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Car Audio

Detailed Introduction to Product Categories in Car Audio

Today, car audio has developed with digital technology as the mainstream, such as: CD, MD, VCD, DVD, MP3, etc. In this field of car digital audio, SONY has always been a dominant player as the manufacturer that developed the CD specification. Two years after the CD was introduced, SONY launched the world's first car CD player, the CDX-5. By 1986, SONY also introduced the world's first car CD auto-changer, the CDX-J10.

a. Types of Car CD Players:

Single-disc, triple-disc (ALPINE 3DM7887E), and six-disc (NAKAMICHI MB-75) players include a radio component. Car CD auto-changers come in four-disc (VDODAYTON CH400), five-disc (NAKAMICHI MB-31), six-disc, eight-disc, ten-disc, and twelve-disc varieties.

b. What is MD?

MD (Mini Disc) is a digital audio system developed by SONY in 1992 that can both record and play back. There are two types of discs: one for playback only, which is optical, and another for recording, which is magneto-optical. During playback, tracks can be easily searched forward or backward. The recording disc allows you to change the order of songs, delete or insert songs mid-recording, making editing very convenient.

MD uses ATRAC (Adaptive Transform Acoustic Coding) digital audio compression technology, achieving CD-level performance in dynamic range, frequency response, and distortion. Its diameter is just 2.5 inches (63.5mm), with a recording time of 74 minutes and a sampling frequency of 44.1kHz. Although MD uses compressed signal technology, most of its original shortcomings have been greatly improved, providing excellent sound quality. When using a 2.5-inch magneto-optical disc, the sound quality is slightly less than CD but barely noticeable.

Why Choose Mini Disc?

MD is a digital recording format. It offers the recording capability of a cassette tape, allowing you to create your own personal music compilations. Additionally, it can be repeatedly recorded over a million times without affecting the quality of each recording. MD is particularly suitable for people who frequently need to record. The digital sound quality of MD can match that of CD. Moreover, features like instant track searching and digital editing push recording technology to new heights.

c. Features and Benefits of MD:

Permanent Recording Quality Feature: When playing an MD, the pickup does not make contact with the surface of the MD disc, so the surface of the MD disc is not easily worn out. Benefit: No matter how many times you record and re-record, MD provides high-quality digital recording effects. Shock Memory Function Feature: A unique electronic shock memory function maintains digital music data. The memory function lasts up to 10 seconds or 40 seconds (depending on the model). Even if the body vibrates and cannot pick up the signal, the music continues to play stably. Benefit: MD ensures continuous music playback, which is great for use in cars. CD to MD Digital Recording Feature: You can edit all your favorite songs onto one MD disc while enjoying digital sound quality. Benefit: You don't have to carry multiple CDs when going out; just carrying one compact MD disc is enough. Professional Editing Function Feature: MD has diverse editing functions including moving, combining, deleting, dividing, naming discs, and editing tracks. Benefit: You can freely modify or create your own favorite recordings. Additionally, special mixing effects can be easily achieved.

d. High-Quality Digital Recording:

Feature: MD is an ideal choice for recording music, meetings, classroom notes, and live music. MD can record 74 minutes of stereo digital audio or 148 minutes of mono audio. Benefit: It can record or repeatedly record any cassette tape without damaging the sound quality, completely being a compact and durable format. Easy operation for playback and deletion functions. Sony Car MD Laser Player Products (Main Functions): MDX-C800REC Single-disc, comprehensive MD editing functions, pre-set time recording function, output power 45W x 4, electronic anti-shock system providing 40 seconds of data memory (16Mbit), wide-bitstream technology. MDX-C6500RX Single-disc, output power 50W x 4, electronic anti-shock system providing 10 seconds of data memory (16Mbit), wide-bitstream technology. MDX-65 Six-disc changer, flexible design, installable at 0°—90° angles, 8x sample filter, electronic anti-shock system providing 10 seconds of data memory (4Mbit), wide-bitstream technology.

e. Common CD Mechanisms:

Common laser player mechanisms are divided into European and Japanese systems. Nowadays, the transmission and optical systems of European CD mechanisms are almost entirely from PHILIPS, while the Japanese system is represented by SONY. The biggest difference between car CD mechanisms and home CD mechanisms lies in the CD clamping method. To prevent CD vibration, car CD mechanisms use an upper and lower clamping method, ensuring that even strong vibrations will not cause the CD to come loose. CD auto-changers use silicon oil airbags and tension springs for shock absorption, and high-end CD auto-changers also use electronic shock absorption, such as SONY CDX-747X with a 12-second electronic anti-shock system (ESP). It can also be adjusted for use at 0°—90° angles.

The European system is mainly from PHILIPS, starting with the CDM-1, which uses a swing-arm tracking mechanism and single-beam design. The CDM-2 is fully aluminum cast with a balanced transmission mechanism, and now mostly uses the CDM-5 mechanism. The characteristics of this mechanism include innovative side-spinning intake, no contact with the data storage area of the CD, short intake time, preventing scratches on the disc, low mechanical noise, next-generation holographic laser head and vibration-absorbing silicone device plus faster-reacting servo system, maintaining better shock resistance and sound quality in various road conditions. Known as the "shock-resistant champion," it is relatively ideal among single-disc mechanisms.

Each large factory in Japan almost independently develops CD mechanisms, but Sony and Sanyo are the main suppliers. Most car CDs use Sony mechanisms. Some mechanisms have developed a triple shock-absorption system; for example, Sony CDX-747X has both mechanical and silicon oil airbag shock absorption as well as an ESP electronic shock-absorption system. Pioneer's inverted mechanism places the disc information side facing up with vibration-absorbing material on a highly rigid disc tray, and the laser signal is read via straight-line tracking from above. A disc-shaped pressure disc of the same size as the disc pushes the disc upwards tightly against the pressure disc, with the drive motor located above the pressure disc; another benefit is preventing dust from quickly contaminating the laser head. Nakanichi's front-mounted six-disc mechanism MB-100 6-disc (1DIN) CD player/radio has the feature of a single mechanism capable of holding six CDs, with a unique truly floating magnetic CD transport device, eliminating all vibrations. Now Panasonic has a front-mounted six-disc mechanism in Toyota Jeeps. Fujitsu Ten has a front-mounted six-disc mechanism in Toyota Lexus 200.

f. MP3 Multimedia Car Laser Player:

MP3 music is the most popular music format today. Compared to ordinary music CDs, it can be downloaded through the Internet, allowing you to compile and burn your own music CD without time or geographical restrictions, while retaining the original sound quality. Simply put, MP3 technology is a way to encode, transmit, and compress regular music formats into smaller sizes without losing the original sound quality. Additionally, due to the small size of MP3 music, a single disc can hold over a hundred songs.

What is MP3?

MP3 stands for MPEG-1 AUDIO LAYER 3 (the abbreviation of Layer 3), which is a computer file format compressed using digital computer technology that converts sound into digital computer files for storing music. Since MP3 files are compressed, storing one minute of high-quality music requires only 1MB of memory capacity, which is ten times less than general storage formats. Therefore, a 650MB CD can store 130 songs, significantly reducing the storage space required. The appearance of MP3 allows more songs to be recorded on a single CD, eliminating the hassle of changing discs! However, the sound quality may be affected after compression, which is acceptable for general music listeners but insufficient for audiophiles.

g. Why do CD players adopt high-bit and oversampling?

High-bit and oversampling are important methods to improve the sound quality of laser players. Oversampling can reduce the attenuation characteristics of low-pass filters, lower phase distortion, and high-bit can reduce the decrease in signal-to-noise ratio caused by digital filters.

In laser players, after digital signals are converted by DAC, although analog audio signals are obtained, there are excess parasitic frequency components that are multiples of 44.1kHz. Therefore, a low-pass filter with a steep attenuation characteristic is needed to filter them out. However, if there is any non-linearity in the subsequent stages, the parasitic frequencies and useful signals will modulate each other, causing serious distortion. Moreover, low-pass filters with good attenuation characteristics also have large phase distortion, which will affect the sound quality of the laser player. Therefore, inserting a digital filter before the DAC for oversampling at 4, 8 times the sampling frequency moves the parasitic frequencies to higher frequencies, allowing the use of low-pass filters with gentler attenuation characteristics, thus greatly improving phase distortion. However, introducing a digital filter will produce computational errors that reduce the signal-to-noise ratio. Using a high-bit DAC can reduce the degradation of the signal-to-noise ratio, such as a 20-bit DAC which can reduce the degradation of the signal-to-noise ratio to negligible levels. For example, NAKAMICHI CD45Z single-disc 20-bit, MB-100 front-loaded six-disc 24-bit. Since the world's first 1-bit (single-bit or unit) DAC chip was produced by Philips in 1987, Philips has applied this single-bit technology to all levels of its digital audio products. Subsequently, some Japanese manufacturers also applied single-bit technology to their Hi-End products. At that time, except for Philips and Japanese products, products from other countries still used multi-bit technology. For single-bit technology, it is actually different mathematical models based on the theory of bitstream technology to process quantized digital data. Due to the outstanding achievements of the United States in single-bit technology in recent years, the Delta Sigma mode has received much praise. The Delta Sigma mode is not only widely used in medium and low-priced digital audio systems, but more importantly, it is also used by many manufacturers in their top-of-the-line Hi-End equipment.

h. VCD and DVD Players:

They are mainly developed for AV systems, and manufacturers do not pay too much attention to sound quality issues. Although their playback sounds very beautiful, they still fall short in terms of expressing the nuances of sound quality. Therefore, those who care about sound quality would not use them as a sound source.

i. Selection of CD Players:

Car CD players are divided into single-disc and multi-disc based on the number of CDs. When selecting, choose according to needs, car model, and audio system. It should also be noted that the price of single-disc players is not necessarily cheaper and multi-disc players are not necessarily more expensive, which is a misunderstanding when choosing a CD player. The value of a CD player cannot be judged solely by the number of discs. High-end single-disc CD players can cost over ten thousand yuan, while a twelve-disc player costs only fifteen hundred yuan. Consideration should be given to the brand, performance, and functions of the machine.

j. Relationship between CD Player, Amplifier, and Speakers:

The CD player is the sound source, the first link in determining the quality of a sound system. The quality of the signal it outputs will affect the sound quality of the audio system. It is part of an overall combination with amplifiers and speakers, none of which can be missing. And when choosing them, consider them at the same level, meaning their technical specifications should be in the same class. This way, the matched sound system will be reasonable. Otherwise, it will either be mismatched or result in unnecessary investment.

Single-disc: Generally, the price is lower and easier to install, but there is no cassette deck, and the CD is prone to scratches when entering and exiting the slot. The shock absorption is poor (except for high-end machines), and manual disc changes are required (CDs can easily get dirty). The Philips CDM-5 mechanism has overcome these drawbacks. Output power is small (if the load is too heavy and the temperature is too high, the laser head protection will affect usage and even accelerate laser head aging).

Three-disc and high-end single-disc players: Higher price, no cassette (magnetic tape) function. From a performance-price perspective, it is not as good as buying a multi-disc player, but some car models do not have installation space for multi-disc players, so this type of model must be used.

Japan Nakamichi (Nakamichi), MB-100, unique design, integrated six-disc CD player, can be placed on the dashboard, allowing direct switching of multiple CDs at the front, eliminating the need for additional changers in the trunk. Uses a lift-storage structure to maximize the use of limited space, accommodating six CDs in the volume of a DIN-sized host. Separate decoding/pre-amplifier, 24-bit D/A conversion, adjustable pre-output level (1V-5V). This model is the preferred choice for audiophiles.

Multi-disc players: The biggest advantage is the large number of discs and storage capacity. Direct control of disc changes by the host is convenient and less prone to dirt, with good shock absorption. Moreover, compared to single-disc players, multi-disc players have cassette (magnetic tape) functionality. High-end models can program CD discs and track names. If economically feasible, it is best to choose a multi-disc player.

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