In this post we learn to make an active loudspeaker system circuit for enabling self sustained amplification of any music source that may be directly plugged in to the active speaker box.


With the advent of ultra modern cell phones, now it has become possible to store huge music data and listen to them with just a flick of your finger. But listening to music becomes significantly pleasing only if it’s hugely amplified and reproduced over active loudspeakers or with systems incorporating a speaker amplifier circuit.

By amplifying a small music signal from either a cell phone or similar source and hearing it over active loudspeakers can become more interesting and the outcome simply amazing. Complete design idea and schematic of a simple speaker amplifier is produced here.

A normal loudspeaker may be a 3-way type with the connected amplifier equipped with the usual bass treble controls etc. No matter how good they may be in their performance, they can never beat the sound quality that is normally achieved through active loudspeakers. Whether it’s by quality or power they are the best sound reproducing gadgets.

Building an active loudspeaker system may look complex but can be very amusing, and once built can indeed become a treat hearing its magnificent response.

Although the cost involved compared to its passive counterpart is much higher, an active system has definitely a clear edge over the passive systems.

Advantages of Active Loudspeaker System

The various advantages of a built in speaker amplifier over the passive design may be listed as follows:

No external amplifiers required and so no cumbersome wiring involved.

No use of passive filter circuits using resistors and inductors means an increase in the overall efficiency of the output response due to the absence of power losses through heat dissipations generally involved with passive filter resistors.

Unlike passive filters, the active filters help to boost the set responses. With passive filters it’s just the opposite, they tend to make the input music response deteriorate to a great extent.

Here we will discuss one such active loudspeaker circuit, capable of transforming even an ordinary music inputs into outstanding reproductions. Let’s read its circuit details.

Simulation and Working

The following points will discuss one such speaker amplifier circuit, capable of transforming even an ordinary music inputs into outstanding reproductions.

The idea is very simple, equalize the inputs by passing them through appropriate lo-pass and hi-pass filters at the input stages, then amplify this dimensioned content to suitable high volumes using ordinary amplifier.

We do exactly as mentioned above; referring to the figure we find that a single IC TL072 which is basically a dual op-amp in a single package is discretely configured into two separate filters.

Active loudspeaker circuit

IC 2A is wired as a standard high pass filter. As the name suggests, the circuit will pass only specified degree of high input frequencies. The cut off frequency may lie around 3 kHz and can be varied by adjusting VR1 and VR2 or any one of them.

IC 2B is wired in just the opposite configuration i.e. as a low pass filter and allows only the specified degree of frequencies iver the lower ranges, the cut off frequency being 2.5 kHz. It will stop all frequencies above this. The response is adjustable using VR3.

The above suitably equalized audio now is simply fed to an audio amplifier for the required amplifications over the connected loudspeakers.

The channel responsible for producing higher frequencies uses a twitter for better optimization where as the other section which handles the lower frequencies is integrated to a woofer for the relevantly bass output optimization.

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