A    Goto Top

A/D   

Analog to digital conversion (or converter). Used at transmission end of broadcast.

Absorption  

Reduction of acoustical energy usually by converting it into heat via friction using soft, fibrous materials.

AC3   

Audio Codec 3. This was the original and more technical name for Dolby Digital. Replaced by marketing mavens when they realized that Dolby's name was not in the title. Some RF modulated, 5.1-encoded laser discs were labeled as AC3. Later versions were labeled as Dolby Digital.

Academy Curve    Goto Top

An intentional roll-off in a theatrical system's playback response above ~2kHz (to -18dB at 8kHz) to minimize noise in mono optical tracks. Some (many) transfers to home video of mono movies have neglected to add the Academy filter during transfer, giving many old movies a screechy sound they were never intended to have. A few home processors have an Academy filter option, making them a must for old-movie buffs. Has been used since 1938.

Acoustic Suspension   

A sealed speaker enclosure that uses the air trapped in the cabinet as a reinforcing spring to help control the motion of the woofer(s).

Active

Powered. An active cross-over is electrically powered and divides the line-level signal prior to amplification. An active speaker includes an active crossover and built-in amplifier.

Addressable Resolution

The highest resolution signal that a display device (TV or monitor) can accept. Caution: Consumers should be aware however, that although a particular device (Digital-HDTV) is able to receive the resolution, it may not be capable of displaying it.

Amplifier    Goto Top

A component that increases the gain or level of an audio signal.

AM   

Amplitude modulated.

Anamorphic  

Process that horizontally condenses (squeezes) a 16:9 image into a 4:3 space, preserving 25 percent more vertical resolution than letterboxing into the 4:3 space. For the signal to appear with correct geometry, the display must either horizontally expand or vertically squish the image. Used on about two or three promotional laser discs and many DVDs. Also called Enhanced for Widescreen or Enhanced for 16:9.

Analog TV  

Analog TV is the NTSC Standard for traditional television broadcasts. Analog signals vary continuously, representing fluctuations in color and brightness.

ANSI Lumens    Goto Top

Industry standard measurement of a projector's brightness. Depending on lamp, optics, and projector design, ANSI lumens range from 200 to 10,000 per projector.

Artifacts   

Unwanted visible effects in the picture created by disturbances in the transmission or image processing, such as 'edge crawl' or 'hanging dots' in analog pictures, or 'pixelation' in digital pictures.

Aspect Ratio   

The ratio of image width to image height. Common motion-picture ratios are 1.85:1 and 2.35:1. Television screens are usually 1.33:1 (also known as 4:3), which is similar to the Academy standard for films in the '50s. HDTV is 1.78:1, or 16:9. When widescreen movies (films with aspect ratios wider than 1.33:1) are displayed on 1.33:1 televisions, the image must be letterboxed, anamorphically squeezed, or panned-and-scanned to fit the screen.

ATSC   

Advanced Television Systems Committee. Government-directed committee that developed our digital television transmission system.

Attenuate    Goto Top

To turn down, reduce, decrease the level of; the opposite of boost.

A-Weighting

Measurement based roughly on the uneven frequency sensitivity of the human ear. The influences of low and high frequencies are reduced in comparison to midrange frequencies because people are most sensitive to midrange sounds.

B    Goto Top

Balanced Input

A connection with three conductors: two identical signal conductors that are 180 degrees out of phase with each other, and one ground. This type of connection is very resistant to line noise.

Bandpass

A two-part filter that cuts both higher and lower frequencies around a center band. A bandpass enclosure cuts high frequencies by acoustic cancellation and low frequencies by natural physical limitations on bass response.

Bandwidth

In audio, the range of frequencies a device operates within. In video, the range of frequencies passed from the input to the output. A range of frequencies used to transmit information such as picture and sound. For TV broadcasters, the FCC has allocated 6Mhz for each channel. For DTV, the maximum bit rate possible within the bandwidth is 19.4 Mbps, which is one HDTV channel. SDTV has a lower bit rate, therefore the bandwidth can accommodate more than one channel.  

Bass    Goto Top

Low frequencies; those below approximately 200 Hz.

Bass Reflex: See Port.

Bipolar

1) The condition of possessing two pole sets. In a conventional (non-FET) transistor, one pole set exists between the base and collector, and the other pole set exists between the base and emitter. 2) Speakers that consist of two driver arrays facing opposite directions and wired in electrical phase with one another to create a more diffuse soundstage.

Bit Rate

Measured as "bits per second," and used to express the rate at which data is transmitted or processed. The higher the bit rate, the more data that is processed and, typically, the higher the picture resolution.

Bi-Wiring    Goto Top

A method of connecting an amplifier or receiver to a speaker in which separate wires are run between the amp and the woofer and the amp and the tweeter.

Black Level

Light level of the darker portions of a video image. A black level control sets the light level of the darkest portion of the video signal to match that of the display's black level capability. Black is, of course, the absence of light. Many displays, however, have as much difficulty shutting off the light in the black portions of an image as they do creating light in the brighter portions. CRT-based displays usually have better black levels than DLP, plasma, and LCD, which rank, generally, in that order.

Boost

To increase, make louder or brighter; opposite of attenuate.

Bridging

Combining two channels of an amplifier to make one channel that's more powerful. One channel amplifies the positive portion of an audio signal and the other channel amplifies the negative portion, which are then combined at the output.

Brightness

For video, the overall light level of the entire image. A brightness control makes an image brighter; however, when it is combined with a contrast, or white level control, the brightness control is best used to define the black level of the image (see Black Level). For audio, something referred to as bright has too much treble or high-frequency sound.

C    Goto Top
 

Cascading Crossovers

Two crossovers used in series on the same signal in the same frequency range causing greater attenuation of the out-of-band signal. For example, using the crossover in a receiver's bass management setting and the one in a subwoofer simultaneously will create an exaggerated loss of signal.

Cathode Ray Tube

(CRT) A