Subject: Re: sony MDR V6 headphones From: RealTime <mandra(at)PEABODY.JHU.EDU> Date: Wed, 25 Sep 1996 13:04:10 -0400bummer. 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(at)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(at)mrc-apu.cam.ac.uk > ---------------------------------------------------------------------------- > -- > chris mandra ///// Deus Ex Machina x x * http://www.peabody.jhu.edu/~mandra/ <-> http://www.charm.net/~metamuse