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
Wow. See what I mean? :)

Thanks for all the input, folks. I used to have the REL and know they are designed for just the low stuff below what any monitor can reach -- hence the setting in the 20s.

I've always just fiddled with my subs until the bass sounds just right in Jimmy Smith's excellent "Dot Come Blues." I trust my ears. But it does seem like reasoned audiophiles have very different "rules of thumb" when it comes to this topic!

Keep in mind that a good low setting won't draw attention to your sub.Done right,nobody should know its on.
The rule of thumb is to set the crossover one octave above the F3 of the main speakers. This much overlap is needed to get a smooth transition. If your speakers are -3 dB at 45Hz, then you should set the crossover to the sub at 90Hz. No matter where the crossover, integration is not easy. You can try to do it by ear, but test signals and an SPL meter will get you there faster and easier.
I've always just fiddled with my subs until the bass sounds just right in Jimmy Smith's excellent "Dot Come Blues." I trust my ears.

Jd...You hit the nail on the head my man.Trust your ears,after all,you are the one listening to your system.
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.