headphones (Bob Carlyon )

Subject: headphones
From:    Bob Carlyon  <bob.carlyon(at)MRC-APU.CAM.AC.UK>
Date:    Wed, 17 Jun 1998 19:17:01 +0100

Some time ago a posted a query to the list about possible replacements for the sennheiser HD414 headphones used in many psychoacoustic labs. I received a number of helpful suggestions, and have been trying out different models over the last 6 months or so. I also sometimes get emails from folk asking what conclusions I came to. This is just to let anyone interested know that I have finally settled on the sennheiser hd250 linear 2, which cost about 125 pounds in the UK. I was particularly helped by T.Hirahara, who sent me an article published by him in the Journal of the Acoustical Society of Japan vol 53(10) p798-806, in which he compares calibrations for many models of headphones both on couplers and real ears. Reprints of that article are available from him at: Tatsuya Hirahara, Dr.Eng. ATR International, Corporate Strategy Planning Division, 2-2 Hikaridai, Seika, Souraku, Kyoto, 619-02 Japan email: hirahara(at)ctr.atr.co.jp One of the best models he describes, the SR Lambda Pro, is no longer made. Another very good one is the sennheiser HDA 200. I tried out a pair of these but found them too heavy and uncomfortable for prolonged psychoacoustic testing. However, Walt Jesteadt's subjects obviously have stronger heads than ours as (I think) he decided to get some The sennheiser HD250 linear 2 is a pretty good third best. Unlike many hi-fi headphones it does not share a ground lead between the two channels, thereby avoiding the electric cross-talk that can occur between channels in such models (e.g. sony mdr-v6). The frequency response as measured on an artificial ear is pretty flat up to about 8 kHz, except for an 8-dB dip around 5 kHz. However, no such dip occurs either in individual or mean real-aer responses, as measured by Dr. Hirahara. The real-ear response drops off above 8 kHz whereas the coupler response increases. Distortion is O.K.: at 500 Hz and above, for a 100-dB SPL output level of the primary tone, all distortion products are at least 60 dB down. At 250 Hz the 2nd harmonic is only 50 dB down but the relative level is >60 dB down at output levels for the primary of 90 dB and less. The distortion does not get worse at lower frequencies (e.g. 100 Hz). The headphones are circumaural but reasonably light and comfortable. I occasionally hear a very slight rustling from the cushions if I move my head (whilst in the booth). One advantage over the 414s is that there should be no problems with sensitivity changing over time due to wear on the pads. Calibrations were carried out by Rhodri Cusack and John Deeks using a B&K artificial ear. I should stress that we have not started using the phones yet for experiments, so don't have any practical experience of using them. However, they do seem worth a try for anyone looking for new phones. I would also strongly recommend Dr. Hirahara's article to those interested in the technical details Carlyon psychoacoustics accepts no responsibility for any damage, accidental or imagined, produced by the use of these headphones. Final responsibility rests with you. Please do not sue me. bob ------------------------------------------------------------------------------ Dr. Bob Carlyon MRC Cognition and Brain Sciences Unit 15 Chaucer Rd. CAMBRIDGE CB2 2EF England Phone: (44) 1223 355294 ext 720 FAX: (44) 1223 359062 email: bob.carlyon(at)mrc-apu.cam.ac.uk ---------------------------------------------------------------------------- -- McGill is running a new version of LISTSERV (1.8c on Windows NT). Information is available on the WEB at http://www.mcgill.ca/cc/listserv

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Electrical Engineering Dept., Columbia University