Hello fellow headfiers,
First, I would like to say thank you. I have learned so much about headphones, amps, and DACs, and am proof that the statement, “Welcome to headfi, sorry about your wallet.” is an inevitability.
I have read several posts on different threads asking about the difference in sound between ¼ inch TRS and 4-pin balanced XLR. Besides the obvious volume increase, I was curious if the added power actually changed the sound in any way.
I decided to set up a simple test that would compare the frequency response between single-ended and balanced outputs.
My test setup was as follows: Room EQ Wizard V5 sine sweep output → MR816x I/O (used firewire input from computer and output via coax S/PDIF output) → coax S/PDIF input on Audio GD NFB-10ES2 → Hifiman HE-500
Sound was captured by a MiniDSP UMIK-1 acoustic measurement microphone, which is connected via USB and has a unique calibration file applied to results.
HE-500 4-pin Balanced XLR Frequency Response:
HE-500 ¼ inch TRS Frequency Response:
(Each test was done consecutively without moving the headphones or mic placement)
Although I wasn't able to match their levels perfectly, there is an obvious change to the frequency response between single-ended and balanced. I'm not sure if this is specific to my setup but I did a total of 4 tests of each and the results were the same. There is a gradual roll off of the higher frequencies starting above 1 kHz. At 10 kHz there is a decrease of ~4 dB, and at 16 kHz there is almost a 9 dB reduction.
These results are very interesting to me. I've heard that more power gives better control over the drivers and improves low frequency response and impact. When listening in balanced XLR, I thought I noticed a more prominent bass. However, these results show that there isn't necessarily a more prominent low end but a less prominent high-mid and treble response.
I did more tests today and found out that my results were most likely due to testing inaccuracies. A slight change in position of the headphones or microphone or a change in pressure to hold the ear pieces together gave remarkably different results.
After doing 5 separate tests with different mic positions and varying pressures, the only constant was that the frequency response didn't change. I've updated the graphs to support this.
I can conclude that there is not any change in the frequency response between balanced and single-ended. However, there seems to be better controlled bass in balanced operation.
FYI the Audio GD NFB-10ES2 is rated at ~7.5 W for my HE-500 with a measured 40 Ohm impedance in balanced output. Single-ended output is ~2 W. Thank you Kingwa for the excellent product!
Edited by cskippy - 10/23/13 at 1:00pm