My friend who owns a pair of classic 4 and runs them with two Rotel RB 970BX amplifiers with great results. Since both amps are in exactly the same. He uses one stereo amp for each speaker. One channel runs the lows and the other channel runs the highs. They sounds better than I could ever imagine for a $2000.00 set of speakers . He uses the stock designed passive crossovers which I modified. The crossovers are now set up with sonicaps, Alphacore 12 awg copper foil inductors, Cardas speaker connectors and better internal wiring. I also replaced the dome tweeters and super tweeters with a new set of Aurum Cantus 2GSIs ribbon tweeters. This also required the removal of super tweeter crossover frequency point. This really made the highs much better. The highs extend way up, and now sound natural and much faster. It was a crazy mod but it made this a world class speaker system. I had to use several resistors to get the new tweeters to blend. I had a machinist machine new faces out of billet aluminum for the Aurum Cantus Ribbon Tweeters so that they would fit in the stock factory NHT holes. I also lined the insides with Dynamat, and had better stands made out of steel, filled sand. It is crazy good. In fact I am going to build my self a set sometime this summer.
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