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I got a second-hand Neewer NW-3000 closed headphone which sounds like there is phase cancellation and no stereo effect. So I tested the headphone with a mixer and distinct tones on each channel; I figured out that each output channel is:

output_channel_right = output_channel_left = input_channel_right - input_channel_left

Then I can listen to my music, but only one of the input channel to the 2 headphone channels (i.e. the same for each ear), providing on balancing everything to the right (or the left) in the audio player...

The headphone speakers sounds good and there is no faulty contact at the plug. So what is wrong? Is it a manufacturing fault? Is the manufacturing fault probably from the jack plug? In another words, could I save these headphones by cutting the cable and change the jack plug only? Is it possible that a wrong connection caused such input_channel_right - input_channel_left result?

2 Answers 2

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My guess: The common ground line is missing - maybe inside the plug, but both speakers of the headphones are as a consequence in series between the hot pins of L and R channel outputs.

enter image description here

You hear only what's the difference of the channel contents.

You only can find where the break actually is. I guess it's inside the plug, but it's only a guess. I have seen headphones where it was inside one of the speaker cases. It can be even in the cable if it has only 3 conductors.

If some other device outputs perfect stereo sound via these headphones, the break is in the device which causes the said sound fault. It may be no fault at all, but a totally different female connector which is there intentionally to make low cost 3rd party accessories like your headphones useless.

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  • Thanks @user287001. Could you explain why removing the ground creates this artifact please?
    – Noil
    Jun 28 at 9:49
  • I thought that the schematic above would be the explanation. The message of the schematic in plain English: There's no path for electric current through the speakers to the terminal "Ground" from terminal "Left" nor from terminal "Right". But theres a solid current path from "Left" to "Right". Both speakers pass the same current i.e. the same signal which occurs, if the output voltages in "Left" and "Right" are other than zero, but not the same i.e. not the exact well balanced mono. Note that, the explanation of the schematic is not an opinion, it's a fact that any electrician can confirm.
    – user287001
    Jun 28 at 10:18
  • Thanks! I guess the schematic is good if you know some electronics. Why does it create a "minus" sign between the 2 channels and not a "plus"?
    – Noil
    Jun 28 at 10:29
  • @Noil 2 points with different voltages against the ground have also a voltage between the points. That's found by Gustav Kirchhoff in 1845. If the voltages to the ground were the same, there would be no voltage between the points. You just hear what's the difference, as already said and also noticed by yourself
    – user287001
    Jun 30 at 17:40
  • Oh I got it, thanks!
    – Noil
    Jul 1 at 22:10
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Go to a brick-and-mortar store where they sell that model. Bring your headphones. Playback the same audio, as mono, from the store's headphones and yours, one in each ear or A/B however it works for you.

You could also try AutoEq to adjust the headphones manually.

The simplest solution might be to ask for a replacement or refund and try a different model.

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