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*** 6000 cuft HT (27L x 22W x 10H) BassTrap Question *** - Gearspace.com
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*** 6000 cuft HT (27L x 22W x 10H) BassTrap Question ***
Old 23rd September 2012
  #1
Here for the gear
 
🎧 5 years
*** 6000 cuft HT (27L x 22W x 10H) BassTrap Question ***

Hi All !


We are having a new home built. Once the home is completed I will begin finishing the basement. One portion of this basement is under one of the garages (the 3 car) so it will have a SpanCrete ceiling. The whole theater will be a sarcophagus of concrete making for some great isolation. I have been planning this new build for the last 12 months or so. I have attached a link to the most current incarnation thus far. My question revolves around the basstraps I am planning. I have two in the rear corners which will be 2ft x 2ft box shaped columns (vs. wedge shaped) from the floor to the first soffit. They will be filled with fiberglass insulation. The traps will be a simple frame with a few wire mesh "shelves" on the inside supporting the fiberglass so it doesn't crush itself due to weight. The whole frame will be covered by a dark colored fabric.

In the front of the room you can see I have planned for a 1ft x 1ft column (floor to 1st soffit). In between these front columns will be a shelf of sorts which extends in front of the screen wall. The face of this shelf will be the baffle for EIGHT 18" IB318 subs.

Anyone see any cons with these basstraps? Any advice/alternatives ?

Any and ALL comments, PLEASE
Rob

Old 23rd September 2012
  #2
Gear Guru
 
1 Review written
🎧 15 years
A little

Concrete should create great isolation from airborne sound, but absolutely not for structure borne sound. Pretty much all isolation is based on breaking the conduction path.
A concrete bunker will support very strong LF modes and BIR. You will need massive amounts of the most effective treatment. If fibre only, I would suggest multiplying your current plan by 8 to begin with.
As best I can estimate, the VPR seems to be the most effective bass trap vs size. Perforated Panel with Porous Absorber trap

RPG make these also.

DD
Old 23rd September 2012
  #3
Lives for gear
 
gullfo's Avatar
 
🎧 10 years
a couple of thoughts - the closets on either side of the screen may be forming a resonant cavity which should be accounted for. another option might be to put the doors to the closets facing into the room and making them less deep and even with the face of the screen. this would then make the depth behind the screen deep enough for speakers, absorption, etc which may ultimately provide a more theater like performance. however in general you'll need a lot of absorption for LF in this room so consider the wall-ceiling corners with soffits, possibly needing some membrane or VPR panels in place etc. so once you design the overall room and screen and electronics etc, after you build the isolation shell, do acoustic measurements and then plan the final treatments based on actual measurements.
Old 23rd September 2012 | Show parent
  #4
Here for the gear
 
🎧 5 years
Quote:
Originally Posted by DanDan ➡️
Concrete should create great isolation from airborne sound, but absolutely not for structure borne sound. Pretty much all isolation is based on breaking the conduction path.
A concrete bunker will support very strong LF modes and BIR. You will need massive amounts of the most effective treatment. If fibre only, I would suggest multiplying your current plan by 8 to begin with.
As best I can estimate, the VPR seems to be the most effective bass trap vs size. Perforated Panel with Porous Absorber trap

RPG make these also.
The HT will be framed with in the concrete structure. The only contact will be the base plates of the framed walls to the concrete floor. The floor of the HT is 2ft deeper than the rest of the basement (12' pour vs. 10' pour) and is completely under a garage, not living space. The side walls will be ~ 2" from the concrete walls behind them. The screen wall will be framed as 2x6 due to the IB subs. Also, the screen wall will be covered front AND rear with 1/2" OSB. The front of the screen wall will also have 1/2" drywall as well. The framed cavities will be insulated.
The side and rear walls will be constructed in a similar fashion except there will only be 1/2" OSB on the inside of the side/rear walls (not both).

I will face the traps with the suggested plastic sheet to avoid absorbing too much mid/high.




Quote:
Originally Posted by gullfo ➡️
a couple of thoughts - the closets on either side of the screen may be forming a resonant cavity which should be accounted for. another option might be to put the doors to the closets facing into the room and making them less deep and even with the face of the screen. this would then make the depth behind the screen deep enough for speakers, absorption, etc which may ultimately provide a more theater like performance. however in general you'll need a lot of absorption for LF in this room so consider the wall-ceiling corners with soffits, possibly needing some membrane or VPR panels in place etc. so once you design the overall room and screen and electronics etc, after you build the isolation shell, do acoustic measurements and then plan the final treatments based on actual measurements.
One closet will be for the equipment rack which will be exposed on the front. The other closet is for symmetry (and access to the IB chamber).

I'll definitely incorporate the suggested soffit traps. When it comes to filling the corner traps with the fluffy stuff, should I not be concerned with the weight of the fiberglass compressing the lower layers? Just stuff the cavity and actually compress it a bit to fit more in?

I'll be re-drawing the side wall cross sections yet again. This time to incorporate the soffit traps!
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