dbx SFX-1 (1984)
Little is documented about the dbx SFX-1 as a standalone component. What survives places it inside dbx's Soundfield One loudspeaker system, the company's first (and only widely publicized) venture into full-range speaker design. The SFX-1 appears to have been the controller/processor for that system, the electronics behind a fourteen-driver-per-channel tower that HiFI/Stereo (July 1984, p.58) described as having "almost unbelievable stereo imaging."
The Soundfield One system was not cheap. Two speakers and the controller - which likely included the SFX-1 - retailed for $2,500. The controller's front panel had a LOW-FREQUENCY COMPENSATION slider to boost or cut deep bass below 100 Hz. It also had a HIGH-FREQUENCY COMPENSATION slider that worked as a spectral-tilt control, so the listener could adjust the overall frequency balance to suit the recording or the room. High Fidelity (November 1984, p.26) called the system a "sit-anywhere" loudspeaker, which suggests unusually wide dispersion.
According to period reviews, the SFX-1 was unusual because it shaped the speaker's radiation pattern. The input signals to the drivers were individually equalized in phase as well as amplitude, and that kind of control was rare in consumer audio in 1984. The reviewer at HiFI/Stereo (July 1984, p.61) wrote that the imaging "lived up to the manufacturer's claims in full measure," and noted that the system's control flexibility allowed considerable variation in the overall sound. No standalone specifications for the SFX-1 - power output, frequency response, input impedance, or dimensions - have surfaced in the available documentation.
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