in.

I've done some preliminary research, including this excellent article posted here recently: http://www.acousticguitarforum.com/f...d.php?t=485329. But I've found a lot more about treating listening spaces than treating recording spaces. And I haven't found much regarding rooms and quiet acoustic instruments, specifically.

So I have some general, rambling questions and I was hoping the experts here could provide me with some guidance...

The Room -- my half-basement. 10' x 20' x 7' rectangular, painted plaster walls, carpeted floor, popcorn ceiling. Desk, shelves, guitar amps, and instrument cases along the walls to a height of 3 or 4 feet. The walls are exposed above that. Clap-test produces a short reverberation with a kind of out-of-phase quality to it.

The Music -- I only record acoustic instruments in this room - mostly guitar. I have a pair of small-diaphragm condenser mics and record either in mono or with standard xy stereo micing. Anything else is direct-in and played on electric guitars or keyboard. One thing I'm wondering: would you treat a room devoted to quiet acoustic instruments differently from, say, a drum room?

Bass Traps -- Bass traps seem to be universally recommended. Are they important in a quiet, acoustic recording space? And do corner traps really need to go from floor to ceiling? As I understand it, the most important areas to treat are in a direct line with the sound source or listening position. Since I usually play seated, the sound source and mic are both about 3' from the floor. A 12x12x24 trap would stand four feet in a corner. Will that have an effect? Enough of an effect? Would narrower corner strips work higher up?

Acoustic Foam -- Things get a little tricky here. As noted, the sound source and mic are typically about 3 feet from the floor. There are desks, amps and keyboards along the walls at the same height. Will the furnishings effect reverberation and frequency response? Should I install foam in the same places I would if the walls were bare -- in other words, behind the furnishings -- and then put the stuff back? Should I put it higher up on the walls?

OK, that's asking a LOT of questions. Even a little guidance would be hugely appreciated. And thanks in advance, you folks are the best.
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Old 10-19-2017, 12:30 AM
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Not a fan of foam stuff. I put in rockwool panels (4" thick wall, 2" thick ceiling). I bought from ATS Acoustics. You might do their free room analysis here:
https://www.atsacoustics.com/page--F...ysis--ora.html

Picture of part of my room here:


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Old 10-19-2017, 05:34 AM
jim1960 jim1960 is offline
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At the very least, I'd put 4" thick rockwool bass traps in the corners (floor to ceiling if you can pull it off, 2'x4' will suffice if you can't) and a three panel cloud over your recording area, assuming the panels are 2'x4'.

Bass traps are absolutely important, I'd say even more so in your space because of its dimensions. You're essentially recording in a tunnel. Without bass traps, those low frequencies will build up and show up on your recorded tracks in unpleasant ways.

I agree with rick-slo in that the foam stuff should be avoided. I started with foam. Foam's efficacy is minimal and not worth the investment, imo.
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Last edited by jim1960; 10-19-2017 at 05:40 AM.
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Old 10-19-2017, 06:09 AM
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actually your room dimensions are perfect. just make sure you dont set up shop in the dead center of the room

bass traps will work and dont need to be super thick as your lowest frequency wont be below 80Hz

using the picture from the post above is a good start. you want walls at first reflection point to the mic treated the wallbehind the mic and the wall behind the performer also treated

the "clap" test is a great indicator of how much absorption you need. A listening room and recording room shouldnt be that diffrerent from each other

Foam does not work ...dont use it. you need broadband absorption....corning 708 is your best choice....followed by roxul safe and sound. you can build your own panels for a fraction of what ATS or other online company will charge...and they are super easy to build


PM me if you want help...I personally hand built my entire dedicated Home theater room which is fully sound treated

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Old 10-19-2017, 06:24 AM
jim1960 jim1960 is offline
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Quote:
Originally Posted by bmoney View Post
actually your room dimensions are perfect.
Everything I've read on the subject has said a "perfect" recording room wouldn't have parallel walls.
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Old 10-19-2017, 06:26 AM
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Quote:
Originally Posted by jim1960 View Post
Everything I've read on the subject has said a "perfect" recording room wouldn't have parallel walls.
i am referring to IN HOME perfect....not gonna find many homes with non parallel walls

regardless...bass at the frequencies a guitar makes will NOT build up in that room..will bass traps help? absolutly they will reduce the ringing...but broadband absorption wll get him 90% of the way there
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Old 10-19-2017, 06:45 AM
jim1960 jim1960 is offline
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Quote:
Originally Posted by bmoney View Post
regardless...bass at the frequencies a guitar makes will NOT build up in that room.
I'm not claiming expertise on this subject but I've read a lot on it and this part of what you're saying seems to contradict what I've read. The OP is playing in a narrow room with a low ceiling. Why won't bass frequencies build up in the corners in that room?
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Old 10-19-2017, 06:53 AM
bmoney bmoney is offline
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Quote:
Originally Posted by jim1960 View Post
I'm not claiming expertise on this subject but I've read a lot on it and this part of what you're saying seems to contradict what I've read. The OP is playing in a narrow room with a low ceiling. Why won't bass frequencies build up in the corners in that room?


You have to understand the length of bass waves and a small room. As long as the room isn’t perfectly square he is fine. An accoustic guitar lowest frequency is 83hz which has a wavelength of ~14’

So he is fine. As all waves higher than 80hz become shorter and shorter.

I have essentially the exact same size Ht 11x17x8 and have no major issues with bass buildup and have no bass traps. Would I benefit from them. Yes. But because the trouble frequencies for a room are below 80hz the traps would have to be 4’ thick to be effective.

Like I said he can get 90% there with broadband traps.
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Old 10-19-2017, 06:54 AM
Truckjohn Truckjohn is offline
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To the OP...

You say you are already recording in there... How is your recording experience in this room going?

Are you experiencing any of the problems you are talking about?
Weird echo's, rumbly hollow bass that doesn't belong, stray "house" noises like pops, creaks, etc.... Do you have to consciously work to avoid clicking noises or tapping noises or whatever?

If its already going well enough and you aren't having problems - why drop a bunch of cash?
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Old 10-19-2017, 08:29 AM
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You are recording in this room - are you also MIXING? The requirements of a mixing room are different than a recording room.

In a mixing room, your desk would be setup facing one of the short walls (but out from it so your head is around 7ft away), and you would have bass trapping on the wall you are facing, and all the corners (floor to ceiling if possible, the wall behind you (maybe in combination with some diffusion), and your side walls would have some traps (only need to be 2" rockwool, not 4") at the 'point of first reflection' and also some 2" traps above you ('ceiling cloud'). And you want as much symmetry in the room as possible, too.
In reality, you may not be able to put yoru mixing desk out that far into the room, and there may be non-symmetrical aspects to the room, so you work with what you have and do the best you can.

BTW, it's easy to make 4" rockwool bass traps that hang on the wall, and can can be removed to be used as gobos to isolate mics from room noise/shield amps or drums when recording.
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Old 10-19-2017, 08:37 AM
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Quote:
Originally Posted by bmoney View Post
You have to understand the length of bass waves and a small room. As long as the room isn’t perfectly square he is fine. An accoustic guitar lowest frequency is 83hz which has a wavelength of ~14’

So he is fine. As all waves higher than 80hz become shorter and shorter.

I have essentially the exact same size Ht 11x17x8 and have no major issues with bass buildup and have no bass traps. Would I benefit from them. Yes. But because the trouble frequencies for a room are below 80hz the traps would have to be 4’ thick to be effective.

Like I said he can get 90% there with broadband traps.
Not really sure what you mean by "fine" but to clarify sound waves do not die at the "wavelength" the wavelength is not the problem. The reflections are the problem and reflection occurs regardless of where in the cycle the wavelength is at, when it strikes a surface. Not to mention that sound travels in all directions, thus there is nowhere in a 20' room that reflections , possible buildup and possible problems are not going to occur, at 83 hz and all the other frequencies as well. So both bass trapping and broadband absorption are advisable, in any room


And BTW Owens Corning does make a 700 series but 708 is not part of that series that I am aware of, 703 is what most commercial acoustic panel absorber mfg. use.
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Old 10-19-2017, 08:44 AM
bmoney bmoney is offline
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Correct. The 708 was a typo. Thabks for correction
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Old 10-19-2017, 09:27 AM
jim1960 jim1960 is offline
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Quote:
Originally Posted by bmoney View Post
You have to understand the length of bass waves and a small room. As long as the room isn’t perfectly square he is fine. An accoustic guitar lowest frequency is 83hz which has a wavelength of ~14’

So he is fine. As all waves higher than 80hz become shorter and shorter.
I'm not sure what you're saying here. Sound waves are going to bounce around an untreated room regardless of their length.

Quote:
Originally Posted by bmoney View Post
I have essentially the exact same size Ht 11x17x8 and have no major issues with bass buildup and have no bass traps.
This goes against everything I've learned on this subject. As far as I know, the only way you'd measure no bass buildup in that room is to do the measurement from a center null zone. As you move towards the corners, the bass buildup has to increase.
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along with some electrics, zouks, dulcimers, and banjos.

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Old 10-19-2017, 09:52 AM
Brent Hahn Brent Hahn is offline
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Quote:
Originally Posted by jim1960 View Post
Everything I've read on the subject has said a "perfect" recording room wouldn't have parallel walls.
Or a parallel ceiling and floor. So we either move into an abandoned movie theater or we work with what we've got.
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Old 10-19-2017, 09:54 AM
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Quote:
Originally Posted by MikeBmusic View Post
You are recording in this room - are you also MIXING? The requirements of a mixing room are different than a recording room.

In a mixing room, your desk would be setup facing one of the short walls (but out from it so your head is around 7ft away), and you would have bass trapping on the wall you are facing, and all the corners (floor to ceiling if possible, the wall behind you (maybe in combination with some diffusion), and your side walls would have some traps (only need to be 2" rockwool, not 4") at the 'point of first reflection' and also some 2" traps above you ('ceiling cloud'). And you want as much symmetry in the room as possible, too.
In reality, you may not be able to put yoru mixing desk out that far into the room, and there may be non-symmetrical aspects to the room, so you work with what you have and do the best you can.

BTW, it's easy to make 4" rockwool bass traps that hang on the wall, and can can be removed to be used as gobos to isolate mics from room noise/shield amps or drums when recording.
Can you elaborate more on a mixing space vs a recording space.

Also, If the the best place in a room to monitor is 38% into the room, would that space also be the best location for mic placement to record in
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