I'd also find that quite interesting.I think it would be interesting to see a review of 15 of the same headphones to get a feel for how extreme unit variance is.
For sh!ts n giggles I did something 'quite' similar a while ago with my collection of 'Made in Ireland' era Sennheiser HD*** sets.
I built the cables so that signal transfer would be identical as well as investing in a Tascam MH-8 multi-channel headphone amp specifically for the test.
The experiment consisted of 4 of the lower range models as well as 2 pairs of HD600's and 2 pairs of HD650's. One of the HD600/650 is a proper, umnmolested, unfkrdaroundwith pair while the corresponding pair had HD600 and HD650 drivers mounted in a HD565 chassis.
So the line-up as HD525, HD535, HD545, HD565, HD600, HD600(565), HD650, HD650(565).
I also have a HD265 which is a closed-back headphone with a totally different SS so I didn't include it.
I don't have the equipment to perform measurements and the listening comparisons were purely subjective but there were some surprising differences noticed. I made notes during the test...and then subsequently lost those notes after I packed everything away again. drrrrp.
But essentially it wasn't as straightforward as 'sound gets better the higher up the model chain you go'. The set I was surprised most by was the humble HD565. This is the model that will remain my absolute favourite, even before the HD600 and HD650!
Shock horror! lol
I now have 7 sets of refurbished HD565's and the next test will be to line them all up to test them. It's just a shame I have no way to determine when during the production run they were made. The chassis components are all identical, there are very slight variations in the colour of the plastics and the size and placement of the graphics but the only thing that really distinguishes them are numbers on the driver capsules which have absolutely no reference that I can find anywhere unfortunately.
HD650(565), HD600(565), HD650, HD600
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