Sub/Speaker Crossover?


Is there an accepted "rule of thumb" when it comes to where to set the crossover between subs and speakers in two-channel?

I have Spendors that go down to around 45 and have always thought it best to set the sub crossover to 50 -- just before the Spendor starts giving out. But I have also read where some set the crossover for similar monitor speakers way up at 100! Or even lower, say 35 or 40.

It seems to me that there should be -- regardless of speaker/sub manufacturers -- a reasoned and correct crossover target. (For the record, I use ACI subs with my SP1/2s and SP100s.)

Thanks to any and all who can educate me. Just seems like, for this one, there should be a "right" and "wrong" approach.
jdmeyers77
After years of searching for the "correct" crossover frequency I have realized that it doesn't exist. The best frequency depends on the type of music you are playing. The crossover should have an easily adjustable crossover frequency (a knob) and you should diddle with it just as you might do with a tone control.
As usual, Bob has hit the IMHO critical points. An illustration from Verity Audio. The Parsifal monitor is down 3 db at 55 hz. The x-over in the Encore woofer is set at 150 hz. Obviously stereo cabinets are required. one more reason to cross high. Unless you use bass busters, there's a very good chance that your worst room mode will be a hump between 80 or so and 125 or so hertz. Properly placed Subs - especially of the drc type - can adress this issue

good luck

Marty