Opinion on crossover frequency for sw

Gentlemen, I need an expert opinion here to see if I'm right. Subwoofer sealed q of 0.5 downward firing, what the heck a Vandersteen 2w driven by a Crown xls 1500 -stock ampxover not working-. My main speaker's f respose is -3db down at 45 hz according to specs. I use the Crown connected to the amplifier's output using a resistance in series to the Crown's rca input. So I figured that if the low pass xover of the Crown is 24db/octave, I should set its lp frequency above the 45 hz natural cutoff of the main speakers to have a proper overlap. I made a graph and it indicates that the the lp frequency should be in the neighborhood of 65 to 70 hz..... so Is this assessment valid?

With a lp frequency at 50 hz -lowest f on the Crown- there is not much articulation by the sw, and raised to 66 sounds pretty coherent and much more integrated. The volume iis another matter which also needs to be considered. Thanks.
 
Gentlemen, I need an expert opinion here to see if I'm right. Subwoofer sealed q of 0.5 downward firing, what the heck a Vandersteen 2w driven by a Crown xls 1500 -stock ampxover not working-. My main speaker's f respose is -3db down at 45 hz according to specs. I use the Crown connected to the amplifier's output using a resistance in series to the Crown's rca input. So I figured that if the low pass xover of the Crown is 24db/octave, I should set its lp frequency above the 45 hz natural cutoff of the main speakers to have a proper overlap. I made a graph and it indicates that the the lp frequency should be in the neighborhood of 65 to 70 hz..... so Is this assessment valid?

With a lp frequency at 50 hz -lowest f on the Crown- there is not much articulation by the sw, and raised to 66 sounds pretty coherent and much more integrated. The volume iis another matter which also needs to be considered. Thanks.
The Vandersteen 2w has output to 20 Hz, a 50Hz 24dB per octave cross would only have it playing one and 1/3 octave of music, frequencies down that low won't have much "articulation". If your main speakers actually have an in room -3dB point of 45Hz, there is no need to cross the subs higher than that, other than the minimum is 50 Hz. Your main speakers probably roll off at around 12 db per octave if sealed, or 24 dB per octave if ported, in either case a 65 to 70 Hz LF LP would be overlapping by over 2/3 octave.

If you are going for flat response, for many types of music (especially anything recorded prior to the mid 1980s) you should barely notice the sub output. You can use swept bands of pink noise (available on test CDs, or downloadable on line) to hear if the volume transition is smooth between the sub and mains.

If you are not trying to achieve flat response, then just go with whatever LP and volume you like.