If you look at Audeze LCD-2 and LCD-3 graphs there is a much bigger variance from unit to unit than these graphs are showing. But once you get over about 2kHz, the measurement technique becomes more critical and the slightest variance in that technique (mic, headphone positioning, sound output levels etc), can provide challenges in graph consistency even if you measured the same headphones more than once. However the Audeze graphs, although smoothed, are not as smoothed as the Senns are. Because of this high level of smoothing it does indeed appear that there is a deliberate change around 6kHz in manufacturing. Below 2kHz, the graphs are very consistent from unit to unit on almost any headphone I look at and so it does also suggest that the graphs are indicating a change in bass response as well. Unfortunately the graphs only go down to 100Hz, and as the graph suggests an upward tick towards 100Hz, it would be interesting to know what it does below that!
Using my HD800 with a soloist, all I can say is that the bass does not sound overblown, or light but my auditory senses suggest "clinically accurate". This could be interpreted negatively when the word clinical is used as to suggest cold and unexciting. I didn't mean it that way at all...just that it feels I am hearing everything I am meant to hear at the right level. In contrast the LCD-3 I also have still sounds fuller and more rounded at those low frequencies, if not quite as detailed. I would NOT say the LCD-3 was slower (and I would certainly hope not for a planar headphone!), but the LCD-3 can give the sensation of a fuller bass at the expense of a very slight level of detail.
Also listening to a drum track from an SACD of Hiromi, I was fascinated about the different portrayal of the drum set with both the HD800 and LCD-3. The HD800 presented the drum kit in a larger studio some meters away from me. The LCD-3 sounded like I was the drum player and arguably seemed to present the timbre of the drums slightly better. But that slight nod to the LCD-3 also becomes its negative when dealing with orchestral music where it can then sound congested like all the instruments are on top of each other. Fascinating differences between headphones...the timbre aspect is likely to do with the darker frequency response of the LCD-3...but the positioning of instruments within the soundspace is the most intriguing. It suggests that you would choose the LCD-3 for a more intimate moment with an artist and a small number of instruments...but the HD800 when dealing with large bands, orchestras etc.
I am sure the differences between yours and mine are unlikely to be audible. But this is very interesting for me. I play the piano and often practice using a Yamaha Clavinova...one of the more recent high-end models. Having a pair of headphones that correctly captures the timbre of the piano is vital for me. Of course this is highly complex as you have to consider the accuracy of the samples in the first place which may have a bias in their own right. An example of a headphone that gets it completely and totally wrong (for me) is the Grado PS 1000...the treble is so peaky and all I can hear is the click sound of the mechanics of the keys (aspects such as the piano hammers are sampled as part of the complete reproduction of a digital piano). It was so distracting I couldn't bear it. The HD800 I listened to about 2 years ago (I don't have the serial) was better than the Grado but still over emphasised the treble and it didn't sound right. This new HD800 sounds very different (I know its a long time ago, but I know exactly which sound I am listening for) because the peakiness that was distracting me is almost completely gone. However the Audeze LCD-3 still wins the day for use with my piano. However I bought the HD800s to use along side my LCD-3 for my Burson Soloist set-up as I have found certain types of music can sound congested with the LCD-3 but open up beautifully with the HD800s. I don't think "one headphone fits all". With loud speakers we have to choose a favourite because we don't normally have the living room space to have several sets for different music genres. But with headphones, if one can afford it, we gain the luxury of choosing the sound/equipment to fit the music. This is why headphones can be a bank breaker if you are not careful!
