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Discussion Starter · #1 ·
I'm in the process of rebuilding my home theater in my 100 year old house. We just took down some load bearing walls, doubled up the joists, and now have a much larger space. Yay!

We had to remove the old lath and plaster ceiling which actually provided nice isolation from the rest of the house. A new ceiling will be put up in a few weeks. Attached is the design that I am currently considering. What do you think? Anything to add or remove? What about mass loaded vinyl someplace?

These are the clips that I'm thinking of using:

http://isostore.com/shop/product/pliteq-genie-lb3/

Attached are images of the current ceiling and my design so far.

Thanks!
 

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Per my Sound Isolation mentor Ted White, the use of caulk was originally specified in that design but he has backed off recommending it. The effect of adding damped mass to the underside of the subfloor is unaffected by whether or not the edges are caulked.

Those are interesting clips and would be a time saver. Thinking about them you need to make sure that the L bracket is firmly attached to the sides of the joists, The engineer in me wonders about the torque that is generated by the long fulcrum arm. Isolation Clips are usually designed for around 30 lbs. Just looking at the clip the weight is about 3x the distance from the fulcrum as the screw in points which translates to a 90 lb tug on the screws, but I see they have holes for 4 screws. Your joists need to be in good shape, firm and hold the screws well. You might be the first on this forum to use them, please report back.

I also see that with those clips you will be restricted to spacing channels for every one or two joist spaces, If the joists are 12" OC then you can do every other joist for two layers of DW

You will need to modify the cross blocking for the channel to clear. That shouldn't be a structural issue. Just notch the bottoms with a jig saw. Probably should have done before you screwed them, Now the screws will actually need to come out before you cut them. Unless you have a different plan.
 

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Discussion Starter · #3 ·
Thank you for your help Jeff!

Per my Sound Isolation mentor Ted White, the use of caulk was originally specified in that design but he has backed off recommending it. The effect of adding damped mass to the underside of the subfloor is unaffected by whether or not the edges are caulked.
That is good news! So the drywall should fit as tight against the joists as reasonable?

Those are interesting clips and would be a time saver. Thinking about them you need to make sure that the L bracket is firmly attached to the sides of the joists, The engineer in me wonders about the torque that is generated by the long fulcrum arm. Isolation Clips are usually designed for around 30 lbs. Just looking at the clip the weight is about 3x the distance from the fulcrum as the screw in points which translates to a 90 lb tug on the screws, but I see they have holes for 4 screws. Your joists need to be in good shape, firm and hold the screws well. You might be the first on this forum to use them, please report back.

I also see that with those clips you will be restricted to spacing channels for every one or two joist spaces, If the joists are 12" OC then you can do every other joist for two layers of DW

You will need to modify the cross blocking for the channel to clear. That shouldn't be a structural issue. Just notch the bottoms with a jig saw. Probably should have done before you screwed them, Now the screws will actually need to come out before you cut them. Unless you have a different plan.
I'm starting to think that these may not be worth the extra effort/risk. Not to mention that a standard clip does make the air gap slightly larger which should mean higher performance. I will contact the isoStore with what you said though and see what they think.

Are WhisperClips the ones that people otherwise suggest?
 

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Discussion Starter · #5 ·
the Honda of clips is the IB1 the BMW is the whisper clip.
I'm looking at the GenieClip low profile some more. Although the blocking is in the way of the furring channel and I really don't like the idea of notching it, I could at least inset the clip such that only the furring channel is hanging down with enough gap such that it doesn't hit against the blocking if it flexes. Since I have an old house, the joists are neither flat or straight. These clips could be positioned vertically to help counter the non-flat joists and they can be adjusted horizontally to counter the non-straight joists. I might buy a few to try before committing.

With regards to the drywall that is mounted to the subfloor, is there a recommended screw pattern that people use?
 

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Discussion Starter · #6 ·
Also, can plywood be used instead of drywall for the top of the sandwich of the hanging ceiling? This would make mounting light weight acoustic products easier since they could be screwed into the plywood. But if drywall is higher performance acoustically I can make it work that way too.
 

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Why not notch the blocking? It will allow you to raise up the channel and minimize any reduction in ceiling height, otherwise the whole assembly needs to hang down below. A notch cut out of the blocking won't have any impact on the structural strength of the blocking. The "extra air gap" between the ceiling and the joists won't make any difference. The goal is simply to keep the ceiling structure from touching the joist structure and transferring vibration.


The easiest way to notch the blocking is probably to use a circular saw and make a vertical cut where you want the notch to be. Whack the section between the cut and the end with a hammer and it will break off, leaving a notch. Of course, you would first need to remove the screw at that end, perhaps replacing it with screws toenailed from the sides, just above the notch.


Why use the low profile clip? Are your joists really so twisted that you need the lateral adjustability of the slot in the low profile clip? Why not use the "normal" L bracket clips like the ones below? If you need lateral adjustability, you could easily shim them horizontally away from the joist with a thin scrap of plywood or something similar.
http://isostore.com/shop/product/pliteq-genieclip-lb-bracket-extension/
http://www.soundproofingcompany.com/soundproofing-products/soundproofing-clips/ib-3-clip/
 

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Although the blocking is in the way of the furring channel and I really don't like the idea of notching it,

With regards to the drywall that is mounted to the subfloor, is there a recommended screw pattern that people use?
notching the blocking will not effect the structural integrety.

screw pattern is 6 per 4 ft strip any thing else is waste. like :::

anything lightweight can be screwed to the double layer of 5/8 drywall you don't need plywood/OSB. If you have heavy items you can use a layer of OSB as the first layer.
 

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Discussion Starter · #9 ·
notching the blocking will not effect the structural integrety.
Oh I'm more worried about the work to do the actual notching, but perhaps it isn't so bad. In retrospect we should have used shorter blocks or pre-notched them. But I didn't know about these low profile options back then.

The only thing semi-heavy I could see myself installing someday are speakers for these new audio formats that have height channels.
 
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