Mackie M1200/M1400 owner manual Emi

referenced to 1 VRMS across any impedance. Commonly used to describe signal levels in consumer equipment. To convert dBV to dBu, add 2.2 dB.

decibel (dB)

The dB is a ratio of quantities measured in similar terms using a logarithmic scale. Many audio system parameters measure over such a large range of values that the dB is used to sim- plify the numbers. A ratio of 1000V:1V=60 dB. When one of the terms in the ratio is an agreed-upon standard value such as 0.775V, 1V, or 1mw, the ratio becomes an absolute value, i.e., +4 dBu, –10dBV, or 0 dBM.

detent

A point of slight physical resistance (a click- stop) in the travel of a knob or slide control, used in Mackie mixers to indicate unity gain.

diffraction

The bending of sound waves around an ob- stacle (Huygens Principle). The longer the wavelength in comparison to the obstacle, the more the wave will diffract around it.

dipping

The opposite of peaking, of course. A dip is an EQ curve that looks like a valley, or a dip. Dipping with an equalizer reduces a band of frequencies. See guacamole.

dry

Usually means without reverberation, or without some other applied effect like delay or chorusing. Dry is not wet, i.e. totally unaf- fected.

duty cycle

The ratio of pulse width to total cycle time.

dynamic

In sound work, dynamic refers to the class of microphones that generates electrical sig- nals by the movement of a coil in a magnetic field. Dynamic microphones are rugged, rela- tively inexpensive, capable of very good performance and do not require external power.

dynamic range

The range between the maximum and mini- mum sound levels that a sound system can handle. It is usually expressed in decibels as the difference between the level at peak clip- ping and the level of the noise floor.

EMI

Electro Magnetic Interference. This refers to current induced into the signal path as a result of an external magnetic field. In audio systems, this is usually manifested as a 60Hz or 120Hz hum or buzz. The source of this noise can be from a ground loop or from the signal wire coming too close to a strong magnetic field such as a transformer or high-current linecord.

EQ curve

A graph of the response of an equalizer, with frequency on the x (horizontal) axis and am- plitude (level) on the y (vertical) axis. Equalizer types and effects are often named after the shape of the graphed response curve, such as peak, dip, shelf, notch, knee, and so on.

equalization

Equalization (EQ) refers to purposefully changing the frequency response of a circuit, sometimes to correct for previous unequal re- sponse (hence the term, equalization), and more often to add or subtract level at certain frequencies for sound enhancement, to remove extraneous sounds, or to create completely new and different sounds.

Bass and treble controls on your stereo are EQ; so are the units called parametrics and graphics and notch filters.

A lot of how we refer to equalization has to do with what a graph of the frequency response would look like. A flat response (no EQ) is a straight line, a peak looks like a hill, a dip is a valley, a notch is a really skinny valley, and a shelf looks like a plateau (or a shelf). The slope is the grade of the hill on the graph.

Graphic equalizers have enough frequency slider controls to form a graph of the EQ right on the front panel. Parametric EQs let you vary several EQ parameters at once. A filter is sim- ply a form of equalizer that allows certain frequencies through unmolested while reduc- ing or eliminating other frequencies.

Aside from the level controls, EQs are prob- ably the second most powerful controls on any mixer (no, the power switch doesn’t count!).

fader

Another name for an audio level control. Today, the term refers to a straight-line slide control rather than a rotary control.

filter

A simple equalizer designed to remove certain ranges of frequencies. A low-cut filter

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