Subject: sony MDR V6 headphones From: Bob Carlyon <bob.carlyon(at)MRC-APU.CAM.AC.UK> Date: Wed, 25 Sep 1996 14:30:18 +0000=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 ---------------------------------------------------------------------------- --