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post #211 of 239 Old 10-04-2016, 05:20 AM
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Most of what I have seen, is you need 6'6" minimum for a reclining row. I think I did mine closer to 6'9" and feel it is fine, but at 6' would definitely be too shallow.

Also, most of what I have read is that for a riser to act as a bass trap, the main dynamic is that bass pressure is mostly on the outer walls, so, if your riser is in the middle of the room, not sure how effective that would be.... this is all just based on recollection of what I have read, not any direct experience with this. If the rear of your riser is against the rear wall, then the rear edge might be good... but then, I would guess you might need even deeper than 6'6" to give room for the openings for the bass trap and the recliners.
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post #212 of 239 Old 10-04-2016, 06:14 AM
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I can certainly manage stretching the riser depth to 6'6". The riser will be in the back corner of the room so that shouldn't be a problem. So you're saying that I would just have to put some floor vent registers along the back edge of the riser? I thought there was also supposed to be some openings in the front face of the riser to absorb the bass.
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post #213 of 239 Old 10-04-2016, 10:53 PM
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Quote:
Originally Posted by BlueWRXPride View Post
I'm going to be starting to build a riser for my theater. The riser will be roughly 8'x6'. I'm not going to be making this an acoustically perfect room, but if I'm making a riser, I figure I might as well see if I can have it serve an acoustic purpose. What are some rough guidelines for size and placement of openings to give me a decent shot of having it act as a bass trap?

Also, is 6' deep enough to have room for a reclining rear row?
I believe 6'6" is the minimum recommended for a reclining rear row - that's what I went with and its a little tight, but do-able.

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post #214 of 239 Old 10-07-2016, 08:42 AM
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7' should be fine too, I'll just do that to be safe. How about cutouts necessary to try to make it a bass absorber?
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post #215 of 239 Old 08-15-2017, 11:23 AM
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Are these vents good for risers?

http://www.homedepot.com/p/Master-Fl...6X4W/100078188

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post #216 of 239 Old 08-15-2017, 11:26 AM
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Originally Posted by mpjmeyer View Post
No. You should pick something with more openess otherwise it's just like closing most of the cutout off again.
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post #217 of 239 Old 08-15-2017, 12:14 PM
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My pick, they will make them in just about any size, I like 4x48.




http://www.hvacquick.com/products/re...Linear-Grilles
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post #218 of 239 Old 08-16-2017, 06:19 AM
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Would only putting one vent along the back side of the riser be a waste? That would keep me from having to notch all the stringers on the adjoining wall since the vent would run perpendicular to them.
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post #219 of 239 Old 08-16-2017, 06:52 AM
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If you used two layers to cover your deck. then just set the blade on your circular saw to the thickness of the top and do a plunge cut for the cuts that run perpendicular to the stringers. The vent will fit right over the stringers, no notching required. When building a riser I either use two layers of 3/4 material or three layers of 5/8.
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post #220 of 239 Old 08-16-2017, 09:06 AM
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Is it OK to put 3 vents in the riser but the two on the side NOT in the back corners? Each vent is 4" x 36". I've got a sump pump hatch in the rear right corner so no room for the vent.

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post #221 of 239 Old 08-16-2017, 09:24 AM
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The bigger your vent area, the better it will work. Your riser is almost 15' wide, but the vent at the back is only 3' wide. I'd try to fit in more vent area.

In order for the vents to be effective, there has to be free airflow between the vents and the volume of air inside the riser. Make sure that the joists don't block the path from the vents to the volume of air inside the riser.
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post #222 of 239 Old 08-16-2017, 09:27 AM
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Quote:
Originally Posted by mpjmeyer View Post
Also, if they are going on top of the risers, you want something that is strong enough to support your weight if you step on it.
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post #223 of 239 Old 08-16-2017, 09:27 AM
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Would 3 layers of 1/2" be ok? I plan on doing 1/2" OSB - Green Glue - 1/2" OSB - Roofing Felt - final layer of 1/2" OSB

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post #224 of 239 Old 08-16-2017, 09:37 AM
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Quote:
Originally Posted by DaveClement View Post
The bigger your vent area, the better it will work. Your riser is almost 15' wide, but the vent at the back is only 3' wide. I'd try to fit in more vent area.

In order for the vents to be effective, there has to be free airflow between the vents and the volume of air inside the riser. Make sure that the joists don't block the path from the vents to the volume of air inside the riser.
The interior joists are 2 x 10s and the riser is made out of 2 x12s so there is some space underneath for airflow although the whole thing is filled with the pink insulation. I do not have any more real estate for any additional vents due to the location of the sump pump, unfortunately. The room is about 14' wide with all the wall treatments.

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Would 3 layers of 1/2" be ok? I plan on doing 1/2" OSB - Green Glue - 1/2" OSB - Roofing Felt - final layer of 1/2" OSB
Yes. I think the recommendation is actually 3 layers of 3/4" but most people only do two layers of 3/4" - I don't see why it would matter if you were at 3 layers or 2 layers to get to 1.5".
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post #225 of 239 Old 08-16-2017, 09:38 AM
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Three layers of 1/2" should be fine. At 1-1/2" it is equivalent to two layers of 3/4". I doubt that it would perform any better than two layers of 3/4", which would be less expensive and faster to install.

If you are going to the trouble of installing 3 layers, make them 3 layers of 5/8" and you will get 1-7/8", which will outperform the two layers of 3/4".

This may be splitting hairs, but if I were doing 3 layers with Green Glue in between two of the layers and roofing felt between the other two, I'd but the roofing felt between the bottom two layers and the Green Glue between the top two layers. That will give you the maximum damping on the surface that is closest to the room.
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post #226 of 239 Old 08-16-2017, 09:43 AM
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2 layers of 3/4" would be faster, but I already have most the 1/2" OSB in the theater ready to go. I would rather carry 3 more sheets of OSB downstairs instead of hauling 8 back up, returning them to the store and carrying 11 back down.

Would this be an ideal roofing felt for a riser?

http://www.homedepot.com/p/Warrior-R...14-0/100086691

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Last edited by mpjmeyer; 08-16-2017 at 10:15 AM.
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post #227 of 239 Old 08-16-2017, 11:05 AM
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That makes sense. I don't know about "ideal", but certainly acceptable. Roofing felt is pretty much a commodity item and any #30 felt should be just fine.
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post #228 of 239 Old 08-16-2017, 12:18 PM
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Any benefit to using 5/8 OSB + 1/4 plywood + 5/8 OSB? I've read several different references regarding sound waves using 2 different materials is supposed to outperform using only 1 type.
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post #229 of 239 Old 08-16-2017, 12:58 PM
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Any benefit to using 5/8 OSB + 1/4 plywood + 5/8 OSB? I've read several different references regarding sound waves using 2 different materials is supposed to outperform using only 1 type.
If you are trying to block sound, then yes. Three layers would be better than two. Unless you cover the entire floor, the reduction of sound transmission through the riser be irrelevant, since the sound would go through the areas of the floor without the riser.

What you are trying to accomplish with multiple layers of material on top of the riser is to make a solid floor that will not resonate. Mass is the main factor. Having two layers with damping in between would add additional benefit. I doubt that three layers would provide a measurable difference from two layers, assuming that the mass was the equivalent.
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post #230 of 239 Old 03-11-2019, 09:46 AM
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Adding some pics of my riser I built over the weekend. Took a lot of ideas from everyone here. I thought I was going to be limited to the original 6 inch riser due to my lower ceiling height but saw a thread where BIG mentioned building a riser booster.

https://imgur.com/a/Yo6PuWK
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post #231 of 239 Old 09-24-2019, 09:35 PM
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Originally Posted by BIGmouthinDC View Post
My pick, they will make them in just about any size, I like 4x48.




http://www.hvacquick.com/products/re...Linear-Grilles
Hi BIG,
Do you have a preference in which mounting option? The spring clips would be the cleanest option, but I am concerned they may not be as secure and rattle over time.
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post #232 of 239 Old 09-25-2019, 06:00 AM
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On the top surface of the riser I use gravity, I get the ones that screw down but end up not using screws. For HVAC use I screw them to walls/ceiling.
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post #233 of 239 Old 09-25-2019, 07:43 AM
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Originally Posted by BIGmouthinDC View Post
On the top surface of the riser I use gravity, I get the ones that screw down but end up not using screws. For HVAC use I screw them to walls/ceiling.
Any thoughts on dropping the registers in place in the riser before the carpet is installed, and then carpeting over them? Should still let bass pass through right?

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post #234 of 239 Old 09-25-2019, 08:01 AM
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post #235 of 239 Old 11-29-2019, 08:00 PM
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I'm getting ready to build a riser for my dedicated HT room. I'm planning on using two layers of 3/4" OSB and filling the riser with 12" of insulation, cutting vents in around the sides and back as suggested throughout this thread.

My question is regarding the type of insulation. Does it matter what type of insulation? at retail, I see both non-sound-barrier, and sound-barrier types. For use as (hopefully) bass-trapping, would I want to use the non-sound barrier type, or does it not matter which? Do the factors that make the insulation the sound-barrier type also stop the cavity from being appropriate as a bass trap? My brain is telling me that that if the insulation is going to mute the sound waves as a sound-barrier, it would possibly prevent the sound from filling the riser as I'm imagining it should since many times in this thread it's stated that the entire cavity should be "connected" by using smaller height beams in the interior. Thoughts?
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post #236 of 239 Old 11-30-2019, 07:59 PM
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Risers 101

^^use bare naked un-faced pink fluffy, fit it per the size you buy, don’t compress it.

You want a broadband bass trap, so no individual areas .... just use say 2” less tall stringers that your outside boards ...

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Last edited by mtbdudex; 11-30-2019 at 08:02 PM.
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post #237 of 239 Old 11-30-2019, 09:26 PM
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^^use bare naked un-faced pink fluffy,
so is there a difference between insulation labelled "sound-barrier" and regular insulation? or is it a marketing thing? It seems to cost more. Not sure if it is beneficial or detrimental for bass trap scenarios...
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post #238 of 239 Old 12-01-2019, 11:19 AM
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Buy these 2 for 12”





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post #239 of 239 Old 12-01-2019, 11:23 AM
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Originally Posted by Cygnus23 View Post
so is there a difference between insulation labelled "sound-barrier" and regular insulation? or is it a marketing thing? It seems to cost more. Not sure if it is beneficial or detrimental for bass trap scenarios...


You’d have to know their Gas Flow Resistance values to answer that ... for our purposes pink fluffy


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