@mapman wrote:
"Also lower bass frequencies take exponentially more power to produce flat response so you better have plenty of good clean amp power in those subs too to carry the load. The more the better. Not enough power in reserve is perhaps the most common cause of bad sounding bass."
Well, it depends on the specifics. Some subs rely on aggressive EQ to go deep. The DEBRA and Swarm systems do not.
The DEBRA and Swarm systems use individual subwoofer modules whose native response is the approximate inverse of typical room gain from boundary reinforcement (which is +3 dB per octave south of 100 Hz, according to Martin Colloms). The Debra and Swarm subs have a native response that falls at about 3 dB per octave from 80 Hz down to 20 Hz. This is a more gentle rolloff that you can get from an unequalized sealed box.
In many smaller rooms this ends up giving you more low end than you need. One option is to invert the polarity of one of the four subs. Doing so often further improves the in-room bass smoothness in my experience. And since small rooms are the ones that usually have the most room for improvement in the bass region, this works out well. This is not the only trick the DEBRA and Swarm systems have up their sleeves - they are highly adjustable in the acoustic domain, and still have EQ available in their amplifier if needed.
One advantage of not relying on power-hungry EQ to go deep is, we’ve never had an amplifier fail due to being over-driven. And we’ve only had one woofer failure in twelve years. That's less than 1%, and it was an 8" woofer (which we no longer use) in an early version of the Swarm.
Duke
Swarm designer