Can the guys using the term elaborate what they mean by "bright midrange" - bright is a term i associate with, and which is usually used to describe, treble. Do they mean "forward midrange"?
Not really sure if this is where I should be responding; apparently some of the thread has been shifted around.
I got some welcome suggestions on my original posts about the measurements of the PM-1 on About.com Stereos. Someone suggested measuring distortion at a lower level, and I'd already done a 90 dBA measurement for SoundStage, so I added that in the chart: http://stereos.about.com/od/Measurements/ss/Oppo-Digital-PM-1-Headphone-Measurements_5.htm.
Note that because no headphone's response is linear, the test level will be well above 90 dB at some frequencies and below 90 dB at others. 90 dBA is just an average, weighted toward the midrange. For example, I measured the level at 500 Hz with the PM-1 and it was 99.9 dB, so this is more or less equivalent to a measurement taken using a 500 Hz reference tone at 100 dB. (Which I don't do because using 500 Hz as a reference frequency would give a big advantage to headphones that have a response bump at 500 Hz.)
It was also suggested that I change the Y axis to a log scale. I wish I could do that, but Clio doesn't offer that option, at least not anywhere I can find. (It uses log Y scale on THD vs amplitude measurements, but not THD vs. frequency.)
Another suggestion was to have a floor of 0.001% THD on the chart. That's a good floor for amplifier measurement, but it's probably lower than needed for acoustical measurements. That's -100 dB. Based on the speaker measurements my colleagues at SoundStage do in the anechoic chamber at the NRC in Ottawa, it looks like somewhere around 0.1% might be the lowest you'd need for a transducer. The 50% max on my chart is definitely high, but I've measured a few headphones that actually got up to around 30%. Not headphones you guys would probably use, of course.
Jay_WJ said (among other things): "One thing to add: Do not generalize too much about correlation between measured performance and audibility. Scientific grounds on this issue (how audible particular levels and patterns of nonlinear (even linear) distortions would be to human ear under various, realistic conditions) are very weak at the moment." Totally, completely agree. AFAIK, the only place we have any decent understanding of the effects of transducer distortion on listener perception is with subwoofers.
The other threads for sicophantic praise only, this threads for anyone who wishes to have an intelligent discussion about the PM-1 :-)
Interesting, I got rid of the HD-650s in favour of the Hifiman HE-400 which, in my system, offerer a superior sound.
That is your personal bias though. You downplay extension so much but LOTS of people in this hobby view it as something critical to a truly "high fidelity" audio experience.
I don't know why you can't just admit to the fact that a relatively early treble roll-off is a flaw in the context of this hobby (not saying PM1 has that, measurements are notoriously bad at >10kHz detection).