Just want to step in here with something. What Jude is showing is that there are some different measurements around - not that others are garbage - just that others are measuring differently. Jude - are yours raw or is there compensation applied? What is the standard?
Reason I'm saying this is that there was similar debate regarding Judes differences with Tylls measurements of the MDR-Z1R (I think). Funnily enough - that was also in the 10 kHz area. I'd want to measure the same IE800S on a few rigs and compare the raw measurements before saying anyone's measurements are garbage. Another interesting thing is that there were more measurements showing a 10 kHz peak around the net with that pair of headphones - in fact I think Jude's may have been the only measurement that wasn't. So when something like this comes up, I'd be holding off any judgement.
Next thing to note - Alex is using my compensation curve for my Veritas on my set-up. It's been calibrated as well as I can to mimic an IEC711 raw measurement, and I already acknowledge that at 9-10 kHz on my rig, my calibration measures lower than it should. Above 10 kHz on my set-up its a crap shoot - the Veritas is pretty inaccurate. However - up to around 8 kHz my measurements on my rig seem to be pretty good. How do I know? Because I had help (from Ken) in getting some accuracy. We both measured the same IEMs (we mailed them back and forth) and I could check and recheck. He also gave me his raw data and I used that to build the curves. Again - from 9 kHz onward I wouldn't call mine accurate - but I have already had 2 manufacturers (other than Ken) tell me that my rig is pretty close to what they are seeing on their own professional rigs at 8 kHz and under.
The important thing though is that while Alex might be using the same brand gear, it is not the same gear. Our mics will be slightly different, our other gear too, and almost certainly how we measure (even the actual ffts etc). I always use the same tip, the same insertion depth , and I have it crudely rigged for the same angle. This is one of the reasons why I can get repeatable results months apart. I also use an amp between the measuring device - and its been the same amp for at least the last 2 years (this is so I have a low impedance when measuring). I guess what i'm trying to say is that my compensation curve is calibrated for my exact measurement set-up. I gave it to Alex and have given it to other Veritas owners because it will help fix some of the fundamental issues with their Veritas measuring low from 4 kHz onward. But you should not expect absolute matching to mine, nor absolute accuracy. I think mine is pretty good for what it is.
Lastly - if Jude is measuring to a compensated standard and the rest of us are not, then there are likely to be huge inconsistencies. So before we automatically proclaim the person with the biggest $$$$ set-up to be the most accurate, and the rest rubbish, lets see what we are actually measuring first ........