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In the Forum: Horn-Loaded Speakers
In the Thread: Infinite Baffle Implementation and "Compression Sub-bass"
Post Subject: The bigger viewPosted by Scott L on: 12/13/2016
 skushino wrote:
Guys, my attention has been elsewhere the past couple of weeks. 
The catalyst for the original post was to go beyond the usual "speakers in a room" approach, and use the room itself as an integral part of the sound.  IB seemed like an attractive way to make this happen.  The IB "rule of thumb", manifold exhaust area >= Total Sd, made me wonder about any potential benefits resulting from purposely undersizing the opening to load the drivers with mild compression.

My original idea was a baffle style IB, similar to the picture from ScottL.  But many users report that wall manifolds require heroic bracing to mitigate flex.  The manifold implementation side-steps around this problem by balancing the physical driver movements.  The sole downside I see with a manifold is managing the exhaust area.  This led to my idea that a purposely undersized exhaust could potentially result in more pleasing bass.  My manifold placement uses the floor / wall boundary to support the bass output as well.  Sound?  Well this is one of those crazy audio projects that will be impossible to predict the outcome until after building.

My woodworker is visiting on Thu to discuss the build.  I expect the manifold dimensions will be defined by building and implementation considerations, like spacing between the floor joists, and bracing.  Will update further.

 Paul S wrote:
Scott, I'm guessing the installation shown in the photo makes lots of LF, but how does it provide balanced, "free air" loads on both sides of the drivers?

Best regards,
Paul S

It's difficult to see in the picture, but this IB build was done in a corner, a "strut out",  behind which was an existing closet of about 500 cubic feet.
The 4 pairs of 15 inch drivers are force coupled at the driver frames AND magnet-to-magnet. The pvc magnet couplers have holes drilled into them, to the same area as the vented pole pieces. In this case, YES, the manifold exit is slightly greater than 8x SD, but I have also done push-pull, slot loaded bass where the slot exit (manifold) is 2:1  (iow 1/2). For some reason I can NOT see the very pictures that I attach, but obviously, you guys do. So, here please see the entire system. The IB handles bass below 60Hz only. Of special note: there is NOTHING between the loudspeakers. I don't need to parade my gear for the whole world to see as if I were some gaudy want-to-be, living in Las Vegas. Besides, anything stacked between the loudspeakers ruins
the image/sound stage.

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