Mixer Tutorial: Crossovers, Speakers and Cabinets

Mixer Tutorial: Crossovers, Speakers and Cabinets

1. Frequency division and frequency divider
Frequency division refers to dividing the audio signal into high frequency band, medium frequency band and low frequency band.
In the process of improving the sound power of the electric speaker, due to its structural characteristics, its frequency coverage range becomes narrower. In order to achieve full-band high-power sound reproduction, the speakers must be made in frequency bands and then combined together for sound reproduction. To give full play to the sound reproduction efficiency of the speakers in each frequency band, the frequency division problem is involved. There are two commonly used frequency division methods in sound reinforcement: electronic frequency division and power frequency division. The former is suitable for occasions with high sound reproduction quality requirements, such as karaoke halls, concert halls, and disco halls, and the latter is suitable for ordinary karaoke halls, ballroom dance halls and multi-functional halls.

1. Electronic frequency division
Electronic frequency division is also called active network frequency division. Its frequency division system needs to be powered. Its frequency division method is shown in Figure 3-1.
As can be seen from the figure, the sound signal is divided before entering the power amplifier. Its advantages are: high sound efficiency, and the power signal sent by each power amplifier is all given to the speakers of the corresponding frequency band. At the same time, behind each power amplifier, except for the speaker, no nonlinear elements are added, so the nonlinear distortion is small and the sound is pleasant. However, the number of power amplifiers used is large, and the main sound reinforcement system is divided into left and right channels, which requires three power amplifiers. If an auxiliary sound reinforcement system is also configured, three power amplifiers are required. In this way, the cost is very high. Figure 3-2 is a schematic diagram of the function keys of the panel and rear cover of the Mu-CO31 electronic frequency divider. When the mode switch is in position 1, it is used for 3-way stereo playback; when the mode switch is in position 2, it is used for 2-way stereo playback; when the mode switch is in position 3, it is used for 3-way mono playback. The inverted phase key is usually not used. Only when the two speakers of the corresponding frequency bands are in reverse phase, one of them can be pressed to get the same phase sound.
After the electronic crossover is connected to the sound reinforcement system, its crossover frequency must be adjusted, otherwise some speakers will be silent. The crossover frequency can be determined in two ways. Determine the crossover frequency of the low-mid frequency band (i.e., the low-end crossover frequency), use the low-mid frequency band speakers to sound, rotate the low-end crossover frequency adjustment knob from left to right, and then from right to left. When it is adjusted to a certain point, the sound of both speakers is louder, then this adjustment point frequency is the low-end crossover frequency. Use the same method to sound from the high-mid frequency speakers, rotate the high-end crossover frequency adjustment knob from right to left, and then from left to right. When it is adjusted to a certain point, the sound of both speakers is louder, then this adjustment point frequency is the high-end crossover frequency.

2. Power crossover
Power crossover is also called passive network crossover. It does not require power. Its crossover method is shown in Figure 3-3.
As can be seen from the figure, the sound signal is first power amplified, and the amplified power signal is sent to the corresponding speakers after high pass, band pass and low pass. This frequency division method is simple, easy to wire, uses less power amplifier and has low cost, but because the frequency division is done after the power amplifier, the frequency division network will always consume some power, making the speaker sound efficiency low. In addition, the capacitors and inductors used in the frequency division network are nonlinear elements, there is nonlinear distortion, and the sound quality is not as good as electronic frequency division, which is the disadvantage of power division. Commonly used power division 3-way frequency division are single element type and double element type.
The power division double element type is clearer than the single element type in the frequency division of the frequency band, and the frequency division effect is better. Some power divisions use a combination of single and double elements, and some use a two-way frequency division method, that is, the woofer takes into account the mid-bass sound, and the tweeter takes into account the mid-high sound. For example: JBL826 is a two-way frequency division system that is easy to work with a combination of single and double elements. The treble part uses dual elements, and the woofer part uses a single element. The treble speaker also plays mid-high sounds, and the woofer speaker also plays mid-bass sounds.

2. Speaker
A speaker is an electroacoustic conversion component that converts sound electrical signals into sound. From the history of development, there have been various types of speakers, such as: electric speakers, electromagnetic speakers (i.e. reed speakers), crystal speakers, electrostatic speakers, etc.
The sound-generating principle of an electric speaker is that the coil with an alternating current signal moves in a magnetic field, causing the diaphragm connected to the voice coil to vibrate, thereby causing the paper cone to vibrate, and then transmitting the sound waves through the air medium. The sound-generating principle of an electromagnetic speaker is to
generate an alternating magnetic field through a coil with an alternating current signal, attract and repel the magnetic sheet, cause the diaphragm and paper cone to vibrate, and then transmit the sound through the air medium. The sound-generating principle of a crystal speaker is to generate an alternating magnetic field through a coil with an alternating current signal, attract and repel the magnetic sheet, cause the diaphragm and paper cone to vibrate, and then
transmit the sound through the air medium. The sound-generating principle of a crystal speaker is to generate an alternating magnetic field through a coil
with an alternating current signal, cause the diaphragm to vibrate, and then transmit the sound through the air medium. The sound-generating principle of an electrostatic speaker is to generate an electroacoustic effect, cause the diaphragm to vibrate, and then transmit the sound through the air medium.
Among these speakers, except for the electric speaker, the other speakers are eliminated because of the narrow frequency range of the radiated sound and the low radiated sound power. The remaining electric speakers are widely used because their radiation frequency range can reach the entire audio range and their sound power can be very large (high-power speakers can be made by dividing the frequency bands and using the combined sound generation method to form full-band sound reproduction).