UREI Model 562 Feedback Suppressor
Five active notch filters, a $488 price tag, and a cure for the howl that ruins every monitor mix.
Overview
Anyone who has stood behind a mixing console in a church hall or a stage monitor rig knows the sound. A room resonance finds its footing, the gain creeps up, and the whole system whistles back. The UREI Model 562 Feedback Suppressor is built to stop that. UREI's own advertising in Mix (July 1979, p.21) asked whether the reader's P.A. gain was "stuck in a whistle thistle," and pitched the 562 for stage monitors, auditoriums, concert halls, meeting rooms, schools, and churches.
The mechanism is a bank of five active narrow-band notch filters, tunable to the most prominent ring modes in a room. Dial them onto the offending frequencies and UREI claimed gain could be increased by 12 dB or more, with intelligibility improved and no undesirable change to fidelity or overall room equalization. The idea is not to butcher the response curve but to carve out the handful of resonances that cause the trouble. Studio Sound (October 1979, p.65) surveyed the unit and noted the notch filters span two ranges covering 60 Hz to 6 kHz, adjustable from 0 to −20 dB, alongside a low-cut filter sweepable from 20-200 Hz and a high-cut from 2-20 kHz. An overall gain control runs from −10 dB to +20 dB.
The tunable high- and low-cut filters are the less glamorous half of the box, and arguably the more useful one in practice. Restricting bandwidth is one of the oldest tricks in sound reinforcement - trim the extremes the system can't reproduce cleanly anyway, and you gain headroom before feedback starts. The 562 puts that in the same box as the notches, so one unit covers both the surgical and the blunt-instrument approaches to taming a room.
The front panel has a bypass switch for A-B comparisons, plus a set-up switch that protects the loudspeakers while the operator tunes the filters. Connections are XLR connectors and barrier strips on both input and output. At $488.00, per UREI's own dealer pricing, it was a serious purchase for a working sound company.
UREI positioned the 562 alongside the Model 525 electronic crossover. The 525's literature described the crossover as designed to augment UREI one-third-octave equalizers and "the unique Model 562 Feedback Suppressor." UREI clearly saw the 562 as a complement to conventional equalization rather than a replacement for it - the equalizer shapes the room, the suppressor buys the gain.
One caution for anyone hunting a 562 today: the model number is a minefield. APSI built a parametrics equalizer also called the 562, a design later resurrected by API under the Arsenal Audio EQ-R24 name, and the two get confused constantly in listings and forum threads. The UREI 562 is the feedback suppressor - five notches, high- and low-cut filters, XLR and barrier strip I/O - not a four-band parametric EQ. Confirm which one you're looking at before money changes hands.
Five notches won't fix a bad system, but they will find the three or four frequencies that are actually howling and cut them out. The bandwidth controls give a second lever when the notches aren't enough.
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