catalogue
(1) Sound source (host)
(2) Speaker
(3) Power amplifier
(4) Capacitors, Balancers, Dividers
(5) Wire
(6) Principles of car audio matching
(1) Sound source (host)
The sound source is the most basic and essential part of audio modification.
(1) Performance of audio source
① Sound quality: Sound quality is the most important factor in choosing a sound system. It includes three aspects: range, pitch, and timbre.
② Function selection: Due to the specific listening space of the car, it has a certain impact on the sound field and sound quality. In order to solve these problems, many sound sources have corresponding function designs, aiming to achieve on-site listening effects.
③ Performance indicators mainly include the following aspects:
◎ Output power: Currently, the majority of the power indicated by the host is music power, ranging from 40W to 60W. The higher the power, the better.
Frequency response: The frequency range that can be heard by the human ear is between 20-20KHz, so this indicator should reach at least this value, and the wider the better (the lower limit frequency is smaller, the higher the upper limit frequency is better).
Signal to noise ratio: refers to the ratio of music signal to noise, measured in decibels (dB). The higher the value, the better. Generally, high-end products have a noise level of over 100dB, with clean and clear sound.
Harmonic distortion (THD), which reflects the degree of reproduction of sound, with smaller values indicating higher levels of reproduction.
(2) Sound source classification: There can be multiple classifications of sound sources according to different methods, and we will introduce them separately below.
① Classified by signal source: mainly including radio, magnetic tape, CD, VCD, DVD, MD, MP3, etc.
② According to the demand for car audio systems: fever type and regular type.
③ Classified by production and sales: OEM \ ODM.
Host classification - Signal source
There are currently two main types of audio sources in car audio systems: the main unit (cassette player, disc player) and the player.
The cassette player uses recording tapes as the sound source and analog technology, which is an outdated product. It is installed on some low-end driving cars and is matched by car manufacturers to reduce manufacturing costs. Its frequency response range is narrow and the noise is high, which obviously cannot be used as a sound source for appreciating music. This will not be discussed here.
The sound sources used by the disc player include CD, MD, MP3, VCD, DVD, etc., which use digital technology.
A player is a new type of car audio source that has emerged with the popularity of digital applications. It uses pure digital audio sources and relies on USB drives, solid-state drives, or wireless WIFI for signal transmission. More consideration should be given to the impact of high temperature, humidity, vibration, and power supply in the car on the product. With the continuous upgrading of the car audio system, it can meet the storage and playback of high-definition non-destructive sound sources, and can also connect with mainstream music sharing platforms, making human-computer interaction more intelligent.
Hosts can be divided into two types according to their working methods
1) Single disc player
2) Dual disc player
There are two types of classification according to specifications
1) International standard: The standard size is 178mm x 50mm, and this specification is called 1DIN. This specification product has strong universality and is the standard specification for most car mounted CDs. It is a mainstream product.
2) Large screen machine: commonly known as 2DIN, with a size of 178mm x 100mm, the width is the same as 1DIN, and the height is twice as high. This specification of products is mostly used in Japanese cars, and the installation position of most original CDs in Japanese cars is this size. Generally speaking, this product is relatively high-end and relatively rare in the market.
The basic working principle of a CD player
1) Signal interpretation system
The laser head reads the signal from the disc, which is amplified by an RF (radio frequency) IC to form an RF signal. Then, it is processed by a DSP to form a preliminary audio signal, which is sent to the audio processing circuit for processing and converted into four channels. After being amplified by a power amplifier, the output is directly driven to the speaker. Another interpretation method is to directly output the audio signal before it enters the power amplifier, which is called RCA signal output.
2) Attendant system
There are two sets of signals: the first set is the laser head reading the signal from the disc, which is amplified and processed by RF and input to the service control IC. The other set controls the signal. Two sets of signals work together on the servo control IC to control the operation of the servo motor, enabling the laser head to accurately and accurately read the signals on the disc.
3) Control system
The control instructions sent from the panel are compiled into different digital signals by the CPU, processed by the DSP and input to the servo control IC to control the operation of the servo system. There is also a set of instructions sent from the panel to the audio processing circuit through the CPU to control the audio processing circuit. During the control process, the panel display screen displays accordingly.
