Wayne Parham Messages: 18752 Registered: January 2001
Illuminati (33rd Degree)
A four π speaker modified to be sealed has no bass. The standard vented version goes lower, which is important for modal smoothing. If you're running three speakers, the center can probably be made sealed but I definitely wouldn't do all three that way. The three π speaker has a little more output below 50Hz, but is also 3dB less efficient through the passband. This may not matter considering the fact that subs are used but it's something to consider.
As for the rest of the comparison - from about 60Hz up - it really is about the midwoofers chosen. Both are really good speakers, and I think both will satisfy the most discriminating listeners. You just have to choose which woofer family you prefer, JBL or Acoustic Elegance.