OK, here we go, the cable comparison, with measurement to back it up.
First, my subjective impressions. The silver cables are a smidge brighter/more forward sounding, cleaner, and have better controlled bass. Rhythm and pacing seem more right with the silver cables. The silver cables are more revealing as well. Overall, I prefer the silver cables to the stock cables for most listening.
I used REW to run the tests, and measured my HD650's using a SHURE WL93. I did not compensate for the mics FR so these images are for comparison purposes only and do not represent the true FR of the headphones.
I hung the headphones, placed the mic inside the ear piece by clipping it to a wire that slid up under the ear pad, then clipped the mic cable to the head band to ensure that any movement of the cable above the headphone would not push or pull on the mic rig. I also did a control measurement after conducting my two tests per cable to ensure that the stock cable still measured the same, and it did as shown in the mic control graph.
The volume chosen was a loud but still listenable volume.
The first graph compares the stock and silver cables unsmoothed:
The silver cables are dark green. There are clear differences here even with the unsmoothed data.
Here is a second comparison smoothed:
The silver cables are dark blue here. It's easy to see the differences between the two in the upper mids/lower treble.
Mic Position Control Graph:
I measured the stock twice, then silver twice, then just to make sure the mic wasn't bumped in switching cables I created this control of the stock cables when I was finished:
The ref is in red compared to the stock trace from the test just above.
Here is a GD graph, (the sine waves are displayed on an axis):
What this tells me, and correct me if I'm wrong, is that the test tones are better controlled with the silver cables in dark green. The fringe of the dark green looks more even.
Last, here is a comparison of two sine waves around 300hz. The stock cable appears more jagged and the silver cables reproduce the sine wave more precisely:
The important thing to note is that while the absolute frequency response is basically the same here, the tone and control of bass is going to be better with the silver cables.
I hope that what I have shown here is that cables can affect the sound of a system. The important thing about this test is that the comparisons were done at listenable (still loud by my standards) volumes, further testing at higher volumes (deafening) indicates that the curves start to merge together as volume goes up. This is important to note for future testing. Objectively the approach to measuring and testing audio should be from a human perspective and not performance absolutes.
Edited by cheapskateaudio - 11/2/11 at 11:43pm