Most of my listening was directly with a Sony CDP-X303ES Compact Disc player, whose professional ¼" headphone jack has more than enough guts to drive these well. While audiophiles listen to whatever life hands them, I personally ran the proof-of-performance on this player with a borrowed
$50,000 ROHDE & SCHWARZ UPL with its optional high-performance analog circuits (that's a benefit of having worked for Tektronix). I know my player is giving me what's on the glass master; do you?
The Sony CDP-X303ES has a 56 Ohm build-out resistor from its dedicated internal headphone amplifier. This would drop the overall level about 1dB with a resistive 300 Ohm load.
The HD 800's actual impedance is about 300 Ohms at DC, then a broad peak of around 650 Ohms around 120 cps, about 350 Ohms at 1 kc, a broad minimum of about 325 Ohms in the upper midrange, and a gradually rising impedance in the treble at about 375 Ohms at 15 kc. The effect of the 56 Ohm series resistor in the Sony CDP-X303ES is to alter response, relative to 1kc, by +0.5 dB at 120 cps, -0.1 dB in the upper midrange, and +0.1 dB at 15 kc. Therefore, used with this headphone amplifier with what seems like significant output impedance, it actually helped sculpt the response in favor of the HD 800.
Used with a amplifier with a lower output impedance, which is usually the case, the brightness I heard should become
worse. In any case, fractions of decibels are usually inaudible, and in this case, are actually making the HD 800 sound better.
