@isostasy and others, my 4th unit of K702 arrived today. As you know I was wondering if the newer K702's have been silently revised, based on the fact that Sean Olive's measurement of the K702 somewhat recently showed that it was really quite different to the K702 frequency responses that we're used to looking at. So I've measured my 4th unit of K702 on my miniDSP EARS and quickly compared it to my Unit 3 K702, and as it turns out there's not that much difference, at least not enough difference to describe the missing 5.5kHz in Sean Olive's measurement. Following is Unit 3 vs Unit 4, the blue line is Unit 3 (don't worry that the frequency response looks strange overall, that's because it's measured on a non-standard rig, measured on a miniDSP EARS):
As you can see there's nothing to suggest that the newer K702's are any different to older K702's, at least not in terms of differences at 5.5kHz which is where the peak was missing from Sean Olive's measurement - as you can see there are no differences at 5.5kHz. So I think any differences between Sean Olive's measurement (which mirrored Crinacle's measurement quite well) and Oratory's measurement is down to measurement protocol or just something associated with the measurement process. I don't think it's unit to unit variation as all my K702 have the same general traits in treble around that 5.5kHz area, although I haven't dug through my measurements of my Unit 1 & 2 to put them on the same graph as I'm short on time right now, but I remember (know) them to be similar in this respect - I'll probably put all 4 units on a graph when I've got more time. So I think it comes down to which measurements you want to use - Sean Olives & Crinacle's that both agree with each other in terms of not having a 5.5kHz peak or Oratory's measurement that has a 5.5kHz peak. I may do some other investigations to work out if my miniDSP EARs measurements show evidence of a 5.5kHz peak when a generic "multi-headphone" conversion curve is applied to the minDSP EARS measurement.
And following is some further general information about the performance of my Unit 4 K702: it's got very good channel matching:
And following are all the individual measurements of both left & right channels of my Unit 4 shown all on one graph (as I measured each channel 10 times after reseating the headphone on the rig each time):
Following some Distortion Measurements, just at an SPL level of 85dB (@1kHz):
Right Channel Distortion Measurements (these look ok I'd say):
Left Channel Distortion Measurements (somewhat worrying peak at 2.5kHz):
My Unit 3 doesn't have the distortion peak that is seen above, I'd have to do some more distortion testing on this Unit 4, this was just a quick one, I've run out of time today. Might revisit some parts of this post in the coming days or week to flesh out some more bits and perhaps to add to any of the points I've investigated - I'll either do a seperate post or update this one.
TLDR: Channel Matching is good in my newly bought Unit 4, and it doesn't vary significantly from my others indicating that a silent revision has not taken place. Following are the production numbers for each of my K702, each K702 that is produced is given a number that is simply their running total of the total number of units they've produced so far:
Unit 1 from yr 2015: 123864
Unit 2 from yr 2020: 204975
Unit 3 from yr 2022: 212059
Unit 4 from yr 2023: 224865
(Sean Olive got his sample fresh from the warehouse 241706 was the number, so his is newer than mine eventhough mine was bought 4 months after he posted his measurement. Oratory measured 230909 as his latest one.....maybe a revision has taken place between 230909 and Sean Olive's 241706, but the fact that the Crinacle measurement of even older (old old in comparison) don't show that 5.5kHz peak and agree with Sean Olive's in that respect - makes me think there's not been a revision. I still think it's something related to the "measurer & measurement procedure".)