Pros: Pleasurable dark Signature, BASS, Comfort, Portability, Value, Replaceable padding, Built quality
Cons: Thin cable, Isolation
The PX100 is proof that something quite cheap and simple can provide as much enjoyment for the end user as something significantly more expensive. That's not to say that they're on the same level of quality as a higher end product, you do get what you pay for. It's a mental thing. There's so much satisfaction to be had in the idea that something so light on the wallet can sound so... pleasant!
The PX100 are a fantastic little portable that I was using back in 2010, before I got my own first pair of headphones, the HD448, and subsequently became interested in audio. The PX100 actually belong to my Mother, she got them with some sort of audio therapy kit she bought a few years back. Whilst she doesn't appreciate them for what they are ("They're just headphones!"), and nor did I when I was using them a few years ago, I reacquainted myself with them recently as I've become interested in having a portable set up, and have come to really like what these are about. I'm likely going to be purchasing the V-Moda M80 soon, but these things are heavyweight performers for their price, no doubt.
These phones are open back supra-aural portables. They're foldable and include a plastic carrying case. The earcups are foam padded, and can swivel 90 degrees. The headband is metal with plastic rimming, has pleather covered foam padding. The headband length can be adjusted, with nice satisfying click feedback. I quite like the design of these phones, it's very compact and light, looks pretty decent and is quite comfortable. I used to find the earpads really uncomfortable, but I believe I was wearing them incorrectly and putting pressure on my upper ear. I now wear them lower down and they feel quite good. Whilst the headband padding is quite minimal, it's perfectly sufficient since the headphones are so light. Replacement padding is readily available for both the earpads and headband all over eBay. Nothing worse than headphones where padding is impossible to replace.
The build quality of the headphone is quite good, too. The hinges of the foldable headband feel very solid, the metal that comprises most of the headband is also great. The plastic bodying is sturdy all over, it's much more solid than you would think by looking at it. The one weakpoint of the build is the cable. It's as thin as you would expect from a headphone of this price range, though if you treat it with care it won't be a problem, and I know these particular phones have been tugged quite violently off my head on more than one occasion over the years, but they've held up perfectly.
The only other design issue is that the headphones are open, which is a good thing for the sound. However, being a portable headphone, it's hardly far-fetched that these will be used in settings where some isolation would be quite welcome. Whilst I haven't used them for this, I can't see these being ideal for a plane, or possibly a particularly noisy train. With volume compensation they actually cope quite well in fast moving cars, and of course if the vehicle is only zipping around town there won't be much noise to worry about. But, nevertheless, if it's a very noisy setting you'll be using these in (like a busy city) then these might not provide the isolation you're after. You can use volume compensation to fix that, but with that comes fatigue and worse battery life. Still, I think their open nature is advantageous for being aware of your surroundings. I feel quite safe being able to partially hear cars coming when taking them on a walk.
As for the sound quality, it's a quite surprisingly good sounding phone. The most impressive part is the bass response. So many small, compact headphones sound really tinny and weak down low, yet the PX100 sounds amazingly full. Not to mention that it's open back, it's pretty stunning if you ask me. Whilst I haven't heard it, from other people's impressions I suspect this might be like a little baby portable HD650. But I shouldn't say things about headphones I haven't heard (too much of that on Head-Fi) *shrug*. Regardless, the sound is smooth. A nice full low end, undisturbed midrange and easygoing treble. The treble is actually the most interesting thing about these phones in my case. My two most recent headphones that I've been using primarily are the Grado sr225i and the Ultrasone DJ1, both are quite bright. After listening to the PX100 again, I gotta say, I rep the dark side of the force from now on. It's so easy going and relaxing to listen to. Granted, the PX100 is probably a little too dark to be completely ideal for my tastes, but it's a small flaw for a cheap headphone.
I've been running these from the Samsung Galaxy S with Voodoo Audio and Poweramp (320 and FLAC). Being used to higher end headphones, it's easy to notice a big difference in terms of clarity and definition, which may be jarring for some. Maybe my ears just aren't as spoilt as others, but I find myself being able to adjust to the sound very quickly and start enjoying myself immediately. It's cool being able to have that open, bassy, dark sound on the go. Of course, these headphones are efficient, so amping is definitely not necessary. But, out of curiosity, I plugged them into my Little Dot 1+. The bass will gain a little more authority and the definition and instrument separation will improve slightly under such a setup. They're nice little improvements to be heard, but they're not enough to make them sound poor from portable rigs in comparison (at least not mine).
All things considered, I think this is a fantastic headphone! It's a surprisingly satisfying performer, built well, comfortable, compact. It ticks more boxes for me than I ever thought they would. If you get your hands on some, you might find yourself to be pleasantly surprised, as I was.
Really, the biggest warning I can give to anyone considering them is don't bother with them if you know you don't like dark sound, because they are definitely dark. But, if you do prefer dark signatures and you want a cheap portable, these should be on your list.