'room within a room' connection tween room via duct silencer

Hi all. I'm searching high and low looking for the correct way to connect my 2 rooms together (the inner room to the outer) via the silencer box. I swear that I read somewhere about using owens corning 703 (or rockwool??) compressed no more than 40% between the two and then finishing it off with some fire-rated caulk. I'm assuming that the space between the 2 rooms should be as big as a standard 703 piece compressed by 40% max? If so, would sound be escaping through this gap? I'm assuming said sound-escapage is preferred to the flanking by a hard, rigid connection? I'd be a happy man if someone pointed me in that direction as it's nigh "crunchtime". Many thanks!!

this is a pic from the Recording manual. The flexible duct is lead impregnated vinyl such as Auralex Sheetblok

Thanks, John! Now.....if only I were that smart when I started this then your solution would suffice. Have a look at the pic below and tell me what you think. I think the gotcha here is that, whereas in your image the connection happens between leaves, my connection happens in the room. Obviously, I'm probably in a "your gonna have to live with it" lesson about all of this but if you could have a look it'd be much appreciated. Basically, I need to know the best way to connect the ultra-beefy silencer box (which extends to my lower room) to the ceiling of my new room. It's made out of drywall so I might have to do a hard connection? Or is there a better, less "flanky" way of doing it? Thanks!

I'm gonna be "that guy" and bump this thread. Anyone have any advice? Thanks!

link your silencer box to the inner frame using Sheetblok.

Thanks again, John! (Can't believe I'm talking with "the man" himself!) Just out of sheer curiousity, what are your thoughts on this: What if I left a, say, 1/2" space between where the silencer box and the drywall meet and filled it with non-hardening silicone caulk?

go away. :)

I'm only positing the silicone idea since I'm a bit pressed for time. That and the fact that I don't have line on the sheetblok yet. Bad idea? OK idea? Horrible idea? Grazi!!?

If it is OK with John, let me see if I understand the issue. The concern is that you have a silencer box that is connected to the overhead joist and penetrates the interior ceiling. Further you are concerned that it will in someway be coupled back to the interior thereby short circuiting your isolation? Or you are concerned that there is a need for insulation that you had not considered? I agree that mass loaded vinyl could maximize the isolation at this point. But insulation is always part and parcel to what is installed in an acoustic environment so it has to be assumed that it is already there. And then use Acoustic caulk...not silicone. You can also trim this area, assuming the trim does not attache itself to the silencer, and reduce the cavity to the smallest degree...then acoustic caulk...or paintable caulk which ever is in your bag of tricks up to this point.

xSpace wrote:

Further you are concerned that it will in someway be coupled back to the interior thereby short circuiting your isolation?

YES!! That is exactly what I'm concerned about.

And then use Acoustic caulk...not silicone.

So I've been using the OSI SC-175 for filling gaps in my beef, etc. But from what I can tell about that stuff is that it dries rock hard. To me, it would seem that if I used this caulk (the OSI SC-175) I would be making a rigid connection that --would seem-- to flank like an SOB. That is, of course, unless you're talking about using some other acoustic caulk that is more "jelly-like" when it dries? As that's what seems most logical to me in terms of stopping flanking. That's why I was thinking of using the silicone as it doesn't dry hard. I swear there was another thread around here where the guy was mentioning something along these same lines of connecting with an acoustic caulk that dried hard enough that he could hear high-heel shoes above him (or something like that)???? I did a brief search....couldn't find it. I wanna say he was a 'software guy' who works for Digidesign or something.....ring a bell for anyone? Built a pretty mean looking studio anyway............... xspace, if you wanted to sketch out the connection you're thinking of I wouldn't be opposed. :lol: I appreciate the response though. Thanks!

"That's why I was thinking of using the silicone as it doesn't dry hard." Yes it does. 100% silicone may be a harder connection than a latex silicone additive. It may to the finger feel like jelly...but it is a connection none the less. If your acoustic caulk is drying rock hard...then there is an issue with that tube/batch. But , just for the record, how long has this caulk been in-place? In any event, a paintable acoustic caulk is still what you want. Granted the siliconized latex caulk is paintable, but may introduce bridging...the 100% silicone is not paintable, and surely introduces bridging. Stick with the product designed to meet your goals, but if you may have a bad tube, bring that up to those that need to know.

Here's the stuff I've been using (and have used multiple batches): http://www.osipro.com/products.pl?id=SC-175 To me, it seems to dry very hard. "Rock hard" might be overdoing it but it is hard, nonetheless.

Yes it does. 100% silicone may be a harder connection than a latex silicone additive. It may to the finger feel like jelly...but it is a connection none the less.

I'm curious why the OSI wouldn't be "a connection" as well? An even more firm one at that. Can anyone else recommend an acoustic sealant that doesn't dry hard? I seem to remember people mentioning some other brand that was more gooey. That's the one I probably want then.

Hi there this is the acoustic sealant I am using which was also recommended to me, the link is where I got mine but not sure if you can get it in the states. http://www.sealantsandtoolsdirect.co.uk ... c50900box9

Roguejackal wrote:

Hi there this is the acoustic sealant I am using which was also recommended to me, the link is where I got mine but not sure if you can get it in the states. http://www.sealantsandtoolsdirect.co.uk ... c50900box9

Thanks, roguejackal. What's that stuff like when it dries? Is it gummy or hard?

Well I would say 'gummy' would be a perfect description, some areas that I finished over a month ago are dry to touch but if you push into them and break the slight 'skin' it is sticky, similar to how it is when you first apply it, :D

Roguejackal wrote:

Well I would say 'gummy' would be a perfect description, some areas that I finished over a month ago are dry to touch but if you push into them and break the slight 'skin' it is sticky, similar to how it is when you first apply it, :D

Huh. Interesting. As that's not how I'd describe the OSI. Any yanks have any recommendations? (I don't think I can find that brand on this side of the pond.)

It is used on building sites all the time in the UK, i'm sure you must be able to find something similar in the US