I've owned the Flat4 for a while now, both the SUI and KAEDE versions, and it's a mixed bag. What it does well however it does better than almost any IEM I've ever encountered: it's a low level detail monster, renders layers in a really impressive manner, and its low-end is mighty impressive in texture and timbre. Personally for me it also gives a really enjoyable internal / heady type of presentation, with a nearly endless inner depth to the sound.

The overall balance however is definitely U-shaped: it'll have too much bass and too much treble for some folks. For me, I don't mind the bass so much (it bothers me less than the IE800), but it's the treble on the SUI that is too glaring at times.

Two thoughts on this however: the first is that Ocharaku pretty much tuned these with foam tips in mind. They package them with Comply, and encourage the use of Comply, which basically helps to tame the upper end. Normally I hate what foamies do to the sound, but in this case it actually works well with the SUI. With a lot of silicon tips the treble is simply too harsh. Secondly the KAEDE model is more refined compared to the SUI, especially in the treble.

I think these are very much in the same spirit of "Japanese treble oni" as the EX700SL. It's a certain sort of treble emphasis that is almost too much for me, but stops just short of the mark. The guy did work for Sony after all.

First thing I can say after owning this IEM: It wasn't meant to be listened in a relaxing mood.

Lucky for me, I kinda like treble excitement in my gears (being tortured for ages by T70 250 Ohm, got the Stockholm Syndrome already).

And gosh, I can't believe all the low level details it presented. I always felt like kinda missing the mids, like the vocal is too laid back to my ears. I guess somehow the graph shows it.

Regarding bass, I felt it wasn't enough to my ears. I've to boost some more bass to listen to Bon Jovi. However, the hi hat portrayed is among the best in any gear I've heard. It was just so transparent. Unlike FAD (any iem from FAD), FAD treble kinda too much to me which makes the high sounds artificial.

The most interesting part of SQ is how it renders the stage. It was kinda.. peculiar, albeit in a nice way to my ears.

Some complained about wearing it makes the users look like Frankenstein or sth. lol