[W.G.D.]

I have a respectable but old(er) 'stereo' receiver, a Sony STR-V55 (along
with a Sony PS-X75 turntable) which I use in a home-office. L-R speakers
are in-ceiling mtd.(!) Sound is fine; however, I would like to pump-up the
low end by adding a subwoofer. Rcvr and turntable can support it;
ceiling-mtd spkrs are OK at best. There is a set of pre-amp out-in jumpers
at the STR-V55's rear. What is the most economical way to derive a
"center-like" 'bass' channel from both L & R channels?

Regards,
Wayne