headphones

[Bob Carlyon <bob.carlyon@xxxxxxxxxxxxxxxxx>]

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@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@mrc-apu.cam.ac.uk
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