@sns His response is right on target.
The wiring is most likely the issue. I just put 2 T/9X's in yesterday and while they were in route I verified the proper wiring scheme to use. Here is what customer service offered:
"Thank you for reaching out. Either a signal ground or earth ground will be fine for connecting the black High Level wires to, though if possible the earth ground screw would be preferred. If you experience hum from the subwoofer when connecting the black wires to this screw, then you could instead try the signal ground and see if this yields improved results.
We recommend starting with both the red and yellow High Level wires connected for each subwoofer, and in most cases this will result in excellent performance and usable signal levels. However, if you find that the subwoofers have too much output, where barely raising their Level controls already results in them overwhelming the output of your main loudspeakers, then you could try disconnecting one of either the red or yellow wire for each subwoofer. This will lower the input signal gain roughly by half, and will allow for greater flexibility when setting their Level controls. The red and yellow wires are functionally identical, though we generally recommend leaving the red wire connected for the right channel subwoofer and yellow wire connected for the left channel subwoofer in these cases."
The low level may be a better option for you. I found that I have very little volume needed for twin subs but am okay with that since it needs so little (about 30% of the volume knob) to mate with the Wilsons. Took me less than 10 minutes to get a good start to proper sound. I'll further tweak it this weekend.
Lots of good tutorials on their website and manuals are also available.
@jacobsrph And yes, check the phase. If sitting next to the mains then 0 is required Put your fingers on the main woofer and sub to verify they are working in the same direction while playing.