LA Audio DLX200 - Manual (Page 16)

16
IMPORTING PARAMETRIC EQ SETTINGS
Care should be taken when importing the EQ settings from other speaker management units as
the results may not be quite what you expect. This is because the 3 parameters of Frequency,
Boost/Cut and Q (or Octave Bandwidth) do not give a complete definition of the actual filter shape.
Although Frequency and Boost/Cut are absolute values, Q (or Octave Bandwidth) is generally only
correct at one Boost/Cut setting. This is usually at or near maximum boost or cut. At all lower
settings, the actual Q will be lower, i.e. the Octave Bandwidth will be wider. The variation in actual
Q can be between almost nothing in a “Constant Q” design to considerable in a “Proportional Q”
design.
An additional source of error can result from confusion between Q and Octave Bandwidth. At least
one other manufacturer calculates Octave Bandwidth by simply assuming that it is the reciprocal
(1⁄x) of Q. This would indicate that a Q of 1 would be an Octave Bandwidth of 1. In fact, a Q of 1 is
really an Octave Bandwidth of 1.39! A clearer indication of the scale of the error is apparent with
a Q of 4.5, which is actually one third of an octave. The reciprocal of 4.5 would imply that it is only
one fifth of an octave.
A simple “rule of thumb” to convert Octave Bandwidth to Q is to divide the Square Root of 2
(!1.414) by the Octave Bandwidth. Alternatively, to convert Q to Octave Bandwidth, divide the
square root of 2 by Q. Although this is not 100% accurate, it will return an error of less than +/-2%
between Q values of 1 and 10.