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Discussion Starter #1
I am ready to begin building my riser! It will be 13’ wide (wall to wall) by 5’ deep. Height is 12” inches with 6” steps similar to this one done by Bass Addict:




I’ve seen a few different build approaches, so have a few questions going in:


1. I was initially thinking I’d use 2x12 boards, but now wonder about building with 2x6 for a “bottom half” and then adding a second 2x6 section on top of it and attaching the two with glue/brackets. I wonder if there is a preferred way to reduce noise, complexity, etc. Planning on using 3/4” plywood on top.


2. Should I attach the rear and side boards to the walls, or just fit it in there nice and snug?


3. This is a second level media room, so do I need to add underlayment since the riser is on top of the subfloor and not a concrete foundation? Also, I see some risers built on top of existing carpet, which I have but had assumed I needed to pull it up.


Thanks for your input.
 

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If you want to keep it simple build a perimeter box of 2x12s hang 2x8s or 2x10 stringers then push it back into place. Add steps in front of the box instead of cutting notches and make them giant sized for a grand feeling. I dislike notch steps as I think they can be dangerous in the dark. You said 5 ft deep, I assume you will only have upright seating. Recliners won't fit.


With a subfloor you can skip the underlayment.


to keep it quiet use at least two layers of 3/4 decking and stuff with loose fill insulation, If you plan to have a lot of guests don't forget step lights.


Pictures from Rawlinsway in no particular order. You can see I built it in two parts, the first is a 12 ft wide piece, because that was how long the lumber was and then a filler for the rest of the width.










 

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Discussion Starter #3
Thanks for the reply and the pics. I wonder why you recommend hanging 2x10 stringer vs using 2x12. Cost? I would think 2x12 would give more stability.


My wife and I like the look of notched steps since we have limited space in the room. I was planning to have step lights and/or rope lighting underneath the decking overhang. Is that not sufficient from safety standpoint?


Final thing you said that worries me. I was planning on getting the Paliser Bullets. Their specs show they an overall depth of 41" plus another 4" clearance from the wall for reclining. I figure if the decking is 60" deep, then that was going to give me about 15" from the front of the seat to the edge of the riser. I guess 15" isn't a huge amount of space (true, the leg rests would hang over the edge when reclined), but I thought it would be sufficient. No?
 

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Using less expensive wood for the stringers offers several advantages.


1) cost

2) Easy of construction, if the floor is uneven you just get the perimeter to sit reasonably flat and whatever undulations exist in the floor won't matter.

3) But the trump card is that it is based on Erskine group design principles of turning the riser into a bass trap. For that to work the entire riser needs to function as a connected volume with insulation, building the stringers shorter than the perimeter acheives that. Of course you need to pop in some vents at the riser wall intersections.


Stability, just add the supports as shown in my picture.


reclining seating requires 6 1/2 ft of riser depth. First the front row is pushed back tight to the front edge, and when they recline the seat comes back a bit. Second your legs and feet stick well past the end of the foot rest. Got to a store with a tape measure and check it out. I think I positioned the chair at 65 inches for this picture.

http://s23.photobucket.com/user/bigmouthindc/media/DSC02942.jpg.html
 

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Discussion Starter #5
Thanks for the helpful explanation as always. One clarification
Quote:
Originally Posted by BIGmouthinDC  /t/1527200/risers-101#post_24604090


Of course you need to pop in some vents at the riser wall intersections.

You lost me there. Can you elaborate?


Perhaps related, why not attach the perimeter to the wall?
 

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they are in the pictures. Standing base waves exert their maximum pressure at the boundaries of the room, the vents act to reduce the standing waves.


Stages are isolated, Risers can be attached. but I wouldn't use the wall as a way of holding up the riser.
 

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Discussion Starter #11
Doing a little research and saw someone say that bass traps have to be tuned to the room or could make things worse. Yikes. Perhaps I should just be happy with a riser that has 2x8 stringers for their lower cost and ease of use, fill it with insulation, and not go down the path of bass traps for my modest media room...
 

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It's akin to port tuning a sub, but more complicated. You've seen reference to port length compensation, or how the port length from one calculator or another is wrong or what have you? There are various correction factors that must be determined for port area and length based on the grill and the proximity of nearby structures, like the wall. Then there are volume correction factors based on insulation and proportions because the theoretical models assume an empty sphere. These sorts of corrections are easy enough with subs, but when you quadruple the volume and don't get a second chance at tuning it, the corrections are more important.


Dennis says there are only two designers he is aware of who have worked out the details and verified the models enough to offer the service professionally. The details are intellectual property; trade secrets, if you will.
 

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Discussion Starter #15
back to basics... for those of us who don't want a highly tuned bass trap but just a nice riser, do we want to build a riser "functioning as a connected volume filled with insulation" if we aren't planning to tune it or make vents?
 

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Discussion Starter #17
Thanks. I did some more research and came across another idea I wanted to ask the experts about...


I saw someone put their sub on the riser behind their back row. As they built their riser, they included a box filled with sand on which the sub could sit. From the pics, the box was presumably isolated from the rest of the riser.


I like the idea of placing my sub in this way. Do I need to build this sand box before I do? What are the problems if I don't? My alternative is just to sit it on the floor.
 

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If you want to provide sand for your subs, do it the same way you would do sand in a stage for a sub: away from the walls and not on a second floor (without consulting an engineer). That's what I've done.




I was sure I had more and better pictures, but I don't. This is 6 0.5 cubic foot bags of sand in a cavity made by two 16" bays of my riser. I scabbed on some scrap OSB to keep the sand from pouring out under the joist, since the rim is 2x12, but the others are 2x8, then I lined with 6mil plastic - stapled in place, then started trucking sand. This cavity was 8' long (nominal) and needed about 16 or 17 cubic feet of sand (some 33 bags, IIRC)
 

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Discussion Starter #19
I think I follow. However, this is a second floor room, and I was thinking about something like this to keep the weight down.
Quote:
Originally Posted by Spaceman  /t/1202525/spaceman-theater-build/150#post_21954356




The sand box is isolated from the rest of the riser, then covered with separate decking piece, then carpet for the sub to be placed on top.


I have 13x13 feet room, so enough for one row of seats but not two. So I do like the idea of moving the row up a bit and placing the sub behind on the riser. My question is 1) is something like the above sufficient and 2) is it critical? Like I said my alternative is to put it on the floor or on the riser with no sand.
 
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