This column aims to give musos, creative types, DJs Techno and Rave producers and such like minded people, enough info so that when the sound engineer or PA operators ask…" What levels ya output, do ya need a DI, what sort of connectors ya got, got all your adapters, waddaya want in foldback etc etc?" they won't be completely stuffed by all this techno-babble!! There are many things to consider, like the various signal levels, inputs & outputs, connectors…etc, etc. and the list goes on! It won't replace lots of hands on experience, but at least by learning some of the jargon you'll know the basics and not sound like a complete beginner!!

BAFFLE : The panel on which the speaker is mounted within the speaker enclosure. The term derives from its original use in preventing or baffling the speaker's rear sound waves from interfering with its front waves causing phase cancellation.

BALANCE : Recording - refers to either the relative levels of the left and right channels of a stereo recording, or to describe the relative levels of the various sounds, instruments and voices within a mix.

BALANCED : In a classic balanced audio circuit, the two legs of the circuit ( + and - ) are isolated from the circuit ground by exactly the same impedance. As well, each leg may carry the signal at exactly the same level but with opposite polarity with respect to ground. In some balanced circuits, only one leg actually carries the signal but both legs exhibit the same impedance characteristics with respect to ground. Balanced input circuits can offer excellent rejection of common-mode noise induced into the line and also make proper system grounding -with no ground loops - easier. Usually terminated with XLR or 1/4" TRS (2-conductors & shield) connectors. For balancing to be effective, both the sending and receiving device must have balanced output and input stages and lines to and from them.

BALANCED LINE : A transmission line consisting of two conductors plus a braided shield, capable of being operated so that the voltages of the two conductors are equal in magnitude (voltage) and opposite in polarity with respect to ground. A balanced line offers common mode rejection or cancellation by attenuation, signals are electromagnetically induced into the signal lines.

BANDPASS : A filter that passes frequencies only between specific upper and lower limits. The filter passes the 'band' of frequencies uniformly, and reduces (attenuates) the level of frequencies below and above the specified frequency points. [See Bandwidth.]

BAND PASS FILTER (BPF) : Filter that removes or attenuates frequencies above and below the frequency at which it is set. Frequencies within the band are emphasised. Bandpass filters are often used in synthesizers as tone shaping elements.

BANDWIDTH : A means of specifying the range of frequencies passed by an electronic circuit such as an amplifier, mixer or filter. The frequency range is usually measured at the points where the level drops by 3dB relative to the maximum. Expressed in Hertz or in musical octaves. [See also Q.]

BASS REFLEX : A type of speaker enclosure in which the speaker's rear sound wave emerges from a critically sized and positioned 'port ' or opening, to reinforce the bass tones.

BELL CURVE : An EQ with a peak in its response curve.

BIAMP : A common speaker set up in pro-audio systems using external electronic cross-overs. The crossover splits the audio spectrum into two bands - high and low frequencies. The bands are sent to two separate amplifiers or channels of an amplifier with the high frequencies sent to the horn and the lows to the low frequency component of the speaker system. This results in increased headroom and dynamic range for the speakers.

BINARY : Counting system based on only two states - 1s and 0s. The heart of Digital Systems

BIT : Binary digit, which may either be 1 or 0.

BOOST : A term used to indicate an increase in gain of a frequency, or band of frequencies, when equalizing an audio signal. Opposite of cut.

BOOST/CUT CONTROL : A single control which allows the range of frequencies passing through a filter to be either amplified or attenuated. The centre position is usually the 'flat' or 'no effect' position. Most often found on EQs.

BPM : Beats Per Minute.

BRIDGE MODE (Mono) :Operating a stereo amplifier in mono via the bridge mode switch, which then makes Channel A output the positive power rail and Channel B output the negative power rail. Since the signal swings between A and B Channels, the output of the amplifier is twice that of single channel operation.

BRIDGING : Connecting one electrical circuit in parallel with another. Eg: Paralleling power amplifier inputs.

BUSS : A common electrical signal path along which signals may travel i.e. a conductor that serves as a common connector to several signal sources. In a mixer, there are several busses carrying the stereo mix, the groups, the PFL signal, the aux sends etc. A separate signal routing to a specified output. In mixer design, a bus usually carries signals from a number of inputs to a summing amplifier. Power supplies are also fed along busses. Originally named after the company that made the wires used to make the common signal path. (They also made fencing wire!!)

Next time we'll look at …the 'Cs'.

In the meantime, if you've got any audio questions give me a yell, send me an email or post a message on roadtalkz. I'm not the font of all knowledge, but if I don't know the answer to your questions, I know enough guru's who will!!

See-ya-later.

Willy T.

Email : willyt-downunderdesk@roadogz.com

This is extracted from the book: "LIVE-AUDIO WORKSHOP: A Hands-on Guide to Rigging and Operating PA Systems." ISBN 0 646 36408 1. © Giraffe Communications 1998. Order via e-mail or at all good Music & Book
shops.

© 2001. Giraffe Media.