Not trying to thread jack but those things are fascinating. Those dual opposed vents on top, appear to be connected to the dampening structures that angle off either side of MTM assembly. Do they help round out mid bass response from the W18's while also eliminating any other resonances that are trapped?
Over built is the first thing that comes to mind, which means you and I have something in common!
They are two reverse tapered aperiodically damped transmission line speakers. They are damped to the point of just producing one peak of impedance. The pipes are tuned half and octave apart. As you can see from the frequency response the hand off between the two pipes is not perfect, but very good. Driver assist from the pipe loading is from 12 to 100 Hz. The drivers are tightly controlled by very uniform loading over at least two and a half octaves. The bass accuracy is astonishing. Roll off is second order in the bass. They are 2 to 3 db down at 20 Hz, 10 db down at 15 Hz and 15 db down at 10 Hz.
This form of loading has its origin in the Gedeckt organ pipe. Paul Voight first did this back in the thirties, but taper now is generally the reverse of his taper.
This is the smaller pipe.
This is the first part of the larger pipe.
It goes around the back of the shorter pipe.
Top view coming up to the undamped port area of the long pipe.
Side view.
An active solution allows the upper driver in the long pipe to carry the BSC for the smaller drivers in the shorter pipe.
Both drivers in the large pipe operate below 60 Hz and carry the LFE signal.
This is the center line.
It uses two coaxial drivers.
Again BSC is active through an electronic crossover. The upper tweeter is a fill tweeter for some cancellations in the 9 to 12 KHz region and flattens response to 20 KHz. A controlled cone of sound is projected over the listening area, and interference between mains and center in minimized. Blend between the three speakers is seamless.
