I need help rewiring some AKG K240DF headphones.

[comuneros]

In this Head-fi post (https://www.head-fi.org/showcase/k240-df.12176/), user asymcon reviews these headphones and recommends rewiring them to improve the sound. Since I'm somewhat handy and I've found that the original cable only goes to one channel (left, and from there it goes through the metal headband to the right channel), I've thought about changing the cable since the cost wouldn't be too high. I'm looking for an unbalanced option like the one with the original AKG headphones.That's why I need your help with some aspects I'm not clear on. There are two options for rewiring them:

1. Like user asymcon suggests, using a Starquad microphone cable for rewiring. These cables have four connections (generally two white wires, two blue wires, and a neutral/ground wire). How would the connection be made? Would I use the two white wires joined together for one channel, the two blue wires joined together for the other, and would the ground be common to both channels?

2. The other option would be a dual cable that is independent for each channel (like most over-ear headphones that have one cable for each earcup). In that case, each cable would carry a signal (left-right) plus a ground wire that wraps around the signal cable. Wouldn't this option be more immune to interference since the signal cable would be protected by a ground wire, and wouldn't it also prevent the signal from reaching the metal connectors on the headband, which would degrade the signal a bit? I've attached photos so you can see the AKG connections.

On the other hand, what cable would you recommend in each case? I'm looking for something not too expensive, around 2-4 Euros per meter. What characteristics should I look for (OFC, for example)? Do you recommend replacing the 6.35mm stereo jack with a better one (for example, a Neutrik) or reusing the one that came with the headphones? Any other suggestions?

And thanks in advance for your help.

 

[AnalogSteph]

Honestly, the stock wiring as shown looks fine to me. Nicely separated ground returns up to the plug (even if 600 ohm drivers are super uncritical in terms of shared ground return resistance anyway; they will care even less about a fraction of an ohm more on one side). Workmanship of the internal connections seems a bit dubious, so I might redo these properly, with heatshrink for the splices instead of the old electrical tape.

The guy on Head-Fi might have gotten one with a bad solder joint or broken wire, or a driver accidentally wired out of phase (which should be easy enough to verify).

Headphone wiring is almost as uncritical (electrically) as speaker wiring. It is being terminated by the (generally very low-impedance) headphone output on one side, so unless you manage to annoy the amp with common-mode RF pickup or something, there's not a whole lot that can happen really. The dominant concerns will be weight, microphonics and longevity - which is why Sennheiser came up with a solution of thin-gauge (about 1 ohm / 3 m), kevlar fiber reinforced wiring. If you can keep the stuff from breaking at the connectors or inside the strain reliefs (which is how it generally seems to fail), it's about as good as you can get. (The more modern stuff with the foamed PU jackets à la HD650 might be better in that regard, not sure.) The rigors of studio use may favor more rugged cable stock along the lines of what AKG used.

I don't know whether you can get anything with silicone jackets instead of the old PVC. You'd think what's good for test leads would also work here, although reinforcement would still be necessary.

 

[solderdude]

One should only recable headphones if:

The cable is too short.
The cable is too stiff.
The cable is too microphonic and changing the cable could help.
The cable is broken.
The insulator is cracked/torn.
You want to use a differential output headphone amp.
You really want a different feel or color.
It seems fun to a DIYer to do this.
The cable is 3-wire, has a relative high resistance of the common return wire compared to the headphone impedance.

A 4-wire cable that joins at the sleeve of the TRS jack is technically 'better' than a 3-wire cable.

Changing a cable for the sound is ... not one of the reasons other than the bolded reason mentioned above.
Regardless what nonsense is written about this subject on the web.

For the K240 (and similar construction) headphones the biggest issue is usually poor soldering to the 'rods'.

 

[comuneros]

Thanks for the information. The driver has a "-" mark on one side. Where does it connect the ground and where the signal (right/left channel) goes? Or does it not matter?

I was thinking of reusing this cable that I don't use anymore. It's an OFC cable. Will it be of sufficient quality?

Thanks for your help!

 

[solderdude]

That cable is probably fine but need a picture of the wires.

Do you plan to use it dual entry or single entry ?

What colors/wires are inside the cable you want to use ?

Do you have a multimeter ?

Connect the tip of the TRS to the 'stripe' connector of the left driver. (signal L)
Connect the Sleeve (of that same cable section) to the 'non-striped' connector of the driver (ground L)
Could be the screen or a wire.

Connect the ring of the TRS to the 'stripe' connector of the right driver. (signal R)
Connect the Sleeve (of that same cable section) to the 'non-striped' connector of the driver (ground R)

You can connect the driver the way the headphones are designed (with both drivers actually being in reverse polarity) by connecting the drivers as described above or... can decide to also address the reverse polarity issue found in all K240 models while you are recabling anyway.


When you want to 'fix' the K240 and get the polarity right you should wire the headphones as shown below:

Connect the tip of the TRS to the 'non-stripe' connector of the left driver. (signal L)
Connect the Sleeve (of that same cable section) to the 'stripe' connector of the driver (ground L)
Could be the screen or a wire.

Connect the ring of the TRS to the 'non-stripe' connector of the right driver. (signal R)
Connect the Sleeve (of that same cable section) to the 'stripe' connector of the driver (ground R)

 

[comuneros]

Sorry for the delay. I have a multimeter. I've attached a photo of both ends of the cable.

I plan to wire both headphones independently so the signal doesn't go through the headband. The only thing that's bothering me is that, as you can see in the photo, the cable has arrows that I assume indicate the direction the audio should "go." I'm not sure if this makes any sense, because the way I'm going to connect it, using the existing mini-jack, the audio would go in the opposite direction (from the mini-jack to the headphones).

Could the arrow indicate that the audio should follow its direction?