Plasterboard/Gyprock walls as bass traps??

[Tukkis]

I read one of Johns post's that said that a typical gyprock wall attached to a stud frame acts as a bass trap. Is this correct??

What frequencies would this cover??

Would the thickness of the gyprock determine the frequencies??

My thickness is 16mm (.62992"). What frequencies would this thickness cover?

If this is true should I make some of Johns low/mid absorbers and place them around the room?

Wouldn't bass still build up in the corners??

I know these are alot of questions but I need someone to clarify this before I start to build.

Thanks heaps
Tukkis

[knightfly]

In Everest's Master Handbook, he states that 1/2" gyp-rock on 16" centers has an absorption coefficient of .29 at 125 hZ, and "even higher at 63 hZ" - he does NOT state what that is, which is common thruout available literature due to the difficulty of testing at lower frequencies. 24" centers should lower the resonant frequency, therefore increase the absorption. Mounting one side of the wall on RC will help even more, by about 9 dB if wood studs are used.

If you're not sure yet what wall construction to use, here's a very useful link

http://www.usg.com/Design_Solutions/...eofcontent.asp

if you're in a hurry, start reading in this section

http://www.usg.com/Design_Solutions/2_3_12D_system.asp

According to USG's specs, their 1/2" firecore sheet rock has a density of about 30 oz/sq ft, which, according to Everest's panel absorber chart would put its resonance at about 65 hZ when mounted on 3-1/2" deep studs. Their 5/8" firecore is 40 oz/sq ft, which would only lower the resonant freq to maybe 60 (interpolation, the actual # is off Everest's chart) This has two aspects, depending on sound PROOFing concerns - 1, the resonant frequency of a wall is the frequency that will get THROUGH the wall the easiest. 2. the resonant frequency of a wall is ALSO the frequency that will be absorbed the most. Kind of a two-edged sword...

I gave a more thorough explanation of walls here -

http://www.homer.com.au/phpBB2/viewtopic.php?t=155

Lot of different ways to build a wall - all of them need to be built air tight (right kind of caulk) or all bets are off... Steve

[Tukkis]

Ok

Well my room is already built. It has 2x4 wood stud frame. 1/2" gyprock double wall construction with a 6" gap in between the walls. It also has 3" insulation in the walls.

My question is, would it be ok to build some of Johns absorbers for the low/mid and place a few around the room and then just leave a few surfaces of bare gyprock for the bass?

Another thing, does bass go through John's panels. I mean low bass that the panels dont absorb. Does the wall have to have no absorbers on it to act as a bass trap?

Thanks
Tukkis

[Roker1]

..If you already have double plaster walls with insulation inside them and you want a bit more of bass absorption, this would probably be an efficient and cheap way to obtain that....
I don't think there can ever be too much bass absorption, but then again, I really don't know much about this stuff....
hope it helps..

cheers

[Roker1]

ooops , the writing under the illustratiuon won't show....
the yellow thing is the insulation (rigid f/glass) and it's obviously mounted in corners, floor to ceiling.....the little black squares are studs that are stuck to the walls and insulation is attached to them.....then you can cover the insulation with nice fabric....bigger the triangle, better the absorption....simple and effective.....
BTW that's from ethan's article on this site http://www.recording.org/users/acoustics/

[Tukkis]

I've seen that bass trap design before.
Would I need the extra bass absorbtion?

[knightfly]

I hate to see wasted time/effort/money, so my advice would be to first build the room, make it sound PROOF, which has almost nothing to do with acoustics inside - THEN, find out what it sounds like before committing all that effort. You WILL need low mid absorption in a smaller room for sure, but how much? All the theory in the world won't tell you that. Only your ears, and maybe a little help from these guys -

http://www.etfacoustic.com/

Check out the Demo Room link - I've so far downloaded the demo but haven't found time to set it up and try it - however, I really like the concept of being able to quantify a room, THEN make changes and see the results. It's very difficult to A/B any two options with only a few SECONDS between tests, and IMPOSSIBLE to do if you have to BUILD something first - Using this tool, you can save the results and compare EXACTLY what changed.

Plus, the stuff is VERY reasonable compared to any of the other similar options I've seen, and it actually claims to work BETTER with a cheesy sound card (it profiles your hardware and CORRECTS for it)

Hope this helps... Steve

[knightfly]

Oh, as to the gyp-rock on wall studs REPLACING real bass traps, it won't - it will have some effect, but nowhere near as much as a real, deep-throat, hanger-infested, absorbent-covered, real live BASS trap.

What John probably meant (Sorry John, not trying to put words in your mouth, spit them out if you dis-agree) is that wall-board on studs has MORE LF absorption than solid, stiff, concrete walls and that needs to be taken into account when computing how much of what kind of acoustic treatment will be necessary for a given room.

Also, even though the per-square-foot performance of wallboard-on-studs is less than that of a dedicated bass trap, you have (probably) 4 walls and a ceiling's worth of area so it could add up to a fair amount of absorption, especially at its resonant frequency... Steve

[BookSix]

Doors suck! I have two in the back wall of my control room, leaving only 6" between the corner and the door. Can I make a smaller trap like Roker1 showed, and still get some effect? Is there away to modify it to make this mini trap more efficient?