Sony MDR-7510 studio headphones
However, using my iPod touch as the music source, the mid range and treble is reduced compared to the 7506's.
This can be compensated for using the graphic equaliser, but I wasn't expecting to do this, nor like doing it.
I would like to a frequency response curve for both headphones showing dB against frequency or a +/- dB tolerance figure added to the spec.
One advantage with the 7510's is that they screen out the background noise better.