I got my hands on a couple of K's earbuds over the last few years and they tend to share a similar house sound. Simply put, they more or less all have 'deep bass, sweet mid, smooth high and open soundstage'. All and all they are warm sounding earbuds that are good for mainstream vocal music, focusing on musicality rather than accuracy/details. When it comes to mainstream music, they can sound excellent, especially on conveying emotion, as long as the listener isn't looking for an analytical sound. This also means they are not the best choice for instruments or classical music. When it comes to White and Black Bell or Poseidon, the above still applies. Here is, however, what they are different in - White Bell is by far the most sensitive to how you wear it. While White and Black Bell share the same housing design, White's particular tuning tends to sound a bit hallow and distance if you get a loose fit. The shiny and smooth plated surface and the small housing really doesn't help to get a really good seal, even though it is quite comfortable. I do strongly recommend using foam, particularly donut or multi-holes variant, in order to get the rather full sounding White.to reveal itself. When you get it right, White will have the most upfront mid and the smallest soundstage (though not actually small) of all three of the newer K's, making it the most vocal-centric of the bunch and great for pop and rock. Black, on the other hand, doesn't care as much about fitting as White (though I still recommend donut or multi-holes foam) since its tuning doesn't highlight any particular frequency like the White, and tends to sound more consistent across the whole range with a wider soundstage and thus making it more versatile when it comes to different music genre. While Black's mid might not be as sweet as White, the overall balance is better. The biggest difference I have felt between the two is that White is more energetic where Black is more mature sounding. Poseidon, in comparison, is really more of a mid-point between the two, striking a really good balance while having the best soundstage and musicality of the three. In a way, Poseidon almost sounds like a full size can.
With this kind of high price tag, talking about price/performance ratio often becomes a moot point. You will definitely find better value in cheaper (though lesser sounding) options than these earbuds. Nonetheless, White and Black are still overall in and around the same high level of SQ as K's previous flagship, the 500ohm Samsara, making them still competitive over the other flagships / second tier. Poseidon, on the other hand, is truly among the best of the best out there. Whether it will suit a person is, however, more than just SQ, but also a preference in music and taste. For example, Liebesleid still excels in female vocal and detail where Poseidon holds more advantage over male vocal, etc.
