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Elevated Seating Platform Questions

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5 replies to this topic

#1 of 6 OFFLINE   Shane-M



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  • Join Date: Mar 09 2004

Posted September 23 2004 - 06:21 AM

Hello All, I would like to build an elevated seating platform for my home theater (recliners will sit on top) and would like to know how to best control low frequency resonance. Fill with Sand? Special internal bracing method? Common sense tells me to use a cross support method, MDF and fill platform with sand....any engineers out there with some ideas? Thanks in advance. -Shane

#2 of 6 OFFLINE   BrianKR


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Posted September 23 2004 - 11:35 AM

Sand is a bit extreme for a seating riser. Most people tend to use double 3/4" plywood for decking with regular or loose/blown insulation between the 2 x (6's, 8's or what have you). Some people don't even have insulation in their risers and some will use a third layer of plywood, usually 1/2". I built my riser with 2 x 10's, double 3/4 plywood w/roofing paper between the layers, and I stuffed it with loose insulation.

#3 of 6 OFFLINE   Andrew Stoakley

Andrew Stoakley

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Posted September 27 2004 - 02:38 AM

Hi Shane,

I agree with Brian, not only would sand be a bit overkill but it would be a total pain in the a#$ to get rid of if you ever wanted to remodel... LOL. I framed my riser with 2x8's in a standard 16" on centre studding frame. I filled the cavities with Roxul's Safe N' Sound batting. I then used construction grade adesive to glue 3/4 construction grade plywood on top. I then used 1" decking screws to attach the top to the frame. I went crazy with the adhesive and screws so as to make sure nothing was moving!! Once that was done I filled in the screws holes and then added 10mil carpet padding and 60oz broadloom. You could jump up and down on the riser and not hear anything Posted Image

Hope that helps.

"Remember kids - no one cares about audio until they can't hear it."



#4 of 6 OFFLINE   Frank Kanyak

Frank Kanyak

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Posted September 27 2004 - 11:01 AM

I built my lower riser with 4x4x8 posts with a 2x4x8 laying on top of that. 1/2 flakeboard on top with nails every 4 inches. Commercial carpet only. My second tier is 2x12x8 with a 1/2 flakeboard and nails every 4 inches. I built additional support beams especially in the middle. Both platforms are stuffed with insulation.
Denon 2805,Monster MK II 5000 Power Center,Logitech 880 Remote Control, JBL S-center, JBL S412p, JBL S26, JBL L1, Tempest Sonosub(tuned to the sweet sound of 16.5 hz). :-)
Panasonic L300U projecting onto Carada Classic Cinema White 88"

#5 of 6 OFFLINE   Rutgar


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Posted September 28 2004 - 12:36 AM

In the book "Premium Home Theater Design & Construction" by Earl Geddes, he talks about a riser that was used to incorporate 4 helmholtz resonators. Each being twice the volume as the previous, so a wide range of low frequencies would be absorbed. Unfortunately, the book doesn't go into details, and doesn't give actual measurments. So, in order to do something like this, you would have to do some research on Helmholtz resonator design. I also believe it would have to be "tuned" to the problem modes of the room, so it doesn't sound like a simple project.

#6 of 6 OFFLINE   Shane-M



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Posted September 28 2004 - 05:59 AM

Thanks for the feedback/input guys....I appreciate it. Rutgar, thanks for the info on the helmholtz resonators... -Shane

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