In an active loudspeaker system the crossover network is connected, in the signal path,
before the power amplifiers. An active crossover network feeds separate signals to the
bass, mid, and treble power amplifiers. The power amplifiers in turn power the corresponding
loudspeaker drivers for the bass, mid, and treble ranges.
This method has several advantages, especially in large PA systems, compared to passive
dividing where the crossover network is connected between the power amplifiers and the
loudspeakers. You get for example lower distortion, in particular distortion that is caused by
loud bass tones which intermodulate with the mid, and treble ranges. An active system also
eliminates the power losses, associated with passive crossover networks.
LAB.GRUPPEN’s ACN C crossovers are designed around a four-pole state variable filters,
which are derived from the theory of analog computers. The most common way to alter
crossover frequencies in such a circuit is to turn a multiple ganged potentiometer. However
most potentiometers have bad tolerances (20 % or worse), and these tolerances affect the
accuracy of the crossover frequencies and the flatness of the summed output.
A better way of altering the crossover frequency is applied in the ACN 2/3C; namely the use
of “Digital Hexcode” switches. This allows the use of close tolerance components, which
result in a crossover frequency accuracy better than 1 %.
By careful selection of these components, an optimum density of available crossover frequencies
has been created, especially in the region between 800 Hz and 2 kHz. This has made it possible
to achieve a continuity of phase and of group delay time together with the speaker system. This
leads in turn to an improved intelligibility in the vocal region.
12, or 18 dB/octave slopes can be ordered as an option. The 24/octave slope has equal phase
at the crossover frequency region, in accordance with Linkwitz-Riley. To achieve flatness in the
summed output, the high and lowpass filters meet each other at 6 dB.
Each of the outputs of the ACN 2/3C have been equipped with shelving equalization, which gives
an adjustable bass boost of upto +12 dB, and a treble boost of upto +12 dB. In the ACN 3C the
mid output has an additional shelving boost, but that works at a lower corner frequency. With the
help of this equalization it is possible to align the frequency response of the speaker system. You
can, for example, compensate the roll-off in the treble of so-called “Constant Directivity“-type horns.
It also means you negate the need, for an external (graphic) equalizer, in several applications.
3-way stereo or 4- and 5-way mono
Switchable crossover frequencies:
32 frequencies between 80 Hz and 4.8 kHz
No dangerous “x10 switches” or frequency knobs on the front
The standard slope is 24 dB/octave. Optional: 12 and 18 dB/octave slopes
Switchable subsonic filters
Front panel gain controls
Mute switch on all outputs
Mono bass switch
Electronically balanced inputs with transformer option