I think the 009 is neutral, but not sterile.
Sterile in my vocabulary means somewhat thinner than neutral, both in mids and bass. The HD800 can be sterile at times. The K812 is not. The 009 is not.
Dry for me means no extra warmth in the sound, but otherwise neutral, and may be a good thing.
My adjective ranking about tonality and the amplitudes of Fourier transform in general (or should I say harmonic composition) is something like this:
sterile < dry < neutral < musical < warm < dark.
Ethereal vs meaty are expressing an orthogonal property that can be characterized by the density distribution of the Fourier transform components, if that makes sense, or should I say harmonic structure.
Another property is time domain behavior, waterfall if you like. Dry-neutral sound tends to be also with fast decay, another good thing.
It is interesting that while I give all credit to neutral sound, I like headphones slightly on the musical and fleshy side, something that probably has to do with the Fletcher-Munson curve so I am likely not alone.
BTW the 009 subjectively seems to have a "lit up" midrange in the 4-6 kHz region, at least compared to most headphones (well, likely the other way around, most headphones have a dip there). If I EQ that down (for experiment, since I hate EQ because it smears things), the 009 sounds more meaty and musical. I could do that also with an earpad mod, but after all left the 009 in original form, it is perfectly voiced. I had similar experience with the AKG 601, which was a very linear and neutral performer, but it sounded dry, even sterile. It is a bit tricky since the equal loudness curves across dynamic range make it clear that no headphone can be tuned perfectly for all loudness levels. However, it is enough to be good enough here. Our brain comes to help, with personal variable compensation capabilities, and I think that is why some people prefer e.g. the 007 over the 009, despite the 007's obvious midrange dip. I for example have higher than normal sensitivity to midrange dynamics, making me sensitive to headphones which sound "lit up" like the 009.
The 507 is dry and ethereal, but its midbass bump and 30 Hz bump makes it out of sterile zone. However, it sounds a bit harder in the upper mids and treble than the 007 and the 009. Tonally it is closer to the 009, but it is not neutral. It has a slight coloration in the upper mids which makes the 007 more relaxed sounding. The HD800 is both more dry and more neutral than the 507, otherwise they sound very similar, although the 507 is more ethereal.
The 007 has a somewhat velvety, caramel, sepia, bloomy tone, both transparent and meaty e.g. on saxophone and wind instruments, and also on violin, more so than the dynamic headphones like Grado, HD800, or then even the 009. Funny thing that my modded 007 sound more meaty and more dynamic than my modded TH900 (down to about 30 Hz where the TH900 takes the lead), which is more meaty and more dynamic than the Grado RS1 and the HD800 at the expense of being too colored.
The 007 is colored when compared to the 009, but not more so than a conrad johnson tube amp vs an Audio Research tube amp, just enough to make more things sound musical.
The 009 is unforgiving both to equipment and recording.
The main quality of my modded 007 is to make instruments sound wonderfully real. I melt when I hear my 007 play the saxophone or double bass or cello or violin, and the percussion hit fast, hard, deep and clean, with great cymbal dynamics, decay and resolution. The 009 is tonally more correct, but the modded 007 feels dynamically better and also less dry and ethereal (the stock 007 IMO doesn't even play in the same league as the 009 in making instruments real). The 007 changes so much with ear pads, pad fillings and headband adjustment that I just hate it. The 009 is much more consistent, and not much to tune there. But the 007 is perfectly good for metal and electronica too, for which the 009 is a bit dry in the bass.
By
n3rdling's @arnaud's description, the L700 may hit a perfect balance. I am very curious to try it against my modded 007. Since I don't recommend the modded 007 to normal people (modded 009 pads too shallow to be comfortable for most people, but fortunately it is borderline with my ear lobes), it may be that the LS700 checks most musical goodies for most people. However, in general, the Lambdas are not more comfortable than my modded 007, so it comes down to sound anyway.
I just wonder when the 009 update will come - perhaps next year? Stax definitely seems to know what they are doing, as things seem to go the right direction, and price didn't change.
Will it be called the Omega 900?
