Looks like we've got quite a big D2 spike at 4kHz, then a correspoding hump in FR at 8.

There's good and there's bad. I thought the treble was too much for MFSL Nirvana or DCC Dio when I cranked it up. I guess I could listen at quieter volumes, but Dio and Nirvana is stuff I personally like to crank up. For classical, jazz or other natural instrument recordings, the K553 is quite good. This is because the FR is fairly flat with a slight downward slope from 20Hz to 4kHz. That's a good thing. No wonky pianos. Even pop recordings, as long as they were mastered without hot treble, were fine. Slight emphasis toward the low end does balance the treble peak to some extent. Finally, it's a closed headphone. Closed headphones are always tough in terms of FR. For example, even the $2000 TH900 has a treble spike. At $119.99, which is where the K553 is dropping, it's really hard to complain. Darn good price for a closed headphone.

https://www.massdrop.com/buy/akg-k553-pro-studio-headphone?s=K553

Anyone else get on this drop?

I got mine today, and I am not super-impressed. They are not bad, and for the drop price, they are actually quite good, but they don't punch much above their weight. Going back and forth between my DT150, the K553 sounded leaner and slower. Listening to "here comes the night" from Arcade Fire - Reflektor, things like the natural impact and decay of a bass string being plucked were missing, and at the same time entire sections of keyboard action were hidden by what was either resonance or just plain distortion (or something else?). It was even worse when I switched from desktop to any permutation of portable, which disappointed the most since the 553 appealed as a far less hungry portable option.

I really like the build / look, and the way the 1/4 adapter is integrated into the 1/8 terminated cable is even more slick than on the HD600. I secretly wanted my reaction to be "wowee! only $120?!!?!?" but alas, they are just "good, for $120."

Hmmm... mod candidate is not a bad idea. First thing would be to pump up the pads and get the drivers a little further from the ears (methinks). I will make a very crude attempt at that and report back.

Recently compared my K550 (only a few months old) and K553 directly, and there were absolutely no differences in sound or build or fit. They literally just rebadged them as far as I can tell.

That 4k distortion spike sounds like glare/ringing. Otherwise it is a remarkably clean sounding headphone for a closed back in this price bracket, although the soundstage could be a bit wider. They strike me as fairly uncolored other than some minor ringing in the upper midrange which is most noticeable with distorted electric guitars and maybe a mild sub-bass boost above what I'd consider flat bass as well.

IMO, the perfect office headphone in this price range, and that's exactly what I use them for. They don't isolate the listener as well as some "monitor" type headphones I've heard, but strangely they seem to leak a lot less than one would expect for how much isolation they provide to the listener.

The pads are definitely smaller than the K7XX and although they are not velours of any kind, they have quite possibly the softest memory foam I've ever felt. It's so soft in fact that some may have trouble with their ear lobes rubbing against the inside of the cup.