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by Paul Sanders
Technical specifications can help you pick the headphones that will work best with your audio equipment. Knowing a few technical terms will make buying headphones easier. Here are the basic terms that can help you decipher the details and choose headphones that will work for you.
Frequency response: This describes the sounds the headphones can reproduce without distortion. Your ears can detect sounds between 20 Hz to 20 KHz, and a decent set of headphones or speakers will match that. The frequency response listed on speakers is a generalization. Because of the physical properties of sounds and speakers, full-range headphones don't reproduce very low or very high notes as well as they produce midrange sounds. But most sounds in music and video are midrange sounds, so they can still provide great listening. Headphones with good frequency response and low distortion will help you hear sounds you didn't know were there.
Sensitivity: Headphone sensitivity describes how efficiently headphones use energy. Headphones with higher sensitivity ratings perform well at varying power levels and don't need to be played at maximum power to put out a good performance, while those with lower sensitivity ratings are harder to damage through heavy use. Headphones for portable use should have a sensitivity rating of above 100 decibels (dB).
Power: Two power levels are listed for headphones and speakers: RMS (short for root-mean-square) and peak power. These ratings describe how much electrical power you can pump through the headphones without damaging them. More volume, of course, means more power. RMS is the safe, steady power level. Peak is the power you can pump through the speaker for very short bursts. Both are measured in watts; peak is usually twice RMS.
Impedance: Electricity flows through your headphones, but it does meet some resistance, resulting in heat, which can damage or wear the components. Lower impedance, measured in ohms, means the headphones have lower resistance and draw more power. This also means shorter battery life for MP3 players and CD players. When using headphones with a home theater, the system will work most efficiently when the impedance of the headphones matches that of the audio receiver. Headphones with impedance ratings above 150 ohms are more durable, but are meant for use with audio receivers and other high-power devices. Portable music players work better with headphones of 60 ohms or less impedance.