I am trying out the 685 S2s now, and my first impressions are something like:
If we were to liken it to headphones, then yes, the Q300s would be like DT880s with their excelling performance in highs , and the 685 S2s closer to HD650s with the mids (just my experience with headphones I've used myself). The S2s have more meat on the bone for sure, but they don't sound as open and spacious, or airy. The sweet spot is also a lot smaller, but this is a given with the tweeter setup. Not really an issue if you know how to toe in (Q300s if you like dancing around your room I guess?).
That being said, I find I'm getting a lot better direction from the S2s, and they seem to be filling the room better than the Q300s ever did. I tested out positioning whilst I played some games (not the best way but it works!) and I found with the Q300s I did have some trouble sometimes with being able to figure out where some things were coming from, but didn't have this problem with the S2s in the slightest. Interesting. (Using the S2s for gaming was also more satisfying due to the deeper and better bass, just to note).
So, a first impression summed up would be something like:
- Better bass for sure
- Less sweet spot, and doesn't come from 'everywhere' like the Q300s do
- Whilst it has less soundstage due to not being as open and airy, direction/positioning seems better
- Fills the room more than the Q300s did
- More of an 'impact', moe meaty flavour.
Q300s are more airy, open, and quite bright in comparison, but to me, can sound 'flat'. Bit of an oversimplification, but describing audio is hard. If you were to ask me in person I'd say 'it goes wham, bam, zing, and then my heart goes doki doki'