The mono NHT SA-3 was made not only to drive the SW3P slave sub, but also to be used in a biamped system the 3.3s and 2.9s or even drive two SW3Ps. It has adjustable gain, variably adjustable crossover and a phase switch. One thing though, unlike the SA-2 or MA-1 which accept both speaker level and line level inputs, the SA-3 only accepts line level inputs.
For many years I had used the SA-3/SW3P combo but in recent years found a combination of a Paradigm X30 and older Bryston 4B to be superior. But this combo would probably cost more than double that of a used NHT SA-3.
For many years I had used the SA-3/SW3P combo but in recent years found a combination of a Paradigm X30 and older Bryston 4B to be superior. But this combo would probably cost more than double that of a used NHT SA-3.