John Sayers' Recording Studio Design Forum Archive

Guys, another question, as I'm getting closer to finishing the electrical and installing the rockwool...

I had planned my walls with 1 layer of 5/8" rock and 1 layer of 1/2" rock mounted on dual-leg RC. But I wonder about mounting stuff on drywall with no wood underneath to grab the screws. Specifically, guitar wall hangers, though I'm sure I will think of other things I want to mount on the walls in the future. I certainly don't want any of my instruments to come crashing to the floor! Is it structurally safe to mount stuff only on the drywall? Should I add (or substitute) a layer of OSB or MDF to my wall to help the screws grab?

I of course do not want to scew anything through to the studs...

Thanks!

I'd find some other way to mount stuff if you can. You can use drywall anchors, but that's punching holes thru your sound isolation. It'd hold the stuff up if you use enough of 'em, but do you want to be putting holes in that stuff?

Those little plastic anchors don't have much of an STC rating. Perhaps if you used them to mount a 1x6 running board to the wall, and screwed your hangers into that- putting anchors into the drywall every 12" or so wouldn't be so bad with the 1x6 over the top of it to help keep sound from screaming right out the wall, and then you could screw stuff wherever you wanted.

Personally, I'd just use regular guitar stands, but if you don't have floor space, this might not be an option.

HTH

Kase answered your question well, but I have a question/concern.

mounted on dual-leg RC

What do you mean by dual-leg RC? RC has one "leg." The only thing I can imagine is hat channel, which has no acoustic affect at all, other than increasing the volume in the wall structure.

Confused;
Andre

I've been curious about mounting as well. My back wall I plan to hang some type of broad band absorber, and was considering using either ply or osb so I'd have something to anchor to.

AVare wrote:What do you mean by dual-leg RC? RC has one "leg." The only thing I can imagine is hat channel, which has no acoustic affect at all, other than increasing the volume in the wall structure.

It's advertized as "dual-leg Resilient Channel". It looks like what is called "RC-2" on this page: http://www.dietrichindustries.com/bigdp ... sories.htm

Please don't tell me I just spent $100 last weekend for something that isn't what I want...

Please don't tell me I just spent $100 last weekend for something that isn't what I want...

For your sake I hope I am wrong, but that stuff looks to be almost identical to hat channel, and otheres down the page you linked.

From Dietrich's http://www.dietrichmetalframing.com/pro ... log_46.pdf

Double leg resilient installation is typically used for ceiling applications with multiple layers of gypsum board. Double leg resilient is easier to install, but offers a lower STC rating.

STEVE! Can you have a look at this stuff and confirm or dispell my concerns?

Andre

It's ok - no one is going to arrest you if you only screw down one leg.

That's what I usually end up doing with hat channel, anyway. Once you screw down BOTH "legs" the stuff isn't a spring anymore.

Don't buy this stuff in the future (unless price is the same as "Z" channel and/or you can't get anything else) but the stuff you have is useable.

Hope this eases your mind.

gdgross wrote:

AVare wrote:What do you mean by dual-leg RC? RC has one "leg." The only thing I can imagine is hat channel, which has no acoustic affect at all, other than increasing the volume in the wall structure.

It's advertized as "dual-leg Resilient Channel". It looks like what is called "RC-2" on this page: http://www.dietrichindustries.com/bigdp ... sories.htm

Looks like Hat channel to me.

Please don't tell me I just spent $100 last weekend for something that isn't what I want...

OK, I won't then

Paul

Guys, Dietrich is a little more conservative on their channel than other manufacturers - for ceiling use, they don't recommend single leg channel, even their RC deluxe - instead, they recommend their dual leg RESILIENT channel, which LOOKS like normal hat channel except for the slotting along the sides of the channel, which makes it resilient.

It isn't as flexible as single leg stuff, which is why STC isn't quite as good - however, at low frequencies the TL would be identical as long as the air gap is the same depth total -

RC doesn't affect low frequency TL whatever, so all you'll lose is a few dB at higher frequencies by using the double leg stuff. Although this makes the STC number lower, odds are you wouldn't notice the difference since most situations have more problems with low frequencies.

However, don't make the mistake of using NORMAL hat channel where resilient mounts are required, UNLESS you also use RSIC clips to decouple the hat channel from structure.

I had the unpleasant chore of informing a member on RO last month that his contractor had screwed up and used the NORMAL hat channel in place of the double leg RC, and he did NOT use RSIC clips - til I finally saw some pix of the project in progress, we couldn't figure out why he had really poor isolation from upstairs noises... that mistake cost him about 10 dB of isolation, mostly because most of the noise was impact and kitchen noises, which are right in the range that RC makes the MOST difference.

Hope that helps... Steve

RC doesn't affect low frequency TL whatever, so all you'll lose is a few dB at higher frequencies by using the double leg stuff.

Its quite possible that I am not understanding clearly what you are saying here. I posted on Aug 23 of this year a comparison of 8 wall systems from IR-761, where the only difference was whether or not RC was used. In every case there changes to the LF isolation. In 7 of the cases, the LF isolation was worse.

http://www.johnlsayers.com/phpBB2/viewt ... highlight=

Confused (I do that naturaly);
Andre

Thanks for your comments, everyone.

Just to clarify, this is not regular hat channel, as the connection between the drywall part and th stud part is not solid steel, but rather a kind of coarse mesh.

So here's another related question, kind of back to the original post. I had planned on using two layers of sheetrock on my interior walls, but I think I've decided to add a layer of some kind of wood. The questions are: what kind (MDF, OSB, or plywood?), where should I mount it in my wall sandwich (in between the two drywall layers, outside or inside) and, if I do decide to go and buy some normal RC, will it support two layers of drywall and a layer of OSB, MDF or plywood?

Thanks!

Andre - "Its quite possible that I am not understanding clearly what you are saying here" - no, it's much more likely that I should learn not to talk while nearly comatose; it's 12-hour graveyard time, and I was trying to get through everyone's questions so I wouldn't be so far behind when I actually have some OFF time...

What I SHOULD have said, is that RC tends to only help HIGHER frequency isolation. I wouldn't doubt that the 761 doc has walls that suffered low freq TL with the addition of RC - generally, it seems to me that since more mass increases TL at ALL frequencies, putting the wallboard layers on RC would Lower the mass therefore worsening the TL. ON the other side of the coin, using RC increases the air gap normally by about 1/2", so that effect would tend to counteract the loss due to decreased mass; just how much I'm not sure.

All these calculations/reasons, etc, are starting to get on my nerves; I'm getting tempted to go the Paul Woodlock approach, and just put 37 layers of wallboard on 2x12 studs with a 6 foot air gap filled with $$$$ of fiberglass, then 2 feet of concrete, and call it good...

JD, what you're talking about IS double legged RC, or Resilient Hat Channel.

As to differing layers, acoustically this will help as long as the mass is equal. You will get a shifted coincidence dip in the different layer, which will smooth out the wall TL at coincidence (typically around 2 kHz) - This will also give you something to fasten hangers to if you want to hang absorption panels, etc - just keep holes minimal and caulk thoroughly, and make sure your walls are filled with insulation; this also helps disperse anything that makes it through a small hole, although it's better NOT to make holes.

The downside is, nothing with a decent degree of mass is as cheap as gypsum wallboard, at least in the US - This is true until you get to maybe 4-5 layers, at which point it can be cheaper to pour solid concrete walls - it's just a lot more messy and labor intensive to do that.

Make sure whatever your material that there are NO EXTRA air gaps - you need to maintain only one air gap and two masses wherever possible... Steve