Got a chance to listen to the S5 today, I have to say, it sounds a lot like the S1's signature... But done right. It's still a bassy signature, but it's done properly.
The low end has a nice large body to it with strong impacts that can boom. The sub-bass texturing has a lot of fluidity to it and can even rumble at times. This rumbling sub-bass gives the presence of a large sound stage; it's quite euphoric. Depth and presence is not a problem with the bass by any means.
The midrange is purely created to be smooth. This sacrifices some details and any sort of aggression that the mids could have, but the straight fluid-smooth midrange you get in return is worth it in many ways (and I'm not one to like colored sound). Vocals have a lush and deep tonality to them. They don't quite hit the higher octaves of the human vocal range, but the depth that the voice has is simply inviting. The upper midrange offers ample clarity to add a bit of energy to the midrange.
The treble has a very comforting snap to it that isn't overdone. Rather, it gives good detailing and offers good extension without becoming overbearing. The upper treble sparkles beautifully with great smoothness to them. They offer good clarity and detailing as well. Extension is ample enough for most instrumentals. It should be noted, however, that the air is missing from these IEMs.
The S5 sound very... Euphoric? Engulfing? Enticing? All three words would easily describe this IEM. It's definitely a very fun IEM to listen to and get lost with.
this my impression too , a bit too much of bass , just tame the bass and this can be an excellent earphone .