Hi ernestov,
No cross over so to speak,the Conrad Johnson preamp has two outputs, main1 goes to the power amp, main2 goes to the JL Audio sub. The full audio signal is low passed (in the sub) at 80 Hz. I suppose they may be too close, but I set them up this way initially and have not heard anything deleterious (first, early reflection from the wall).I did move them in about 2 or 3 feet from the sidewall but I did not hear any improvement in how they sound. I run the sub with the M1’s,not at a high level. The sub fills in the lowest reaches, 20-40 Hz and supplements 40-80 Hz.