Bose 901 VI flat?

That's right, USE the equalizer and see if you like it. If so, great, and find a way to implement the equalize. If you don't like it, cut bait and look for something else

They only sound "decent" with the Bose EQ- in your case probably in the tape loop. I think the EQ adds up to 18 db of gain in both bass and treble...you really have to use it.

I have to weigh in.  I had 901 vi’s with 100 wpc and they were a disappointment and I sold them.  I now have them again, but now in a large and difficult room, with a 10” Martin Logan sub, powered by 650 wpc mono’s.  They are astonishing in that room.  As good as anything I’ve ever owned and my go-to system.  

Nobody is more surprised than me.  In the right situation, they are more than they were ever cracked up to be.  From my experience, they need lots of power first.  Next, a sub to round out the low end.  Last, the right room.  

You must run the equalizer, which is old enough now to need re-capping.  The drivers on these are bulletproof and will last a very long time.  I’m so impressed with these, KEF Ref 5’s are being sold and I’m eyeing my new La Scala’s too.

Wow...hard to believe.

The 901 Series VI was never much for bass imho.

They sound absolutely great though as mid/highs with anything lower than ~500 hz is removed from their signal.

Though I AM a bit of an uncouth barbarian.... I use the heck out of a separate eq also, just leave the bose eq centered and adjust tone control with either receiver bass/treble (mid if it has it) or separate eq.

Don’t forget placement either, big difference depending on where they are placed.