On 12/31/2017 9:14 AM, Adrian Tuddenham wrote:
None of the reviews mentioned frequency response measurements - indeed,
I got the impression that none of the reviewers would have known how to
make them, how to interpret them properly or, in some cases, what they
were.
I think that's true. Reviewers can write their subjective opinions, but
few are equipped with even basic test equipment. For example, when
writing about a computer audio interface, "Mic preamp gain: 56 dB" means
nothing because you never see that gain. What's significant is input
level at maximum gain that produces a specific digital level. I connect
a signal generator, crank it up to digital full scale, and record the
level, so in my review I can say: "Minimum mic input level for 0 dBFS:
-42 dBu." But most readers don't know what that means, but, oh, boy,
they sure can compare gain numbers.
The sig-gen was 600-ohms output and ran
through one of the distribution rack buffers which again delivered from
600 ohms. I seem to remember that I wondered about that at the time and
repeated the test with a completely different low impedance driver - but
although I have forgotten the details, I'm sure it made little
difference.
It would be interesting to check it out, and also check the transient
response. Mostly these days, people are interested in knowing how loud
the earphones will play, and manufacturers have started making
headphones that expect to get their power at lower voltage and higher
current, which means lower load impedance and lower source impedance.
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