Feedback The transmission of current or voltage from the output of a device back to the input, where it interacts with the input signal to modify operation of the device. Feedback is positive when it's in phase with the input and negative when it's out of phase.
Flat When a speaker's response is described as "flat," that's a good thing. It means that the speaker can accurately reproduce a signal that is fed to it without adding unnatural coloration to the sound. Specific frequencies don't sound too loud or too soft.
Enclosure The container of air that surrounds the rear of a speaker driver.
Frequency response The human ear responds to frequencies from approximately 20 to 20,000 cycles-per-second, or Hertz. A speaker's frequency response indicates how much of that range can be reproduced.
Hertz (Hz) The unit of sound frequency; one Hz is equal to one cycle per second. The range of human hearing is 20-20,000 Hz. Points of reference: low "E" on a bass guitar is 41 Hz; middle "C" on a piano is 262 Hz; cymbals can go out to 15,000 Hz.
Imaging The ability of a speaker to reproduce spatial information in a recording so that you can visualize the relative positioning of individual voices and instruments as you're listening.
Impedance The load value (in ohms) that the speakers present to the amplifier — the amount of resistance to the flow of current. While playing music, a speaker's actual impedance constantly fluctuates; however, speakers are usually given a single nominal impedance rating for easy comparison. Low-impedance speakers (4 ohms or less) can cause problems with receivers or amplifiers that are not designed to deliver large amounts of current.
Kilohertz (kHz) One thousand Hertz.
LFE input Found on some powered subwoofers, this special preamp-level input accepts the "Low Frequency Effects" signal that's output by digital 5.1-, 6.1-, or 7.1-channel home theater receivers, ensuring proper bass reproduction. This type of input doesn't route the signal through any processing inside the sub which could potentially interfere with the low-pass crossover built into the receiver's bass management circuitry. Some powered subs feature an unfiltered LFE input/output — the output sends full-range signals minus the low frequencies back to a receiver or preamplifier's "main in" jacks for even more precise sonic control.
Midrange The middle of the audio frequency range. Also used as a term for loudspeaker drivers designed to reproduce this range.
Motor structure The part of the speaker that moves a diaphragm to produce sound. The motor structure basically consists of a voice coil that sits inside a cylindrical magnet. Alternating current is pumped through the voice coil, which constantly changes its magnetic polarity. As the voice coil alternates between being attracted to and repelled by the magnet, it moves the attached driver to create sound.
Home Audio Glossary of Terms has been created to inform and educate individuals interested in building a home theater environment. These home audio terms relate to all words beginning with the letters F through M, such as feedback, flat, enclosure, frequency response, Hertz (hz), imaging, kilohertz, LFE input, midrange, and motor structure.