The Axis Voicebox EBS Extended Bass System is not a subwoofer. It is designed specifically to blend seamlessly with the extremely fast woofers of high-performance loudspeakers in a way that avoids the bass problems of typical subwoofers and full-frequency range floorstanders that go well below 50Hz. It does this by taking advantage of psycho-acoustics, i.e., how the human auditory system perceives and processes sound.
In a full-frequency range loudspeaker system the bass and mid-range drivers are crossed over at an appropriate frequency point (and with a high rate of roll-off on either side of this frequency) so that the bass is spectrally flat with respect to the mid-range. Unfortunately, this causes excessive excitation of standing waves and room mode resonances in the listening room. The result is fat and slow “woofy” bass with poor transients. This affects bass content and the sub-harmonics of low-midrange content.
Integration of the main loudspeakers with the Voicebox EBS is done with the EBS’ Frequency and Volume controls. The Voicebox EBS has a somewhat slow roll-off at all cross-over frequencies. When properly dialed in the Voicebox EBS plays bass frequencies at below spectrally-flat levels, but just loud enough to provide the listener’s ears with hints of the fundamental frequencies of bass notes whose higher-order harmonics are produced by the main loudspeakers.
This synergism between main speakers and the Voicebox EBS gives the ear/brain a much better overall perception of the bass content, but at loudness levels that largely avoid creation of standing waves and excitation of room modes. Instead, what you hear is fast, clean, clear and precise bass with unprecedented definition.