"Works well *IF* you find a good pair"3.0 starson by flying.dismount
Pros: decent performance for the price
Cons: poor quality control- bad solder joints!
Summary: I picked up a pair of these based on the decent set of reviews here as well as the good price but when I took them out of the box and tried them at home, they weren't anywhere as good as the ones at the store.. Playing around them some more, it seemed that the noise reduction only worked in one ear (put a finger over the microphone and the noise should increase, and then decrease again when you uncover the mike- on my unit, this only happened on the right ear, the left mike seemed to be inactive)..
Rather than just return them right away, being the curious engineering type, I decided to open them up, after all, they are not working properly anyways.. (In case anyone else wants to open them up (or needs to replace a slipped ear cushion) there are 5 screws under the ear cushions: 4 right at the edges of the fabric speaker covering, and one near the bottom under the fabric)..
Inside each earphone, there's an independent microphone and a Japan Radio Corp. 2076 audio amplifier chip. Each microphone has a simple lowpass filter at its output and a trimmer resistor to vary the microphone level. The mike is connected to the amplifier's inverting input, and the signal from the phono cord is connected to the non-inverting input of the amp, resulting in an inverted version of the external noise being added to the speaker output, and if the mike level is adjusted just right, the noise is cancelled out..
Such a simple circuit, so what could be wrong? Well, first I checked power, and both earphones had power, so that wasn't it.. Perhaps the trimmer was adjusted improperly? I tweaked it around and it made no difference at all.. Hmm... I decided to scope the output and tweak the trimmer to see if there was any signal being output (so imagine me with a scope probe held in one hand and a screwdriver in the other, and doing my best to hum a 300Hz tone while watching the scope and tweaking the trimmer).. Initially, it looked like the trimmer was intermittent- there was signal only at certain positions on the trimmer, so I decided to inspect the trimmer a bit closer with a magnifier and lo and behold, the darned trimmer was not even soldered on one of its terminals, and it was only making contact with the circuit board when I happened to push on the trimmer just right while I was tweaking.. A bit of solder fixed that up, and when I reassembled the headphones and powered up, the left phone worked, but the level was way out because of my experimental tweaking, so I had to open it up again- this time, while it was opened up, I popped the outer cover off the enclosure, exposing an adjustment hole so that I could tweak the unit while wearing it.. I turned on the vacuum cleaner in the next room and tweaked the trimmer until the the noise was reduced as much as possible..
I decided to open up the right one as well and double check the solder connections and re-tweak for maximum noise reduction, and inspecting the trimmer under magnification, this one was soldered, but only just barely, so I touched this one up and tweaked it, and the resulting set of headphones now perform very well indeed!
I'm willing to bet that most if not all of the poor reviews of these headphones are likely due to a poor solder connection at that trimmer- there is one terminal that is very short, so it appears it is simply not picking up solder during the reflow process- in mine, the trimmer on the left phone wasn't soldered down at all, resulting in the left phone not having any noise reduction capability until i fixed as described above..
Now, bad solder joints like this should never have made it past QC (and ideally, they should have changed the part to something with a bit bigger leg so that it's easier to solder reliably), but the basic circuitry is sound (and very simple) so if you get a good pair (try them at the store first if you can), they do actually perform quite well..