Frequency response: Frequency-response specifications in full-size loudspeakers are generally pretty useless in predicting sound quality, but headphone frequency-response numbers are even worse. Manufacturers have routinely exaggerated frequency-response figures to the point that they're irrelevant. Even the flimsiest, cheap headphones routinely boast extremely low bass-response performance --15Hz or 20Hz -- but almost always sound lightweight and bright. Generally, bass buffs will be happier sticking with larger 'phones.
Over-ear and on-ear headphones effectively block out outside sounds, allowing you to hear your music or whatever else you're listening to crisply and without distraction. Over-ear headphones are sometimes known as full-size headphones because they completely envelop the wearer's ear. This results in what's known as passive noise reduction, which makes these some of the most-preferred headphones available. The only drawback is that your ears and the skin around your ears can get warm and sweaty. These are usually the heaviest type of headphones.