I think the riser design is pretty much settled. I had to lower the height a little to fit under the sills. That involved moving to 2x6's and adding an extra layer of 1/2" plywood. I also picked a grate, Fibergrate 878872. I need about 16' and it comes in a 48"x48"x1".
Quick question. Should the backing on the pink insulation removed? It seems like it would reflect some sound and degrade it's acoustic properties. Do they sell it without backing?
My sketchup model is coming along nicely. Now that the riser design is done, I will probably start a new thread for other more general design challenges. Here is the current revision of the model. Hopefully someone finds it useful.
Here is the updated design. I'd appreciate any thoughts.
I'd say your biggest concern would be the acoustic impact of having a square shaped room.
EDIT: If you buy the faced, it will give you the opportunity to secure it to the sides of your 2x6 joists and thereby prevent it from ever falling down. I say the sides because that still leaves you the ability to glue and screw the first layer of decking to the top of the joist and not the insulation paper.
For some reason, faced rolls are so much cheaper than unfaced batts around here. Something like $0.25/sq. ft. vs. $0.55/sq. ft. Needless to say, I went with the rolls and peeled off the facing when needed. Otherwise I just used them faced even though they don't need to be faced in my application.
Diamante Build in DC - Double Drywall, Green Glue, Drywall Furring Channel, Riser, Stage, Bass Trap, In-Wall Speakers, BG Radia, JTR Captivators, Seymour AV, Sony HW-50ES, Sherbourn, Panasonic, Middle Atlantic, Lutron Grafik Eye, Baffle Wall
I'm not really qualified to make this statement, but I'm going to anyway , my first thought was I bet that sectional is going to make a pretty good bass trap. Big and fluffy, and it takes up a lot of space out in the middle of the room. It would be interesting to know the before and after modal response with the sectional in and out of the room.
(I hope that doesn't sound argumentative. I'm just trying to confirm my observations match your experience)
BTW, those 7 seats against the back wall will have rather horrid sound quality (presuming those sitting in the seats didn't pay for the room, I suppose they can suffer). More to the point, however, is those 7 seats add 3,500 BTU's to your cooling requirement and 105 CFM/hr of air exchange.
It sounds like I need to go back to the drawing board and figure out a way to open up the design more. Maybe I will just drill a bunch of holes and try to find a porous carpet pad. Drilling 200 holes through three layers of plywood sounds pretty tedious, but doing it all with grate is going to be cost prohibitive. Does anyone have a suggestion of what hole size and spacing should be?
I am aware that the back row is difficult audio wise. I have a plan with some dipoles that I think will help and was planning to review it in a new thread once I had the surround speaker in the model. The use of this theater is mainly for family and I prefer more of a family room feel, hence the sectional. The back row is really for sporting events when we need extra capacity. Translation, I will rarely sit there.
I realize that traditionally, the diffusive speakers are usually used on the sides. Placing the tripoles on the back wall seemed like the only way create a soundfeild behind the back row. I have drawn a 90 degree dispersion in the elevation, which I know is inaccurate, but it helps to show who will be in the direct sound field. Also, the SS-150's are a three way design with a forward facing HF and LF drivers. It should act like a directed radiator for the people on the sectional.
I also included an overlay with Audessey's recommended angles to each speaker from the primary position.
Any comments on positioning or type? Is there a way to get a better soundfield for the back row without sacrificing the front?
Won't help the problem.
Not sitting there ... will help.
I'd be interested to know what you are defining as the problem. One of my biggest home theater pet peeves is when a surround speaker is too close and becomes 'localized'. I find it very distracting and that is really what I am looking to avoid. I realize that the back channels will be overly diffuse/muddy for the back row, but the direct radiating side channels should help a little. Directionally it won't be great, but tripoles should help to make that better.
Is there some other acoustical issue that I am missing?
Home Depot (and others) have the spring steel wire used by contractors to hold the insulation in place. They are slightly longer than the distance between 16" O.C. joists. You just press them up between the joists and they hold the insulation in place.
Screwed down using screws that are long enough to penetrate both layers into the riser's joists. Use the grey colored exterior deck screws with minimum 3/4"+ screw length beyond your combined deck board thickness.
I am building a riser that resembles yours - build with broadband absorption (taming room nodes) in mind, in the width and length dimension.
See construction pictures below
With pink fluffy equivalent:
Riser is placed three feet from the rear wall and up against the left wall. It is 1 foot high, but will have a separate, smaller 8" high riser on top, with built-in buttkickers and placed on rubber feet at the side-ends.
I placed pond liner behind each opening, to minimize high freq. absorption. I will front the sides of the riser with GOM wrapped frames, to resemble the sidewalls. The floor on the riser will be an oak hardwood floor placed on two layers of OSB with greenglue. My ceiling is treated with 5" OC703 behind black GOM.
Last edited by Jacob B; 11-09-2015 at 05:36 AM.
I ended up building the riser similar to picture I posted above. I had a contractor doing the work and he built it a cheaper way instead of the way I designed it. It is similar, but has no ports on the front. He also did me a 'favor' and bought denser insulation than i requested. It was one of many issues with the contractor.
Doubled up the plywood, used a lot of Green Glue and I'm happy with the solid feel. No vibrations, noises, etc. If I could do it again I would use a tighter grate. The carpet has a weird effect on the grate and I think it will wear oddly over time.
Here are some pics.
Here is another thread will some more pictures.
It took me a long time to get my IB system right and haven't tested with/without the riser port covered. I used a MiniDSP EQ and mic. I had some technical issues with software and then a laptop soundcard with issues below 30Hz. I also had some technical problems with my wife who took exception to the amount of time I put into this project. So I just got the IB calibrated a couple weeks ago. Here is the final graphs at the main listening position for both subs:
I am pretty happy with the results, especially in a room that is close to being square. I'll have to test with and without the trap at some point, but I have several other punch items I want to get to first.