I'm running Serenity Acoustic Super 7s, one of only 7 made before the company went out of business. It uses a quad of BG Neo 10 midrange drivers crossed over to a BG Neo 3 tweeter in a wave guide. Bass is handled by dual 12 inch powered servo subwoofers from Rythmik Audio in an open baffle configuration. Subs handle bass from 20hz to 200hz, and the midrange/tweeter handles everything from 200hz to 20khz.
Basically my Inspire amp drives the top part of the speaker, from 200hz to 20khz. That part of the speaker is 97db efficient and has a very, very, very flat 7 ohm impedance. Almost a perfect speaker for low powered tube amps.
