EDIT: Click here for an excellent pad mod from dxanex!
Let's please keep this thread on point, fellas.
To my ears, the AKG K550 is a headphone with a great deal of potential. It's fast, detailed, uncolored, spacious, fairly neutral, and free of excess grain. Conversely to my and others' praise, however, they've been criticized by some for being thin, bass-light, and treble-centric. A few of these detractors have also stated that these negative traits are diminished when pushing the cups closer to their ears. Likewise, even those who have sang its praises have cited finicky fitment as a necessary evil. From this general sentiment, we can draw the conclusion that the fatal flaw of these headphones is a physical one. After using my "modded" K550 heavily for the past three days, however, I can confidently say that this issue is correctable (for most) through the implementation of two highly effective and fully reversible tweaks.
Before moving on, please note that the K550 is a BIG headphone and, without highly additive modification, (i.e. custom ear and headband pads) it simply will not be compatible with smaller heads. This is the only headphone that I've personally ever found proper sizing at the smallest setting and I do not consider myself to have a small melon. Additionally, the earpad diameter is amongst the largest I've encountered. Those with an average sized cranium but gaunt facial structuring may also encounter issues with the stock pads. Also, I apologize up front for any terrible cell phone photography.
FIRST TWEAK: Bend that headband!
In my initial impressions of the K550, I implored owners to "man up" and bend the metal headband to create a better fit and increase clamping force. However, I also cited the very top as causing some initial discomfort. That being the case, I decided to bend the headband further.
-Align the very center of the headband across your wrist like a watch. This will avoid creating a peak or crease.
-Place the thumb and fingers of your other hand on the plastic adjusters on both sides. Judiciously apply pressure. It will bend the most at the very center, but since this is the segment that will flex outward the most upon putting it atop your head this is desired.
Even exertion of pressure/weight across the entire headpad. Before bending and also after my first (admittedly reserved) attempt, there was a focal point in the very center. The way to ensure proper fitment is to put the headphone on at your ideal position and press down on the points at which the metal headband meet the plastic adjusters. If there's space between your head and these parts of the headband, then further bending is required. Keep going until there is no "give" and every part of the headpad is touching your cranium. The end result is both improved comfort and clamping force. A picture of how my headband appears post-tweaking:
SECOND TWEAK: Stuff those earpads!
Personally, I find the faux leather covering and internal sponge-like material used for the K550's earpads to be incredibly plush. However, the lack of firmness combined with the excessive tension of both the vertical and horizontal cup pivots creates a recipe for a headphone where optimal positioning is, frankly, a pain in the ass. Stock, I found myself searching for a good seal 10-15 minutes into a listening session. Repositioning the cups and compensating for the way that the pads "sink down" each time they're moved to ensure that a seal is achieved and the cloth driver covering was not touching my pinna was a major hassle. Furthermore, when it was necessary to leave my listening area temporarily re-finding this position from essentially square one was downright obnoxious. I've never had a similarly frustrating experience with another headphone, period. Full size Beyerdynamic-level comfort and hassle-free "set it and forget it" positioning this was most certainly not.
My apologies for what may be considered a lack of pictures through this section. Although this tweak only took approximately 15-20 minutes total, I don't feel like ripping all of the "stuffing" out to obsess over uniformity again since I consider myself to be more OCD than most.
-Remove the earpads by placing a finger under the wall of the interior and gently push outward. From there, grasp the outside of the pad and gently tug away from the cup, working your way around the perimeter. After about 2/3 of the circumference is detached, the rest should easily slide out from the plastic groove. Also, for those of you who have replaced Beyer pads before, note that these are comparatively much more elastic and creating deformities is not of great concern. They're leagues easier to work with.
-Place a finger inside the back of the pad where the pleather meets the fabric and pull the internal plastic ring out from underneath the lip. Work your way around just as you had done to remove the pads. You'll notice that the fabric is stitched to the earpad making reassembly easy. After this, grab a tennis ball and play fetch with your dog. All work and no play makes Jack... errr... Justin a dull boy.
-There may very well be a better material that can be utilized to stuff these, but due to both availability (stole some from the woman of the house) and pliability I opted for cotton rounds. I stacked two on top of each other, folded them in half, and tucked them under the pleather lip of the pads end-to-end working my way around the perimeter. The length of them worked out to be nearly perfect with no overlap! I then took a singles, folded them in half, and inserted them atop the double-stacked ones staggering them with the initial rounds' positioning filling in the "gaps." Since they're cotton, you can further fill in empty space by pulling them apart a bit. It's unavoidable that they'll be a touch lumpy, but since this will essentially be beneath the super-comfy spongy material (this stays... do not remove it!) that originally populated the pads you'll never actually feel it.
-Reassemble the pads by carefully tucking the cloth/plastic ring back beneath the lip. The cotton should stay in place beneath the spongy material sufficiently well, but I'm sure a lack of finesse could cause it to "float" into undesired locations behind the pad walls.
-In what I feel is a critically important precaution, take some scotch tape and carefully remove any excess cotton/fuzz/etc. from both the underside of the cloth earpad screen and the plastic driver cover. You wouldn't want anything nasty getting stuck in the driver, would you?
-Remount the earpad to the cup. There's a convenient notch (again, a leg up over Beyer work) that will help you get started. Insert part of the lip into this notch and twist until about 2/3 is held in place. From there, pull slightly on the outside of the pad working your way around the circumference until you reach the notch again. Grip the exterior of the pad, rotate, and the remaining bit should fall into place. Let your own level of OCD dictate how well aligned the interior cup letter needs to be and continue to rotate as appropriate.
-At this point, you should notice that the stuffed earpad is noticeably larger than the unstuffed one. Your excitement level will likely increase with this observation, but keep it in check while you carefully repeat the above steps with the other pad. When finished, hold the headphone up triumphantly within your line of sight and admire the results of your efforts. Hans Gruber will approve.
To eradicate the finicky seal scourge that is seemingly to blame for the mixed K550 reviews. You should be able to pick these up, quickly adjust the cups to the approximate center position, throw them on your head in your ideal position, and immediately notice an increase in isolation. Personally, I was shocked at just how well this tweak worked. The increased size and firmness of the pads goes a long way in offsetting the unforgiving cup pivots. Combined with the optimized headband, a hassle-free large cup seal is created that is reminiscent of Beyers... not what I expected but, pleasantly, exactly what was achieved. Upon pumping music through them, you should be able to press in the cups without hearing sonic changes. The acoustic improvements previously described by others that cited a lack of clamping are now ever present.
Firstly, a possible drawback. While I find the headband to be more comfortable, the earpads are less so. The increased firmness means that they're more noticeable for the first half hour or so of listening and the additional isolation spells increased heat. However, the cloth driver covering no longer rubs against my pinna; a definite pro. Additionally, my longest listening session with these changes in place has been approximately 3 hours, during which I experienced no outright discomfort and never felt the need to take them off.
The positives, in my opinion, far outweigh the above negatives. As previously stated, a hassle-free seal is achieved creating improved isolation and better overall sonic performance. Before implementing these tweaks, I had no idea how much bass I was missing. In terms of quantity, I would put them on par with my Cardas'd HD600. (which is to say perfect to my ears) Quality-wise, I'd rank them ABOVE the HD600 for being faster, tighter, and more precisely layered. Body and tonal weight is increased, but may still be ever so slightly less than ideal. Still, it's never a distraction, unpleasant, or jarring because of a lack of realism. Treble is both well extended but also well controlled and, even at moments of sibilance at the fault of the content, (these are highly resolving cans... no hidden imperfections here) is always kept at a distance to avoid being harsh or piercing. Notes, from top to bottom, are better rounded and devoid of any superimposed edges. All the positives are retained from stock: spacious, airy, fast transients, great soundstaging, highly resolving, devoid of warmth or coolness coloration... etc. Pairing this modded K550 with the Nuforce Icon HD that I recently "downgraded" to equates to my most satisfying sealed headphone experience to date: increased spaciousness, tonal weight, a nice bolstering to the bottom end... but now I'm just gushing.
As I've previously stated, the AKG K550 is available in the United States at a major retailer (Best Buy) that offers a full money back refund period. Take them home, "optimize" them to your head, and give them a proper audition. If they aren't for you, get your money back, retain the gained perspective, and share your opinion with your fellow Head-Fiers.