My solution to a similar problem (in my case, incorporating a passive 15" Tannoy sub, along with another 12" sub). I use wye, or siamese connectors, for tapping into the L/R low-level signals for the two subs, at the preamplifier.
One signal goes to the 12" sub, the other to the Tannoy. It is here where I input the signal to a DBX 223 xs equalizer, (which can be purchased very cheaply), and from there to the amplifier for the passive Tannoy sub.
This setup works well for me, I get plenty of good clean bass, without affecting the two stereo channels' frequency response.
XLR to RCA adapters are necessary for the DBX unit, but they can be had for $8-$10 at Parts Express these days.
Best of luck, regards,
Dan
One signal goes to the 12" sub, the other to the Tannoy. It is here where I input the signal to a DBX 223 xs equalizer, (which can be purchased very cheaply), and from there to the amplifier for the passive Tannoy sub.
This setup works well for me, I get plenty of good clean bass, without affecting the two stereo channels' frequency response.
XLR to RCA adapters are necessary for the DBX unit, but they can be had for $8-$10 at Parts Express these days.
Best of luck, regards,
Dan