So far i have tried: hifiman 262, hifiman he400, grado gr10, grado sr60, koss porta pro. The sound profile was not changed when paired with the ak100. They sounded the same but clearer and more detailed. The only one that has been problematic is the grado gr10. For some reason, it has been difficult to get consistently good sound from them. So far, my favorite pairings are the hifiman headphones.
The Gr10, like most MAs or BAs have a rising impedance in the highs and will have a corresponding rising high frequency with an output impedance likw that of a stock AK100. All your other phones are single driver dynamics which are generally flat impedance. The RWAK100, clip, Ipods would not exihbit this in a noticable way even if they are not as good in other respects. It would be very disappointing for someone whoes favorite IEM was say an Ortofon EQ-7, GR10, TF-10 or any Phonak etc.
Edited by goodvibes - 1/31/13 at 8:29am