BSS Audio FDS-318, User Manual

Page: 7 / 36

7
Crossover advantages
3.0 Other advantages
The drive-units in sound reinforcement systems utilising active crossovers
benefit because:
• Steep rolloffs are readily attainable. The -24dB/OCT rolloff in the BSS FDS-
318 active crossover rapidly discharges out-of-band energy. At one octave
below the crossover point, power received by the driver has dropped to less
than
½
% (or 1/200th) of full power
. The result: Bad sound resulting from out-
of-band resonances is effectively masked immediately beyond the crossover
frequency (
See Figure 3.1 ). This contrasts markedly with passive crossovers,
where slopes in excess of -12dB/OCT are rarely achieved, and power rolloff is
4 times less rapid per octave.
• If one frequency range is driven into clip, drive-units and horns in other
frequency ranges are protected from damage, and distortion is kept to a
minimum.
• Direct connection of drive-units to the power amplifier cut out loss of
damping factor, normally inevitable, thanks to the appreciable resistance of the
inductors in passive crossovers.
Amplifiers benefit too from the use of active crossovers. As they do not handle
a full-range signal, clipping produces far less harmonic and intermodulation
distortion. The results: Momentary overdrive sounds less harsh. Also the
amplifiers' dynamic headroom is generally higher, and heatsink temperatures
can run lower.
Fig 3.1 Crossover
Terminology