This article is part of a series; see Speech Reinforcement.
PolyFusion 755: of interest, but very old. The 755 may be difficult to obtain, but it is the only device I know of that uses simple frequency shifting instead of narrow notch filters (and is marketed as a suppressor). See the Rane publication “Understanding Acoustic Feedback & Suppressors”.
dbx 215s: recommended for certain cases. This dual channel 15-band equalizer is great for making minor adjustments during live use.
Peavey CEQ280a: of interest, but very old. This is a 29-band equalizer with automatic room equalization and a pink noise generator. It is simple and seems to work well, though room equalization with sine sweeps is better (as is done by the TOA M-633D). It is recommended to completely disconnect the RTA input before live use: on multiple units a connection there (balanced cable only, no microphone) has caused intermittent noise on the equalized signal.
Lectrosonics EQ1: of interest, but very old. The EQ1 might be a possible (better?) alternative to the CEQ280a, but it is not easy to obtain.
TOA M-633D: recommended. This mixer offers an excellent set of features: 1U rack space, automatic feedback suppression, automatic room equalization with sine sweep, plenty of input/output channels, and a simple analog interface. See Design 3 which integrates this mixer.