I have very large mains (dynaudio c4s) and just a single sub for now (parts express DIY 18" ultimax). I thought I was a prime candidate for FR mains. However after a bunch of experimentation and in room measurements I found High passing them give better subjective and objective sound. I did land at a relatively low freq of 50hz though.
When I tried to align the sub with the speakers playing full range, they would always ad in some spots and subtract in others. These interactions were pretty substantial in amplitude as well. In the end I was able to make things much smoother in the listening position with the speakers high passed. The added available dynamic range of relieving the mains of spectrum less than 50Hz is a big plus as well, even with 120 lbs per mains.
For smaller less LF capable mains I would definately be high passing the mains. I had some snobophile objections to using a minidspHD for this purpose originally because I wanted to avoid the extra ADC and DAC operations for the mains, but I made the switch to minidsp SHD as my pre to preserve my delicate sensibilities. I am sure the reality is that the ADC is less harmfull than a distorting small woofer trying to make real bass.
When I tried to align the sub with the speakers playing full range, they would always ad in some spots and subtract in others. These interactions were pretty substantial in amplitude as well. In the end I was able to make things much smoother in the listening position with the speakers high passed. The added available dynamic range of relieving the mains of spectrum less than 50Hz is a big plus as well, even with 120 lbs per mains.
For smaller less LF capable mains I would definately be high passing the mains. I had some snobophile objections to using a minidspHD for this purpose originally because I wanted to avoid the extra ADC and DAC operations for the mains, but I made the switch to minidsp SHD as my pre to preserve my delicate sensibilities. I am sure the reality is that the ADC is less harmfull than a distorting small woofer trying to make real bass.