Checking in with a few questions

Eggman · Post by **Eggman** » Tue Jun 29, 2004 6:23 am

Hey All,
I have made studying the info on this and several other forums part of my daily routine for the past few months. I've found answers to most of my design and construction questions. I think I have learned more at this site than did during several of my college careers.

I've also spent these last few months moving wiring, pipes, ductwork etc and building up the mass of the existing ceiling in the 21'x 20' area that will be my LR/CR studio space. I've added three layers of drywall between the joists, carefully sealing with acoustic caulking (I've used three cases of 29 oz. tubes). I've framed a wall to isolate the studio from the rest of the basement and hung three layers of DW (5/8 1/2 5/8) on the outside. I've been mind-numbingly meticulous in sealing any and all cracks. I've sealed the concrete block walls (which were filled with concrete) with several coats of Dry-block paint. So...I am reasonably certain I have a sealed outer shell with a good deal of mass.

Now I am ready to begin the inner rooms. My plans are/were to float several layers of T & G plywood on pt 2x4s turned sideways on 1/2 neoprene. I will compress the 2" rockwool in the cavities when I lay the floor. Then read today on the recording forum about the "drumskin effect".

1. Will my floor become some sort of resonating membrane that will add new issues/problems? My goal is to have the most isolated live room that I can practically build (w/o pouring a floting concrete slab). My headroon is only 7' 6" now, before the RC 5/8+5/8 ceiling and floated floor, so every inch I save will be noticed. I also don't want to use sand. Am I good to go with the method I just described?

2. If I build my inner walls with steel studs, no RC is necessary, right? How about the double wall between the LR and CR. If I use steel for both, won't this in effect be like using RC on both walls, which I understand (or don't) is a bad idea?

Just when I think I have some understanding, I read a little more and find advice that is the opposite to what I read in another post.

Keep up the great work. Now I know why my last studio/sound mitigation efforts performed so poorly.

I hope everybody has a good, safe and musical summer!
Doug

Post by **John Sayers** » Tue Jun 29, 2004 8:13 am

1. Will my floor become some sort of resonating membrane that will add new issues/problems? My goal is to have the most isolated live room that I can practically build (w/o pouring a floting concrete slab). My headroon is only 7' 6" now, before the RC 5/8+5/8 ceiling and floated floor, so every inch I save will be noticed. I also don't want to use sand. Am I good to go with the method I just described?

Multiple lywood layers should make the floor solid/massive enough to work fine. The more massive the lower the resonate frequency - in fact I suggest it would act more as a low frequency absorber - mind you I haven't read the article you refer to.

2. If I build my inner walls with steel studs, no RC is necessary, right? How about the double wall between the LR and CR. If I use steel for both, won't this in effect be like using RC on both walls, which I understand (or don't) is a bad idea?

RC only has a use when you have one wall. i.e. you have drywall on both sides of a single stud wall.

In your case you are using separate walls for each skin so you are fine.

cheers
john

Eggman · Post by **Eggman** » Tue Jun 29, 2004 8:38 am

Thanks for your quick reply, sir. I will work with confidence on the next phase of my studio and continue learning from all the people who have generously given their time and advice on this forum..... Doug

knightfly · Post by **knightfly** » Tue Jun 29, 2004 9:34 am

John's right on both questions - between the high mass of your floor, and the fact that you'll be slightly compressing the rockwool under the floor will kill any resonance you may have experienced.

If you want to post exactly what you're considering for your floor (spacing of joists, spacing of rubber and size of contact area, duro of rubber, type, thickness and # of layers of plywood, etc, I can estimate what frequency it would resonate at if there were NOT 2" rockwool between 1 1/2" frames, but it might be a waste of time. If you're using 1/2" rubber, though, then the RW won't be compressed much at all - in that case, you might want to consider cutting strips of regular R-11 fiberglass insulation maybe 8" wide and laying them down the centers of the RW before laying the floor - this would give enough damping to ensure control of the "drumhead from hell" thing... Steve