Be aware that all Axiom subs to the date use a single input, unless you want to use the high speaker input, which IMO defeats the purpose of having the amp there, as you are using your amp to feed the sub, and just the Xover is used...what requires a dedicated output from the stereo amp, for subwoofer use, or create a box to sum the two channels, without mixing them...which 99% of the time is not available. That was the main reason I opted for a Velodyne, that, as many other subs in the market, use the two channels and sum them internally, and I'm very happy with it, as it offers also room corrections, different EQs (which I do not use) and many other features that Axiom subs does not offer...Not saying that they are bad or worse, just different, and had special requirements, a real shame I do not have a dedicated pre-out for sub use in my Marantz...
