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Discussion Starter · #1 ·
My home theater room is in the basement, it's a 10x20 room with a drop ceiling.

The other day I was doing some testing w/Avatar (yes, the loud scene where the mother tree falls) - and I had the volume up. I have subs that are calibrated (and EQd with BFDs).

The floor above was vibrating - the low frequencies were hitting the ceiling and passing through to the floor. Has anyone found a solution that they like for trying to deaden the ceiling itself?

I've thought about stuffing with pink fiberglass - and using rockwool/OC705(or some other accoustic treatment - but that gets expensive).

My understanding is that most insulation grade fiberglass - is really only effective at absorbing higher frequencies. I'm trying to see if there is something that I can do - since rebuilding the room (ala room within a room type construction) isn't a possibility.
 

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What is it you're trying to accomplish? If you're trying to stop sound from transferring up through the floor insulation won't help (though it is recommended to stop cavity resonances.

How fiberglass absorbs with direct waves vs how it acts between a hard sub-floor and ceiling is completely different as there would be zero high frequency absorption as those waves will be reflected by the ceiling. It will, however, damp the cavity and allow it to act like an absorber as opposed to a resonating drum.

Bryan
 

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Discussion Starter · #3 ·
What is it you're trying to accomplish? If you're trying to stop sound from transferring up through the floor insulation won't help (though it is recommended to stop cavity resonances.

How fiberglass absorbs with direct waves vs how it acts between a hard sub-floor and ceiling is completely different as there would be zero high frequency absorption as those waves will be reflected by the ceiling. It will, however, damp the cavity and allow it to act like an absorber as opposed to a resonating drum.

Bryan
Sorry - I wasn't very articulate about what I wanted to accomplish.

I really would like to to cut down on the vibrations on the floor above (and prevent the "resonating drum" effect). I'm not concerned about the actual noise transmission to the room above.

So, from the sounds of it, stuffing the floor joists above the dropped ceiling - would mitigate the drum effect a little bit?

Thanks for your advice.
 

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The insulation will do little in combination with the dropped ceiling as Bryan said. The dropped ceiling lacks mass. A drywall ceiling has a lot of great mass.

The dropped ceiling is also poorly sealed.
 

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Ah. Drop ceiling is a different story altogether. The bass will go right through that like it's not even there. Insulation between drop and the subfloor will help with overall broadband bass control but there's no cavity to resonate. The best thing to do would be adding a layer of 3/4" MDF to the underside of the floor above with Green Glue between layers.

If that's not feasible, cut drywall pieces to sit on top of each ceiling tile to add some mass. You'll need to beef up the hangars on the ceiling grid though.

Bryan
 

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Discussion Starter · #6 ·
Sorry - I thought I mentioned that it was a dropped ceiling in the first post.

I guess I thought that the space between the drop ceiling and the floor above would act like a cavity - but that makes sense. Little mass and leaky.

So, if I could totally rebuild the ceiling (without isolating the ceiling from the floor joists.. I don't have enough height) ... what would be the best practice?

Glue MDF to the sub floor - and install drywall?

Last time I talked about installing drywall - I was talked out of it by people that kept talking about the acoustical benefits of a drop ceiling.
 

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I suspect that you'd actually lose LESS height with channel and drywall rather than the space it takes to drop a ceiling grid down.

Bryan
 

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Discussion Starter · #9 ·
You can recess the clips as an option to preserve height
Cool. Thanks for that suggestion - I totally forgot about using clips.. I'm familiar with RSIC clips - it looks like whisper clips are similar.

I had not seen people use clips for ceilings before - but that makes sense.
 

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Discussion Starter · #10 ·
I suspect that you'd actually lose LESS height with channel and drywall rather than the space it takes to drop a ceiling grid down.

Bryan
It would. Whomever installed the drop ceiling only installed with about 2 in of clearance - which makes it a pain to change/move panels.

How would MDF on the subfloor and drywall screwed to the joists (like a traditional ceiling) compare to just using the clips w/drywall?

My only concern is it seems like when I look at calculators for acoustical clips - it seems like it ends up being a few hundred dollars - even for just a 10x20 room.
 

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Doing those things instead of clips will likely not cost a lot less but will still perform pretty well. I'm assuming that the insulation is a null cost as it should be done in either case.

By the time you figure 2 layers of drywall and the Green Glue to go between layers, it's probably a wash for 1 layer of drywall, 1 layer of MDF, and Green Glue between MDF and subfloor.

Bryan
 

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Discussion Starter · #12 ·
Thanks for all the comments.

You've given me a lot of food for thought if the time/money becomes available to dramatically change the ceiling.

With a newborn due in a couple months - sounds like I'll just need to turn it down for the time being. :) :)
 

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I used green glue with great success for my basement hometheater with a drop ceiling. I used the green glue on the FIRST FLOOR floor above the hometheater's drop ceiling.

I still get sound that flanks thru the AC duct work. But the sound leaking out of the basement to the floor above is much improved.

description and measurements here:

http://www.avsforum.com/avs-vb/showthread.php?t=1136101
 

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You could always use staggered joists to hang the new drywall ceiling. Probably cheaper than clips. As long as you don't have HVAC ducts, plumbing, etc taking up space between the existing joists.
 
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