Hello and "THANKS IN ADVANCE"

The 901s need equalization, the 601s don't. The only way to run both properly would be with two stereo amps with the 901 equalizer only connected to the amp driving the 901s. It doesn't matter what equalizer you use, it can only be one or the other, not both. 

This feels like going back to the 70s,  or do they still make the 901s.

baylinor

... do they still make the 901s

No, Bose stopped making them a few years ago. The 901s had a long run, though, even if many audiophiles didn't approve.

I think @russ69 is correct has to how to connect both the 901s and 601s at the same time.

A friend of mine had some 901s hanging by wires from the ceiling  in the mid 70s. For what I knew then, they were awesome. Enjoy.

The eq that runs the 901’s is a proprietary eq that nothing like a regular eq. A standard eq is increasing an incremental frequency. The 901 eq is adding gain across a wide spectrum. When they say it could damage other speakers they are talking about crossovers that can’t handle the gain or current it puts out. I still have my 901’s. They hang in my garage. They are good party speakers if you like loud with no soundstage or imaging. I hooked them up one day in my reference system and then hooked up my 301 (used for front surround) and the 301’s sounded so much better. Friend had 601’s in high school and always liked their sound for what we did. Smoked a ton of weed and hash, dropped some acid and cranked hard rock and metal. Great memories but not serious reference quality.