I use reference 4 headphone and I have a number of headphones. I like the results in my mixes. When I use ref 4 with my Senn HD600.....Sony MDR V-6.....Senn HD598.......Status Audio CB-1.....and Philips SHP9500......the resulting output sound is all very similar....almost amazingly so. When I use ref 4 on my ATH-M-50 and ATH- M-40 headphones the sound is not very much like the others. Basically they lack high end clarity it seems.
So....why is that? Is it basically because those two models don't take EQ very well or are not able to actually reproduce the changed EQ? By the way.....the ATH M-50's and the ATH M-40's are both genuine and were both purchased at guitar Center.