Very brief comments of Solitaire T vs ML 5909 vs Focal Bathys vs B&W PX8.
I owning the Bathys and px8 recently but returning them so my comments about this 2 headphones are from recent memory, but even a few minutes of audio memory isn't 100% reliable. I still owning the 5909.
I think that if you giving this 4 headphones to 100 people in the street, more people choosing the Bathys, then the px8, then the 5909 ONLY IF ANC is on (because you having more bass), and then the ST. So, now after my unscientific survey, this is how I see, very generally, this 4 headphones.
The Bathys is the winner for general public because is have a big / grand sound with very good soundstage that can impressing people easily. For me, unfortunately, I finding 2 problems. One is the mids are never convincing and are sounding a little too recessed, even after using EQ that is helping but not really solving the problem, and I also needing EQ'ing bass down with more music that necessary. The other really HUGE problem for me personally is the, for my ears, extreme volume changes between only one volume step (up or down) and other in iOS and macOS. This is so frequently horribly frustrating, and after all this time and many complaints Focal doing nothing for solving this problem. Also, the EQ isn't covering the frequencies I really want changing, but still not so bad.... The Bathys design isn't my style at all, is looking, for me, a little ghetto for my taste. Other aspects I don't like but don't mentioning now.
The px8 I immediately need using EQ for decreasing bass and increasing treble in the app's EQ. I still own the P7W that sharing some sonic aspects but the P7W, even after 6 years, is very more correct in the mids and treble performance even when EQ isn't available. The px8 is more about adding too many spices / flavourings and having very good construction quality. The design in general is very nice, but one thing I really, really not liking about this headphone is the very prominent "bowers & wilkins" writing in shiny letters in the earcups ("Look at me AND I look expensive!!").
ML 5909 having a design I don't like, but construction quality is really excellent, the best of all this 4 headphones, in my view. Funny but I actually appreciate the cheap look design because isn't attracting attention at all (I prefer wearing this in public than px8 ands Bathys). The 5909 is, in my opinion, the only headphone that really competing in sound quality with the ST, but the 5909 is adding a bit too much spice in the treble area, giving enhanced detail in less realistic way than you finding in the real world. This is a little more problematic at more high volumes where is becoming fatiguing with some music. Also, the sound isn't consistent in all modes, but the 5909 is still really very, very good.
The ST, the boring sounding headphone with not sufficient spices and even a small soundstage...
The ST for me is the very more honest headphone that is the more close like a clean (boring) window representing audio in a more honest and natural way, either from studio quality recordings, or from venues with good acoustics (so, so, so many venues have terrible acoustics!...I often laughing when people so frequently saying X headphone sounding just like live concert...I usually think "I don't want this headphone")
This are very brief comments and I can saying a lot more but I think the is sufficient.
My personal ranking: ST > 5909 > Bathys >> px8.