When we finished the Exotica Monitors, we felt a strong urge to develop a 3-way model using these drivers so we could extend the bass response down toward 20Hz. The problem is, the Seas Exotic drivers are high sensitivity drivers and large high sensitivity woofers require very large cabinets and still don't play all that deep. So we searched around for another alternative.
We finally decided that the only way we could develop a reasonably-sized speaker that played down to 20Hz or there about would be to develope a powered woofer section. And that is what we did.
But rather than simply use a normal plate amp, we decided to opt for a servo-control amp that would insure tight, accurate and musical bass. The servo circuit takes its input from the regular speaker binding posts. So no separate preamp signal is required. And what it does is kind of amazing.
The servo circuit measures the input and determines exactly where the woofer cones need to be in order to reproduce the signal at its input. The woofers themselves have a second voice coil that is also hooked to the servo circuit. So the circuit can precisely determine where the woofer cone is. And if it is not exactly where it needs to be, the circuit adjusts the gain of the amplifiers, on the fly, to force the woofer cone into the precise position required. The result is extremely accurate bass.
And there is plenty of power to play with. There is a 300 watt amp behind each of the woofers, for a total of 600 watts of bass power in each speaker cabinet.
The powered woofer section was the key to designing a speaker of moderate size that can reach down to 20Hz for a truly full-range musical experience. And we didn't have to give up any sensitivity in the process. So these speakers have very lower power requirements and can be easily driven with just about any amp.