FBT QUBE SP27 - Manual (Page 34)

Filter Type High pass factors Low pass factors
Bessel 12dB/Oct. 1.45 0.69
Butterworth 12dB/Oct. 1.31 0.76
Bessel 18dB/Oct. 1.37 0.73
Butterworth 18dB/Oct. 1.19 0.84
Bessel 24dB/Oct. 1.35 0.74
Butterworth 24dB/Oct. 1.15 0.87
Bessel 48dB/Oct. 1.39 0.72
Butterworth 48dB/Oct. 1.08 0.93
Crossover Filter Slopes
It should also be noted that the turnover frequency displayed on the screen is the -3dB point for all types
except 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 display.
Please note that unlike conventional analogue crossovers, crossover points and slopes are set with absolute
accuracy since component tolerance problems do not occur.
Please see page for details of how to adjust the high and low pass crossover filter settings.
A further advantage of the SP27 Series 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 0 3S steps
(0.1mm).
Please see page for details of how to adjust the delay times.
To convert from units of time (i.e. milliseconds) to units of distance use the following formula:
1 millisecond = 343mm (1.126ft) @ 20C (68F)
To calculate time delay for a known distance, use:
Time delay =
20.06 x 273+C
where C is the temperature in C.
To simplify this equation at 20C.
Delay time in milliseconds =
(Distance in meters x 2.192) or (Distance in feet x 0.955)
Note: Centigrade = (Fahrenheit –32) x 0.5555.
Time Alignment
.
Distance in meters
32