Pros: Looks, Build Quality, Decent tonality and fairly flat FR from midrange down to bass, no treble emphasis, decent soundstage for a closed headphone
Cons: Serious peak and resonance in one spot in the upper mids ruins an otherwise decent headphone
When I first listened to these headphones, my initial two thoughts in this order were:
1. Wow these sound pretty fast and also fairly even
- 15 seconds later -
2. Wow something is wrong with the upper mids
These headphones feel very well built. I can't speak to their longevity or durability, but they are nice to hold, feel sturdy, the movements are tensioned well and feel solid, there's no creaking of cheap plastic. The finish feels durable and well made. One of the better headphones out there IMO for it's apparent build quality and finish.
They look very nice when sitting on your desk, and in pictures. A good design, but they are one of those headphones whose looks don't entirely translate to looking good when worn. They have all the right shapes and dimensions relative to each of the parts, but the whole thing is just too big to look very good. For their size, I'd say they don't look too bad as they are slim, so they don't stick out horizontally very much and give you the alien mind probe look that grados and many closed headphones do. The headband is slim too since it comes together at the top of the cups, so it doesn't have that gigantic and unnatractive arc that the older AKG's have like the K240. The headband hugs the sides of your head well. Still, the cups are huge even on my big noggin.
Very good except that the earpads just aren't thick/deep enough. Huge design flaw IMO because everything else was done very well for an extremely comfortable headphone. The cups swivel in a really nice way since they have a good amount of friction in the movement, so you can place them at the right angle for your head, and they stay there. Headband is comfy and is the right shape. But the earpads aren't thick enough to keep the grill over the drivers from hitting your ears. With such huge, soft earpads this is a pretty big fail IMO. I tried putting the foam donut shaped inserts that Hifiman has in their earpads into the K550 earpads, increasing the thickness, and it had no effect on the sound and made them supremely comfortable by simply increasing pad thickness. So as long as you don't have huge ears they should be fine. Or if you don't mind a little pressure from the grills. it doesn't hurt too bad on my big ears, but it just would have been so easy to avoid this situation. I get the feeling they didn't do much real world testing on these and got carried away with computer modeling.
They overall have a flat, balanced sound from bass to midrange with good tonality, and with a treble presence that is in balance with that part of the spectrum, which is very rare for headphones. But there is a serious problem spot in the upper mids that ruins this headphone. A resonant peak in a small part of the upper mids. I would describe their overall sound as a slight rainbow shape FR, though leaning upwards towards the upper mids for enhanced sense of clarity. They also can sound kind of fast for a closed dynamic. Not ortho or stat fast by any means, and not Grado fast, but maybe 6/10 for speed. Not bad.
Good not great. It extends down plenty low, it seems flat, there's no apparent midbass hump, bass does not bleed into the midrange or vocals in the slightest but is also well integrated with the midrange. There's no "bass + mids" or subwoofer effect where the midrange and bass feel separated by gaps in the spectrum. They have a cohesive transition from bass to mids, likely from a fairly flat FR. But bass is a bit low in quantity despite what the FR measurements suggest. The bass is in the background on these phones, with emphasis on the midrange. Not for bassheads at all. Bass is not bad quality, but it sounds kind of dry and a bit soft, whereas better headphones have more definition and dynamics and detail in the bass. Not bothersome, especially since it's in the background. I'd describe the bass as being just enough to provide a foundation and not sound too lite, but too low to sound totally neutral- it keeps your attention on the midrange. It gets out of the way so to speak, for better or worse.
I'd say the treble on these is very similar to the bass. Good not great. There's no emphasis in the cymbal range as far as I can tell. If anything it sounds a bit recessed in the upper treble. Nothing sticks out at you here or is glaringly bad. But the treble is not that clean or precise sounding. It is a bit rough/textured or papery sounding. Like the bass, I'd say it's a backdrop for the mids. Not a treblehead headphone either. Yet despite this lack of apparent brightness, these phones have a strong sense of clarity about them. I think this is what people like in this phone. They don't sound dull or rolled off or warm at all. Likely because of the slight lowering of bass volume, along with the emphasis in the upper midrange, the "clarity" range in the FR.
Here's the problem. Both the bass and treble on these are both presented as a backdrop for the midrange but there's a serious problem in this area, so these phones wind up failling short for bassheads, and treble heads, and then have issues in the midrange. First the good part.
The heart of the midrange and the lower midrange is done pretty well. Vocals have both the proper richness for a male voice like Tom Waits or Chis Isaak, which is surprisingly rare- they don't make vocals sound thin despite the lack of bass emphasis. They also don't sound overly rich at all. Chris Isaak's voice sounds very good. Vocals also give the proper air and breadth to female vocals like Emmylou Harris or the Audiophile favorite Allision Krauss. But sometimes vocals reach up into the problem spot and sound off.
Upper Midrange Issues
There is a spot in the upper midrange that has a pretty bothersome resonant peak. I kept wanting to call it "glare". The upper midrange glare isn't the most peircing or painful I've heard in a headphone but it is very bothersome and might be described as severely "jarring". It doesn't seem to cause me to reach for the volume knob as feverishly as some phones have, but it does keep me from turning them up and leaves me in a state of fear wondering when something is going to hit this problematic range and if it is going to hurt, since it seems to be right on the threshold. Any instrument in that range sticks out way too loud, and looses proper tonality as the sound in that range gets mangled by resonance and takes on a plastic tonality. You can clearly hear the coloration being added to what should be the original signal. This is partly because it's such a specific problem spot. You can sometimes hear an instrument or voice go up in the range and suddenly jab at you by suddenly increasing in volume while taking on this plasticky resonant glare. The decency of the lower part of the spectrum gives it a "surprise attack" quality which is what generates the fear and hesitancy when listening. If there was an instrument that existed only in this range, I am doubtful you would be able to hear what instrument it was. Some recordings play well with this problem spot and it's not grossly apparent because of the frequencies being excited by that recording and the particular balance of the recording (if the recording has a peak in that spot too, it's clearly going to be worse). But even on these recordings, this spot gives the whole spectrum a cheap plastic headphone feel kind of layed over the sound, as if you are listening to some very good throw away headphones. I kept thinking of them as the best airline headphones ever. Much better extension, tonality, more flat, but still plastick-y.
Overall good size for a closed headpone, has a spaciousness about it, but there's something strange about it as well. It's almost like there are 2 soundstages happening at once, the lower part of the spectrum sounds more spacious to me than the upper mids/treble, which sounds more constricted. This gives them a lack of coherency, or a kind of bad crossover effect, where the sound is a bit disjointed. I think this is because the resonance artifact in the upper mids destroys soundstage by getting in the way of the "trick" the headphones are playing on your perception. Soundstage is also destroyed by a "driver dildo" that was installed on the back of the driver creating a tiny chamber behind the driver rather than the comparatively larger size of the earcup. I'm guessing it was placed there in an ill conceived attempt to control the bass, but I have modded a pair of these by removing this dongle, and correctly damping the cups, and the soundstage becomes more coherent.
Good looking, sturdy closed headphone that is fairly comfortable and has a mostly well balanced, even sound except for a very problematic part of the upper mids that sticks out sorely and ruins them. However, this part may not bother everyone. If it doesn't bother you ie if you're not sensitive to resonance or FR irregularities, and you are looking for a well balanced headphone erring on the side of being a bit basslite for the sake of clarity, and you want good soundstage these may be a good choice for you. If you are not bothered by Grados you may not be bothered by this resonant peak. however, Grados have much more natural tonality, for example vocals sound more life like. I recently had an MS1 here and despite their colored signature they sound better than the K550 in every way except may soundstage width. There's no plastic tonality in the MS1's signature.
Here is a picture of the inside of the K550's cups. The lack of damping here contributes to the resonant peak, but after spending time with my modded pair which has damped cups, I have found that it is also being caused by the driver itself. Damping the cups helps, but doesn't fix the problem. The small rubber thing in the middle of the light gray circle around the driver, is the "driver condom". This seals around the driver and makes a small enclosure size behind it. The light gray area are vents, though they seem to be closed off with solid plastic.