I thought the ATH-M50x was, but for look and a detachable cable, exactly the same as the ATH-M50. Isn't it the case? How would you compare it to the MDR-7520? Why do you recommend the ATH-M50x over the MDR-7520?
Not so flat? So what's the FR bias?
Have you tried the K812?
I think the M50 and the M50x are almost identical. But I feel the M50x has slightly powerful low-bass. The MDR-7520 is obviously clearer than the M50x. But the M50x is more comfort and cheaper than the MDR-7520. So I recommend the M50x to the person who want to buy more music instruments and do not want to spend much money for monitoring system. The MDR-7520 is not so flat. Its sound is just like "turning VCF resonance knob to the right". Recently, some audio shops sell K812, but it is too expensive for me (now I want moog Sub37 instead of K812, lol).