[Les Cargill[_4_]]

Adrian Tuddenham wrote:
Les Cargill wrote:

Adrian Tuddenham wrote:
What I've tried:

In the past I've been pretty happy with AKG K-240 (they fit me fairly
comfortably, the sound is pretty "natural" to my ears, not fatiguing)...
but they could be a bit better in the detail and clarity department, and
they don't isolate the room at all. I could end up buying a pair if I
don't find anything I like a lot better

Sorry I'm a bit late contrubuting to this thread:

I measured the frequency response of a pair of early-model AKG K-240
headphones some time ago and found they had a huge dip of about 20 dB in
the HF range. Both left and right transducers demonstrated this at
nearly the same frequency, so it appears to be an inherent property of
the design, not an individual faulty unit.

The AKG K-44 showed some minor wobbles in the frequency response curves
with a rise at the lowest and highest frequencies, but overall sounded a
lot better than the K-240.

I have just tested the AKG K-52 and found that is is better than both of
the above models, wth no obvious wobbles or other deficiencies. At
first I was puzzled by an apparent falling-off around 3 Kc/s, but
clamping the earpieces a little more firmly to the test rig removed
this.

My conclusioin is that, of the three models teated, the K-52 is the best
for flatness of response as long as it is properly positioned on the
listener's head. The K-44 isn't bad and the early-model K-240 is a
waste of time and money.


Adrian - how do you couple a headphone transducer to a microphone for
measurement? By using a dummy head?

Make up a stack of thick hardcover books about the same thickness (and
density!) as the space between my ears. Allow the headphones to clamp
themselves over the stack and slip a couple of electret pressure
microphone capsules on thin wires into the cavities.

Ah. So for some models of 'phones, there is effectively no cavity, and
I suspect making one would munge the measurements severely. So I wonder
is a piece of whitewood with a hole drilled to have the electret's
surface flush with, or slightly under the plane of the wood would
work?

Connect the
headphones to an audio signal generator, connect the mic capsules to a
small recorder with suitable phantom power (Tascam DR-04) and read the
sound level off the recording level display. The measurements are good
to a dB or two - and are going to be far more accurate than the accuracy
of most budget headphones (and some expensive ones).

If there are any acoustic artefacts that need investigation, they will
change if the mic capsule positions are changed or the air cavity shape
is altered by compressing the earpads. If they don't change, then they
can reasonably be attributed to the headphones themselves



That's interesting - thanks for that. I would have thought you'd want
the geometry of things to be pretty rigidly controlled; didn't think of
moving the elements as a control like that.

--
Les Cargill