Originally Posted by Armaegis
Can you make some graphs of each headphone separately with and without the resistor?
I would also be interested in seeing data using an amp with a higher output impedance, as that would (I think?) have a noticeable affect on damping factor, although I'm not sure if that would show up on an SPL graph.
Here are the individual frequency response graphs without level matching offsets:
DT880 250 ohm version, 0 ohm source impedance
DT880 600 ohm, 0 ohm source impedance
DT880 250 ohm, 100 ohm source impedance
DT880 600 ohm, 100 ohm source impedance
These are all the measurements I have. Yes, the added series resistance interacts with the headphone's impedance, modifying the frequency response and reducing the low frequency damping. However with the 100 ohm resistor, I don't see any low frequency peaking which is an indication of the bass being underdamped.
Originally Posted by Shike
What's the process you use for measuring? Is it a multiple run with averaging or something else? What is the accuracy from run to run? Is there anyway headphone positioning could have caused this?
I know I'm asking a lot of questions, but it's surprising to see such different results in relation to Headroom.
Headroom uses different equipment than I have. For my tests, 5 measurements were taken and averaged for each curve. I positioned the headphones as identically as I could for each measurement. There is some difference in low frequency SPL in the range 20-80Hz on the 600 ohm curves which may be due to the 18.5Hz data point increments and MLS signal. It's easier to get consistent low frequency measurements using swept sine.