An audio glossary of terms
A box-type speaker with a sealed cabinet that traps air and uses it to reinforce and control the woofer. This approach is said to produce tighter bass.
Bass reflex (or ported speaker)
The opposite of acoustic suspension. It is a speaker cabinet that features an opening that extends the speaker's low-frequency response.
A speaker with two drivers wired "in phase," meaning both drivers fire together. They produce a larger sound stage than traditional speaker designs.
Used to direct particular bands of sound to their appropriate drivers, crossovers include three types of filters: low pass, to filter out high-frequency energy; band pass, to filter high- and low-frequency energy but leave a band in the middle untouched; and high-pass, to let high-frequency energy through but filter out low frequencies. A basic example would be in a two-way speaker in which only two drivers are responsible for reproducing the entire audible spectrum of sound.
A measurement that describes the relative intensity of sound or the differences between two power sources.
Drivers mounted opposite one another and wired out of phase. Similar to a bipolar speaker, except the drivers fire at separate times, resulting in an expanded sound stage.
The way in which sounds at different frequencies spread out into the room from a loudspeaker.
The unit used to measure frequency that equals cycles per second. For example, 20 Hz means that sound waves are completing 20 full cycles in one second.
How accurately an instrument or voice is represented within a sound stage.
A measurement of resistance in ohms. An 8-ohm speaker would have more resistance to the flow of electricity than a 4-ohm speaker.
Frequencies in the middle of the audio spectrum. It is approximately 200 Hz to 3,000 Hz (3 kHz).
The unit of measurement for DC resistance and impedance. Something has a resistance of 1 ohm if it produces a voltage drop of 1 volt when a single amp of current flows through it.
The time relationship between sound waves. If two waves equal in frequency start and stop at the same time, they are in phase. If one wave starts after another, it's out of phase.
Reaction of sound within an environment to specific frequencies, which can result in vibration and other unwanted noises that detract from performance.
A measure of how much sound is produced from a speaker for a specified level of input signal. The standard measurement is written as something like "89 dB SPL/1W/1m," which is read as "89 decibels of sound pressure level at 1 watt, 1 meter." Translated: If you put the equivalent of one watt of power into the speaker, it will play at a volume of 89 decibels when measured from one meter in front of the speaker.
The area in which a speaker throws its sound.
Initially started by movie director and producer George Lucas to improve the quality of audio and video. The organization has its own proprietary standards that must be met in order for an AV component to be THX-certified.
A speaker driver that reproduces high frequencies, typically from 3 kHz to 10 kHz.
A speaker driver that reproduces low frequencies, typically below 200 Hz.