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To be sure, the Black Hole isn't a complete solution. There's zero mapping or modeling of your room's modal patterns. There's no comprehensive surgical linearization of frequency response or decay times, evenly throughout the entire space. It's with his Spatial software calibration that Clayton performs a full measurement suite first on each speaker directly (speaker correction), then in the seat (localized room correction). This alters signal in the digital domain before the speakers put it into the room. The Black Hole only applies very basic and localized counter-phase output. This happens in the analog domain after the speakers. That's less accurate, less comprehensive, only partially effective and generally somewhat haphazard. It's no silver bullet. It's no substitute for passive devices or DSP. It's an adjunct which would seem particularly effective below 60Hz. Even so, any partial but demonstrable minimization of just one major mode would be a far more substantial benefit than whatever cables, pucks, cones or even certain component swaps could bring to the table. The average Black Hole adopter with a serious bass problem—that would be most of us—should thus be quite happy with the ratio of expense versus results and convenience.

Where the Spatial software mirrors the Black Hole hardware is in the 3rd-party concept. With Spatial Clayton relies on software that's proprietary to PureMusic. To that he adds various readily available plug-ins, an Apogee mic preamp and the same Dayton microphone. His chief contribution is signal routing and remote measurements plus calibration. With the more basic Black Hole it's all 3rd-party. Clayton's real contribution is the fearless idea—openly based on the expired Pass patent—then packaging the necessary off-the-shelf ingredients for plug'n'play. The Black Hole is not about designed here. Clayton didn't design or build the subwoofer, mic preamp, microphone or inline attenuator. And because there's no DSP, any greenhorn DIYer could replicate the basic recipe. A craftier solder slinger could even figure out how to install the minute delay line which compensates for the physical offset between microphone and woofer diaphragms.

If set up as recommended behind the listener, the Black Hole doesn't really alter what happens in front of you. If there's mud and boom occurring—definitely in the four front-wall corners—the effects thereof will still reach your ears before the microphone behind you reads it and the sub compensates (and then only in one specific spot). That's why Clayton Shaw very correctly calls it an active acoustic pressure reduction device. Inherent in the concept of dealing with acoustic energy rather than an electrical signal is that the microphone captures not just music. It sees music plus non-hifi-generated LF noise. If you've ever measured background levels when you think your room is dead quiet, you'll already know that a 30dB noise floor is very low. Unless you live very remotely in the country side, it's possible only very early in the morning. 40dB during the day is very good. Inner-city denizens might measure 50dB or more. If no music plays but the Black Hole is on and set with its gain well up as recommended—you'll hear this immediately between tracks—it will produce a steady-state drone far louder than bad transformer hum. This I found most aggravating. Was that amplified background noise?

Our townhouse rental occupies two floors. I sometimes enjoy a hot soak in the tub whilst music plays in the downstairs living room. I'm thus familiar with what bass sounds like in the bathroom. With the Black Hole nearly all of the bass was gone, period. No longer exposed to any direct sound, only reflected acoustic energy, I heard far more (complete) bass cancellation than in the listening seat. This suggested that it might really be my neighbors who'd most appreciate the Black Hole during my music sessions.

Arrow marks the Black Hole - 1 meter behind the chair against the side wall
WIth my writing desk semi-diagonal in the closer rear corner of the living room, that chair sits deep inside strong bass turbulence. For entertainment I always listen to music while I write. Then I use the balance control on my ModWright preamp to fake up more stereo than mostly mono which facing the left speaker entails otherwise. Here again I noticed the efficacy of the Black Hole. The usual boom notes in that corner were—poof—gone. I didn't do a comprehensive walkabout within the room to check up on more cancellation effects but cooking in the kitchen far behind the listening seat mirrored the bathroom effect. I again clocked significant bass elimination as though a tone control had been turned fully counter-clockwise.