Whatever I quoted is specifically what I was responding to. In this case, it was the suggestion that the manufacturer not sending him the target curve is somehow dodging, and/or that discussing channel matching is dodging. I believe Ken Ball described to some degree in a previous post generally how they do matching, and that's about as much process detail as you get from most manufacturers.
My point with the HD800's was showing how the same model of headphone has differing sensitivity from unit to unit (at least at 40 Hz; and at somewhat higher frequencies, too, as evidenced by the harmonic distortion spurs), but it was consistent for both channels per unit. Matching, then, is actually a very important step. It's obviously not the only important step, but it is obviously important.
If you watch what I believe is Tyll's last InnerFidelity video he shows the Klippel system MrSpeakers uses to do multi-parameter driver matching. Others use it, too, but most manufacturers don't publicly discuss their
specific procedures and processes in that regard as openly as Dan Clark does in that video.
I was also making the point that with headphones and earphones we can get measurement variations. we measure several seatings and average to get the curve -- that if we saw no variation, we'd simply measure once. Picking a random headphone from Tyll's database -- and looking at the variation in frequency response -- you see things like this (Fig.1 below):
(Above) Fig.1 Example of frequency response variance of the same headphone from different seatings, from InnerFidelity (https://www.innerfidelity.com/images/AKGK240Monitor.pdf)
That's the same headphone, being measured by Tyll Hertsens, on the same fixture, and probably in the same measurement session.
In addition to stellar driver matching by Sennheiser, another thing that makes the Sennheiser HD800 easier to get consistent measurements with is its shallow, firm earpad design. The HD800/HD800S earpads do not compress/deflect like super plush earpads can, making very consistent measurement positioning and repeatability -- and achieving symmetry of both channels during the seating process -- far easier than with headphones that have thick, soft, squishy earpads.
For IEMs, there's going to be some variation, and you're likely to run into it more with some designs than others. For our measurement fixtures, for example, an IEM that fits into the concha and essentially locks into place firmly -- something like, for example, a Sennheiser Momentum True Wireless (Fig.2,3,4 below) -- is much more likely to give more consistent seat-to-seat measurements, in our experience, with the type of human-like GRAS anthropometric pinnae we use here on both fixtures (GRAS 45CA and GRAS 45BB-12). I'll measure the Solaris (and will post results when I do), and I imagine it won't be as consistent from seating to seating (as the Sennheiser Momentum True Wireless), as it's a large-body IEM (Fig.5,6,7,8 below), and there's more room for movement in the ear, even after it's seated -- it just doesn't nestle its entire shape into the ear as completely as the Momentum True Wireless.
All of this, and there are also varying degrees of unit-to-unit variation with any headphone or IEM.
(Above) Fig.2 Sennheiser Momentum True Wireless in GRAS anthropometric pinna.
(Above) Fig.3 Sennheiser Momentum True Wireless in GRAS anthropometric pinna.
(Above) Fig.4 Sennheiser Momentum True Wireless in GRAS anthropometric pinna.
(Above) Fig.5 Campfire Audio Solaris in GRAS anthropometric pinna.
(Above) Fig.6 Campfire Audio Solaris in GRAS anthropometric pinna.
(Above) Fig.7 Campfire Audio Solaris in GRAS anthropometric pinna.
(Above) Fig.8 Campfire Audio Solaris in GRAS anthropometric pinna.
