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Ceiling Speakers - Vibration Dampening

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Old 09-22-2005, 02:59 PM   #1  
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Default Ceiling Speakers - Vibration Dampening

Hey, I am installing ceiling speakers in my house on the first floor. The front speakers will be directly below my son's room (he is 2). I have done some research on speaker boxes, etc. to reduce the vibrations, but everyting seems to be made for new home systems. I don't want to cut anymore ceiling than necessary.

Here is my idea. Can I stuff some pillows (foam) between the speakers and the 2nd story floor? There is about 8 inches of room. Will this reduce the sound and vibration felt/heard on the 2nd story? Is this a fire hazard?

Thanks for your help.
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Old 09-22-2005, 03:12 PM   #2  
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Just use regular fiberglass insulation and stuff it up in the cavity as best you can. It won't interfere with the speaker operation and will dampen the sound being transmitted in the cavity.

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Spyder
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Old 09-22-2005, 03:21 PM   #3  
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Quote:
Originally Posted by ucla92
Here is my idea. Can I stuff some pillows (foam) between the speakers and the 2nd story floor? There is about 8 inches of room. Will this reduce the sound and vibration felt/heard on the 2nd story? Is this a fire hazard?
Thanks for your help.
High end mobile sound installers - bus conversions and pricey autos (limo, car doors) plus some avionics apps use a special material that works perfectly - it is a " of RUBBER foam on each side of a sheet of lead about 40mils thick - the lead (mass) isolates the path by allowing the rubber to absorb all the vibration -only rubber absorbs vibration - plastic (styrofoam) doesn't nearly as well -glue it on a piece of plywood and screw the plywood to the floor above the speaker -unless the supplier has a better method

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Old 09-22-2005, 04:10 PM   #4  
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Many in wall/in ceiling speakers have "back boxes" for installation such as yours. What speakers are you thinking of?
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Old 09-22-2005, 04:54 PM   #5  
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Default Polk

Polk rc80i. It's funny, on polk's website it tells you to stuff fiberglass or pillow stuffing directly behind the speaker to dampen the rear wave.

http://www.polkaudio.com/homeaudio/p...den/?helpid=39
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Old 09-22-2005, 05:23 PM   #6  
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Quote:
Originally Posted by ucla92
Polk rc80i. It's funny, on polk's website it tells you to stuff fiberglass or pillow stuffing directly behind the speaker to dampen the rear wave.http://www.polkaudio.com/homeaudio/p...den/?helpid=39
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some sort of damping material, such as fiberglass or pillow stuffing, directly behind the speaker to dampen the rear wave of the speaker. This will minimize coloration.
I understood your question to be that you wished to decrease the transmission of the enclosure (joists,subfloor, etc) vibration through to the second story floor - If you are trying to decrease the cavity resonance by diffusing and delaying the wavefront (infinite baffle) then that is an acoustic requirement not a mechanical one - are you posing a question or a proposition?

Last edited by maicaw; 09-22-2005 at 05:25 PM..
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Old 09-22-2005, 05:37 PM   #7  
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Default Vibration/noise to 2nd floor

I guess my knowledge is not that technical. Right now we have rear in-ceiling speakers that are below our bedroom. When I crank it up, you can hear a noise/vibration from the rear speakers in my bedroom.

We are now installing front in-ceiling speakers and they are under my son's room. I want to eliminate/reduce the vibration/noise heard in his room.

Thanks.
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Old 09-22-2005, 05:53 PM   #8  
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Polk doesn't make a back box for their 8" speaker. Their sales pitch is they use the entire space as an infinate baffle.

We have installed a number of TruAudio CPi 8 with their back boxes.
See: http://www.truaudio.com/products/in_...pup/cpi_8.html
And www.truaudio.com and select Accesories then Back Boxes.
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Old 09-23-2005, 09:23 AM   #9  
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rbink, thanks for the link to truadio. Do the back boxes only work for your speakers or for any 8" speaker? I live in Orange County, CA and noticed the headquarters are in Laguna Niguel. Thanks.
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Old 09-23-2005, 10:37 AM   #10  
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They may work for the Polk. They may not want you to put an inferior product to theirs in them however.
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Old 09-25-2005, 04:27 PM   #11  
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How are polks inferior to truaudio?
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Old 09-25-2005, 05:05 PM   #12  
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Quote:
Originally Posted by ucla92
.... I don't want to cut anymore ceiling than necessary..
The rubber mat material the feed stores sell for horse trailers would probably make an excellent vibration absorber - It's cheap and easy to cut and install thru the speaker hole - but it smells like old tires and would be flamable - but no more so than wooden boxes. - haven't used it myself so far because I had scrounged enough of the expensive foam/lead material mentioned earlier
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