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The woofers occupy their own sealed chamber of ca. 40 liters cubic volume. With the passive version the customer can choose between sealed and vented loading. The active is always sealed. For one, two 180-watt amps per speaker take up space to eliminate a port tube. More importantly, why bother with vent boosting in the first place when amplitude can be controlled actively to make an honest 20Hz if desired?
The twin 22cm units with carbon-fiber membrane work toward this goal in push/push config with inductive motion sensors. Their real-time positioning feedback affords instantaneous correction in the drive electronics. Such a servo arrangement not only enables true 20Hz extension (which given the drivers and enclosure parameters wouldn’t be possible otherwise) but achieves significantly cleaner stop and go performance than passive solutions are capable of – claims the Aachen speaker house.
Semi-active drive does have very real advantages. Those could make one wonder. Why aren't similar solutions more popular? Really, why sacrifice the flexibility of adaptive performance by going fully passive? Within reason bass amplitude is variable. This no longer requires front-wall proximity for added warmth which could compromise soundstaging. Increase bass output instead. Or when neighbors and domestic peace mandate a lighter bass balance and close-wall placement, reduce bass output to avoid boom. So simple, so convenient!
Then there’s the positioning of the filter network. Active places it ahead of rather than behind the amplifier. This connects amp and driver directly to improve damping factor which, all else being equal, results in superior control. That advantage compounds yet further with self-corrective servo circuitry just as—hello—the Avancé exploits fully.
Which begs a question. Why not fully active? One possible reply is to not take away from the endless mix’n’match choices of which hifi fanciers are so inordinately fond. Sonic differences between third-party amps and semi-active boxes should be less than usual since the amp inside the speaker remains the same. Semi-active speakers also open the doors to low-power amps which no longer must deal with power-guzzling woofers and their more reactive behavior.
Going active even in part is more expensive of course. The amp-fitted Audiodata Avancé costs €6.130 more than its passive sister. If you already own your power amps that is. If not, certain savings are possible by shopping for smaller cheaper amps. Brute perfectly matched force is handled already. But enough friend zone now. I was ready for the end zone.