DP200 Page 16
Crossover modes
Four crossover modes are provided :-
2 way dual, 2 way stereo, 4 way mono and 3 way + Sub ‘Split’. Note: 2 way stereo
mode is identical to 2 way dual but with 'ganged' adjustment of parameters. Please
see block diagram. All crossover modes feature adjustable crossover frequencies
with a choice of slopes, 2 bands of driver compensation e.q. per output and delay
time plus limiters for each output. A powerful 6 band parametric equaliser is also
provided on each input for room equalisation. Phase reverse is provided for each
output.
Filter slopes
A choice of Bessel or Butterworth slopes at 12/18/24dB per octave and Linkwitz-
Riley at 24dB per octave are provided. Since Low and High pass functions are
separately adjusted, asymmetric slopes are easily achieved if required. It should
also be noted that the turnover frequency displayed on the DP200 is the -3dB point
for all slopes except 24dB Linkwitz-Riley where the -6dB point is shown. If the -6dB
point is to be used for the Bessel or Butterworth filter, take the required crossover
frequency, multiply this by the appropriate factor from the following table and then
select the closest available frequency on the DP200's display.
Filter Type
High pass filter factors
Low pass filter factors
Bessel 12dB/octave
1.45
0.69
Butterworth 12dB/octave
1.31
0.76
Bessel 18dB/octave
1.37
0.73
Butterworth 18dB/octave
1.19
0.84
Bessel 24dB/octave
1.35
0.74
Butterworth 24dB/octave
1.15
0.87
Please note that unlike conventional analogue crossovers, crossover points and
slopes are set with absolute accuracy since component tolerance problems do not
occur.
Time Alignment
A further advantage of the DP200 over conventional products is the provision of an
independently adjustable delay section for each output. This allows the true arrival
time from multiple drivers to precisely aligned rather than relying on the compromise
'phase adjust' approach. Delay time is adjustable in 21 micro-second steps (8mm).
To convert from units of time (i.e. milliseconds) to units of distance use the following
formula : -
1 millisecond = 343mm (1.126ft) @ 20
°
C (68
°
F)
Output Limiters
High performance digital limiters are provided for each output with control over
attack time, release time and threshold level parameters ( see page 22 ). This level
of control allows the user to balance the required subjective quality of the limiter
against the driver protection requirements. It does also mean that an incorrectly set
limiter may sound awful! In particular, as with all limiters, using too fast an attack or
