Pros - Affordable, heavy-duty build, great sound quality for price, swivel features
Cons - Not as comfy for a portable
Value: For an asking price of $55-60, it is a very good deal. The sound quality is above average for this price point. Best buy among the SJ series and will give you a taste of entry-level "HiFi" sound.
Audio Quality: Against its little brothers the SJ11 and SJ33, the SJ55 headphones stands-out by a mile. It has this mild touch of HiFi sound into it. With that, I'll be comparing this can to the WS55.
Lows: The bass of the SJ55s seems to have more power, more punch than the WS55s. While the WS55s have better bass extension. Compared to AKG K518LE, the bass of this can is definitely better. I thought the K518LE bass are a bit muddy and distorted.
Mids: Just like most Audio-Technica headphones, they have warm sounding vocals. Tuned for female vocals.
Highs: Somewhat lacking and rolled off. Don't expect this cans to stand-out with acoustic and live music though.
Design: If you have a Pro700Mk2 headphone, they are exactly the same without the headband padding. They look like a miniature version. There's no structural weakness I can see with the design. The plastics are sturdy, it will survive falls, it won't break when sit upon. It also folds to a portable size, just like the Pro700Mk2s, and also offers the same swivel features. Isolation is very good even at 50% volume it blocks outside noise. Leakage is also well controlled, at 80% volume you barely hear a thing leaking out of them. The cups have aluminum rings on them, they look like plastic, but Audio-Technica confirmed they are aluminum. This aluminum rings are made to provide stability and prevent vibration from the sound the driver produces.
For a very affordable and small headphone, Audio-Technca really got technical into this. One caveat on these cans that consumers might now like, is it doesn't have any padding on the headband area. But, since it is so light it's not going to be an issue.
This should be a good can when listening to silent rooms like libraries. Great for studets.
But, compare to the WS55. The WS55 stands out with its classy aluminum ear cups.
Comfort: Good but not great. This might be a deal breaker for some. But, since these are advertised as a DJ portables it is quite good, it creates a very good seal but doesn't have this James Bond Girl thigh lock clamps like the Pro700Mk2s. The ear pad sits on your ears might be uncomfortable for some.
If you grade this as a consumer portable, then this would fail since comfort is one of the most important aspect when it comes to portables.
For a DJ portable, these are above average, very good seal, it blocks noise in and out, with one ear it is comfortable.
Update: After resting them on my desktop speakers, it did stretched some, comfort level has improved a notch. With velour pads, comfort level changed significantly while suffering mild leaks at 70%
Overall: I would recommend this headphones for DJ on the go. A cheap alternative to those HD-25s. Above average SQ for the price. Very durable withstands stress test quite well. Doesn't I don't see any structural weakness. It is primarily made out of high-grade plastics, very solid. I can fold down to size and will fit your hand bag. It does fit on my walking-shorts, but I don't think they'll fit with my pants.
For a portable DJ headphone at $50, these are very good. They are marginally better than those overpriced AKG K518LE DJ; however, I thought those cans has better styling/build.