Crossover Network9 Comments

Loudspeaker is a very important component of a hi-fi system.By adding a crossover network to the system of speakers, the low, high and mid-range frequencies can be separated and fed into a woofer, tweeter and mid-range speaker respectively.

Fig. 1 Wiring diagram for three-way crossover networkPARTS LIST

C13.3 f 50v N.P.

C24.7 f 50v N.P.

C33.3 f 50v N.P.

C43.3 f 50v N.P.

C50.68 f

C61 f 50v N.P.

R13.3 2W

R24.7 2W

R36.8 2W

The given circuit uses four inductances of 0.1, 0.2, 0.3 and 1 mH, each having 70, 100, 120 and 200 turns of 18SWG wire on the johnson-john adhesive tape bobbins having 2.5 cm length and 2.5 cm dia.The speakers used have an impedance of 8-ohm each, and the circuit can be used for amplifiers with output rating of a maximum of 50 watts RMS per channel.

Fig. 2 air coreThe capacitors used are non-polarised type, which can be made by connecting end to end two capacitors of double the required value, as shown. All the capacitors are 50V type.The crossover frequencies are 500 Hz and 2.5 kHz. All the inductors are air core type. Resistors are 2W type.

Fig.3 the making of a non-polarised capacitor, using two electrolytic (polarised) capacitor of twice the desired value.Since a high frequency producing tweeter generally sounds very loud compared to the mellower outputs of a woofer and a mid-range speaker, the tweeters output can be reduced by introducing the attenuation circuit shown in Fig. 4. Using one-pole, four-way switch S1, the tweeters output can be reduced to a desired extent or allowed to pass on unattenuated to the speaker.

Fig. 4: Tweeter attenuatorCare should be taken to connect the tweeter and the woofer in opposite phase.