John Sayers' Recording Studio Design Forum Archive

As I understand it, metal "studs" are somewhat flexible, and so can be used as a RC, so, can I just use them as the framing, and not have to buy RC pieces?
Then just attach sheetrock to the studs?
What do you think?
Thanks
David

David, this thread covers most questions you might have on wall construction EXCEPT the one you just asked -

http://johnlsayers.com/phpBB2/viewtopic.php?t=598

I've since found that the answer to your question isn't as cut-and-dried as once thought. It depends on what weight of studs you use, and whether they're Structural grade or Non-Load bearing types. The non-loadbearing types are typically 25 gauge and are flexible enough not to need RC - unfortunately, you can't rest a ceiling frame on them. You need the Structural type (usually around 20 gauge) which are NOT flexible enough to qualify for RC replacement status.

One way of getting around this would be to use the lighter studs on walls that don't have to support anything - you can sometimes use isolated wire hangers (special isolators on each support wire) for ceiling frames and suspend the entire ceiling inside the walls, keeping a physical gap of about 1/8" to 1/4" between walls and ceiling, then caulking well with acoustic sealant

Another thing that's not evident when looking at STC charts is that they tell you NOTHING about how your bass guitar and drums are going to blast through your walls, because STC curves are only calculated using frequencies from 125 hZ through 4000 hZ. The lower the frequency, the harder the isolation is to accomplish. Mass and distance are about the only things that help here, along with physical separation of acoustic elements to avoid flanking noise.

For low frequency attenuation, NOT having RC is OK even in wood stud or Structural steel stud walls - stiffness and mass are what counts for lows.

Hope that answered your question... Steve

Hi Steve,

Been a while since I posted this, but I think you definitely answered my question. Basically I'll use the more flexible metal studs for the walls, and hang the ceiling on RC suspended inside the walls.
Should work great.
In this case, would I also not need to put the walls between the neoprene layer at the ceiling, as you show in that fantastic diagram? is the metal stud flexible enough, or should I still sandwich it between the 'spring'?
Thanks again A TON. I'd be nowhere without you
David

I'm not sure which "fantastic drawing" you're talking about, since I do so many fantastic drawings but basically here's what happens when you start combining materials - let's say you have a single lightweight steel stud - across the wider of its two short dimensions (not length) it is fairly flexible since there is typically 3" of light gauge metal to flex. Across the shortest dimension (the flanges) it will be stiffer, since the flanges have rolled edges and a shorter straight section. Lengthwise, unless the stud can "bow" in the middle, it will be stiff (like a pool cue used end-wise in the normal fashion)

Now, you take several of those studs and tightly fasten a few layers of wallboard to one or both sides - with the partial exception of the WIDTH of the stud (perpendicular to the surface of the wallboard) you've just built (effectively) a TRIANGLE, in that the lateral stiffness of the wallboard can be considered as a brace to keep the studs from skewing along the length of the wall. Same as using plywood siding on a house frame - doing that eliminates the need for diagonal bracing, because the plywood IS the diagonal bracing.

The end result is a wall that doesn't want to stretch or shrink VERTICALLY, so for all practical purposes it is rigid.

You don't want rigid connections between the different wall surfaces in a sound room, this is what we're trying to get away from. That's why I show neoprene on top of intersecting walls, but also a GAP - the neoprene in that case is ONLY there for insurance against sagging ceilings making solid contact with walls. The caulk is your seal against air leaks, anything else should not make hard contact between intersecting boundaries.

Oh, if your ceiling situation is such that you NEED that wall for support, you can use neoprene between ceiling joists and the wall - but then, the wall studs would need to be Structural grade, which are stiffer and would require RC (if you're using double stud wall framing, you could do one frame structural and one frame light gauge, bear the ceiling joists ONLY on the structural ones, and do the rest as my drawing. This should at least equal RC, and probably exceed it.

Hope that helped... Steve