Installation guide

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Channel
A single audio entity where one or more outputs are related to a single input. An amplification
channel is used to indicate all the processing (including the PDC hardware) up to an amplifier
output. A processing channel indicates all processing on the PDC from a single input to one or
more outputs.
Confidence
An indicator of the quality of the measurement. It is not the same as signal to noise ratio (SNR),
but it is related. In fact, it is often better than SNR, as the measurement technique that we use
goes some way towards eliminating noise. Confidence is also a measure of how much the room
reverberation has died off before the next cycle of measurement begins - if it has not rolled off
enough the measurement will be corrupted and a low confidence will be reported.
Confidence can be improved by increasing the number of sweeps, increasing the period of each
sweep, decreasing background noise, or by adjusting the measurement volume. There is an
optimum measurement volume - too low and the background noise will become relatively loud
(reducing confidence), too high and distortion will start to occur (again reducing confidence).
Correction/Correction Filters
A digital filter used to correct frequency and phase-response errors in loudspeakers, and or
rooms.
Crossover/Crossover Filters
A device for limiting the frequencies to different drivers in a loudspeaker.
dBFS
Input or Output level in decibels (dB) relative to full scale.
Decibels is always a relative measure and for dBFS it is relative to the maximum, or clipping,
level of the input or output. The relative measure is always 0dB hence in the dbFS scale all other
possible values are negative since 0dB is the maximum level. dBFS is commonly used in digital
systems since there is no concept of gain only attenuation.
dB-SPL
Sound Pressure Level. Typically levels above 120dB cause pain to the listener.
Decibels (dB)
Relative measure on a logarithmic scale. Decibels is used in audio systems since the human ear
perceives volume level on a logarithmic scale. Decibels is always in relation to a reference level,
which is always 0dB.
Dispersion
An undesirable effect in loudspeakers which causes different frequencies to propagate at different
phase velocities, also known as moding. Dispersion is commonly related to poor off- axis
performance. Dispersion occurs mainly in woofers and mid-range drivers when the input
frequencies to the driver are too high. The frequency at which dispersion occurs is related to the
diameter of the driver cone.
Distortion
There are two types of distortion – harmonic and non-harmonic. Distortion in this document
always refers to the harmonic case and in the case of sound reproduction, relates to an
undesirable effect that the SPL requested from the media (compact disk, DVD, etc...) is not
linearly related (by a simple gain factor) to the actual SPL delivered by the loudspeaker system.
Harmonic distortion produces output frequencies which were not present at the input but are
harmonically related – i.e. same tone but different pitch.
Driver
One of the electro-mechanical speakers located in a loudspeaker cabinet.
Group Delay