[asymcon]

Hey fellow Sound Science lurkers.
About 2 years from now I acquired my first high impedance headphones, no other than AKG K240DF. The first listening made my jaw drop and I had to sit down - I was that blown away by the clarity, compared to K701 and newer K240 MKII. The only bothersome factor in the frequency response spectrum was 9-10kHz peak so I immediately opted for recabling with well proven Van Damme Miniature Starquad cable. I was more of a subjectivist back then. 

 
Starquad is dirt cheap by audiophool standards, about $3/metre, but in contrast with all the uber-expensive junk, it's a well-proven cable frequently used in studio environment and built to last (another reason for recabling). As usual I terminated the negatives at the end (near the 1/8" TRS). 
Suddenly the headphones came alive, the bass had more presence and the peak was gone. This shouldn't be happening with 600Ohm drivers, right?
 
Fast forward one year into Jan-2016, I still love my K240DF, but this recabling thing seems suspicious, could it be McGurk effect?
I purchased another pair (I wanted a backup anyway) and did side-by-side comparison. The difference was still there, with original cable the headphones suffered the issues above. I did extensive measurements of resistance and capacitance with DMM (Mastech MS8226), yet the Starquad actually measured a little bit worse (higher capacitance) open circuit.
 
Finally in Dec-2016 I did another test with my switchbox and found very noticeable difference when I inserted the stock cable in between the signal. Stereo separation was a lot worse, which I also confirmed with test signals (1kHz to the left, 500Hz to the right). To ensure the validity, I also invited some of my friends and switched the box without them knowing. And yes, they complained about the same thing. 
 
To cut to the point - could any of you recommend me a testing method how to measure this difference? 
I'm visiting a friend tomorrow who has decent Rigol oscope - what is needed to measure say capacitance and impedance of a cable over target frequency response? Can it be done with a regular oscope and only 8bit FFT? 
 
Thanks for any input

 

[watchnerd]

   
I'm visiting a friend tomorrow who has decent Rigol oscope - what is needed to measure say capacitance and impedance of a cable over target frequency response? Can it be done with a regular oscope and only 8bit FFT? 
 
Thanks for any input

 
You don't need to use an oscope.
 
A Fluke or similar multimeter will measure capacitance and resistance.
 
http://en-us.fluke.com/training/training-library/test-tools/digital-multimeters/how-to-measure-capacitance-with-a-digital-multimeter.html
 
http://en-us.fluke.com/training/training-library/test-tools/digital-multimeters/how-to-measure-resistance.html

 

[castleofargh]

if the question is about the sound out of the headphone, then that's where measurements/ listening tests should be done. some usb mic and a little macgyverism to record the headphone in a correctly sealed condition could probably tell what is what.
 
for crosstalk to become a noticeable problem, I would imagine a conjunction of high level crosstalk in the amp(shouldn't happen in high impedance headphones but not all amp designs are equals), and high level in the cable(could it be a soldering problem?). I find it very hard to notice crosstalk in music unless it comes licking the -40db below music. that's something I can achieve with a sansa clip and low impedance IEMs, and that's about it for the stuff I've owned.

 

[asymcon]

   
You don't need to use an oscope.
 
A Fluke or similar multimeter will measure capacitance and resistance.
 

It seems you misunderstood my post. I already did DC measurements for capacitance and resistance:
 

  I did extensive measurements of resistance and capacitance with DMM (Mastech MS8226), yet the Starquad actually measured a little bit worse (higher capacitance) open circuit.

 
AC Impedance cannot be measured by conventional DMM. 
 

  some usb mic and a little macgyverism to record the headphone in a correctly sealed condition could probably tell what is what

There has to be more precise methods than slapping a USB condenser near the transducer and call it a day. 

Dummy load and sine sweep might be a way to go. 
It's also important to rule out everything else, we're measuring the cable and not the headphones. 
 
Here's what I can do
Sine sweep from 10Hz to 40kHz sourced from possibly neutral DAC (X5II comes to mind), use of cable splitter and feed one way through the cable (and to Rigol probe 1) and the other straight to Rigol - both loaded with 600 Ohm resistors. Then read the amplitude difference. 
As for crosstalk, sine sweep in one channel might do the trick. 

 

[asymcon]

I've tested the stock cable today on that Rigol DS1504Z, and unfortunately the results were inconclusive. I'll try to come up with more precise testing method.