John Sayers' Recording Studio Design Forum Archive

Sorry for reposting the same question, but I don't think I was clear the first time and I really need some advise.

Ok, this was the original message now let me rephrase that. All I really need to know is:

Can I put 1' or 16" bass traps in the corners?
Or does it have to be 2x4 bass traps?

And will eight 16" bass traps in between acoustical panels be sufficient enough for my room?

Any advise will be appreciated in helping me accurately fix my control room.

Once Again Thanks,
Ozzie

Hi everyone, I am new to the Recording studio design forum, and this is my first time posting a question. I hope ya can help me. I built a little control room with a booth in my brothers warehouse . The control room is 11'.5" X 11'.10" x 8' (W/L/H) and the booth is 5'.9" X 5'.9" X 7'.10" (W/L/H) with sliding glass doors. I built 9 -2 X 4 acoustical panels made out of 703 and frabric and also two 8" tube bass traps made out of Quik-Tube building forms, Filled with R-13 insulation and wraped in vinyl. I was going to build more tube bass traps but the 1' tube bass traps are to big for my little controlroom, so I'm going to change them to the real traps style. I hear a lot of bass when I stand back so I'm tying to fix it with bass traps. My panels have a 2' space in between them. So, can I build 16" bass traps in between and 1' bass traps in the corners or should I build 2 X 4 bass traps in the corners with 16" acoustical panels in between or something else maybe. The bad thing about my room is I have parllel walls and the sliding glass doors are close to one corner and my walk through door is close to another corner so the 2X4 bass traps won't fit in all the corners but the 1' ones will. I don't no how to figure out what's exactly wrong with my room but I'm trying to learn. I was hoping some one had something close to what I have and would be able to tell me what they did to fix it. I have a painted slab as my floor, acoustical celing tiles on top, and sheetrock on the walls, plus 20/20 biamp nearfeild monitors. If ya need some more information just let me know. I'm so sorry for making this so long.

Thank You All
Ozzie

P.S.
I will post some pictures if I can and I'm sorry if they are too big I'm kind of new to this computer posting pictures thing and also can ya take a look at my booth? I know it needs some fixing too, but I'll come back to that later after I fix this problem.

P.S.S.
I don't want to really cut into the walls or move the panel because I'd mess up the walls when I glued the panels the first time but if i have to in order fix the room up then I will. I deal with rap and R&B mainly for right now and once again I am sorry.

Looks like Thomas may be kind of tied up momentarily, so I'll see what I can do -

First, there's no need for apologies - your pix are plenty small, the only problem is when they get bigger than about 500 x 700 they cause people to have to scroll sideways to read the text.

Your room looks tall enough that you could put your existing round traps in the corners, stacked two in a corner - if that's the case, then that's where they should be to begin with. Corners are where ALL room modes terminate, so those are the best places for traps.

Being tight for space, your next best place for traps (especially panel traps) would be in the upper corners between walls and ceiling. In a small room, panel traps seem to be a good way to go - less space, lower frequency trapped.

Remember that positioning in the room can change your percieved bass a LOT - I'm including a screen shot from one of my favorite room mode calculators, available at

http://www.harman.com/wp/index.jsp?articleId=131

I entered your room dimensions into it, and here's the results - for each room modal frequency, the graph is high where sound level is high for that frequency, and the graph is at zero for that frequency's NULL points. As you can see, moving sometimes as little as a few INCHES will change what you hear.

I'm not saying your room doesn't need trapping, they all do - but you may be able to lessen the effect by shifting position of your head or speakers or both, according to these modes. Don't forget vertical placement, it's just as critical - you do NOT want your speakers or head to be exactly centered between floor and ceiling, for example -

I'll check back to see if you need more info on this... Steve

First off let me thank you Knightfly for the reply. Your right about the tube bass traps, They do take a lot of space up and that why I'm going to build panel bass traps. My main concern right now is can I use 1' or 16" bass traps in the coners? Do you think it's sufficient a nuff or do I need 2 x 4 bass traps? You recommended putting bass traps in the upper corners and etc., But the same issue comes up I only have 16" give or take on top. I don't really want to move my acoustical panel so I was think of putting 16" bass traps in between them . Do you think that will be sufficient a nuff for my room? Your advise is very important to me since I'm a rookie that doesn' t really know what he's doing. I also looked at the axial standing waves chart but I don't understand it. Can you Tell me were I can go and read some information that will break it down for me so I can understand, I feel so left in the dark. I will try to draw some examples of what I'm trying to do so you can get a better understanding of what I'm trying to say because I feel I'm not clear some times .



Thank you
Ozzie

P.S.
I'm sorry for the long reply and the stupid repeated questions I keep on asking but I'm the type of person that needs direct answers.

Ozzie, first of all I want you to understand that in my book, absolutely NOBODY who is trying to LEARN has any reason whatsoever to apologise for it. We all learn in different ways and at different rates - some of us learn some things faster than average and other things slower. If it's any help to you, I've been studying this field in my spare time since about 1983, I've bought probably between $300 and $400 worth of books on just acoustics and sound proofing, and it STILL confuses the crap out of me sometimes. In fact, I just ordered another book by Phillip Newell that runs about $70, and I once again expect to be thoroughly confused for awhile.

Try to keep this in mind before you rush to apologise for wanting to learn - Anyone who puts you down for trying to improve your self in ANY way, isn't worth peeing on if they were on fire. I have absolutely NO USE for that type of person, and I feel so strongly about this that if anyone tries to do that here they will find themselves out on their ass. Period. Any way I can do it.

I'll try to put together a few links to some of the better explanations of modes, etc, that I've come across -

http://www.recording.org/users/acoustics/waves_wl.html

http://www.tubetrap.com/articles/db1191.htm

http://www.customaudiodesigns.co.uk/help.htm

I'm going to have to give up and hit the sack for now, but I'll check back and see if any of these helped explain some things for you - if not, I'll try to give a basic understanding of modes and waves in a room when I'm a little fresher... Steve

My bad Knightfly for taking so long to reply, I got caught up at my real job and for some reason the forum wouldn't let me log in. Well I'm in now and I did read your links with the information and they were helpful to some degree but I'm still confused.

Ok, this was the original message :

Can I put 1' or 16" bass traps in the corners?
Or does it have to be 2x4 bass traps?

And will eight 16" bass traps in between acoustical panels be sufficient enough for my room?

I know this is my third time asking the same question but do you think this is a good idea or a bad one? What do you suggest I do to my room?

I would like to thank you for those word of inspiration and I'm glad your trying to help me out . I know someday I'll understand all of this better but until then it's back to reading, math and taking your expert advise.

P.S.
I put this picture so ypu can see what I'm trying to do. One more question if my idea ain't good do you think I should try to redesign my room like the drawing on Wall Units?

Ozzie, a couple questions and a couple answers (not counting, so don't hold me to numbers here)

First, bass traps work best at corners. A 2-way corner is good, but a 3-way corner is best. So the best place for bass trapping is where two walls and either a floor or a ceiling come together.

Tube traps absorb bass by converting the air motion from bass waves into heat - in order to do that, they need to be away from the wall by 1/4 wavelength of the frequency you want to absorb. Unfortunately, they are ROUND, so there is very little of the absorbent where it really needs to be. The only advantage here is that the round shape also makes them more broadband, but overall they are very inefficient use of space.

Standing them up in the middle of a wall makes them almost totally useless, since only a small portion of their absorbent is in the right spot.

Panel type traps work on the principle that vibrating their front panel takes energy, which is then removed from the sound spectrum and converted to heat. For a panel trap to work well, it needs to be at the point of highest PRESSURE (a wall or ceiling) instead of at the point of highest VELOCITY (1/4 wavelength AWAY from a wall or ceiling) - Sooo, panel traps are more efficient use of space (but also more narrow in their absorption)

Supposedly, according to the formula for frequency of a panel trap, the size of the panel doesn't matter. Realistically, though, the smaller they are the less they will vibrate - the less they vibrate, the more time you wasted building them at all, since they have to vibrate to work.

I'm not clear on what you mean by a 2x4 trap - if you mean a front panel that's 2 feet by 4 feet, then yes - much smaller than 2 feet and the panel won't vibrate much at all, so nothing happens.

From the look of your drawing and pix, you've got your desk in front of the LONG wall - so yes, if possible the "wall absorber" room would work better. Just don't build the rear corner absorbers as slats, they need to be non-reflective broadband absorbers for almost all small rooms.

One way you could get around the size problem would be to mount panel traps horizontally above your absorbers, but mount them diagonally across the corner between wall and ceiling. Like this -

Hi Knightfly, My bad for taking so long again. I read what you suggested about putting the panel bass traps on top of the ceiling but I'm not sure if I feel safe with the panel bass traps above my gear. I have really bad luck believe it or not but I'll keep an open mind. I was thinking what if I switch my drawing around and put my panel bass traps were my acoustical panels are at now and put 16" acoustical panels in between them and if the amount of bass traps ain't sufficient enough for my room. I can still build 4- 2x 4 portable bass trap panel with 3" or 4" of 703 inside on some speakers stands for the coners . Ok here it goes

10- 2 x 4 bass trap panels with 1" of 703 inside. (Ethan Winer " building a better bass trap" style but not in the walls.)

8 - 16" acoustical panels with 3" or 4" of 703 insde wraped in fabric

and maybe
4- 2x 4 portable bass trap panel with 3" or 4" of 703 inside hooked on some speakers stands for the coners .

Do you think this will work for my room?

Thank You
Ozzie

I'll try to be plain enough this time - Bass traps don't work unless they're in corners. Placing them in the middle of a wall is a waste of time. If you mount the panel types sturdy enough, they won't fall on your gear.

If you build the units shown in John's Bedroom studio, making sure that the REAR two corners are NOT slat absorbers but just 703-covered corners, your room will work.

The way it is now, it's oriented the wrong way for best sound. You need to be facing the LONG way of the room when you're at the mix position.

You can leave the wall panels you already have - if there's room, build the slant-faced slot absorber wall units for in between the wall panels you already have up.

Building a bass trap with smaller than 2 foot wide front is a good way to waste material and time. The larger panel is necessary for proper excitation, without which all you have is a sealed box.

I hope that helped clear things up... Steve

Hi knightfly or would you rather I call you Steve ? Ok I been reading everthing you said along with other stuff on the fourm and I'm starting to see the light.

If you mount the panel types sturdy enough, they won't fall on your gear

I have acoustical ceiling tile and I don't know what I can use to hold up the bass traps.

The way it is now, it's oriented the wrong way for best sound. You need to be facing the LONG way of the room when you're at the mix position.

My CR is 11'.5" X 11'.10" x 8' (W/L/H) does the 5" make a diffrence or I'm not understanding something right here?

You can leave the wall panels you already have - if there's room, build the slant-faced slot absorber wall units for in between the wall panels you already have up.

I know the slant-face slots absorber wall units are for the side walls but are you saying to put them in the front and back walls also? I just want to make sure and do they have to be the length of the wall or can I make them 2' X 4'?

I have been looking at CR designs and all the front and back wall absorber have 4" of insulation. I have 1" of 703 on my walls is that sufficient enough for my room or should I go to 2" or 4" of insulation?

I also read something about placing the wall absorber 2" or 4" off/out the walls? Can you give me some more info on that? I 'm thinking it as to do something with that 1/4 wavelength.

Ok, I know I'm getting on your nerves about these bass traps and I'm sorry. I know I need bass traps in the corners and the rear two corners are NOT to be slat absorbers but just 703-covered corners, but I need to know which one will work better in my room as far as the front corners are concern? Should I make

A. RPG B.A.S.S Traps style

B. Realtrap style

or

C. build the units shown in John's Bedroom studio

but all bass traps will be portable ( on speaker stands) so I can move them out the way when I'm recording and use them when I mix.

Do you have any info on how to build RPG B.A.S.S traps or is it just like building John"s units with a solid wooden front instead of the slots ?

Thank you
Ozzie

"I have acoustical ceiling tile and I don't know what I can use to hold up the bass traps." - Good point - if you cut thru the acoustic tile to find solid mounting, it may ruin your isolation (if that's a factor)

"would you rather I call you Steve " - Either, as long as you call me "in time for dinner"

"My CR is 11'.5" X 11'.10" x 8' (W/L/H) does the 5" make a diffrence " - Forget it, didn't realise the dimensions were that close...

"are you saying to put them in the front and back walls also?" - No, only on the sides, with the deepest parts toward the front of the room (speaker end) - They won't do much if you make them narrower than 4 feet, or shorter than floor-to-ceiing. Their purpose is to break up flutter echoes and to keep Early Reflections from smearing your Stereo imaging at the mix position.

"I have 1" of 703 on my walls is that sufficient enough for my room or should I go to 2" or 4" of insulation?

I also read something about placing the wall absorber 2" or 4" off/out the walls? Can you give me some more info on that? I 'm thinking it as to do something with that 1/4 wavelength. " - That's exactly what it has to do with - maximum absorption takes place where the sound wave's VELOCITY is greatest while it's trying to get through the absorbent. By going from 1" to 2" absorbent, if they're both mounted against the wall, you improve the lower frequency range of absorption from 3390 hZ to 1695 hZ - 3" gets you down to 1130 hZ, and 8" gets you down to 424 hZ (all these are 1/4 wavelengths of the frequencies listed)

If you use thinner absorbent, you can get lower frequency effects by mounting it away from the wall. The material won't absorb as MUCH at those frequencies as the thicker stuff, but it will absorb. If I were you, I'd double up your 1" 703, possibly TRIPLE it, and move it off the wall by 3-4 inches.

"so I can move them out the way when I'm recording and use them when I mix. " - If you're recording real instruments and not electronic ones, I would NOT do that - the idea is to even out the response of the room - this applies whether you're recording or mixing in the room.

I don't have much of anything on RPG's B.A.S.S. units, other than they are soffit located for best absorption. You could actually, if you built sturdy brackets, mount brackets coming out from the wall up near the ceiling, and hang the Ethan Winer type panel traps there... Steve

Hi Steve a.ka. knightfly, Ok a few more questions:

"so I can move them out the way when I'm recording and use them when I mix. " - If you're recording real instruments and not electronic ones, I would NOT do that - the idea is to even out the response of the room - this applies whether you're recording or mixing in the room.

I do rap and R&b and all my music is electronic, so are you saying it's ok to make portable bass traps then? I think I found away to get my bass traps were I need them to be but just in case it doesn't work out I want to have a plan B (portable bass traps).

"are you saying to put them in the front and back walls also?" - No, only on the sides, with the deepest parts toward the front of the room (speaker end) - They won't do much if you make them narrower than 4 feet, or shorter than floor-to-ceiling. Their purpose is to break up flutter echoes and to keep Early Reflections from smearing your Stereo imaging at the mix position.

What I wanted to know is, is there an alternative to the slant-faced slot absorber wall units? What if I build the slant-face slots absorber wall units without the slant-face slots and replace it with pegboard or plywood with holes flat across with no slants and place it horizontal.(picture 3) The dimensions would be 8' W x 4'H x 8" D. Do you think that would work?

I also came across a product called " Flutterfree" from RPG (picture 1) that can do the same as the slant-face slot absorber wall units. "Flutterfree provides flutter echo control as well as bass absorption". I was thinking what if I build some slots shaped like a snake with 703 behind it?(picture 2) I know I'm probably getting you confused so I'll try to put some pictures up. Ok, and if all else fails can I make some portable slant-face slots absorber wall units. Example instead of them being 8 feet, the height of my walls, can I make two 4' pieces units and stack them on top of each other and lean them against the walls to make 8'? I know why do I want to make everything portable because my studio is small and it gets smaller when you have 10 people in it; plus I don't really like the way the slant-face slots absorber wall units look.

Thank You
Ozzie

Hey Ozzie,

I hope you don't mind me jumping in here. Great discussion and I would second basically 99.99% of what Steve is telling you. I couldn't resist commenting on one thing, just for clarification:

knightfly wrote:I'll try to be plain enough this time - Bass traps don't work unless they're in corners. Placing them in the middle of a wall is a waste of time.

This is true for most low frequency problems. However, the lowest axial modes do indeed benefit from "traps" located in the middle of walls, a ceiling, or even a floor. (Though, I have yet to see a trap in the middle of a floor! )

The pressure build-up that Steve describes happens across an entire boundary for an axial mode. Which boundary will depend on the direction of the standing wave. (I.e., front-to-back, side-to-side, or up-and-down.)

Of course, corner traps help with these build-ups (if they're big enough). The corner is part of the boundary, afterall.

However, if there is a real big problem at - say - below 50 Hz, properly placed wall-mounted traps usually need to be considered. The catch is that they probably will take up a lot more space versus corner-mounted ones.

Having said all of that, I would absolutely second all of what Steve suggests for your specific application. (My intention was only to clarify the wall boundary/axial thing.)

Best regards,

Jeff D. Szymanski
Chief Acoustical Engineer
Auralex Acoustics, Inc.

BTW - for a great illustration of modal pressure distribution, see the following link:

http://ceae.colorado.edu/~muehleis/clas ... waves.html

Ozzie, making units stackable is fine, I understand the space thing for sure - and the Flutter-free will help flutter problems without loss of highs, and if spaced far enough off the wall with absorbent behind it would also absorb some lows (but not VERY low, it takes several FEET for that)

What that will NOT do is give you a cleaner Stereo image at the mix position - that's the MAIN reason why the slat units are slant-faced.

I've not heard what parallel walls with high freq. diffusion sound like, partially because the stuff is expensive for an experiment and partially because my gut tells me it wouldn't work (we NEED the phase anomalies that are produced by various stereo processors, that's how they accomplish a lot of their "magic", and diffusing that information back to the ears seems counter-productive to me)

I hope you can accomplish NOT moving your bass traps around, I sort of misled you with that statement about acoustic vs. electronic. Your room is something you need to "learn" in order to make good mixes, and changing it around all the time will only make learning impossible. What I did NOT take into account when I said that is the fact that you would STILL hear things you didn't like if you took out the bass trapping, and might decide to modify your electronic sounds based on bad room sound. Not good.

I hope that helps, I know how much "fun" it is to try and "stuff a 20 pound dog into a 5 pound box"... Steve

Jeff, good to see you here - Welcome to the board, I appreciate your insights and hope to see more of you. Thanks for that cool link, already added it to my bookmarks so I can share it with others as need arises... Steve

Interesting!

Some questions are begging.

1) floor, corner mounted RPG style corner bass traps. Specifically to attack below 100hz - would this not be advantageous?

2) large bass traps half way down the side length of the room, isn't this a good idea too?