CROSS OVER CIRCUIT

Cross over circuit

Cross over circuit

Introduction

The following is a design and manufacture of 2nd order loudspeaker cross-over circuit for use with a given two-way speaker. The speaker system has two driver units, one of which operates best a lower frequencies and the other at higher frequencies. It is therefore necessary to split the audio signal from a 25 Watt audio power amplifier into two separate streams, one to connect to each driver.

Discussion

Crossovers devices in sound systems create the desired operating frequency range of the speakers. Speakers are so designed to operate within a certain frequency range. They do not accept frequencies that are not in this range. If a high-frequency speaker (tweeter) apply a low frequency, the sound image will deteriorate, and if the signal is still strong, the tweeter "burn."Tweeters need to work only with high frequencies, and the woofers have to get the total sound only low-frequency range. The rest goes to middle band midrange speakers (Midwoofer). Therefore, the task is to divide the crossover sound on the right (optimal) frequency bands for the respective types of speakers.

Simply put, the crossover - a pair of electric filters. Let's crossover has a cutoff frequency of 1000 Hz. This means that one of its cuts filters all frequencies below 1000 Hz, and passes the frequencies higher than 1000 Hz. Such a filter is called the high-pass filter. Another filter that passes frequencies below 1000 Hz, called the low-pass,. Graphically, this crossover operation is shown in Figure 3. The point of intersection of the two curves is the crossover frequency is 1000 Hz. In the three-way crossover there's another mid-range filter (band-pass), which transmits only the middle frequency range (from about 600 Hz to 5000 Hz.) Figure 4 shows the frequency response of the three-band crossover. 

The order of sensitivity of the crossover

Procedure sensitivity is the ratio of the output signal (dB) to the crossover frequency of the input signal provided that the intensity of the input signal is constant. Typically, sensitivity (the slope) is described as the ratio dB / octave. Because of the sensitivity of many mathematical reasons crossovers is always a multiple of 6 dB per octave (6 dB / octave). First-order crossover has a sensitivity of 6 dB / octave.Second-order crossover has a sensitivity of 12 dB / octave, the third order - 18 dB / octave, and the sensitivity of the fourth-order crossover is 24 dB per octave. 

Consider the low-pass filter of the third order with a cutoff frequency of 100 Hz. As mentioned above, this crossover will miss only the frequencies below 100 Hz, and the frequencies above 100 Hz would cut. Cutting frequency will be as follows: all frequencies above 100 Hz will save output from the filter 18 in intensity Multiple dB depending octave to which they belong. That is, the frequency of 200 Hz (the first octave above the cutoff frequency) will lose its intensity by 18 dB, the intensity of the frequency of 400 Hz (second octave) dropped 36 Hz, and the third octave (800 Hz) will weaken by 54 ...