(3) Technical parameters of the amplifier:
1) Output power
① The nominal power is the maximum undistorted power of the power amplifier, which refers to the power that the power amplifier can output when the total harmonic distortion is less than 1% under a load of 4 ohms and a 1kHz sine wave signal is input. The power indicated by power amplifiers in the general market is this power.
② Rated power, also known as continuous sine wave power, is usually half of the nominal power.
③ The working power is the power output by a power amplifier during operation, which is related to the size of the input signal. When the input signal is zero, the working power is zero. The larger the input signal, the greater its operating power. The value is dynamic.
④ The peak power of music refers to the highest peak power of an instantaneous music signal when the total harmonic distortion is less than 1%. Indicates the instantaneous characteristics of a power amplifier, typically exceeding 4 to 8 times the rated power.
2) Distortion: An ideal power amplifier should amplify the input signal and faithfully restore it without any changes. Expressed as a percentage, the smaller the value, the better. The total distortion of HI-FI amplifiers ranges from 0.03% to 0.05%. The distortion of power amplifiers includes harmonic distortion, intermodulation distortion, cross distortion, clipping distortion, transient distortion, transient intermodulation distortion, etc.
3) Signal to noise ratio: refers to the ratio of the signal level output by the power amplifier to the various noise levels output by the power amplifier, expressed in dB. The higher the value, the better. The signal-to-noise ratio of general household HI-FI amplifiers is above 60dB.
4) Output impedance: The equivalent internal resistance presented by a speaker is called output impedance.
4, Capacitors, Balancers, Dividers
Capacitors are electrical components used to store electrical energy and compensate when the rear system current is too high and the car power supply cannot be supplied in a timely manner. Generally, there are more speakers installed in audio systems, and when the power required for bass is relatively high, capacitors need to be installed. Currently, the most commonly used ones are 1.0 Farad and 1.5 Farad, with prices varying depending on the capacitance.
5, Car audio cable
Car audio systems are connected by wires, and in practice, most faults and noise are generated on wires. Seemingly unimportant wires are actually crucial in audio systems. Good wire quality requires safety, good anti-interference ability, and low attenuation.
Generally, there are power cables, audio signal cables, speaker cables, control cables, and grounding wires.
(1) Power cord
① The power cord has a main power cord and a branch power cord.
② When the power line is falsely connected, there will be a potential difference between the power amplifiers, which will cause AC noise and seriously damage the sound quality.
③ The main power cord should be protected by a fuse tube, which should be as close to the power source as possible.
④ There are strict regulations on the size of wire specifications and the power they can withstand.
⑤ Thoroughly remove any dirt from the power connector and tighten the connector.
⑥ When wiring within the automotive power system, it is advisable to avoid wiring near the generator and ignition device, as motor noise and ignition noise are radiated into the power line.
⑦ The principle of laying power cables and audio cables inside the vehicle body is consistent.
Require stable current and voltage, low impedance, and low current attenuation. The selection of power cables is related to power, and high power cables often have high current, so thicker cables need to be selected. Materials generally use pure metal wire with high purity, and experienced enthusiasts may use pure silver wire. The insulation material used to wrap the power cord not only has good insulation properties, but also needs to be able to withstand high temperatures.
(2) Signal line:
Require good anti-interference ability, ability to reduce signal attenuation, good contact, and prevention of oxidation at the joints. Some top-level signal wires often use specialized alloy materials, snap ring plugs, and are gold-plated on the surface of the plugs to prevent oxidation.
(3) Speaker cable: Different power speakers should choose different numbers of speaker cables
① When selecting 16g~14g cables for high pitched speakers, attention should be paid to skin effect.
② The mid-range speaker cable requires the selection of 14g~10g cables
③ The bass speaker cable requires the use of 10g or smaller cables
Attention should be paid to the protection of the wire entering the car door, and the impact of door closing and window lifting on the wire should be considered.
It is best to use welding to connect the speaker cable to the speaker.
The speakers are all double stranded wires.
(4) Control line
① The control line is the startup signal line for various audio equipment, which is usually led out from the CD head, so that the switches of each equipment are controlled by the CD head.
② In some systems, the current of the startup signal output by the CD head is too small, and subsequent devices require a slightly larger current to start.
(5) Grounding wire
① Grounding is often overlooked in wiring, but in reality, its role in the system is as important as that of power lines.
② Grounding wire method. Remove the paint from the grounding point of the vehicle body with sandpaper and secure the grounding wire tightly.
③ Concentrate the grounding of each module in the audio system in one place.
④ Do not approach the wiring of the on-board computer.
⑤ The grounding point should be as close as possible to the ground wire output point, making the ground wire as short as possible. An excessively long ground wire will greatly increase the possibility of noise generation and increase resistance.
(6) Car audio wiring
① The lower the resistance of the car audio cable, the less power is consumed on the cable, and the higher the efficiency of the system.
② The smaller the resistance of the wire, the greater the damping coefficient. The larger the damping coefficient, the greater the vibration of the speaker.
③ The larger the cross-sectional area of the wire, the smaller the resistance, and the larger the capacitance current value of the wire, which allows for a larger output power.
④ No matter what wire, it should be avoided to connect it as much as possible, because it is too short and can be used again after connection. The connection point is often the root cause of future failures.
⑤ Selection of power supply insurance: Insurance value=(sum of total rated power of each power amplifier in the system x2)/vehicle power supply voltage balance value.
8, Matching principles
(1) Basic configuration
The car audio system is basically the same as a home audio system, consisting of a combination of components such as a CD player's sound source, a power amplifier that amplifies the music signal containing the program source, and a speaker that serves as the sound outlet.
Most power amplifiers installed in the host have very low output power. If you want to achieve better sound quality or drive higher power speakers, it is necessary to install one or more power amplifiers.
Increasing the number of speakers can also be considered. Using only one speaker on each side has a narrow dynamic range, making it difficult to achieve the same effect as home audio.
(2) The principle of system balance
① Price balance
② Balance of pairing
③ Principle of high-power output
④ The principle of natural playback of sound quality
A perfect sound system will bring you both auditory and visual enjoyment.
(3) Configuration form
1 host+4 speakers; 2 hosts+power amplifier+4 speakers; 3 hosts+power amplifier+4 speakers+subwoofer
There is also an electronic splitter and equalizer between the complex audio configuration host and power amplifier.
The main device that reflects music style is the speaker, and compared to selecting the host first, selecting the speaker and matching it with devices such as amplifiers has greater flexibility. So the first step in purchasing is to choose the speaker that suits you, and the first step in matching is the issue between the speaker and the input device.
