Pros: They make great earplugs, slim plug, decent sound, muffle outside noise
Cons: Short cord, blocking out noise can be a con as well
The JVC Marshmallow headphones are a decent pair of noise blocking or noise cancelling headphones. These headphones retail for $20 and you can find them just about everywhere. While I don't think these are worth the $20 price they command, they do have some good qualities. They are hard to find on sale, but if you can catch a sale then they might be a good purchase.
This is my first pair of noise cancelling headphones and they work sorta well for that purpose. Actually, what I use these most for is earplugs. They really do make a great replacement for standard earplugs. I don't even attach an MP3 player to them, I just use them as earplugs. Going to a noisy concert or bar, just pop these in your purse or pocket and enjoy a bit of peace. They are much harder to lose than earplugs and you can use them over and over again.
These headphones muffle out background noises, they do not completely block background noises. If you are standing next to a huge subwoffer then you will still feel the thump thump thump of it, but the sound that gets to your ear will be reduced. You can still hear things through them, like your friend talking to you or if you are at a concert you will still be able to hear the concert just fine at a reduced volume. If you are trying to block out noise from a bus or airplane you may have to get a better pair of headphones.
Since these block out noise you probably want to be careful in what situations you use them and how loud you turn up the volume. The volume turned up just a little on my MP3 player is plenty loud enough for me to hear through these headphones if I am in a quiet area.
Like most noise cancelling earbud headphones you get feedback when the cord rubs against your clothes or if you rub the cord. This isn't too bad though and its not a major issue, but might bother some.
The marshmallow name comes from the type of foam used on the headphones, it feels like a marshmallow. You have to squish the foam to stick it in your ear. They bounce back to normal shape as soon as you take it out of your ear. The package comes with 2 sets of foam pieces, one smaller and one larger. The package states the foam will wear out over time, which is kind of a shame since they do not sell replacement foam pieces. It would be nice if you did. When the foam wears out it looks like you will have to buy another pair of headphones..
The sound on these when listening to music is a bit on the tinny side. You have to really shove them in to get the bass effects, but when you shove them in properly they seem to work better.
The headphones seem to get uncomfortable over time, especially if you are shoving them way into your ears. If you are looking for a pair of headphones with all-day comfort, this probably isn't the pair you want. You can probably wear these for 2 hours at most before you start to experience discomfort from them. If you don't shove them in properly they will fall out and be annoying. A lot of people say these are really comfortable, but I don't think they are that comfortable.
The cord on these is definitely short, and shorter than most other headphone cords. You would think for $20 they could give a couple more inches of cord. The short cord may cause problems for some people, but its not too much of an issue for me, I do prefer a slightly longer cord though.
The plug is not angled, and it is a slimline plug that is compatible with iPod as per the package markings.
These headphones do seem to last, I have had mine for a few months but have not used them extensively but I did beat them up using them as earplugs a couple times and they still sound just as good as the day I bought them. The foam doesn't seem to show any signs of wearing out yet even after a few months of use. I expect them to last a while longer.