The K550 mkII (same model as the K553 mkII, just different US/EU naming) is the successor to the original K550 and K551 released in 2012. There are no visual differences between the old K550 and the newer one (except the fact that the K550 mkIII has a removable cable). The K550 mkII has revised drivers. The K361 and K371 replaced this serie.
still have some issues with the comfort on these AKGs, the headband padding is too thin and hurts my skull, and the pads, extremely soft, are not very deep.
○ Release : 2015
○ Current status : In production
○ Type : Over-ear / Closed-back
○ Measured weight : 305g
○ Impedance : 32 Ohms
○ Sensitivity : ~101dB/mW
○ Average used price : $70-100
The K550 mkII/mkIII is possibly the most “neutral” closed headphone I’ve heard so far (I did not try the Sine which is considered quite neutral as well).
The bass, provided you can get a good seal, goes really low and gives a good rumble in the sub-bass area, around 30-70hz. The midbass is very neutral and does not bleed into the midrange.
The midrange is very full ; it overall has good timbre but it might sound slightly nasal around 2 khz, a colouration I often find on AKGs headphones. Some people describe the K550 mkII/K553 as mid-centric, and I can understand that given the non-emphasized bass.
Treble is quite good ; no harshness in the lower region (4-7khz) and decent presence around 10 khz, even though it can be a little strong for some folks. I find the top octave extension a bit missing, with a smooth air region.
Do they sound open ? Yes, to some extent. More than the average closed back under 300 bucks, but the soundstage is not that wide – a bit larger than an HD600. Resolution is solid for the price.
The K550/553 (mkII/III models) is a very nice closed-back under $200. Good build quality, balanced sound and correct isolation. My only gripes are the average comfort (on my head) and the midrange that sometimes sounds a bit nasal and artificial. The new K361/371 are safer alternatives, and can be bought new.
Measurements & Resources
Treble is a bit too elevated in the 8-10khz region. Except that, very balanced response for a closed-back. Low-treble is quite recessed. Modest subbass lift below 60hz.