Pros: Neutral sound, crazily good soundstage and imaging, build quality
Cons: Frogbeat's customer service not at the top of the game at the moment
With the C4, Frogbeats has produced a truly excellent CIEM.
The entire frequency range is done very well from top to bottom. While there technically is a slight suckout in the upper mid-range, I only notice it when listening to frequency range sweeps. These were intended as studio monitors, and it clearly shows- the sound is clean, transparent and uncolored.
The true strength of these monitors lies in their soundstage and imaging capabilities. While they're still inferior to a good full-sized open back, they really don't miss out by much.
Build quality is excellent at the same time, with shells very nicely buffed, vivid colors and no bubbles or imperfections anywhere.
The only issue is the less than perfect customer service from Frogbeats at the moment as I believe they are rather overwhelmed with orders. Build times are fairly long, and emails take a while to be replied to. Hopefully once things on their side become less hectic, things will settle back down. IMHO, they deserve a chance.
All in all, very worth a look into if you're after a neutral monitor.