TrueFi is a program that purports to generate a flat sound. For the most part, it does--maybe a bit too flat, in fact. It wildly boosts bass on cans with a lot of rolloff (e.g. HE400i), which seems to muddy the sound a bit. Most audiophiles don't like strong bass for this reason, but like variations on flat-ish curves. There is a bass modulation option, but you can't control the parameters of the low-shelf filter, just a slider from -8 to +8 dB. There are options to fit to age (just a treble boost, frankly). It works well enough with my ATH-MSR7's, as they are fairly closed and have a nearly-flat FR curve anyway, so the changes aren't too drastic. It sounded decent on my HE400i, with a hasty and panicked 5dB bass reduction, but the TrueFi filter really reduced the detail and perception of space/soundstage. Vocals sounded, I must admit, extremely lifelike. However, what I was left with was indeed analytical, but didn't feel nearly as huge as the 400i normally feel. It was like someone put a tennis ball in a diamond vice. Sure, it was a diamond, but a tiny, flawed, boring one. I prefer it for indie music, but for 80's darkwave, modern synthpop, any sort of rock, and other detailed, crowded, treble-loaded music, it takes the life out of it. I much prefer my own "flat"-ish equalizations...they preserve a lot of soundstage and iron out the most egregious treble-mountains of non-consensual ear-violation. I wish I hadn't paid $80 before realizing there was a free trial. This is, I'm sure, excellent for inexpensive headphones, but once you get into upper-mid-fi or hi-fi, you're much, much better off just looking for a can that works for you--with the soundstage, imaging, PRaT, transient response, and FR curve you want, and leaving preset equalizers alone.