Equalizer APO Documentation Wiki
In short, it's a system-wide parametric EQ for Windows 7 and newer. Finally, there's a reason to upgrade from XP!
Anyway, Equalizer APO's configuration is based on text files. There's no GUI. It's not exactly user-friendly, but the genius is that you can use REW with a measurement mic to determine the appropriate filters, save the EQ to a text file, and source the file in EQ APO's config. If you want to make manual tweaks, changes are loaded instantly as the text file is saved.
I'm using it to flatten the response and extend the low-end of my champagne-glass Harmon Kardon computer speakers at work. There's a noticeable improvement, and I've got useable bass down to 40Hz now, whereas before it was more like 100. Trade-off: I had to set a preamp gain of around -11.5dB (-6dB overall, plus most of my filters have negative gain as well). Since I generally don't rock out at work, I'm fine with this.
After I made those measurements I manually added one more filter, a low shelf filter, to implement a house curve. I didn't take any measurements with that active, but it makes my music sound good anyway, at least from my seating position. Sounds like crap from my co-worker's chair, but that's not my problem. (To make it sound better for him, I'd need to move my woofer, which would require an extension cord + re-routing my satellites' wires. I like the guy OK, but not enough for that much effort.)
I could probably flatten some more. I think I read somewhere that EQ APO will handle up to 100 filters, and I'm currently using 21. But this is close enough for government work.
