Pros: Fantastic bass presence, balanced sound signature, stylish aesthetics, lightweight
Cons: Not the most comfortable, some build quality issues, awful connector, overpriced cables, lack of replacement pads
Before I begin this review, I would like to point out that I have owned two of these headphones. The first unit was a used pair that seemed to have more damage than Amazon Warehouse suggested, and my current unit, I purchased for $100. This was a total bargain, and I would argue that it is worth the price - provided you can deal with the complaints that I have for these headphones. You can't get the cream of the crop at $100-150, but that doesn't excuse some of the issues I have.
Packaging & Accessories:
Out of the box, the accessories list leaves quite a bit to be desired. Not that I mind, of course, since I'd rather buy a cheaper pair of headphones with less accessories than a more expensive one with a lot more (I prefer buying my own accessories aftermarket). It does come with a nice pleather carrying bag, which fits the headphones reasonably well. I have to make mention of this because I have owned another pair of headphones where the cans barely fit into the included bag (Sony MDR-X05). Aside from that, it comes with a flat cable - thus the FC model name - that feels surprisingly sturdy for how flexible and snaky it is. The cable is incredibly thin and yet feels as though it would survive getting snagged on the edge of a table, and indeed, it has.
Having said that about the cable, the choice of connector almost ruins the purpose of a removable cable. It uses the MMCX standard - same as Shure IEMs - and it must be said that it is not suited for these headphones. It will stay in place quite well, but god forbid you can shove it into the ports out of the box without a lot of elbow grease. Because I had a problem with my first pair where the connectors were loose and the audio would cut out in one channel, I tried to be incredibly cautious plugging these in. It took a shocking - and almost downright unacceptable - amount of effort to install, but I got them. These connectors are not meant to be removed repeatedly. Once they're plugged in, the only other time you should ever remove them is if you need to replace them. The choice of connector makes little sense to me, as MMCX is a tiny connector better suited to IEMs. Why they would shoehorn it into an on-ear headphone's design is beyond me. They could have just used a 2.5mm or 3.5mm connector with a locking mechanism.
That's not the only problem I have with the build quality, however. One other issue I encountered with my original pair that's beginning to manifest is crinkling noise. Originally, I concluded that this was coming from the diaphragms, but considering that it hasn't affected the sound quality and it sounds too tinny to belong to the drivers, I'm beginning to think it's the enclosures. After prolonged use, they could start crinkling every single time you put them on. Another owner tells me that this is normal, but I would argue that it shouldn't be. WTF Onkyo?
If you're the kind of person who supra-aurals don't do much for in terms of comfort, you can probably stop reading this review. This is hardly the most comfortable headphone I've ever worn. For extended periods of time, the wearer might begin to feel the usual use discomfort, which is easily remedied by a small break. I'm able to handle this, but to those who can't stand to have anything resting on their earlobes, be warned. It doesn't help that the pads are not memory foam. If you're the type of person who prefers their headphones to 'break in' as opposed to simply having memory foam-stuffed pads, then you might like these.
Despite the usual supra-aural issues, however, this is a very lightweight pair of headphones, and I can see a lot of people enjoying this. The headphones are quite large; not to the point of being a circumaural headphone like some people say, but noticeably larger than the usual on-ear. Which makes quite a bit of sense, as the enclosures house 40mm drivers. The headband is adequately padded and clamp are quite small. The only discomfort one should reasonably expect comes from the pads - which aren't replaceable if they wear out over time due to the lack of replacement pads. There may be a pair of aftermarket pads that would fit on these, but Onkyo does not sell any; they only sell overpriced cables, which I will get to soon.
Starting with isolation, these headphones are above average. I suspect the dense pads are part of the reason for superior isolation relative to other headphones, but they aren't the last word in isolation, either. Being on-ear, they won't seal you off from the outside world the way an IEM or a larger closed headphone would. However, for the daily commuter, it is more than adequate unless you sit on a very noisy bus.
Now, the sound itself. If you read the pros and cons already, you'll note that I wrote that the bass presence is "fantastic" despite having a balanced sound. There is a bit of recession in the mids, but it is not quite dramatic enough to describe these as v-shaped. The low end on these cans really brings instruments like the bass guitar to life. When listening to "Breed" by Nirvana, I had never felt such a presence from the bass guitar with other closed headphones. It was so clear and would have taken the show if not for the exceptionally treble-y guitar and cymbal banging. "3's and 7's" by Queens of the Stone Age, likewise, had very fun bass that brought the guitar to life, and would engage the singer. However, the slightly recessed mids in both of these songs meant that the vocals were overwhelmed by the instruments - but not by a whole lot like most mainstream headphones.
Although treble on these headphones is not what I'd call recessed, it is anything but fatiguing. The treble energy is present, but this sounds like a headphone forgiving of poor recordings. Female vocals from the likes of Courtney Love in "Reasons to be Beautiful" by Hole come to life more than any other pair of headphones I own.
Male vocals, on the other hand, are lacking in some songs. The aforementioned song from Queens of the Stone Age leaves something to be desired in Josh Homme's singing; that said, not all male vocals are equal. The issue is not quite as pronounced in songs like "God Is On The Radio," where the male singer's voice is present in lower octaves. Likewise, in "Papercut" by Linkin Park, Mike Shinoda's lyrics aren't overcome by the exceptionally bassy sound. Never at one point could I definitely say that the bass on these headphones was drowning out any part of the music. It goes without saying that songs with higher pitched vocals such as "Paranoid Android" by Radiohead will not have the mild recession problems.
What may be the most interesting part is that these headphones aren't actually best in a quiet room or in a loud commute, but rather, something reminiscent of a coffee shop or restaurant. I find myself wanting to use these headphones as much as I can in more relaxed environments such as classrooms, where I can study in peace while drowning out the noise from other people who are studying or tutoring.
I would say that at $150, these cans represent a great value. Had the Audio Technica ATH-M50s still been floating around this price, I would suggest people buy the Onkyo ES-FC300s instead. However, with the release of the ATH-M50x, I would say that both headphones have a fairly equal footing and whichever one you would like to buy comes down to personal preference. I find the ATH-M50s incredibly overrated in terms of sound, personally, and would argue that if someone is after sound quality, the ES-FC300s represent a far better value. But then, it comes down to elements unrelated to the sound such as comfort. If you're able to find these headphones at the $100 price point that I bought my second, unused pair for, then I would go as far to say that it's a steal.
Unfortunately, that's where the budget recommendation ends. Replacement cables exist for these headphones, but forget them. I've seen a few floating on eBay, and the "audiophile" cable included with the Onkyo ES-HF300s is incredibly overpriced. I have not seen it anywhere priced for anything less than $50. That's too much money to spend on an MMCX cable, especially when Shure replacement cables can be had for about half the price. The flat cables aren't much cheaper than the crazy-expensive HF cable, which I doubt are any better or worse as far as sound quality is concerned. But then, I haven't used them because I would rather buy another pair of headphones with that $50. (EDIT: I went browsing eBay and happened across an HF cable that only cost $35; still too expensive, but not $50 expensive.)
After writing this entire review, I'm left wondering to myself if I was too harsh on these headphones. I would argue that no, I was not. Sound quality is not the only thing that a good headphone has to concern itself with, despite what any "audiophile" might suggest. I cannot wear Grado headphones for more than two seconds, for example, and that is not hyperbole. These headphones do everything they need to at their price point and leave little to be desired, however, especially when you're being given such outstanding sound quality. There's not a whole lot that $150 can buy you, but even for that street price, these headphones are a fantastic purchase. Unless you have a problem with the terrible connectors and you absolutely need the best comfort you can get, you will not regret buying these headphones.
EDIT: It bears pointing out that although the connectors can stop working in the worst case scenario, they will stay in to the point that you can press your knee down on the cable and it's more likely the headband will extend completely before the connectors pull out. These are very durable connectors... so long as they work.