Re: sony MDR V6 headphones

[RealTime <mandra@xxxxxxxxxxxxxxx>]

bummer.

chris

On Wed, 25 Sep 1996, Bob Carlyon wrote:

> =46ollowing Brian Karlsen's request on the list for recommended headphones,
> and chris mandra's recommendation of the sony MDR V6, I recalled talking to
> soren buus about some problems with crosstalk on these headphones. I
> reproduce soren's comments below:
>
> -----------------------------------------------------------
>
> Many Hi-Fi earphones are prone to crosstalk between the two
> earpieces.  The problem is notable in the Sony MDR-V6
> earphones, which otherwise are excellent earphones.  The
> problem results from a shared ground wire for the
> two earphones.  If you feed one earphone a signal while
> the other is connected to the output of a driver amplifier
> (which may or may not be producing a signal--it doesn't
> matter), the current fed in to the first earphone will divide
> between the shared ground and the other earphone in
> proportion to the impedances to ground at the point where
> the two earphones are connected to the common ground.
> This results in some of the current from the first earphone
> taking a return path through the other earphone, such that
> cross talk (in antiphase) occurs.  Our experience is that this
> cross talk is roughly 30 dB below the signal in the earphone
> that is used.  The cross talk can be eliminated by not
> connecting the unused earpiece, but of course that is only a
> workable solution for monaural experiments.
>
> The cause (and amount) of cross talk can be visualized as
> follows:
>                                                  (Amp output=3D
> (Signal)                                    virtual ground)
>    Left                 Ground                   Right
>      |                           |                             |
>     >                         >                             >
>     >                         >                             >
>     >        Wire         >                             >
>     >    resistance  >   (about 1 ohm)>
>     >                         >                             >
>      |                          |                               |
>      |                          |                               |
>      --VVVVVVVV----|----VVVVVVVV-----|
>           Left                          Right
>         Earpiece                Earpiece
>      (63 ohm)                  (63 ohm)
>
> When the left earphone is fed a signal of, say, 64 mV the
> 1-mA current, which must return after passing through the
> left earpiece, divides between the shared ground and the
> right earpiece, whose "hot" end is connected to a virtual
> ground (as far as the left earphone signal is concerned).
> Thus, slightly less than 1 mA returns through the shared
> ground (doing no harm) and slightly less than 1/64 mA
> returns through the right earpiece and the right "hot" wire
> (making an antiphase cross talk with an amplitude of about
> 1/64th of that in the left earpiece).
>
>   This problem of cross talk surely is not unique to the Sony
> MDR-V6, but applies to any (usually, Hi-Fi) earphone, which
> uses a shared ground wire.  Because it is a question of
> relative impedances, the problem is usually greater the lower
> the impedance of the earphone is.  Certainly, the 63-ohm
> nominal impedance of the Sony MDR-V6 makes it a
> significant problem.
>
> S=F8ren Buus
> ECE Dept.
> Northeastern University
> Boston, MA 02115
>
> E-mail: buus@neu.edu
> ___________________________________________
>
> I hope these are of some help
>
>
> bob
>
> ----------------------------------------------------------------------------=
> --
> Bob Carlyon
> MRC Applied Psychology Unit
> 15 Chaucer Rd.
> CAMBRIDGE CB2 2EF
> England
>
> Phone: (44) 1223 355294 ext 720
> =46AX:   (44) 1223 359062
>
> email: bob.carlyon@mrc-apu.cam.ac.uk
> ----------------------------------------------------------------------------
> --
>

chris mandra                                      /////

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