Small Room Acoustics

Gabriel Acevedo

New member
Thanks!

thanks, jhbrandt and every one who has pitched in. the tips are greatly appreciated. I have ordered a couple panels i will be placing around the room based on your suggestions. Also ordered some mid quality studio headphones to start with. im going to DIY some gobos with corning 703 once I get the supplies and time. heres a picture of the room, clutter gone!20141003_175922.jpg
 

Btyre2013

New member
to Gabriel, I suggest you make your own DIY bass traps, build 4 of them and stack them in the left and right corner floor to ceiling, rip all that foam off and replace it with fibreglass or rockwool in fabric attached with hooks on the wall and steel wire, eyehooks are good for this, if you use the correct materials it won't cost a fortune and it would make a far bigger improvement than how the room currently is. The sloped ceiling is good though
 

bLUiVORY

= Mojo Worker =
This is very informative and a godsend of a service to home studio-types. Thanks for sharing your wealth of knowledge and experience, John, Jimmys69, Btyre2013 and all.

I’ve got a bit of an unusual situation (natch); maybe you guys can put me on the right track.

My room’s two abnormalities (we won’t even start getting into mine…):

A. My small space (see pic) is 8’7 x 12’11”. However, it has a sharply sloped ceiling. The low end starts at 6’5” and rises to 13’. So that’s one oddity.

B. Since I am the one who built this %$&^$ thing, I know for a fact that all six surfaces have insulation between the wood framing. The four walls are typical 2” x 4” construction, 16” o/c with 3½” fiberglass insulation. The room is on the NW corner of the house, on the 2nd floor. And I insulated the interior partitions and floor for sound deadening purposes. The low end-wall and one of the long walls have 3 ½” R-13, the tall end-wall and other long wall have 3 ½” R-11. The sloped ceiling has 8” pink fiberglass (can’t recall R value) and under the hardwood floor and plywood subfloor is 3 ½” R-11.

At the moment, there’s not much, if any, live playing going on. This room’s acoustics are of concern to me primarily for mixing.
Floor is hardwood, ceiling and walls currently drywall.

So, my questions:

I was planning on installing some decent acoustic ceiling tile on ceiling – yea or nay?

Which end wall would you face, tall or short?

Plan for walls is to eventually have approximately 66% absorptive material; 33% random reflective material such as stone and/or random wood shapes – yea or nay?

What does all that insulation behind every surface do for me as far as bass trapping?

Studio Dims.jpg
 

mjbphotos

What?!?
That's a very narrow room, so I'd set up the desk on the short wall to the right (6-1/2' ceiling). Corner bass traps (4' thick or go for superchunks) all the way to the ceiling in all 4 corners. Ceiling cloud above the mixing area (2" thk min). First reflection points on side walls might be tough - probaly going to overlap the door on one side. Probalby need some traps on the back wall, and possibly in that 13' ceiling-wall corner. Start with the corners and cloud, see how that works.
 
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jhbrandt

Acoustic Design
That's a very narrow room, so I'd set up the desk on the short wall to the right (6-1/2' ceiling). Corner bass traps (4' thick or go for superchunks) all the way to the ceiling in all 4 corners. Ceiling cloud above the mixing area (2" thk min). First reflection points on side walls might be otugh - probaly going to overlap the door on one side. Probalby need some traps on the back wall, and possibly in that 13' ceiling-wall corner. Start with the corners and cloud, see how that works.

+1

Actually, I would recommend starting with reflection points and BACK WALL. Corners and cloud can come second. You will see big difference with back wall treatment. Actually, with the ceiling angle, you many not even need a cloud trap.
So to recap: Face short wall that is 6' 5" high. Trap reflection points, back wall and corners.
NOTE: The room volume is small and therefore you will need MORE trapping than you think to bring things under control. ;)
Cheers,
John
 

bLUiVORY

= Mojo Worker =
Thanks for the replies.

But I'd still like to know if all six sides (ceiling, 4 walls, floor) being insulated count towards bass trapping.

Thanks
 

jhbrandt

Acoustic Design
bLUiVORY,

I replied as I did above because too many folks see random details on the internet about what kind of built-in trapping frame construction offers. My friend Andre Vare calls it 'Invisible Alpha' trapping.

It DOES offer trapping, but the trapping offered depends heavily on a great number of factors. A few of those factors mass, insulation depth, type of insulation, distance to the next rigid partition, the bending modulus of the partition, etc. It is not an easy answer and varies greatly from build to build. So, Don't count on it. ok?

You should hire an acoustic engineer to determine the frequency of resonance that your 6 partitions offer. That information can help you when you design/determine the amount and depth of trapping needed.

I had mentioned earlier in this thread, I think, that most enclosures will have a limit on the lowest usable frequency. This is the point where wave response crosses into what is called the pressure zone. IOW, the room dimensions are too short to support half a full wavelength.

Example: a room with the longest dimension of 14 feet (4267 mm) will have an axial mode at 40.4 Hz. This is the LOWEST frequency accurately reproduced in that room. NOW, it IS possible to produce sound from a loudspeaker that is lower in frequency than the pressure zone boundary.. BUT, one must take care not to overload amplifiers or woofer cones in the process. Sometimes, especially in ported loudspeakers, the possibility of woofer coil burn-out is high during attempts to drive the pressure zone.

That said; Frequencies are perceived and record-able, but producing them with certain equipment becomes problematic. In-Ear headphones work in the pressure zone of our ear canals and are designed to drive the ear canal.
Ported sub-woofer systems are not designed to drive a pressure zone. ;)

The treatment for any room should be designed FOR the system of the room/building. This is the reason why one thing works well in one room, but requires a much different solution in another. You need to know the crossover frequency of your walls and ceilings.

Cheers,
John
 

bLUiVORY

= Mojo Worker =
Good evening, John.

Thank you for the the follow-up post. This greatly clarifies the/my situation.

The comments here have spurred me to dig into these aspects of acoustics and the subsequent actions necessary for correction of real-world, specific situations.

The last time my friend Bob Hodas...

Bob Hodas - Acoustic Analysis

came back home to Michigan from California and visited me, five or so years ago, I was a little ways from retirement and nowhere near this stage yet. Think I'm not kicking myself in the butt over that? :spank:

I've got some studying to do.

And then I need to see when Bob is going to be back in town... :D

Thanks for your time, John.
 
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bLUiVORY

= Mojo Worker =
Just a check to see if I'm getting this correct.

The longest dimension of my space is the diagonal length along the juncture of the ceiling and long walls. See drawing with newly added dimension:
Studio Dims .jpg

This dimension is 14'6".

Is 14' 6" still valid as the longest dim., even thought it's not the conventional length, but rather a diagonal meas. of a sloped ceiling?

14.5’ = Axial mode of 38.8hz?
 
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jhbrandt

Acoustic Design
bLUiVORY,

Your longest dimension applicable is 12' 11 1/16", which gives you an axial mode of 43.7 Hz.
a diagonal reflection will strike 4 room surfaces and is described as a Tangential mode. A reflection that strikes all 6 surfaces is called an oblique mode. ;)
If you need help, send me an email.
Cheers,
 

JG96

Active member
I want to start putting traps in my corners but all of my corners have things preventing me from building big traps. 1 Corner has a Sliding closet door, 1 has a door that opens into the room and the other two have windows that span from the center of the room to almost the corner on either side. How can I place traps without renovating my entire room?
 

mjbphotos

What?!?
I want to start putting traps in my corners but all of my corners have things preventing me from building big traps. 1 Corner has a Sliding closet door, 1 has a door that opens into the room and the other two have windows that span from the center of the room to almost the corner on either side. How can I place traps without renovating my entire room?
Put the traps on wheels so you can move them out of the way easily and don't need to attach them to the walls. Or rig up a way ot hang them from the ceiling/wall when needed, the rest of the time, stack them up somewhere.
 

JG96

Active member
Put the traps on wheels so you can move them out of the way easily and don't need to attach them to the walls. Or rig up a way ot hang them from the ceiling/wall when needed, the rest of the time, stack them up somewhere.

Thats a good idea. Ill try and flesh out a plan next time I am home.
 

JG96

Active member
Now I am thinking that Superchunks may not be the way to go in this room. I wouldn't be able to build them particularly thick/deep. Maybe some soffit type builds in the ceiling corners. I was thinking about building four of these and popping them in the corners Peter-Calandra-Homebrew-GIK-Screens.jpg They would be easy to tuck away when not needed and I could use them as a booth and bring them to location recordings.
 
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