Axiom Home Page Forums General Discussion Home Theater Possible Bass Trap in Wall Cavity

Hello everyone,

I am reaching out to see if my idea of using an old fireplace wall cavity as a make-shift bass trap is worth considering or if it will be unlikely to have any meaningful benefits. A summary of the room (currently under construction - we had a flood several months back):

Approximately 23ft x 24ft x 7ft6". Not a dedicated area, is open to rest of home via stairway. 7.3.4 setup with the following:
- Axiom M80, VP180, QS8s, QS10hps, two DIY sealed 18" subs, one PSA S3601, four RSL C34E MKII atmos.

The flooring will end up being a floating subfloor (dri-core insularmor) with LVP plank on top, area rug between the MLP (two seats) and the front LCR. There is an HVAC channel that runs through the middle of the ceiling, which will be drywalled, and on either side there will be a drop ceiling using USG/CGC Mars acoustical panels (2ft x 2ft) - 4" space between drop ceiling and ceiling joists.

Projector and screen (acoustically transparent) will be ceiling mounted. I do not currently have any room treatments but am planning to buy three 2ftx3ftx2" panels for front wall just behind LCR, and one 32"x4ftx2" panel behind the MLP on back wall. I am also considering two 4ft high (16" x 16" depth) bass traps to be placed on floor in two of the four room corners - behind the right channel speaker, and on the right wall behind MLP (this one will be in front of a MDF cabinet door, but it will be opened infrequently). The other two corners will not be possible to place bass traps due to a door and bar cabinetry.

MLP is about 2/3s front wall, and 1/3 from back wall.

Due to room limitations, the right front speaker is placed very close to built in painted MDF cabinetry (not yet on-site), the left speaker is fairly open to the other half of the living space. Other than the front and rear wall abosrption, I am unsure how else I can easily add any other type of treatments to the room (absorption or reflection) but am open to any and all suggestions.

Attached to this link: https://postimg.cc/gallery/qp1ncQq , you will find various photos of the current state of the basement, and a rough diagram made using GIK Acoustics free online room builder utility (all green items are speakers, the big radiators are supposed to be subwoofers - they did not have a subwoofer icon to place in the room), I also added an old photo of the room for additional context.

On to the actual question: At the mid-point of the right wall in the room (fairly close to MLP) will be a 6ft wide x 7ft high x 14" deep stack ledgestone wall with a gas insert fireplace, the bottom of which will be approx. 8" from floor. Behind this brick wall and framing will be a further cavity where the old fireplace was vented (approx. 6ft high, 3ft wide, 16" deep).

If I were to fill both of these cavities with a combination of something like owen's corning 703/705 and fluffy pink insulation, and then have two or three false vents (say 4" x 8" each) near the floor (under the fireplace), could it allow for sound to pass behind the brick wall and get absorbed by the insulation, thereby acting as a very large bass trap? Sort of how a large seating riser is sometimes dual purposed as a bass trap?

Any thoughts, insights, suggestions, questions are welcome.

Thank you in advance,

Photo thumnails below (not sure if this will embed properly):