a/c registers in riser? - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 15 Old 02-10-2015, 06:11 PM - Thread Starter
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a/c registers in riser?

Hi all,

So dedicated home theater build underway.....just had an awesome riser built...filled with insulation......now the big decision....do i cut two holes in it to put ac registers in for purposes of bass traps?

I got a few recommendations to do so, but very leery of cutting into the riser. Is it worth it? Can I make it worse?

Thanks!!

Keith
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post #2 of 15 Old 02-10-2015, 08:38 PM
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You should, and if you do, you'll get a broadband base trap. Hopefully, you sealed the riser completely. Place at least three registers along the perimeter, very close to the walls. One along the back wall, and one on each side wall, biased toward the back. My registers are pretty big (4x36). The concept works well, but the riser should be sealed so that the perimeter ports are handling the airflow. I also put three layers of plywood down with green glu in between the layers.
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post #3 of 15 Old 02-12-2015, 03:40 AM
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There is an article by DE on it.. if you search this forum you will find it.

The key, as Ben mentioned, is the riser must be sealed. I've never seen a sealed riser except when it has been planned ahead specifically for this purpose.

Tim

Last edited by Mr.Tim; 02-12-2015 at 03:44 AM.
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post #4 of 15 Old 02-12-2015, 07:19 AM
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What is a sealed riser? besides the tops how would you seal the rest of the joints? a liner below the pink fluffy?
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post #5 of 15 Old 02-12-2015, 07:37 AM
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Quote:
Originally Posted by iamjason View Post
What is a sealed riser? besides the tops how would you seal the rest of the joints? a liner below the pink fluffy?
You want to use roofing paper underneath your riser to isolate it from your concrete foundation, as well as provide a moisture barrier.

As for "sealed" I believe they are referring to just having no air gaps in the perimeter of your soffit (eg: holes for electrical/network/etc) other than the holes you cut in the top decking. If you have holes/gaps fill them up with caulk.

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post #6 of 15 Old 02-12-2015, 07:55 AM
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oh ok - mine is on the 2nd floor and will have carpet under it so i think that will be good -
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post #7 of 15 Old 02-12-2015, 10:25 AM
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Not sure what I was trying to ask here. Typo or something, glad everyone ignored it lol. I think I was asking about something else.

Last edited by Jesterss; 02-16-2015 at 09:56 AM.
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post #8 of 15 Old 02-13-2015, 02:25 PM
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having built a number of Erskine designed bass management risers I'm scratching my head over this sealed concept, certainly weren't in his plans. I think you are confusing a tuned trap with the ones Dennis designs.
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post #9 of 15 Old 02-13-2015, 02:53 PM
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Quote:
Originally Posted by BIGmouthinDC View Post
having built a number of Erskine designed bass management risers I'm scratching my head over this sealed concept, certainly weren't in his plans. I think you are confusing a tuned trap with the ones Dennis designs.
Right you are Big. I took the time to search for the article here on the forums and it is about broadband absorption. It also has a link to another riser absorber and a post from you regarding a third.

For some reason I had in my head that it was a tuned trap.

Tim
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post #10 of 15 Old 02-13-2015, 04:54 PM
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Quote:
Originally Posted by BIGmouthinDC View Post
having built a number of Erskine designed bass management risers I'm scratching my head over this sealed concept, certainly weren't in his plans.
Implementation detail

 

 

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post #11 of 15 Old 02-14-2015, 05:09 AM
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No, just not needed for his type of bass management riser.
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post #12 of 15 Old 02-14-2015, 04:43 PM
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Based on the plans, I would agree, but as you know, the plans don't always include everything that is needed. It would not surprise me if the riser was always intended to be sealed, just never communicated... essentially reserving proper implementation to those willing to pay DE & Steve the big bucks to build the room. Similar to the trim being mounted parallel with the walls in DIY builds because that's what the plans say.

Considering the source, I wouldn't be too quick to dismiss. It was a DE designed riser build with Steve onsite to help with construction of the room. Possible he picked up some implementation details us poor shleps with just the plans were unaware of?

Reason I clicked on this thread was to see thoughts on running the actual HVAC lines & vents on the riser. I have to do a 2' riser at this point, but could I save some ceiling height by running HVAC in the riser instead of a soffit around the room? I was also thinking of putting the projector in the riser and having HVAC down there would be beneficial for cooling & exhaust extraction.

 

 

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post #13 of 15 Old 02-14-2015, 06:24 PM
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don't you have 11+ ft ceiling heights? why would you need to save anything, I also thought the design of the soffit offered one of the opportunities to stiffen the walls.
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post #14 of 15 Old 04-01-2015, 07:03 PM
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11' 6" after drywall. I have gotten used to the tall ceiling. It helps make the room feel spacious. 2' riser + 1' soffit would reduce height to 8.5'. It also makes the projector shoot into my face when I get up. We bought a hold over system for the living room. My wife instinctively ducks down when passing in front of the LCD flat panel.

Stiff walls are a DE thing. If you look at some of the KYDG projects they actually avoided DD in the past because it makes the walls too stiff. Maybe it's make or break for the way EG builds rooms. No one else I've talked to thought it was that big of a deal. You've built a lot of EG rooms since mine. Are they putting that detail in the plans now?

 

 

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post #15 of 15 Old 04-02-2015, 03:04 PM
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You do not need to air seal a riser to make it into a broad band bass trap. Just put as many holes in it as you possibly can. The maximum number you can put it in is always going to be limited by your need to walk on it and not fall into it and will represent a small percentage of total surface area.


If you want to make it into a tuned Helmholtz then it does need to be air sealed, and you'd need to carefully design it and probably also tune it once built.

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