The WP8's go down to 21Hz...not sure of the 7s but the normal THX crossover recommendation of 80 Hz is probably too high a cossover for your speakers. There are other things to consider like the low pass crossver of your surrounds and your room dynamics.
Without a sound equalizer like that found on the Velodyne DD series, you may have to play with the phase and polarity settings after picking a spot where the subwoofer sounds loudest and tight and also fits into your decor. Avoid somewhere in the center of the soundstage or room. A few feet from a wall or corner near one of the main speakers usually works best. Then experiment with phase and polarity settings to see if the bass gets louder and tighter. I suggest doing the above with the sub's crossover or (not both) your processor set at around 50 Hz given the low end capability of your WP7s.
You can then adjust volume so the bass blends in and so the sub doesn't draw attention to itself; it should seemlessly blend into the sound of the main speakers. Then go down 5-10Hz until you hit the low pass of the WP7's low pass of around 21-25Hz and listen for the best overall bass that is tight, not boomy and blends seemlessly into your main speakers sound.
Without a sound equalizer like that found on the Velodyne DD series, you may have to play with the phase and polarity settings after picking a spot where the subwoofer sounds loudest and tight and also fits into your decor. Avoid somewhere in the center of the soundstage or room. A few feet from a wall or corner near one of the main speakers usually works best. Then experiment with phase and polarity settings to see if the bass gets louder and tighter. I suggest doing the above with the sub's crossover or (not both) your processor set at around 50 Hz given the low end capability of your WP7s.
You can then adjust volume so the bass blends in and so the sub doesn't draw attention to itself; it should seemlessly blend into the sound of the main speakers. Then go down 5-10Hz until you hit the low pass of the WP7's low pass of around 21-25Hz and listen for the best overall bass that is tight, not boomy and blends seemlessly into your main speakers sound.