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Discussion Starter #1
Hey guys,

I'm currently in beginning stages of designing my home theater in my basement. It will be in a 18x25x7.5 rectangular room. The room will contain 2-4 diy ~10cft 18" subs, ascend towers and center with RAAL and 4 surround speakers. Screen is 130" projector located somewhat off-center on 25' wall. I am very new when it comes to acoustical treatment, and I only have my research on a few forums to go off of.

My question really boils down if to using 1/8" sheetrock walls as a kind of panel absorber bass trap will benefit over just building normal walls and trying to bass trap inside the room. The 1/8" sheetrock walls will be at least 8" from the concrete/adjacent room walls with insulation filling the gap (but not touching the sheetrock). I can seal the cavities behind the wall airtight as well if needed.

I'll likely have enough room in the two back corners (where the subs will likely be located) to put some 30" fabric faced superchunk bass traps, and my low (7'5") ceiling will be fabric covered with insulation to help it "appear" taller acoustically. Also, behind my front screen/towers I could (if recommended) do a false fabric wall (or scatter plates if high/med absorption is too much) and put in a larger 2-3 ft deep superchunk trap by expanding into an unfinished bedroom ,only about 10ft of 25ft wall can be expanded though. So, this would result in a 10x3 section added onto a rectangular room, making it irregular shaped, so I'm unsure if it would hurt more than benefit or not. I have some primitive Microsoft paint drawings that I have attached, the first is the room layout, the second is the proposed walls/insulation trap design.

Any input is appreciated!
 

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Hey guys,

I'm currently in beginning stages of designing my home theater in my basement. It will be in a 18x25x7.5 rectangular room. The room will contain 2-4 diy ~10cft 18" subs, ascend towers and center with RAAL and 4 surround speakers. Screen is 130" projector located somewhat off-center on 25' wall. I am very new when it comes to acoustical treatment, and I only have my research on a few forums to go off of.

My question really boils down if to using 1/8" sheetrock walls as a kind of panel absorber bass trap will benefit over just building normal walls and trying to bass trap inside the room. The 1/8" sheetrock walls will be at least 8" from the concrete/adjacent room walls with insulation filling the gap (but not touching the sheetrock). I can seal the cavities behind the wall airtight as well if needed.

I'll likely have enough room in the two back corners (where the subs will likely be located) to put some 30" fabric faced superchunk bass traps, and my low (7'5") ceiling will be fabric covered with insulation to help it "appear" taller acoustically. Also, behind my front screen/towers I could (if recommended) do a false fabric wall (or scatter plates if high/med absorption is too much) and put in a larger 2-3 ft deep superchunk trap by expanding into an unfinished bedroom ,only about 10ft of 25ft wall can be expanded though. So, this would result in a 10x3 section added onto a rectangular room, making it irregular shaped, so I'm unsure if it would hurt more than benefit or not. I have some primitive Microsoft paint drawings that I have attached, the first is the room layout, the second is the proposed walls/insulation trap design.

Any input is appreciated!
I personally would look into flipping the room and have 2 rows of 4. That layout would create some viewing angle nightmares... The long way would create a better acoustic plan from what I can tell. Then again the hall and sliding door do throw a kink into that plan. The room is wide enough at 18 feet to allow you to get away with a few options with flipping the room. some of the guys here would be better suited to help you then me. The unfinished bed room how big is it ? could some rel estate be taken from it to create an entry from the hall to mid theater room. Got any pictures of the space ?
 

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Discussion Starter #3
Thanks for the suggestion, but I don't have the WAF to cover the window permanently with a screen Also, we already have the couch/tables we want in a temporary room, and it doesn't fit well along the width of the room.

The unfinished bedroom is large, much larger than a guest/teenager bedroom needs to be, so cutting 3 ft off the length is no problem.
 

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Why so wide? And with that 3' of bedroom space available, would something like this be an option with the Mrs?


And there's always the possibility of two rows with the extra 3' depth, when combined with the narrower width.
 

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My question really boils down if to using 1/8" sheetrock walls as a kind of panel absorber bass trap will benefit over just building normal walls and trying to bass trap inside the room.
You'll probably get some membrane absorption from very thin drywall, but you have no assurance it will be at a frequency range that's useful in your room! So I suggest normal drywall and normal bass traps.

You also need more than just corner bass traps. With the large reflecting wall directly behind the listeners, you'll do best by making the entire wall one giant absorber. Ideally you'll put 4-inch thick 705 rigid fiberglass spaced a foot off the wall, with R38 fluffy fiberglass filling the gap. That not only covers the entire wall, but also handles the wall-floor and wall-ceiling corners, plus much of the wall-wall corners too. Of course, you also need reflection panels on the sidewalks and especially on the ceiling.

--Ethan
 

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Discussion Starter #6
Why so wide? And with that 3' of bedroom space available, would something like this be an option with the Mrs?


And there's always the possibility of two rows with the extra 3' depth, when combined with the narrower width.
Thanks for the suggestion, however, we have decided we like one large single row over multiple rows (something we have in the temp room now) for get togethers. Also, my drawing is somewhat skewed, in that the distance between the sliding glass door edge and the hallway is only about 11ft.

You'll probably get some membrane absorption from very thin drywall, but you have no assurance it will be at a frequency range that's useful in your room! So I suggest normal drywall and normal bass traps.

You also need more than just corner bass traps. With the large reflecting wall directly behind the listeners, you'll do best by making the entire wall one giant absorber. Ideally you'll put 4-inch thick 705 rigid fiberglass spaced a foot off the wall, with R38 fluffy fiberglass filling the gap. That not only covers the entire wall, but also handles the wall-floor and wall-ceiling corners, plus much of the wall-wall corners too. Of course, you also need reflection panels on the sidewalks and especially on the ceiling.

--Ethan
Thanks for the suggestions Ethan. Off the back wall, if I put 4 inch 705 / rest R38 what do I face the bass trap wall with to not absorb too much highs (or do I even need to worry about that for the back wall?) Would you recommend the front wall also having this mix of insulation, and is making the room "non-rectangular" worth this addition. Also, when you say "reflection panels" are these absorbers (ie 703/705 panels) to cover the reflection points or a hard reflective material to prevent too much mid/high absorption from my highly absorbing fabric covered ceiling.
 

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Absorbers on the rear wall behind you need to absorb all frequencies including mids and highs. Those are very strong, very damaging reflections. Especially when the wall is not very far behind you.

Yes to more bass absorbers on the front wall. You could use FRK rigid fiberglass there to absorb even more bass while reflecting some mids and highs.

Yes, by reflection panels I mean absorbers at reflection points:

Early Reflections

--Ethan
 

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Discussion Starter #8
Absorbers on the rear wall behind you need to absorb all frequencies including mids and highs. Those are very strong, very damaging reflections. Especially when the wall is not very far behind you.

Yes to more bass absorbers on the front wall. You could use FRK rigid fiberglass there to absorb even more bass while reflecting some mids and highs.

Yes, by reflection panels I mean absorbers at reflection points:

Early Reflections

--Ethan
Ethan, Thanks again for the help!
 

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I'd use a single layer of 5/8" damped drywall (e.g Soundbreak XP). It will provide better MUCH results than a single sheet of normal drywall. You will still need in room bass trapping but you have given yourself a good foundation rather than having normal sheetrock which resonates at a few frequencies. If you are framing off the concrete wall then also do 24" OC framing. You should have insulation in the cavity. Whatever you do, do not just put the sheetrock on furring strips on concrete. That's a recipe for a horrible resonance.
 

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What are the main advantages to using acoustic fabric like this:
http://www.acoustimac.com/dmd-acoustic-fabric/

compared to a breathable (can blow through) fabric like/similar this: http://www.walmart.com/ip/David-Textiles-Easy-Care-Travel-Knit-Fabric-by-the-Yard-58-W/34185816
The DMD is supposed to be very nice, I've heard. It will probably have a nicer overall finished look to it. More importantly - check into the flame retardant characteristics of anything you hang on your walls. I think that the DMD fabrics are safe while generic fabric not designed for architectural installation might not be. Double check.
 

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Thanks for the suggestion, however, we have decided we like one large single row over multiple rows (something we have in the temp room now) for get togethers. Also, my drawing is somewhat skewed, in that the distance between the sliding glass door edge and the hallway is only about 11ft.



Thanks for the suggestions Ethan. Off the back wall, if I put 4 inch 705 / rest R38 what do I face the bass trap wall with to not absorb too much highs (or do I even need to worry about that for the back wall?) Would you recommend the front wall also having this mix of insulation, and is making the room "non-rectangular" worth this addition. Also, when you say "reflection panels" are these absorbers (ie 703/705 panels) to cover the reflection points or a hard reflective material to prevent too much mid/high absorption from my highly absorbing fabric covered ceiling.

I have one row - 14' wide La - Z - Boy sectional sofa. With both a 122" diagonal 16:9 screen and a 128" diagonal 2.35:1 screen, with seating at 11.5' to 12', it work just fine. Viewing angles are fine too.




 

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My question really boils down if to using 1/8" sheetrock walls as a kind of panel absorber bass trap will benefit over just building normal walls and trying to bass trap inside the room. The 1/8" sheetrock walls will be at least 8" from the concrete/adjacent room walls with insulation filling the gap (but not touching the sheetrock).
I've never seen 1/8" sheetrock. Is it available at building supply warehouses or only from specialty sound suppliers?

1/8" sheetrock seems like it would be very fragile and hard to work with. Hardboard would be more durable. It's 1/8" thick and available at HD, but I don't know if it would have the same acoustic properties as the 1/8" sheetrock you're using.
 

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I've never seen 1/8" sheetrock. Is it available at building supply warehouses or only from specialty sound suppliers?

1/8" sheetrock seems like it would be very fragile and hard to work with. Hardboard would be more durable. It's 1/8" thick and available at HD, but I don't know if it would have the same acoustic properties as the 1/8" sheetrock you're using.
I don't think I've seen 1/8" either - in 20 years of construction. Maybe 1/4" sheet rock, but 1/2" and 5/8" is way more common.
 

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Hey guys,

What are the main advantages to using acoustic fabric like this:
http://www.acoustimac.com/dmd-acoustic-fabric/

compared to a breathable (can blow through) fabric like/similar this: http://www.walmart.com/ip/David-Textiles-Easy-Care-Travel-Knit-Fabric-by-the-Yard-58-W/34185816

Just trying to see if spending 2x as much will be worth it. I also don't want to compromise the absorptive nature of my ceiling and rear wall by using bad fabric
I would go for the DMD. Between it and the sheet of mineral wool insulation, I would add a layer of this stuff:
https://www.onlinefabricstore.net/black-fleece-fabric-.htm
Both the DMD fabric and the fleece fabric are 100 percent polyester so they are fire retardant. The fleece prevents loose mineral wool fibers from creeping into and escape through the DMD fabric, makes the panel look nicer by completely hiding the mineral wool insulation from view (because the DMD fabric is a see-through type of fabric), and absorbs sound just like the mineral wool insulation does.
 
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