My exprience first with KEF 102/2 monitors then with KEF 104/2 floor standing speakers is that the KEFs sound more open and transparent when frequencies below 80 Hz are shunted to the Velodyne HGS-15. I've heard people say this about other speakers as well. In my system, the sub integrates seamlessly with the mains, and does not seem to be a source. So even if I had a pair of Sophias, which I do like, I'd still cross over to the sub at 80 Hz. BTW, listen to the Bach Toccata and Fugue in D minor etc. before discounting content below 40 Hz.
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