As a lifelong audiophile, I'm on a constant quest for the perfect headphones. I travel a lot and need headphones that are small, light and are good at blocking out external noise. Etymotic makes several types of passive noise cancelling headphones, of which the ER-6 is the "entry level" model.
Passive noise cancelling means that the earphones do not use any sort of electronic circuitry to filter out external noise. Rather the ER-6 fits blocks sound by completely blocking the ear canal. I found them to block noise around me quite well even with no music playing. Even on a lound New York City subway, I was able to keep the volume level of my music at a low level and still not hear the rumbling of the trains.
The ER-6 are earbud style headphones, meaning they insert directly in to the ear canal. They come with two types of interchangeable tips - a dual phlanged rubber tip and a foam tip. I found the rubber tips to be far more comfortable of the two. When inserting the tips, be sure to wet them with a touch of saliva - it helps them slide in more easily.
The ER-6 comes with an extra long cord and a stanard 1/8" headphone jack. The extra length on the cord can be nice, but it can also get in the way sometimes, getting tangled on clothes.
From time to time, the small earwax filter on the ends of the headphones can get blocked up with earwax. When this happens, you have to use a little tool (included) to replace the filter. The proceedure only takes about a minute and is quite simple. Spare filters, as well as rubber ear tips can be purchased directly from Etymotic's website at reasonable prices.
Sound quality of the ER-6 is good. They are a little light on bass, so if you use them to listen to a lot of bass-heavy music, they may not be for you. I found the upper ranges to be quite clear, as well as vocals and midrange. Overall, considering the size and cost of the ER-6 the sound quality is quite acceptable.
Overall, I'd have to give the ER-6 a thumbs up. They are small, light-weight, and sound good for the price. They remain very comfortable to wear, even after several hours of use. If you are in the martket for a set of earbuds, these are a great choice.