What does this mean? You're just saying Carbon is louder than HV, so the knob is at a diff place now?
Mostly a difference from the headphone version, not the amp? How small is small here, compared to a given dynamic/planar? HD660 size? HE6? Mobius? DT880? Larger than L300?
No, as I wrote before, the Carbon is much cleaner but warmer (having more in the deep bass as well as tamed-down treble), and the bass-heavy character becomes more apparent as the volume goes up. So I am more comfortable listening at a lower volume to reduce this as the sound still has clarity and punch. If I do this on a lesser amp, the sound simply becomes weak and unenjoyable.
I was even thinking of reversing the port mod, might be more natural in the deep bass, but then I would have even bigger hump to deal with in the mid-bass.
I am still finding it bass-heavy on well-recorded music, so the Lambda Pro complements it nicely (for example, Pink Floyd - The Dark Side of the Moon just plain better I think, more balanced and powerful) where the opposite can happen. Even though this amp brings it down a lot, it can still be too thin and bright, it's just the Lambda Pro's character. Or I can start fiddling with the EQ on the Mk2 as well in the bass region, etc.
The Mk1 version should be more balanced but in this configuration it is missing liveliness from the sound (whether I am listening at a low or high volume)
So a really a case of small differences making a big difference in overall character at this level.
As for the stage I am not too bothered, as long as it is not claustrophobic and with the Carbon it is not like that at all. The Mk1 is wider and more expansive sounding, but in this configuration, it might not have a nice balance in all dimensions, it has potential for more, just not with this amp (and/or source).
What I also observed with this level of amplification that the Stax headphones in general have so much clarity, that they can "get away" with quite a bit of tonal mismatch, as long as I don't find it annoying (by being too wispy, harsh dry, analytical or lifeless) I can get used to it rather well.
For example, the 007 plays a particular instrument in a "correct" way (meaning I can hear how clean its transients are or how nice the tone is in that small part of the music) and the brain just fills in the rest.
Casing point is the Sigma Pro, where it is obvious that the bass is booming no matter how well the Carbon can control it and giving much more clarity, it would probably still need a big dose of EQ. But, as I wrote before about this headphone, after a few minutes I just pick up that sound and enjoy it quite well (although I think it can reach a higher level after more tweaks). Flawed, but very organic and enjoyable and the Carbon is definitely recommended for it.