Axiom Home Page Forums General Discussion Home Theater Home Theater Riser Construction

Hello to all of my Axiom buds... sorry I've been absent for awhile. Withdrawal has finally set in and I'm back (at least until baby arrives in a couple of weeks).

One final project I'm trying to get done before then is to purchase chairs and build a riser in our theater room. For the few of you who have been here or read through my old posts while planning the theater, you'll remember that I have a sloped ceiling on one end of the room and as a result a fairly low screen height. I've settled on the chairs I'll be putting in. I found a great deal on the Berkline 45004 model if anyone is interested. Getting them for about 60% of what my dealer wanted to sell them for locally.

Picture:


To overcome the low screen height, I need to build a decent-sized riser in the back of my room that will look over the chairs in the front row.

I've used the riser theater calculator to determine the height I need and am now moving on to try to construct the riser. (a scary thought, as I am about a 4 out of 10 on construction skills)

I've put together a model for the construction in Google Sketchup, which if you never have used it is a terribly useful tool for projects like this.

The first picture is a basic model of my theater room showing where the front/rear row of seats will be. (probably less useful than the second drawing, but included just in case)


The second model shows the actual blueprint for the riser. The simple design comes from a lot of reading over at AVS forum and a few other sites. The dimensions are 6' deep by ~93" wide x 20" tall with one step about half-way up. I realize this is a bit tall for a single step, but there's limited real estate to put in a second step and also the design gets more complicated than I can easily manage with multiple steps.

It is essentially two large boxes made of 2x10 boards stacked on top of one another and framed across with more 2x10 boards on joist hangars to provide the flooring surface. The riser will be stuffed with insulation to dampen the sound and then topped with two layers of 3/4" plywood (separated by 30lb roofing felt to minimize vibrations). I've also read that you can drill holes in the front and back of the riser to allow for better sound transmission (apparently to increase bass frequency response in the room?), though I haven't figured out if I'll do that yet as I don't totally understand the reasons for it. (I have very good bass response now and am not sure if messing with that is the right way to go, though I realize that adding a 100 square foot hollow box is likely to change the profile a little!). With all that said, the blueprint:


Once constructed, I'll be putting a pad and carpet over it to match the rest of my room.

With that incredibly long lead in, is there any advice the theater / construction gurus in the audience would offer?

I'll probably start putting my required parts & tools list together tomorrow and plan on building Sunday. I figured before I start nailing boards together I'd better at least run this by someone to make sure I haven't overlooked something terribly obvious. I appreciate any advice from anyone who has gone through this before (or even if you haven't).

Thanks,

Jason

Jason,

When I went to hear Klipshguy's system, his riser was quite high - not sure of the exact height, but I would guess it was similar to the one you're building. While sitting back there, I noticed the higher frequencies were attenuated. I'd consider tilting the mains back, or putting them on risers as well. Just my 2 cents.

Good advice Shawn, thanks for chiming in. If I can manage to build a 6x9 riser that doesn't fall over, building something for the speakers to sit on should be a piece of cake.

Jason,

I had a riser built in my theater also. It's not as high as yours (only one step instead of 2), but it is plenty high to get an unobstructed view of the screen from the back row.

I'm glad you mentioned you will be stuffing it with insulation. The guy who did mine did not stuff it and it really did create a resonance chamber in the room. Make sure you get the most dense material you can and really pack it in there. Since it is for sound absorption, and not for insulating heat, pack it really dense.

The bass response will definitely change once the construction is complete. Since I know you have the BFD, and have been using REW, it will be very interesting to see a plot before and after (before you re-equalize). Please post the results when you are done, I'd love to see the impact.

Also, one more bit of advice... Wood is cheap, so put as much cross bracing in the chamber you can before you insulate. Make it as rigid as you can.

Where I live, 2x10s are pretty expensive. Structurally speaking, you could build the whole thing out of 2x6s with a single layer of 3/4" plywood and it would be plenty strong and rigid. I'd do a single box of 2x6 with short legs to get the proper height and wrap the sides with plywood for stiffness.

I'd also recommend using construction adhesive and screws (deck screws, not drywall screws) on the plywood decking. Joist hangers are a good idea, but put a little pad of roofing felt between the joist and hanger

This will also be more stable over time. Building it out of solid wood like you show increases the likelihood of wood movement over time, which will cause the joints to loosen and eventually start creaking and squeaking.

Good luck. This is a pretty straight forward project as long as you take your time and measure twice before you cut.

Thanks for the advice guys. Joe -> the only problem I see with using 2x6's is that the end product needs to be just over 20" tall, so even if I did 3 boxes out of 2x6s on top of each other topped with a sheet of 3/4" plywood, I'm only up to 17" or so (before carpet).

I haven't gone to Home Depot yet to price this out, so if the 2x10's are really that expensive I might be motivated to get more creative.

Thanks for the advice on putting roofing felt between wood and joist hanger. Sounds like a likely place for some creaking/squeaking, good plan.



Joe, can you please clarify what you meant by this? "building it out of solid wood" What would the other option be?

Thanks again guys...

Jason

Jason,

You and your wife are a great looking couple, I'm sure that baby is going to be a looker.

I think I either used 2x8's or 2x10's for my riser, then wrapped with padding and carpet to match the rest of the room carpeting. I also have pieces cut and angled in each corner to make it rock solid as well as 3 2x4 cross members to help support the plywood. It is very heavy, however, I attached moving buddies on each corner so I can easily slide it around the room if needed.

The key is you have to allow enough height so the front row heads don't get in the way. I also had to raise my screen up a bit to accomplish this...

I have seen some built with lips on the top level that are big enough to allow putting rope lighting around the perimeter. Might be a consideration for letting people see the steps in the dark, especially with the multiple steps you will have.