Accudio Pro iPod/iPhone equalizer app for numerous headphones
The Accudio app does a perfect job of correcting the high-frequency peak around 9-10 khz with the Beyerdynamic DT770-32LE headphone, and raises the presence level around 3-6 khz slightly, without any negative effects on the remainder of the spectrum. The DT770-32LE uses different earpads from the rest of the DT770 series, which changes the sound, so perhaps this correction was accidental and could have been worse. In time perhaps I'll know more.
In a second case, Accudio turns the warm and soft-sounding B&W P5 into a thin, shrill-sounding headphone, ostensibly because the P5 measures as warm and soft, thus needing bass reduction and a treble boost. No bass reduction was needed for the P5, and the treble boost should have been very modest. But since the version of Accudio I have does not have EQ curves for v-moda headphones, I applied the P5 curve to the v-moda M100, then turned the top sliders down a couple of notches to mitigate the treble boost, and got an improvement in sound with the M100.
I tried the Accudio EQ curve for the ATH ESW9, and it raised the treble too high for my ESW9a, so I turned down the top sliders a notch and got a good overall improvement with the ESW9a. There was no EQ curve for the ESW11 or ESW11Ltd, so I tried the ESW10 setting for that headphone, and got some improvement there as well. I tried the Phiaton MS400 setting, but that produced no improvement at all, making the sound too thin. Since the black MS400 I have sounds so much different from the black and red MS400 I had a year ago (and the fit is way different too), I suppose the Accudio MS400 curve wouldn't be expected to work with the black MS400.
A most impressive difference was with the Apple Earpods, i.e. the purchased version with Apple controls. The Dirac DSP app turns the OK but slightly bright and harsh-sounding Earpods into an audiophile's dream signature - warm, strong but tight bass, crystal-clear mids, and excellent treble with no peaks or harshness. Accudio does very little correction to the Earpods, reducing the harshness slightly but also cutting back on the bass, and the reduced bass has the unfortunate effect of making the treble more prominent, so the reduction in harshness is netted out to little or no apparent difference.
My experience with Accudio Pro so far suggests to me that it's like a much-expanded version of the Apple i-device EQ settings, meaning it's hit-or-miss as to which EQ curve gets closest to ideal. The advantage of Accudio isn't just more settings though, it's the fact that after you get a good approximation with a given setting, there are 5 sliders available that can be used to further tweak the sound. Unfortunately, one of the apparent bugs with Accudio occurs when you switch settings to try another one, for the same or a different headphone. When you switch back to the prior setting, the 5 sliders are back to zero, losing any tweaks you made. Since these adjustments may be the result of a lot of intensive listening comparisons, they should be written down so they're not lost.
Accudio Pro was priced at $4.99 USD in Apple's app store, and lacks the A to Z quick-find buttons under 'Songs' that the Apple player has and the paid Dirac apps also have. Scrolling back and forth through 2700 songs is not fun. Adding playlists doesn't help in this case. I have to wonder also what the creators of this app intended for headphone sound signatures, since the P5 curve for example is a sonic disaster.