Any info from a sales rep should be taken with a shaker full of salt. Since their subs don't have it, you don't need it...that's what I'd expect to hear from them...are they going to say their subs are defecient because they don't have it?...not likely
I concur. Anyway, the proof is in the pudding. The Descent and Depth are two of the most musical, powerful, and fast subs on the market. I don't think they added servo control to "correct" a faulty design. They spent a lot of time and money to research innovative ways to design a sub that can provide tons of power, stop and start on a dime (to keep up with their electrostatic panels), and sound good with movies or music. By all accounts, they succeeded admirably.