There are different kinds of loudspeakers like Tweeters, Mid-range Speakers, Sub-Woofers and Woofers which can reproduce the voice in their own particular frequency bands only. In an audio play back device, the entire audio signals are separated into different bands and are applied to the corresponding type of loudspeaker. The Tweeters are normally fed with frequencies above 5 kHz, Mid-range speakers are fed with frequencies in the range of 300 Hz to 5 kHz, and Sub-Woofers with 300 Hz to 40 Hz and Woofers are fed with frequencies below 40 Hz.
The entire audible voice spectrum stretches from around 20Hz to 20 KHz and there is not loudspeaker design which can reproduce all these frequencies with the same effect. The Woofers are made to produce subsonic sounds (below 20 Hz) and there are musical instruments which can produce frequencies above 18 KHz. To reproduce all these sounds different types of loudspeakers are fed with their own band of frequencies extracted from the music.
The filter circuits that are used at the output side of the audio device which filters out different band of frequencies and use them to drive different type of loudspeakers are called Audio Crossover Circuits. Three-way cross over circuits are very common in output side of the audio devices which filters out frequency bands for Tweeters, Mid-range Speakers and Sub-Woofers. This tutorial discusses the design and implementation of Two-way audio cross-over circuit using Active filters for quality filtering.
Two Way Active Audio Crossover Filter