I have searched the forum but cannot seem to find the answer to my question.
If I were to build a false wall of a certain material, how would I know which frequencies will pass through and which will be reflected? Do you konw of any litterature or web-site stating something like material, thickness and lower limit of frequencies it reflects?
The reason I ask is, that I am looking to build a baffle wall where I will have lots of space behind it which would work perfectly as a bass trap to mitigate the length mode. I would still like to use the wall for the extra SPL from 80'ish to 200hz for the LCRs though, which means it should reflect from 80hz but lower frequencies should pass right through.
I'm no expert but here are my thoughts. If possible I think it's way better to have a really hard speaker wall with some damping on the outside so that the bass gets maximum reinforcement and then have the trap in the back of the room. You want the bass to pass your ears with full force but then be damped.
Bass traps are about reducing standing resonant waves not about killing sound that would pass your ears, If you have openings in the baffle wall near the room boundaries (walls, floor, ceiling intersections) and fill that space behind the baffle wall with absorptive material it will absorb some bass energy.
Looking at the specs on the M2: Continuous/Peak SPL@ 1m 117 dB /123 dB
Then add the Sub18 which claims: Maximum Peak Output (2π) 137 dB SPL As an add-on to JBL’s M2 Master Reference Monitor system, the SUB18 allows three times greater output from the system.
Are you sure you need the extra SPL from a baffle wall? I am questioning doing one for my room. It's not as easy to build as I thought it would be. It also takes up space, making the finished room seem smaller. I know I don't need the extra SPL. I was going to do it for SBIR, but JBL is advising the M2's should not be flush mounted in the baffle wall.
Where did you read that JBL does not recommend flush mount? It goes against everything I have read from JBL so far.
I guess the SPL is good enough without the baffle The previous times I have heard baffle wall installations, I think it has improved sound-panning as well. I am currently inclined to do the semi-baffle where it will not extend to ceiling/floor. I think it would be a mistake to not use the space behind the baffle for bass trapping.
Refarding theater designer, I actually asked Nyal, but unfortunatey he does not provide service outside the US. (I'm from EU).
This is exactly what I did. While I'm hazy as to how much space is behind my baffle wall, it's at least 20 inches packed with pink fluffy insulation, except for the subwoofer locations. The baffle wall has gaps on either side of the center baffle wall section to allow additional sound to enter the gaps and be absorbed by the fluffy (don't remember the expected frequency to be absorbed). I have not measured (don't have subwoofer amp yet), but my theater & baffle wall designer is Nyal Mellor of Acoustic Frontiers in case you want to ask them about the science behind such a design.
Same here, and it sounds like same basic design. I talked to Nyal and he said there are still benefits to doing it and encouraged me to follow through with it.
If you do have someone design the baffle wall, Nyal's plans for it are very detailed. I got a 3D model that shows the exact size & location of every piece of wood. That's a companion to the PDF which lists all of the acoustic treatments & implementation notes for the baffle wall. From a documentation / clarity perspective, I thought it was excellent.
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