Thanks to the help of several head-fiers such as xnor and odigg, you can actually calculate the FQ deviations with a higher Zout if you have the impedance curve data available. Here is the information for the HD650 - xnor, feel free to correct me if I'm wrong. The HD650 does have a humpy impedance curve and this should be interesting.
1 Volt applied to 300ohms with a 15ohm output (damping factor of 20) produces:
dB = 20*log (v1/v2)
Voltage 1 = baseline impedance of HD650
1V/315 = 0.00317A
0.00317A * 300ohm = 0.9524V
Voltage 2 = impedance peak of 475ohm @100hz
1V/490 = 0.00204A
0.00204A * 475ohm = 0.9694V
dB = 20*log (0.9694/0.9524)
dB = +0.15dB @ 100hz
Therefore, with a damping factor of 20, you have an entirely inaudible FQ increase of 0.15db @ 100hz. Let's see what happens when you decrease the damping factor to 1 (300ohm Zout)
Voltage 1
1V/600 = 0.0017A
0.0017*300ohm = 0.5V
Voltage 2
1V/775 = 0.00129A
0.00129*475 = 0.6129V
dB = 20*log (0.6129/0.5)
dB = +1.8dB @ 100hz
Therefore with a damping factor of 1, you have an entirely audible 1.8dB boost @ 100hz. Very audible, but given the wonky FQ response of most headphones anyway (+/- 5dB), it won't ruin your day. I won't lie, lower Zouts produce a flatter FQ response.
Quote:
Originally Posted by
Shike Quote:
Originally Posted by
maverickronin So you don't really need more than a damping factor of 1 for a typical headphone then?
Depends what you consider typical. If you look at the impedance graph at headroom if it's a flat line it's considered resistive and higher output impedance will just make them less efficient without showing huge FR changes. Headphones like the Sennheiser HD650 which varies greatly based on frequency on the other hand will deed a damping factor of roughly 1/20th or better at said frequency to minimize or mitigate impact of it.