Phenomenal. I was skeptical of this EQ due to its radical & unorthodox approach to equalization, but that changed pretty quickly.
COS comes with a spectrum analyzer, an EQ (with up to 51 EQ bands), and 15 'ceiling' bands. When using the "conform spectrum to ceiling" feature, COS will adjust the EQ so that the spectrum matches the ceiling band curve. You can freely adjust the EQ bands too if you'd like, but then you miss out on the 'deep magic' Ayaic included with this EQ: (from the manual).
"When it comes to mixing music professionals and beginners alike often find the equalization process to be one of their greatest challenges. How much low end does the bass require? How bright or smooth should the hihat sound? How phat should the guitars be? How do I get the vocals to stand out? Ultimately because of variances in amplifiers, drums, microphones, FX, mic placement, etc. there can never be a "one method fits all" approach. However there is one thing that every instrument, percussion, guitar and vocal track has in common...they are all just noise. Just as the spectrum of light is the ceiling of perfect color...white, pink and brown noise are the ceilings of perfect sound.
Everything we hear flows along the spectrum analyzer lines of one of these noise ceilings (0, 1.5, 3, 4.5, 6 db p/oct). We can tilt them by either negative or positive values and they remain extremely musical. By mixing multiple instances of noise ceilings with any multiple of +/-1.5db tilt you can create the ceiling shape you need to equalize your source material perfectly."
This is why I love this plugin. I mean, what I truly love about this plugin is that it actually works. It has worked wonders with everything I put it on, and it really is due to the 'ceilings of sound' strategy that Ayaic chose to go with.