Audio Engineering

718 Chapter 24

amplifi er into a “ speaker-driving fi lter ” has the advantage of minimizing superfl uous
hardware and signal path complexity.

Otherwise, the active crossover, along with the power amplifi ers, is placed in the
loudspeaker enclosure. This creates an “ active enclosure, ” “ active speaker, ” or “ Tri-amp
cab ” (if three way; else “ bi-amped-cab, ” “ quad-amped-cab, ” etc.) that has the advantage
of hiding the complexity and offers a fait accompli , but takes away the fl exibility that
touring PA users often need.

Active systems are widely used in pro-audio, for installed and touring PA systems, and
studio control room monitors. In nearly all cases, stand-alone active crossovers, discrete
power amplifi ers, and individual enclosures are brought together. In high-end hi-fi ,
discrete active systems are comparatively rare, except in DIY circles. Active speakers are
becoming somewhat more common, at least in the United Kingdom and Europe.

24.1.4.9 Bi-wiring

Bi-wiring is a “ part-way house ” to having a low level active (or passive) crossover.
A separate speaker connecting wire is provided for each drive unit, or for each frequency
band ( Figure 24.7 ). This lessens interaction and intermodulation that is otherwise caused
by communal speaker cabling.



 HF

LF

High pass

crossover

Low pass

crossover

Speaker enclosure

Speaker

cable

Speaker

cable

Amplifier Paralleledset of

terminals

Figure 24.7 : Bi-wiring improves sonic quality by avoiding superimposition voltage drops over

the greater length of the output stage to speaker connection, as otherwise LF signal currents

upset the hf’s driver signal’s purity, and even vice versa.