Need riser advice

[Tonto]

Hello all

I'm ready to build my riser. I read somewhere that adding rigid fiberglass (RF) would help with absorbtion. In the post, the builder said he cut circular holes in the leading edge. Don't understand all this, was this an attemp for Helmoth Resinator type affects? Since my room is contructed (my wife wanted to remodel our kitchen & I took advantage to extend the upstairs at the same time for my theater room). The room is 214" L X 137 1/2" W X 96" H. Due to a load bearing corner, I had to taper in the last 45" of the left wall @ the screen wall corner. I had the opposite wall tapered in to match. The entry door is in the left, tapered section of the wall. All this leaves the screen wall 112" wide. I did this for cosmetic reasons & the room looks very balanced. My concern for absorbtion is because the rear wall, @ the right end is where a closet door is located (equipment room) & where the corner trap should be placed. If I build one, it will have to be hinged to allow entry through to door.

I have not picked out my chairs yet, but they will be theater style & motorized. Based on these room demensions, what size should I make the riser & how do I know how much (if any) RF to stuff into it. Do I need to fill it all or just in between some of the divisions. And do I need to cut the holes in the front edge. From this point on I am DIY . I'm prety handy but on a tight budget.

An added note, I had the left & rear wall offset studed (they connect to other rooms in the upstairs) & insulated with 4" roll insulation. 6" insulation under the floor & above in the attic (theater is above the kitchen). I wish I could have reserched more before we did the addition, would have done things a little different. Anyway this is what I have to work with.

I'm open to any suggestions/advice, thanks guy's.

[bpape]

The riser needs to be filled FULL with insulation. Standard wall insulation will work just fine. You can compress a little but not a lot.

LARGE holes in the face won't act as Helmholz resonators - they just allow the face to act as a broadband absorber - even right through the carpet.

Any chance of posting a top view sketch of the room?

Bryan

[Tonto]

Thanks for the reply Bryan. I have very limited computer skills so I will have to get a friend @ work to show me how to do that. I'm sure this will be a big help as I will be treating the entire room. I saw a post that recommended absorption/diffusion locations. I plan on doing all these things including a ceiling panel absorber. Things I can build myself. I'm sure I will be asking questions as I go.

The main thing is that I have high expectations for my room. I'm a very meticulous kinda guy & I tend to do things as such. So real world solutions/advice will be very much appreciated. Just so you will know, I plan on using a projector (haven't picked one yet--would like it to be 1440P), already have a PB13U & will be getting the MTS 7.0 line of speakers soon. Always have been a Yamaha/Denon fan, but all that is up for discussion as it will be another year for those purchases.

What size should the holes be in the front of the riser?

[bpape]

Make the holes as big as you can while still leaving sufficient support.

You'll have to plan for a reasonable amount of bass control and the rear corners will almost be a must with no fronts available. Also, those angled walls and the balance of the front wall will need to be treated fully.

Bryan

[salvasol]

You need to know the dimension of your seats to calculate the riser size

You need to measure the height of the person seated in the front row, width, etc. ... your riser can be btween 10" - 16" depending on the seats.

There is a calculator floating around ... let me see if I can find it

[Dennis]

Holes in the face of a riser will have minimal effect. If your riser extends the entire width of the room, holes on the top of the riser near the walls will be helpful. More helpful if the riser extends to the back wall and you place those openings in the corners. Use a standard floor mounted HVAC register to hide the holes.

[salvasol]

Quenten:

Here is a calculator you can use to design the riser ....

http://www.theater-calc.com/

Good luck

[bpape]

Hi Dennis

Good to see you here. I'll agree that if you can cut some decent size openings by the back wall, that'll likely help a bit more.

Bryan

[Tonto]

Thanks for the reply guys, here is a picture of my room--not to scale, but how it looks. Now that I know a bit more about treatments, I guess I should have left the right wall untapered & used a base trap shapped to match. Again I am wanting to build this riser so that it multitasks. Spacers will be the width of the insulation (standard stud spacing). Should I put HVAC vents in each division, or just the corners. The riser will be from sidewall to sidewall with a stepdown into the equipment room (step up same side). The front of the riser is not a support concern, I could fashion hole/holes in any configuration. Rectangle with HVAC covers, 1 large hole, 2 large holes, 4-6-8 small holes etc. (& carpet over them), what do you think?

Also, I haven't done the math yet, but if both end slots are not exactly standard stud spacing, would the be any benefit to adding vertical RF (floor-sidewall edge) to make up the difference, or just stuff in more roll insulation. I can also add RF to the back edge (like a chunk), or should this be along the back wall-ceiling edge. Again, looking not to have to redo things later. Thanks guy's.

[bpape]

I think the suggestion was to make a long opening the full width of the riser and then just carpet over it. It'll be behind seating so no big deal. The more surface area the better.

The bass will go right through the carpet.

Bryan