A matter of inches

Lissnr · « **on:** 29 Jan 2009, 01:09 am »

This may be a silly question but I need a real answer for it nevertheless; and I thank all responders in advance. I am currently building a dedicated listening room (a detached garage) which is still in the "exposed studs phase" and have a chance to make the width of the room vary by the thickness of 1.25" depending upon whether I use double layers of 5/8" drywall per side wall OR try to individually cut 22.5" wide pieces between my [24" on center] studs, attaching to the inside of outside walls, and apply only 1 layer as the actual inside wall. It would be a much more involved and time consuming task cutting each piece individually to attach to the inside of the outside walls... not to mention removing all the nails and screws sticking through that are holding the vinyl siding to them. I could use a sawzall on many of them and a pliers on the ones I couldn't reach with the blade (you know: bending the nail back and forth at the base until it finally breaks off...). I could use some silicone or liquid nails as an additional sort of vibration barrier after the nails were removed but I'd still want to screw them all in too, to be sure nothing ever loosens up later. The fiberglass insulation would go next, slightly squished I guess, due to the 5/8" less depth of the 2"x4" studs...and then the regular inside 5/8" layer for the inside wall. The room will be 13'1.5" if I DON'T save the space, or 13'2.75" if I DO. I will use green glue between the 2 layers if I put them together, but if I don't, I may try the special absorption tape to line the studs if I only use a single layer. Speakers are Apogee Duetta Signatures which are not as side-wall critical as many cone speakers but still need about 1'-1.5' minimum distance away. I know it sounds trivial but with this moderately narrow room I'm thinking I could use all the width I can get. Length is 17'8" and a peaked roof starts at 6'8" high on the sidewalls up to 8'11" along the centerline. I'll be able to use all the GIK 244's as well as diffusors, etc as needed because it is dedicated and therefore no WAF. Flooring will be wall to wall carpet on dense padding on 3/4" ply above concrete. I've been sweating all the other "small stuff" on this project so I figured 1.25" qualifies too! Thanks in advance. Grant

MaxCast · « **Reply #1 on:** 29 Jan 2009, 01:50 am »

My guess is two layers of 5/8 with green glue.

Lissnr · « **Reply #2 on:** 29 Jan 2009, 03:59 am »

Thanks for the vote. BTW, the reference to GIK wasn't meant to be absolute or exclusive... I meant to be generic about bass traps overall and am open to whatever will work the best in my application... perhaps another question in a later thread?

richidoo · « **Reply #3 on:** 29 Jan 2009, 06:25 am »

The acoustic treatments you have planned will more than compensate for the small change of resonant frequency from narrower walls. Use modecalc to see what will happen. You may find the narrower room to be slightly better or worse modal distribution, but it's academic because it's a small difference and you're treating for bass echos anyway. If the dipole speakers are each 1/2" closer to the sidewalls that won't be noticable either. You will lose insulating efficiency by squeezing the insulation, and all that screwing and cutting is a lot of extra effort. I bet you would rather be listening to music!!

The double layer sheetrock / greenglue treatment is only for isolation. You said you are detached, so you don't need to keep the music in, it dissipates quickly outside to not bother anybody. Maybe you want to keep street or neighbors' noise out - then soundproofing is a good idea, but double walls might be overkill, because outside sound is well dissipated by the time it hits your garage. A little research will be worth your time.

Have fun with your project - You lucky dog!

Rich

Lissnr · « **Reply #4 on:** 30 Jan 2009, 04:24 am »

Thanks for the explanation. It would be nice just to do the double layers, as it certainly is a lot easier. I am somewhat concerned about keeping the noise from getting out, just to play it safe with the nearest neighbors, which is why I'm going with the double 5/8ths. I only have a single layer of 5/8ths on the ceiling and hope that'll be enough from going out the roof. it's on furring strips with R-13 between. I'll have some pictures as it develops further. Thanks again. Anymore opinions are welcome. Grant

Big Red Machine · « **Reply #5 on:** 30 Jan 2009, 11:10 am »

Fitting drywall inside the studs really doesn't buy you anything except wprk and frustration. If you want to isolate the room the drywall should be the heavy mass part and isolated form the studs. If you add double dw to the studs w/o isolating it you will still transmit out and back through the wall studs via the dw. Sure it will be quieter, but not what it could be if you used hat channel and isolator mounts. Also the ceiling must be done the same. Caulk the joints before taping.

Lissnr · « **Reply #6 on:** 30 Jan 2009, 11:02 pm »

Thanks for the update. I'm sure hat channel and isolator mounts would be exactly what I'd use if the room was attached to the house... there's nothing like that type of "separated isolation". In my application I feel I'm fortunate to be un-attached and am hoping to get by with lining the inside edge of the studs with something called "Super soundproofing isolation tape" which the drywall then attaches through. The application is to place 2 layers of this 1/8" thick (by 1&7/16th" wide mylar-on-one-side) self sticking tape which should only add less than a 1/4" of thickness once it's 'squished down' by the drywall. I figured this was a step in the right direction as compared to directly mounting against the bare drywall. Combined with the green glue between the 2 layers [of the 5/8th's dw] I'm hoping I should conceivably be able to raise the volume safely to unsafe levels (not that I DO, but it's nice to know I CAN...). I hadn't thought about caulking the wall to ceiling joints however... that's something else I will definitely do. Corners too, to be sure...BTW, I just couldn't manage 2 layers of 5/8" drywall on the ceiling so I'm hoping the one layer and the roof itself (just replaced/fixed, with new tar-paper and shingles to prevent leaks) will be quieting enough??? I believe the actual roof wood is some type of 3/4" hardwood...Well, I'd better pick up another case of caulking. Thank you. Grant

thunderbrick · « **Reply #7 on:** 1 Feb 2009, 05:42 am »

I have done so many (non-audio) room re-fits that maybe I can comment on this. I am no sound treatment specialist, but I would definitely avoid the drywall between the studs and don't see the advantage of 2 layers of 5/8 DW. That's a lot of cost and weight, and probably 2 1/2 inch drywall screws.

If you want to put something between the studs, why not glue 1" slabs of Dow blue board foam in the spaces? Quick, non-messy and has insulating properties.
I've done double-layer drywall on a ceiling, but for other reasons. I just don't think the double layer drywall is worth the effort. There maybe some rubberized treatments that could go on the studs before the drywall goes up but I wouldn't know what it could be.

My .02 worth

Having said this, my house had the garage converted to a big family room, and the floor was sloped and cracked. It took me four full days to jackhammer the whole damned thing out, and many months to lower the dirt, level it, install radiant heat tubes, and re-pour the slab for my eventual man cave.. My wife (and my contractor who helped) both thought I was nuts for doing it that way. They may have been right, so consider that when you read my advice..............

MaxCast · « **Reply #8 on:** 1 Feb 2009, 01:02 pm »

Another option is to use 24" centers on two walls and add 2x4's on the other walls to get different spacing. You could then add a double layer of 5/8 to one or two walls. What you would be doing is changing the resonant frequency of each of the walls.

Make sure you run all the wires you need in advance.

bpape · « **Reply #9 on:** 1 Feb 2009, 02:51 pm »

Fitting drywall between the studs will decrease the depth of the cavity and the thickness of the insulation. This will also raise the resonant frequency of the structure which means it will be excited by sound coming in and getting out at higher, and more common frequencies.

I'd recommend the double on the inner sides with the Green Glue.

Bryan

planet10 · « **Reply #10 on:** 1 Feb 2009, 05:04 pm »

The extra stiffness of even a contiguous layer of drywall iver pieces put between the stud is significant. Adding a second layer will improve stiffness even more. If glued as opposed to just screwed you also get the advantage of a constrained layer.

All this will make bass reproduction more predictable and give more room gain (making it easier to tailor the bottom end response)

dave

Lissnr · « **Reply #11 on:** 1 Feb 2009, 10:06 pm »

This is great, all the input is very much appreciated. Obviously there are differences of opinion on whether the extra work between the studs is [tremendous] labor well rewarded .... combine this with the answer to the original question of saving the last 1.25" [NOT needed/noticeable in the big scheme of things] and I've pretty much decided NOT to cut and install all the DW between them. I have been advised by a friend who has his own little trick that he said worked very well on his basement ceiling as an effective yet very easy application: he used the extra heavy gauge tar paper, available anywhere/Home Depot, etc , to line his ceiling and said it was very effective. -He opted for the thicker of the 2 grades available, (was it 2 or 3 mil compared to the 'standard' 1mil?? or something like that...). I had some regular tar paper laying around and actually did one of the other walls already, just for fun because I had it (my South facing wall, which I completely framed out from scratch as a free-standing interior wall for max. noise reduction). So the 2 side walls, which are under discussion here (most notably my WEST wall, which is on the edge of my property closest to the neighbors) might benefit from the tar paper - against the inside outer wall too, stapled up snugly between the studs... followed by standard R-13, the sound-proofing tape glued to the inboard edges of the studs, 5/8" DW, green glue, 5/8" Dw.... All edges between walls and ceiling to be caulked first, then spackled/taped, and every possible crack/seam/opening anywhere I could find has been/will continue to be addressed as if the room was a fishtank which can't leak! ..and I'd like to think that I'm in pretty good shape. BTW, I re-measured the width again today, I was slightly mistaken before and currently have bare stud to bare stud 13'5" before the DW... this would mean 2x5/8" per side ='s 20/8" yielding an actual width of 13'2.5"... Not too bad. Thanks for all the input everyone. Always welcome to more. Best regards, Grant

MaxCast · « **Reply #12 on:** 1 Feb 2009, 11:08 pm »

Grant, hard to tell where you are on the construction phase. There are many recommendations I an more can give.
Here is my thread from my basement construction. A half the points will apply to you.
http://www.audiocircle.com/index.php?topic=49063.0

Lissnr · « **Reply #13 on:** 2 Feb 2009, 10:45 am »

Thnks MaxCast, I've been reading these threads for several months in order to get ideas and came across yours as well. The link to it has been a good refresher about the important points and I appreciate it very much. I can see several similarities overall. BTW, after I finish a few more 'miscellaneous' items I'll be ready soon to run the romex, hook up outlets, hang the double sheetrock, and lay the floor (it was always my intention to use Dri Cor but I wasn't sure if everyone was familiar with it or not). I was planning on doing the walls BEFORE the floors... should it be reversed??? Floor first instead??? I thought the sheetrock could be hung with just a slight gap above the concrete floor of the garage and then later I'd butt the dri-cor either tight against it, or with a little 1/8"-1/4" gap or so to de-couple the floor from the walls... later I would caulk that gap, then cover it with the padding, wall to wall carpet, and molding. Yes/No? Thanks again. Grant

MaxCast · « **Reply #14 on:** 2 Feb 2009, 01:25 pm »

You're welcome, Grant. I'm not sure on the floors. I guess if you ever wanted to replace the floor is would be easier it the walls were not on it. Is there a threat of water in this room?

If you want isolation in or out, caulk everything. I did build boxes around all my outlets and lighting. It added time, but not much cost. Get a case of good silicone caulk, you'll use it all.

Are you putting two layers on the ceiling? If you do alternate ceiling, wall, ceiling, wall.

bpape · « **Reply #15 on:** 2 Feb 2009, 02:14 pm »

If you want the best in isolation and you're going to do all the other things (seal and box outlets, lights, switches, baffle the HVAC, etc.) then build the walls on top of the Dri-Cor. Caulking still applies.

Bryan

JLM · « **Reply #16 on:** 2 Feb 2009, 03:34 pm »

Seems like a great deal of confusion here....

A detached structure won't need isolation (except from air borne sounds, like wind or traffic).

So green glue, caulk, boxing in electrical boxes, tar paper, channels, and isolators will do very little.

Building the studs closer than 16 inches on center and/or doubling up on (and gluing) the drywall will help make the walls/ceiling stiffer and raise the resonsant frequency. This is a good thing because there is less acoustical energy at higher frequencies for the same sound pressure level to excite the walls/etc. Some advocate varying the stud spacing (8 - 16 inches). Forget about trying to drywall between studs, better to adjust the height/length of the room if you're really worried about it.

Items that are important, but haven't been mentioned:

Windows (a big no no).

Door (use insulated fiberglass exterior door with weather seals).

Ventilation (use insulated/lined flexible ductwork as a sound baffle).

Electrical (use dedicated audio circuits with a common/independent ground, ideally use cryo'd hospital grade red receptacles, wire to the top of the panel if possible). Hopefully your power is clean.

BTW I have a well designed audio mancave and it is the most important "component" of the system simply because I can listen when I want to what I want and as loud as I want. Reducing background noise is also huge.

bpape · « **Reply #17 on:** 2 Feb 2009, 03:46 pm »

I would disagree that isolation doesn't help. It most certainly does. Remember that isolation is a 2 way street. It's keeping sound out as well as keeping sound in.

As for raising the resonant frequency of the structure, generally, we try to do just the opposite. While there is more energy in the bass in general, there isn't a lot of content in the 20ish range so that's where we try to shift it to. Raising it just puts it in the range where more outside things come into play.

If you want to alter spacing on the studs to better spread resonances (and absorptive qualities of the walls themselves) having stud spacing at 16" and 24". I usually use 24" on the front and rear walls (longer distance, lower modal frequencies) which lowers the resonance. 16" on the shorter width measurement is fine there.

Bryan

Lissnr · « **Reply #18 on:** 3 Feb 2009, 04:23 am »

This is getting interesting and all the advice is much appreciated. I'll recap a few items/issues, and goals for the sake of clarity:
* Isolation in my application is predominantly to keep my noise IN, away from the neighbor's house west of me, approximately 25' away. The added benefit of lowering the noise floor inside is good gravy ... I would like to make the room capable of virtually undetectable sound from 5' away, with 100db of music blasting inside : picture: 3 A.M. Saturday night, IF I'm ever inclined...
(note: I never listen at 100 db but DO often listen at 3 A.M. Saturday nights and don't ever want to be concerned about it...)
* The roof is new, but will only have the 1 layer of 5/8" Dw, already mentioned
* There is no concern anymore, about water seepage, as I spent the first 75+ personal man-hours of this project waterproofing the entire perimeter with 4 gallons of Karnac #19 flashing cement coating under and over new 22.5" 2"x4"'s placed horizontally between every wall stud where they meet the concrete foundation. I'll post some pictures sometime.. a LOT of work...
* I will take the time to box the switches, light fixtures, and especially the outlets. Note that the outlets will require a lot of time for this considering I have 6 dedicated 20 amp lines, 4 of which will have 2 outlets on them for 1 amplifier at either of 2 locations (to improve room configuration flexibility and the use of mono blocs, bi and tri-amping configurations and self powered subwoofer(s) also on their own line) as well as 3 separate "analog dedicated outlets" and 3 separate "digital dedicated outlets" on the other 2 x 20A's, total ='s 14 outlets. Add 2 more dedicated 20A's of 2 outlets each for the winter use space heaters ...then the 2 more 15A lines for another 6-8 (minimum) regular commercial grade outlets (all the 20A dedicated previously mentioned are Hubbel 5362's) for the miscellaneous floor lamp(s), H/T projector and associated receiver, etc., and any "normal use" items...[which will be completely separate from my primary 2 channel system] and we're now over 24-26 outlets and counting....
* Speaking of HVAC, I'll be cheating on this, at first at least: with such a moderate sized room with plenty of insulation I'm going to try to get by with 2 or maybe 3 space heaters for the winters (I'm in NY) -those oil filled ones seem to do a good job. My tube amps will also act as 'junior space heaters' too. Summertime I'll add a window A/C unit which I'll crank up while my tube amps are warming up (1/2 hr or so will be fine) and then shut off during listening. There's only one 32"x44" window and the one insulated fiberglass exterior door. A/C unit will be removed for the remaining 9 months and the window will be heavily sealed/covered with a home-made MDF and sound -absorption -material cover/box.
* The 24" on center studs already have a diagonal bracing between them running from the top corner of the wall to the bottom center, and then back up to the other end in a big "V" shape, effectively changing the inner cavity volume from stud to stud. This precludes the need for adding more studs (as in creating some 16" on center) in order to control common resonances .
* I'll do the Dri-core AFTER the walls because I don't want the floor 'trapped forever' but I will caulk the entire perimeter below the double drywall (approx 1/4" to 1/2" or so gap???) first, so that there is no chance of noise seeping under and around where it all meets.
I will try and remain conscious of every crack and seam I can... BTW, I'm already almost done with my 3rd case of caulking just on the work I've been doing so far...
Hope this answers more Q's than it raises but thanks again to everyone... I'm still listening. Regards, Grant

MaxCast · « **Reply #19 on:** 3 Feb 2009, 01:19 pm »

Grant, for total isolation you would need to float the walls and ceiling. As much noise (vibrations) travels through dry wall to stud to frame connections. Think garage doors openers. You can usually hear them through out the house. This floating requires clips or better yet a free standing room in your room. Both of these require losing interior dimensions.

100db will be heard out side.

I assume you will be putting lights on their own circuit. Don't use canned lighting unless it is boxed (heat issues too). For fun, put a dedicated line on the long wall in case you ever want to rotate your room. Put a ac line and conduit in the ceiling if you ever see a desire for a projector. If you have a desk not against a wall put an AC line under the desk.