I have, in the last week, implemented MathAudio for Foobar2000 in my listening room. The results of the measurements done with a Cross Spectrum Acoustics calibrated Behringer ECM mic, and the suggested room correction curve resulted in adjusting the system response for frequencies below 200 Hz.
I use dipole subwoofers (2 of them) to crossed over to Linkwitz LXmini speakers, It is somewhat troublesome to correctly match levels between the dipole subs and the LXminis. My initial level setting was determined by outdoor ground plane measurements. After setting up the system in my room, I made additional level adjustments between the sub and mains. MathAudio suggested additional tweaking of the levels. The MathAudio plug in allows level adjustment on the fly during playback and the overall system sound has improved as a result. No corrections were needed above 200 Hz. I am very pleased with the result and the price (free). For those who use Foobar and have subwoofers that need to be integrated, this is a tool worth looking at.