Well that certainly is counter-intuitive. What isn't clear to me, then, is what becomes of the room modes? Since they are determined by LWH measurements, shape of the area, etc., how can an additional sub change a fundamental of the room? Or is it a matter of moving it around to a more desirable (less audible) place???? The science of multiple subs says the exact opposite. What the secondary subs do is to cancel out some of the modes created by the other sub. Eliminating modes by definition fixes the problem at that frequency. Here is the actual measurements across multiple seats with one sub from my article on bass optimizations: http://www.madronadigital.com/Library/BassOptimization.html
Now with four subs:
We see clear improvements. The reason is that by eliminating some of the room modes we have actually widened the sweet spot, not made it worse.
Looking at the 3D spectral plots it looks as if that's what is happening, with the results rather precisely defined for uniformity in a specific area... It would be interesting to see how the plot would look if the corrections were acoustic and not with additional subs? Wider/broader areas of acceptable performance perhaps? Have you compared them?
I didn't mean that the speakers were directional. The angle of the speakers pointing downward from the soffit is very similar to the angle of the whole rear wall trap in the back of the room. It's a full width/height slot trap with the slot side facing forward and tilting back starting at about 2' above the floor. Looking at the blueprints, there's a resonating chamber full width at the base (below the 2' level). It looks like the incoming sound is expected to reflect off the trap's back wall (perpendicular) at the opposite angle downward to its arrival. It would meet stiff fiberglass and reflect backward to the wall again at the opposite angle downward, and finally on down to the resonant chamber where it would be absorbed and effectively disappear.Bass frequencies radiate in all directions. Not sure what you mean about directional speakers in this regard. How did you find out it was doing nothing?
The slots are alternating 1.5" solid, 9/16" open to trap, 5/8" thick redwood. There's a layer of burlap and 2" solid 703 type fiberglass sheets before entering in the compartment. I only have blueprints, no specs about what each area trap is targeting frequency-wise.
I noted LF standing waves when standing at the rear trap, and measured them as well. If the trap was truly effective I should not have a build up there. Also, adding ceiling high corner bass traps at each corner of the rear of the room made a significant change in response in the listening position.
There are other full height small-slot traps at front sides and middle sides of the room, and a ceiling mounted trap with large chamber behind it (ceiling attic). They all have the usual burlap and 703 fiberglass sheets as first-encountered after the slots. None of these other traps have any LF standing waves in front of them.
Inlines in just the sub channel would not be too signficant unless they were really really poor.And you are saying that with respect to inline electronics that are only in the path to the sub?
--Bill
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