Well, I am speaking of volume levels around 8 to 10 o'clock. The Yamamoto shall be optimized to Audio Technica phones, low impedance .... (but work for high impedance phones, too). Strange behaviour ..... and it sounds really fine with the RS1. It sounds fine with the T1, too, but with a very tight bass. I thought a bad (impedance) match would lead to a wooly bass ... and low treble.