Bass trap/diffusor-type thingy

[Consul]

I've been considering something like the following to get some bass trapping and high-frequency diffusion happening in my nice and small room (click thumbnail to enlarge):



It would from there, of course, be stuffed to the gills with rockwool. It's 23 1/2" high by 24 1/2" wide by 12" deep at the center. My thinking is that I could knock out a bunch of these relatively quickly, and then stack, hang, and suspend them as needed.

Also, keep in mind that this is a sketch, showing only what is necessary to get the idea across. The final design would have better structure.

 

[mitsos]

I am no expert, but I don't know how much diffusion you really need in a small room. Anyway, I think it's a good idea.... my friend made some similar squares but shallower and open in front . He hung them with screw hooks, two hooks on top and bottom, near the corners. That way you only hook one panel to the ceiling/wall/beam/wherever, and then hang others below it. It works well, you can change them around until you get them working the way you want, and the fact that you're building duplicates makes it real quick to build.

I'd be interested to know how this works out.

 

[beatpoet]

Here's what I did:

They got a couple of layers of acoustic tile over 3/4" ply.

I figured a good stuffing with regular insulation would suffice:

They have since gotten covers on them.

Haven't tested the room yet...

If I needed a cabinet like this phone shelf I built it like this:

I also have a 5' diffuser made into a pretty nice looking bench. I cut 'D' shapes out of a couple of pieces of ply and made helmholtz style 'doors' on the bench.

 

[Svart]

Small rooms don't need diffusion, they need absorption.

Small rooms already have surfaces that are extremely close to the source and spreading reflections around in a dense room will only make the source seem less detailed and more 'washy'.

Ask me how I know.. :roll:

I would build broadband absorbers like you see on a lot of websites, 2'x4'x4" filled with OC70x compressed fiberglass or rockwool. I personally bought mic stands(99$ for 10 special at Musician's Friend) and hung the absorbers on them. Now I can move them around the room and create the atmosphere I want. Bring them in a tight circle for dry vocals/drums or around the perimeter of the room for a more open sound.

There just isn't much else you can do with a small reflective room other than make it dead. I fought with mine for years. You just can't hear the problems with your human ears but the mics pick this stuff up like nothing else in the world. I spent years screwing around with mics, preamps, etc and could never get things to sound as good as I expected until I bought a ton of sound absorption.. It made all the difference, really.

Anyway, to get back answering your initial question, as you have the diffusor drawn, the areas between the hard surfaces form helmholtz resonators and will absorb only at a specific frequency. You can alternate the widths of the voids and hard surfaces and get more of a broadband absorption/reflection if you want but I don't think you are going to get a very wide band of frequencies unless you do this across a whole wall. Even then most acoustical engineers measure the room nodes and tune their resonators to deal with the peaky nodes.

since bass is one of the biggest problems with small rooms(the corners are very close to the source/mic) you could try the poor man's bass absorbers which are nothing more than the 10$ insulation rolls at Lowes/HomeDepot stacked in the corners and covered with a screen. I think you can even use the bales of celluloid insulation too.

 

[Consul]

I already have the insulation. I was just hoping for a more intelligent way to apply it.

I was reading F. Alton Everest's "Sound Studio Design on a Budget", and he sings the praises of diffusion, even in rooms smaller than mine (which was one of his case study projects). He put curved and skyline diffusers in, along with bass traps (he used tube traps) and wall absorption. Since my room also has to function as a bedroom, I was hoping I could get a hybrid approach to work.

However, I was concerned about making a Helmholtz resonator, like you brought up. I was hoping that spacing the vertical spars far enough apart my prevent that, but probably not. I might be building two different kinds of units.

 

[beatpoet]

Here's an updated picture of those traps w/ theater curtain for the main wall.

Here's the aforementioned bench with a large diffuser to hide (soon to be) curtains. This is going to be the only 'live' spot in the room, so I shouldn't be in too much trouble It may get some treatment if it becomes an issue, but I figure a room is no good without some 'character.' The 'character' in this room happens to come from 100yr old boards.

I made a sealing cover for the window, but it weighs 100lbs and might just get replaced with a soft trap that slides up behind the diffuser.

One layer of carpet with throw rugs everywhere makes three layers in spots.


I hope I'm helping somehow... My main point should probably be that I *did* measure the room before any treatment and found significant audio damage in any parallel surfaces 7-8 feet apart.

 

[bcarso]

It may seem like a shameless plug, as I am a friend of his, but I would hasten to acquire Toole's book just out and ponder some of the results on room acoustics.

True, he is focused on listening environments and not studios per se, but I think the material applies pretty closely.

 

[rod gervais]

[quote author="Consul"] I was reading F. Alton Everest's "Sound Studio Design on a Budget", and he sings the praises of diffusion, even in rooms smaller than mine (which was one of his case study projects). He put curved and skyline diffusers in, along with bass traps (he used tube traps) and wall absorption. Since my room also has to function as a bedroom, I was hoping I could get a hybrid approach to work. [/quote]

With all due respect to Alton Everest, I don't agree with the approach of diffusion in small rooms - and always head in the direction of broadband treatments, corner traps utilizing absorption (The SST's (Studiotips Super Traps), with ceiling clouds and then covering first reflection points on the side, front and back walls.

If you can get SST's into all 4 corners (ceiling to floor) that would go a long way towards helping to tame your LF issues.

Sincerely,

Rod

(PS - Toole's book is definately a good one to have in your library)

 

[Consul]

Okay, broadband absorption it is! I'm still going to endeavor to create a single absorber unit in that approximate 2'x2'x1' dimension using cheap materials. Something that will be light, look decent, and stack or hang easily. Thank you for the help!

 

[rod gervais]

[quote author="Consul"]Okay, broadband absorption it is! I'm still going to endeavor to create a single absorber unit in that approximate 2'x2'x1' dimension using cheap materials. Something that will be light, look decent, and stack or hang easily. Thank you for the help![/quote]

you can do that quite easily with rigid fiberglass - you are better of in the corners with either 4 or 6" thick materials - but 3" would be opk for the rest of the room - and 703 (3 pcf) fiberglass is fine - you don't really need the heavier stuff.

Just understand that build up of pressure zones for LF tranmissions are the greatest at tri corners (where wall meets wall meets ceiling for example) and next is the corners themselves (and that includes ceiling to wall corners as well as wall to wall corners) and then the body of the walls/ ceilings are the lowest sound pressure zones - which is why floor to ceiling applications in the corners take out so much of the LF energy.

Rod

 

[Consul]

Well, I already have the rockwool. I just need something to "hold it in place", as it were. Something that stacks, hangs, and would be easily portable. If all goes well, I'll start my final stretch for an undergrad degree about 60-70 minutes away, and it might be cheaper for me to get a place nearby the uni I'll be going to than to drive that distance every day. That means I'll want to be able to tote my studio with me.

This is my solution so far, and it's not all that great physically, though acoustically, it does work:

http://flickr.com/photos/dmlandrum/2089171183/
http://flickr.com/photos/dmlandrum/2094637644/
http://flickr.com/photos/dmlandrum/2094639800/

A cabinet-like solution like I want would also allow me to double up the thickness of the insulation. I have plenty of the stuff.

 

[Svart]

Looks good. I'd make it around 6" thick, that seems to be the consensus for bass absorbing panels from the pros.