I would use my phone's EQ if I could set custom EQ curves.
I made a file in Audacity of sine waves, played in sequence of about one second each, that matched the EQ sliders in iTunes. Whenever I bought a new laptop, new speakers, or new earphones, I'd play that file on Repeat and play with the EQ until there were no "peaks" in the sound (peaks color the sound worse than holes, and are more annoying to my ears). Once satisfied, I saved the finished EQ curve with the name of whatever device I was using.
It worked pretty well. Music was more natural and stereo separation seemed better.
I tried saving custom settings to music files on my iPods and iPhones so they'd be available, or at least correct the sound output, but it never worked. I pretty much gave up.