Greg & Trandanny: I am using a vertical line array of very small surface area E-stat panels for tweeters. The line array offers better vertical dispersion and offers sustained output into the farfield. This helps to overcome some of the limiting factors in terms of problems that people run into with limited SPL's with panel type speakers. The use of multiple panels of limited surface area also helps to minimize the effects of beaming that one gets when using one larger panel to do the same job. I have appr 800 wpc driving these arrays with the impedance that they present to the amps.
Mids are handled in a similar fashion. I'm running E-stat panels that are 12" wide by 36" tall. There are two of these, one stacked on top of the other. As mentioned above, this acts as a line array and helps with maintaining a higher SPL at the seated listening position. It also minimizes the problems associated with limited vertical disperion i.e. changes in sound when you move your head, or the differences that you hear when laying back, sitting up straight or standing up. Once again, i have appr 800 wpc driving these arrays with the impedance that the amp sees.
Lows are handled by four woofers per channel. These are configured in a rather unique array. In order to duplicate the radiation pattern of the panels and achieve proper blending, they are configured in a bi-polar arrangement and are running in a push-pull configuration. The cabinets are both sealed and stuffed with a low Q design. The stuffing helps reduce the impedance peak at resonance making the drivers far more controllable. It also helps to minimize cabinet vibration. Using fiberglass adds apparent volume to the internal size of the box, increasing low frequency extension. Use of a low Q in the tuning means that the bass is phenomenally tight and well controlled with no ringing.
Bi-polar bass designs reduce room loading effects to a great extent ( as mentioned by Duke / Audiokinesis in many of his posts ). It can be tricky to set up though as anybody with bi-polar or omni speakers will tell you. When you do get it right though, bass response sounds phenomenally clean and natural.
Using a push-pull configuration in the manner that i am lowers distortion by appr 50% at low frequencies and slightly increases bottom end extension. Since the woofers are working in a push-pull configuration, each "motor" shares the load. While one woofer is pushing air away from the box, the other is compressing air within the box. As such, the work load on each voice coil is reduced and transient response is increased. This also reduces distortion to a great extent.
If you've ever read any test measurements on speakers, the woofers are typically producing somewhere in the area of 5% - 10% distortion under load at low frequencies. I am probably at less than 2% due to the approach that i'm using. Part of this is due to the push-pull arrangement and the other primary reason would be the fact that i have multiple woofers sharing the load. As such, none of them are ever "pushed".
The drawback to this approach is that you need two drivers to do the work of one i.e. one produces a positive wave while the other a negative wave. Since you are running two identical drivers in parallel, the impedance is cut in half. That is why i have four drivers, in effect giving me the output of two "super duty, low distortion" woofers. In order to overcome the amount of reflected EMF ( ElectroMotive Force or "voltage" ) in such an arrangement, you need to have a lot of muscle. As such, I have an easy 1000+ wpc driving these.
The tweeter and midrange amps are products of the "old" Threshold Corporation. I don't know anything about the new company at all. While both the tweeter and mid amps are rated for the same amount of power, they are different models. One has more "air" and i use that for the tweeters. The other has slightly increased warmth, so i use that for the mids. The woofer amps are Perreaux's and seem to work quite well for this application. I am running Goertz MI-2's for the tweeter and mid panels and i am have two runs of Fulton Gold for the subs. For those of you that have never seen Fulton Gold, it is made up of fine strand four gauge conductors : ) Sean
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