Found This Site Too Late...Help

Yup... That's why the doors in my design are farther apart than my walls. Hopefully the extra space between them, coupled with the fact that I'll probably have some absorbant material (most likely rockwool insulation) on the walls between the doors, will help minimize the "doors as weak link" issue in my case. 8)

Makes sense. I've got a roll of limp mass vinyl, 4'x30'. Would it help if I added, say, two layers to each door (exterior steel type)? Or, in the alternative, get two wooden doors and laminate them together with a layer of LMV between them for a BIG beefy door.

If your exterior doors are foam filled, adding MLV can help increase mass - filled doors also means they will each act as only one leaf (good thing) - but the most important thing you need to pay attention to is your SEALS. Without good seals, it's not gonna matter much WHAT doors you use. Also, don't worry about sound bouncing around between the wall leaves - the insulation will absorb it, and if you leave porous venting from the doorway into the wall cavity this will actually IMPROVE isolation of the doors a bit, helping them to "catch up" with the walls. Watch out for door knobs, etc - good way to lose whatever iso you've gained. Paying attention to detail and actually dismantling your door knobs to check for potential air leaks will help... Steve

OK...Thanks again Steve, Sharward and Len. :D So the cavity in the air lock can simply be covered with cloth, for asthetic reasons only. The door seals I thought about using are the refrigiator type magnetic ones. I thought I'd remove the existing seals and replace 'em. Also, on the inner door, I'll use surface mount pulls so there's no holes in the door. On the outer door, same thing, pulls but with only a deadbolt lock instead of a door knob. Seem reasonable?

I don't know if you want a dead bolt lock on the outside door. I would think that would be a code violation since you could lock someone in (accidently) and if you did a good job with isolation, never know it. len

Maybe doing something like this would be better... :roll:

len-morgan wrote:

I don't know if you want a dead bolt lock on the outside door. I would think that would be a code violation since you could lock someone in (accidently) and if you did a good job with isolation, never know it. When I first saw that, and I know you meant it sincerely, I couldn't help but laugh :P len

Actually, I meant a deadbolt in the sense a key is needed on the outside but a basic "turn latch" on the inside so you couldn't get locked in.

Then you're covered. Dead bodies in the vocal booth can be bad for creativity. Make sure you don't loose any isolation through the lock set though. It's pretty thin metal and requires a BIG hole in your door. len

Well, I've solved the doorknob conundrum. I bought two steel exterior type foam filled doors, one that opens right and out and one that opens right and in. I'm using a keyed entry (regular doorknob) on the outer door (have to be able to lock it). I think I'll make two gaskets from LMV. For the inner door, I bought a heavy duty pnumatic door closer, like you might find in a resturant bathroom door. I'll be using a "push panel" and a pull handle. That door had no precut hole so that's good. I'll add some LMV to both doors for added mass and cover them with an attractive cloth of some kind. I've looked for refrigerator type magnetic seals but so far have been unable to find any. The current seals on the doors are pretty decent but I'd like the magnetic ones. Framing of the new walls got delayed until Wednesday. That'll give me time to dream up some type of way to ventaliate the room. Thanks again ya'll!

I'm sure Keith (Sharward) was at least snikering to himself when I wrote that, although I think he's too much of a gentleman to have admitted it. If you've been following my build thread here, you'll remember that my builder and I drywalled ourselves into the vocal booth with only a drywall gun, a handfull of screws and some duct tape at our disposal. Good thing I watched MacGyver all those years!!! :-) len

Guilty as charged. ;-)

Would this idea work for ventilation? I'm thinking of constructing a box from pressure treated plywood and mounting an attic fan on it. This will create a draw or negative pressure in the room which would draw fresh air in through the inlet. I thought about constructing the "ducts" out of 4" PVC pipe or the conventional fiberglass lined flex duct. Is this feasable and would there be signifigant sound leakage. Thanks.

The basic idea will work; but not with 4" line, I'd go at least 8". And not PVC, you do NOT want any RIGID coupling between inner and outer leaves. The flex ducting will work, but you need to watch for any kinking that will reduce the cross-sectional area; this stuff is notorious for doing that. You'll need to figure out some braces, brackets, etc, that will keep it from collapsing at turn points. By going from 4" to 8", you'll cut your air velocity (assuming the same CFM) to 1/4 what it would have been (2x diameter = 4x area) - this will reduce any noise due to air movement by a HUGE amount while maintaining good air flow. Noise due to air movement is approximately = to the 4th or 5th POWER of the velocity, so a fairly small decrease in velocity = a LARGE decrease in noise. If you're in a dusty area, I'd put the fan on the outer end of the INLET side and put a furnace filter in front of it, which should be changed/blown out regularly - this will put a slight positive pressure in the room, so when you open the door it's more likely that dust will blow OUT of the room instead of INTO it. You might look for "booster fans" - these run quiet, they're round, and they can be inserted in the line anywhere (don't put one near your studio space, better at the OTHER end) - they're available in 4", 6", and 8" - possibly other sizes as well. HTH... Steve

Thanks Steve! Wow what great info. Will those openings on the outer leaves, if they're 8", cause much reduction in TL?

You may have to have separate fans for fresh air intake and for exhaust. The sucking action at the exhaust fan is probably not sufficient to suck air in from the fresh air inlet. It will somewhat, but it might not be enough to meet code. The cool thing about the Fantech unit I'm getting is that the fans are integrated into a single unit. I believe there are also adjustments that can be made to keep the intake and exhaust pressure in balance. Remember that you may have to prove on paper that you'll have the proper amount of ACH -- air changes per hour -- in order to meet code. Don't count on the CFM ratings on the fan itself to get you over that hump -- ducting length, ducting type, ducting size, the number of bends, etc., all increase static pressure and thus reduce the effectiveness of the fan(s). In my case, I'm using a system that is actually designed for an entire house, yet I'm only using it for a single room -- I think that "overkill" factor prevented my having to provide detailed specs in terms of static pressure in my ducts. --Keith :mrgreen:

Another door note: I used the roller ball catches but even when they are set really tight if you shut one door hard the other door pops open due to the air pressure inbetween the doors. I have not really come up with a work around for this apart from just shutting the doors slowly!!. I may have to spring for a couple of heavy duty compression latches at some stage but that's life JG

Great point, John! I never thought of that, and yet it makes perfect sense.

John, You should also look on the bright side of your door situation: You obviously have done a very good job on sealing your space or this wouldn't have been a problem for you! Just a thought: How sealed is the space between the walls? I think you said you used some sort of particle board between your windows and doors covered in cloth. I wonder if a "weep" hole or two might allow the pressure to escape but not (too much of) the noise. len

Man, those heat recovery ventilators are expensive. :shock: I can't seem to find a "one room only" kind, all I find are whole house. My room's only 2,380 cu ft. I like the idea of the effeciancy but the price is steep!

Well this ventilation is really a pain! :evil: I'm very worried that the sound will leak at the places where the duct penetrates the leaves. I've seen other ideas about silencers (Sharward's). Is that an effective solution? Thanks

Yes, the HRVs are pretty pricey... And as I've said before, they have two sizes: big and very big. They're intended for entire houses, not just a single room. However, entire houses have windows. Most studios do not. You're using a mechanical ventilation system to take the place of windows. Therefore, they have to be pretty powerful -- enough to exchange all of the air inside the room within a certain number of minutes when activated. That magic number is dependent upon building codes in effect in your township. Mine aren't necessarily the same as yours. Keep in mind that the fan's throughput rating (measured in CFM -- cubic feet per minute) is not the whole equation. Adding ducting, silencers, and bends will result in static pressure that reduces the efficiency/effectiveness of the fan. So, you start with a really high number, account for the losses, then end up with a smaller number that needs to exceed code. I admit to not doing those calculations in my case -- I think I was able to get away with not because I'm pretty sure the fan is overkill. (It does have different speed settings, so at a lower setting it may drop to down to just plain kill. ;-) ) The main reason I'm going with the HRV isn't the heat recovery aspect; it's the "all in one"ness of it that impresses me. Plus the filtering mechanism is nice. There's also the ability to tune it so that incoming and outgoing air flows are in balance (no negative or positive pressure in the room, in theory). It's also supposed to be fairly quiet. I am confident in the silencer plan because, well, what's good enough for Paul Woodlock is good enough for me! :lol: He had lots of great advice on his plan and great supervision during his build, and the results are nothing less than stellar. Mine's kind of the "baby Woodlock" version. ;-)

Hey there, Still making progress, slowly but surely. :D Framing of inner room will start after Christmas. I think Len had asked me to take readings of the SPL's as I progress, so here goes: My reference sound has been a song off my new CD. What I do it take a boom box in the garage near the rear wall, crank it up (turn the bass control up as well on it) and play the song. I take readings on the choruses only as they're the "loudest". When I'm done with the test, I leave the volume and bass knobs alone (only use the boom box for this purpose). Originally I had a layer of OSB, then 2x4 studs, 5/8" rock on the inside wall, then furrning strips (thought they'd help :oops: ), and another layer of 5/8". SPL's then: Inside: 105db Outside: 68db Total TL: -37db Today I measured my "beef up" wall only (OSB and 2 layers 5/8" rock 'tween the studs and caulked). Inside: 105 db Outside: 65 db Total TL: -40db So a gain of -3db and a TL of 40db overall. Not bad for basically two layers of 5/8" and some OSB. So the furring strips actually hurt the TL, rather then improve. I think Steve said every 3db drop is a 50% reduction of sound pressure...is that correct? One other thing...what would be a good material to line the silencers with? I'm not crazy about fiberglass, due to the potential of the small particulates being cast into the air. Finally, found some reasonable heat exchangers: http://www.iaqsource.com/index.php?modu ... +exchanger The CFM looks like it'll work for me, as my room is only 2,560 cubic feet. Here's the manufacturer's site for other fans and stuff: http://www.suncourt.com/

Made for the job - the right stuff

Nashtalon wrote:

So a gain of -3db and a TL of 40db overall. Not bad for basically two layers of 5/8" and some OSB.

That's not quite correct if I understand what you did exactly. You have the SAME amount of material (2 layers of dry wall) but by only changing the arrangement, you have increased your TL by 3 dB. Isn't it cool when you can prove theory! :-) If anyone disbelieves the some of what is espoused here, they should be pointed to this post to show that it really DOES work that way! len

Thanks Steve...I've tried Home Depot and Lowes but neither had this product. Any idea who might? Yeah, Len, who would've thought that teeny little 1" airspace would actually hurt the TL? Go figure. :D Any comments on that heat exchanger?