Author Topic: Complete idiot question about measuring continuity on headphone cable  (Read 591 times)

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Offline Mp3

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Hi Everybody,

I got 5 sets of cheap headphones in the mail. on 2 of 5 sets the phase is backwards.

I took the drivers off so i could test the wire to the 3.5mm plug with my multimeter. I set it to continuity and tried measuring to all 3 points on the 3.5mm plug, but got continuity on all points......

I'm trying to figure out if the wire is wrong or the markings on the drivers are, how should i tell?
Pace ADS200, Jabe UD-1200, TS-100
HP 3478A, Fluke 45, UNI-T UT71A, several fused DT-830B
Power Design TP340 & Siglent SDS1052DL+
 

Offline GadgetBoy

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Re: Complete idiot question about measuring continuity on headphone cable
« Reply #1 on: August 15, 2018, 05:25:38 am »
You'll get continuity on all points because of the coil in the speaker. You'll need to de-solder the driver before making any continuity tests.

Sent from my ONEPLUS A3000 using Tapatalk

 
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Offline homebrew

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Re: Complete idiot question about measuring continuity on headphone cable
« Reply #2 on: August 15, 2018, 05:29:54 am »
Hi Everybody,

I got 5 sets of cheap headphones in the mail. on 2 of 5 sets the phase is backwards.

I took the drivers off so i could test the wire to the 3.5mm plug with my multimeter. I set it to continuity and tried measuring to all 3 points on the 3.5mm plug, but got continuity on all points......

I'm trying to figure out if the wire is wrong or the markings on the drivers are, how should i tell?

Just use an Ohm meter and measure resistance. Your coils will have some impedance that will help to detect if it is a dead short (i.e. pont-to-point connection) or if it is measured across the coil.
 
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Offline drussell

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Re: Complete idiot question about measuring continuity on headphone cable
« Reply #3 on: August 15, 2018, 05:46:06 am »
The Tip-Sleeve DC resistance should read the same as the Ring-Sleeve.  Measuring from Tip-Ring should read twice the DC resistance of the previous measurements when taken with your typical multimeter.

That doesn't tell you if one of them is wired backwards and therefore out of phase, of course, but that is very easy to hear when you listen to any mono or stereo signal.  If it is wrong, reverse the +/- wiring on the pair of leads to either one of the headphone capsule "speaker" drivers and it will cure your phase-reversal problem.

If you want to be fully correct from a technical sense, by convention a positive voltage on a + terminal on a speaker driver relative to the - terminal should normally push outwards on the diaphragm.  You won't normally hear a difference in most typical applications regardless of whether + is pushing out or - is pushing out as long as all the drivers in your system are in phase.

Matching phase between disparate units is the reason for the positive-differential-voltage-is-outward standard convention.

Edit: This gets trickier when you start to add crossovers in speaker systems, etc. where the phase shifts you're dealing with aren't 180-degrees, but that's another topic.   :)
« Last Edit: August 15, 2018, 05:48:13 am by drussell »
 
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Offline Mp3

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Re: Complete idiot question about measuring continuity on headphone cable
« Reply #4 on: August 15, 2018, 05:47:04 am »
Thanks to all. I've desoldered the wire from the headphones and was able to make my measurements :-+
Pace ADS200, Jabe UD-1200, TS-100
HP 3478A, Fluke 45, UNI-T UT71A, several fused DT-830B
Power Design TP340 & Siglent SDS1052DL+
 


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