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-   -   Headphone cable crosstalk - how to avoid? (http://www.diyaudio.com/forums/headphone-systems/7727-headphone-cable-crosstalk-how-avoid.html)

halcyon 17th November 2002 06:19 PM

Headphone cable crosstalk - how to avoid?
 
I'm purchasing a set of headphones that runs the headphone cable only to one side of the headphone (i.e. they don't split visibly to two different wires outside the headphone cup).

Inside the first cup there are a connection spots for the left and right cup signal wires respectively AND a shared common ground which then leads to both cups.

The standard cable that comes with the headphone is therefor a three wire cable with a shared ground along the whole of the signal path after the headphone amp.

Now, I'm concerned about crosstalk due to the shared ground and especially the low impedance (40 Ohms) of the phones.

I've seen measurements (for Sony MDR V6) that shows that the crosstalk noise components can rise up to the relative level of -30 dB compared to the signal level.

This is clearly not acceptable for my purposes.

Is there any way I can hack/modify such headphones (by building my own cables) in order to reduce this type of crosstalk?

I'm sure I could get rid of it with proper cable construction and IF I could have separate ground contacts for each transducer. However, I don't think I'm brave enough to tear apart my $300 USD headphones band in order to fit a separate ground wire for the second cup.

So, can anything be done (to crosstalk) just by exchanging the cable, if the contact at the end of the headphone has only one place for the ground to which both transducers are connected?

All help / corrections are welcome.

Best regards,
Halcyon

PS I'm an electronics novice, but you don't have to treat me with silky gloves. If I can't understand the explanation with my own books (and net searches) I'll ask for a clarification.

lohk 17th November 2002 10:14 PM

Are you kidding ?
Did you hear crosstalk of the cables ?
Common cables is "common" practice with headphones, ane there is no crosstalk (specially with low impedances).
The crosstalk you hear happens in the electronics "before" the output.

halcyon 18th November 2002 06:10 AM

No, I'm not kidding.

I have seen actual measurement data of headphones which have a shared common ground and with which the crosstalk components exist at the relative level of -30 dB below signal.

These tests were conducted by expert psychoacousticians and audiometric personnel who specialize in the audibility tests.

Their recommendations NOT to buy any headphones with a shared ground (unless you have a way of measuring it's crosstalk components) sure looks valid to me.

Most high quality audiophile and studio headphones have a separate ground wire for each cup.

Not all, but many of them.

Honestly, what make you think that I am kidding?

Have you not heard about cable crosstalk (induced by shared ground) before?

regards,
Halcyon

peranders 18th November 2002 07:18 AM

Some headphones have shared ground and this can result in a little bit crosstalk. When the cable is separated into two wires all the way from the connecter to speaker elements, you will get better separation. My (quite good) Sennheiser HD545 reference (in fact most Sennheiser phones) has separate cables all the way.

I think though that your concern is a little bit "overkill". In order to get good stereo you need 10-15 dB channel separation. Compare to the good old vinyl with approx. 20 dB channel separation.

Have you tried the headphone experts at www.headwize.com ? try also www.head-fi.com

halcyon 18th November 2002 08:36 AM

peranders,

I'm trying to locate a suitable closed circumaural headphone pair for psychoacoustic testing. Hence I have a higher requirements for crosstalk immunity than with normal listening (if not for anything else, but so that nitpickers can't shoot down the test setup based on that).

Thanks for the tip on head-fi and headwize. I have discussed the problem in Head-Fi forums (but not yet at headwize). I have done extensive searches on the issue on the net and read the relevant parts in 'Loudspeaker and Headphone Handbook' (2001 ed.)

The trouble is finding people who have actually constructed their own replacement cables and actually measured their crosstalk when connected to an actual pair of headphones with a shared ground connector.

Currently I don't have the needed measuring equipment (nor enough trust in my skills) to test myself, which makes life a little bit more difficult :(

But back to my original question:

Can something be done to alleviated the normal three cable wire and a shared common ground contact in otherwise high quality pair of headphones?

peranders 18th November 2002 08:57 AM

Quote:

Originally posted by halcyon

But back to my original question:

Can something be done to alleviated the normal three cable wire and a shared common ground contact in otherwise high quality pair of headphones?

Yes! Use headphones with separate cables like Sennheiser or change cables at your headphones.

I had long time ago a 3 x 0.4 mm sqr to my speakers. The cable was 10 meters. The resistance of the common ground cable was not small, 1.4 ohms in each wire and 4 ohm speakers.....not audiophilic connection..:yikes:

Don't forget that you have crosstalk in your head also!

halojoy 18th November 2002 10:57 AM

Also 3.5 mm stereo-plug uses Common GND
 
Also the very much used 3.5mm stereo plugs use common GROUND.
And the headphones use that or 6.3mm stereo "teleplug".
I do not like it.

I want to be able to put the common ground at the place where I think it is best.
The RCA phono plugs use separate,
which makes it easy to use separate cables.
These cables could be joined by some sort of clips, or those things
used to hold together cables inside electronics.
Or some tape.

peranders 18th November 2002 12:17 PM

Quote:

Originally posted by peranders

I had long time ago a 3 x 0.4 mm sqr to my speakers. The cable was 10 meters. The resistance of the common ground cable was not small, 1.4 ohms in each wire and 4 ohm speakers.....not audiophilic connection..:yikes:

.... I ment 0.4 square millimeters = 0.437 ohms! Still it was noticable. :yes:

valveluver 12th March 2003 03:02 AM

headphone crosstalk
 
The phones shouldn't crosstalk. Make the measurement through the amplifier. The low source impedence should keep the crosstalk down. If you are making the measurement with one side disconnected, put a 4.7 ohm resistor across the side under test to simulate a real world condition

UrSv 12th March 2003 09:40 AM

Re: Headphone cable crosstalk - how to avoid?
 
Quote:

Originally posted by halcyon
I'm purchasing a set of headphones that runs the headphone cable only to one side of the headphone (i.e. they don't split visibly to two different wires outside the headphone cup).

Inside the first cup there are a connection spots for the left and right cup signal wires respectively AND a shared common ground which then leads to both cups.

The standard cable that comes with the headphone is therefor a three wire cable with a shared ground along the whole of the signal path after the headphone amp.

Now, I'm concerned about crosstalk due to the shared ground and especially the low impedance (40 Ohms) of the phones.

I've seen measurements (for Sony MDR V6) that shows that the crosstalk noise components can rise up to the relative level of -30 dB compared to the signal level.

This is clearly not acceptable for my purposes.

Is there any way I can hack/modify such headphones (by building my own cables) in order to reduce this type of crosstalk?

I'm sure I could get rid of it with proper cable construction and IF I could have separate ground contacts for each transducer. However, I don't think I'm brave enough to tear apart my $300 USD headphones band in order to fit a separate ground wire for the second cup.

So, can anything be done (to crosstalk) just by exchanging the cable, if the contact at the end of the headphone has only one place for the ground to which both transducers are connected?

All help / corrections are welcome.

Best regards,
Halcyon

PS I'm an electronics novice, but you don't have to treat me with silky gloves. If I can't understand the explanation with my own books (and net searches) I'll ask for a clarification.

That is pretty much the standard problem AFAIK. Most people concerned about this just rip their headphones apart and fit a new connector on the side without one. Depending on the model this might look good or not. I say that is the approach.


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