Had the chance to demo the headphones at a local electronic store today, so here's my preliminary impression about the headphones :
So basically the difference between ES-HF300 and ES-FC300 is only the cable; as mentioned before, HF uses 6N-grade OFC cable whereas FC uses flat-type standard cable. The headphone body itself is practically the same; no difference in sound or build whatsoever. This means the 6N cable better justify the price difference; the difference in sound is indeed noticeable compared to the standard flat cable, I'm hearing more depth and separation, but that's all I can tell and I'm not sure if that's enough to justify the price difference.
Build & Comfort
The headphone's aluminum body feels sturdy and well-built, no rough edges or clunky parts. The earpad is on the thick side, and the surface material is quite comfy. The headband clenches quite tightly, although the supple, thick earpad negates the tightness. All in all the fit is quite good, the headphone sits tightly on my ears without hurting it, and stays that way after 20 minutes or so demo-ing it. Not sure about extended use (2 hours+), but so far so good.
Lows : It's definitely not for basshead, though the bass itself is not anemic in any sense. The bass is there, but the quantity is definitely not MASSIVE, perhaps just a tad bit north of neutral. Decay is medium, not too short or too long. The one thing that impresses me about the bass is the amount of air movements; combined with the deep-ish extension it makes for enjoyable bass to me.
Mids : Vocals. It's the vocals. There are a lot to like from the mids. Vocals are leaning towards the thick side, rendered clearly and beautifully, if a bit too glorified for my taste. Placement wise the vocals sits behind lows and highs, but for some reason it keeps drawing me in, making me end up focusing on vocals. Other than that guitar twang sounds quite realistic. All in all I think the mids is the selling point of these earphones.
Highs : I can't seem to put my hand (or more like, ear) on it, but there seems to be a bit of a suckout around 8k, followed by a slight peak near 10k~ region. Nothing too disturbing though, other than that highs is on the crisp & brighter side, but not bright enough to be annoying. Extension don't ask me, my ears can't hear anything past 15k-16k region
Soundstage & Separation : Size-wise the soundstage isn't massive, but it's big enough for me. Instrument placements and separation are well-defined with lows, mids and highs all taking their own space around my head without intruding each other. Lows and highs sits closer than mids.
Other : I think it has a shallow V-shaped FR curve. Good clarity top-to-bottom but especially from 1k to 10k region.
Can be driven straight of an iPhone without problem, doesn't scale up that well to amps and whatnot since there's not much difference sound-wise when ran out of my Go-DAP X compared to straight iPhone.
iPhone 4S and Go-DAP X with files ranging from 256 Kbps AAC up to ALAC lossless.
Note that this is only preliminary impression based on 20-minutes demo! Also, what I hear is not necessarily what you'll hear!
Personally I think as a whole the headphones are quite good considering it's Onkyo's first portable headphone. Bassheads or those in Beats camp should look elsewhere, but for the price, It sounded good-but-not-groundbreaking to my ears.
I wanted to try the IEM as well, but my local electronic store doesn't have it at the moment, so maybe next time.
I just got a pair of the ES-FC300 an hour ago. Been testing them out on my Sansa Clip+. I think your assessment is good based on my initial impressions. They do seem to have a slightly v-shaped response, but the bass emphasis does not extend into the lower mids, which I tend to dislike the kind of warmth that adds. So far the bass response related to the rest of the spectrum seems like my Audyssey EQd HT setup with just a little extra bump on the midbass and lower bass frequencies (like maybe a few db, but hard to guess, yet where I like it). Bass is nice and tight for the price point. Treble is a touch bright in a nice way that brings out detail, but not so much or too sharp as to be overly fatiguing at the volumes I listen--has just a little bit of that sparkle. To me, they sort of fit in that vein of the MDR-V6 and ATH-A900X amount of bass and treble emphasis. Given how difficult it is to find a truly neutral headphone, I think anyone looking for something fairly neutral might want to give these a try.
Also, I wear a XXL hat size. These pads and cups are good size for me for on ear headphones, whereas the DT1350s I had were a little too small, and I always feel like the JVS HA-S400s are really more optimal for a smaller sized head. Not saying that I think they might not fit someone with a smaller head--just that for big guys who really would like to get away from smaller on ears that are obviously designed for the average consumer and not for them, these will be a pleasant surprise.
Once they are broken in a little (I definitely believe some break-in usually helps), I'll post some brief impressions of how they compare to my AKG K550s and SR225is. I'm also looking forward to seeing how they sound with my ODAC and Asgard 2--whether or not that brings out any extra clarity and detail resolution.