04-22-12: Ngjockey
>Personally, the concept of the drivers facing each other seems counter-intuitive for a dipole.
There aren't enough pictures to see what's going on with the Celeston, although opposing drivers are fairly common.
W-frames let you get more displacement out of a given enclosure (spouse approved, or in Monte's case a pair of nine foot towers not four) volume and provide force cancellation to limit structure borne vibrations which could pose problems with floppy floors radiating and sound transmission.
http://www.linkwitzlab.com/woofer.htm
Previously I stated that in a domestically friendly 14" deep enclosure excrusion was 4X that of a monopole and by 20Hz you have 8X the excursion. That's enough to get noticeable movement at high levels in a 70 pound enclosure with a pair of forward facing drivers at the bottom. It's not audible on a rigid floor (radiation from the rocking cabinet is dipolar and therefore rolling off at 6dB/octave due) but could be problematic otherwise.
>The effect would be much the same as a boxed speaker. Ya, I can see how it bring more control to high Q drivers and reduce that boomy sound.
It has nothing to do with a boomy sound.
>The "Direct Servo", along with suitably designed drivers, ameliorates that condition to some degree.
Using electronics you can adjust the system high pass response to pretty much anything you want. Siegfried Linkwitz likes a second order high-pass Q=0.5 with resonance at 20Hz. It sounds good and I've never bottomed my woofers on music (I'm getting 105dB peaks on acoustic recordings with a lot of dynamic range and have had modern music at 95dBC SPL average). John Krevosky has suggested allowing a third order roll-off below system pass-band so subsonics are less an issue (second order acoustic roll-off means excursion is still doubling with each octave lower at a given program material level until you pass the woofer's lowest pole which can be in the single digits for a low-Q woofer). That can be a problem with vinyl though.
