Magnepan 1.6 active 24db slop better than stock?

Had the 1.6 and did exactly what you are considering - biamped with 24 db slopes. This was a few years ago and I can't remember the xover frequency but I am guessing it was around 1.5k. It was much more transparent with tighter bass. I played with the phase of the tweeter and I think I preferred normal phase. It's pretty easy to try this yourself. The speaker also becomes much more efficient.
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Thanks Grege,I'm going to hook up one channel passive,straight shot right out of my preamp to one amp to passive crossover.No other sub, Magnepans only.Then on the other side I'm going to hook up two way active, Magnepans only no other sub.Back and forth with balance.May the best crossover win.

Sounds like a good plan Swordshield. Please report back your findings. That QR tweeter can go WAY lower than the standard passive xover, I think I went as low as 900 Hz with interesting results.

I sure hope your wrong about freq.Manuel says 600Hz.Just got them going tonight,got the active set around 750Hz ,I thought for good measure to start out at.I want to retube my amps(just got amps- old tubes) before I make any conclusions.My mag .5's crossed over at 1000 Hz.I just set my 1.6 (active side) at 1000Hz [you freaked me out],were did you come up with this 900Hz.Manuel says exactly--- CROSSOVER SYSTEM Acoustical 600Hz, am I misinterpreting something here, is the word acoustical saying something I don't know.Don't want to fry them.Again (please) were did you get 900Hz?

The electrical crossover is 1600 (maybe 1500).

The accoustical crossover is where the woofer and tweeter SPLs are equal. If you have a spectrum analyser, connect the tweeter with inverted polarity and look for a deep notch in the frequency response.

The inverted polarity of the tweeter is correct for the stock tweeter crossover (12 dB). For a L/R 24 dB crossover normal polarity is correct. (Otherwise you get that deep notch).