Car HiFi
Car HiFi is a collective term for hi-fi devices and systems in motor vehicles.
In the car hi-fi area, special components are installed in vehicles or existing ones replaced in order to meet higher sound demands. The purpose is to improve the performance or the characteristics of the music system in the car.
In the vehicle tuning scene, attempts are also made to set visual accents and integrate the system into the overall appearance of the vehicle. The standard factory systems of the car manufacturers are not enough for many vehicle owners. Although there are options on the part of automobile manufacturers today to install audio systems according to special specifications, this is often associated with high costs.
power supply
The operating voltage for the car hi-fi components is usually taken from the on- board network of the carrier vehicle. When the engine is running, the on-board electrical system voltage is generated by the alternator , otherwise it is provided by the starter battery . The no-load voltage of the vehicle electrical system is usually between 12 V (battery voltage) and ~ 14 V (battery charging voltage of the alternator). For optimum operation, especially of the power amplification output stages, a supply voltage that is as constant as possible - especially in the case of load requirements - is necessary (→ low internal resistance of the voltage source). In order to meet this requirement, various measures can be taken to reduce the internal resistance of the voltage source "seen" by the output stage:
- Replacement of the starter battery with a special battery with a lower internal resistance
- Installation of one or more additional batteries
- Installation of one or more capacitors (also called PowerCaps )
In particular, the parallel connection of several batteries can also provide large currents required over long periods of time. Capacitors, in parallel with the operating voltage, reduce the on-board voltage drop in the event of brief power demand peaks. One installation variant when using at least one additional battery is to disconnect the main battery using a cut-off relay . This enables the car hi-fi system to be operated with the engine switched off without discharging the starter battery required to start the engine.
Car radio
The term head unit is often used for the car radio in the car hi-fi scene . Modern car radios are equipped with an integrated 4-channel amplifier, but the output power is limited. This limitation is physically in the supply voltage of max. 14 V of the electrical system is justified.
speaker
Loudspeakers with an impedance of 4 ohms are usually used in vehicles. Loudspeakers that cover the front of the car are known as the front system. For example, they can be installed in the A-pillar , the front doors or in the dashboard. Some manufacturers offer pre-assembled components for various vehicle models for installation in the front doors, for which the term doorboard has become established in the German-speaking tuner scene. The term rearfill is often used for components in the rear area .
In the car hi-fi area, subwoofers are often built in , which are designed for the sole reproduction of low-frequency sound waves. Due to their size, they are often installed in the trunk of the car. When using a subwoofer, the use of additional power amplifiers is recommended.
Power amplifier
External output stages (amplifier, amp, amplifier) are used for higher demands . Since the on-board voltage is not sufficient for higher performance, the required operating voltage is generated via a voltage converter . This enables output powers in the kW range. External power amplifiers are usually activated from the car radio using remote lines (control cables). When the car radio is switched off, the output stage is in standby mode , and only a small quiescent current is drawn from the vehicle electrical system.
Problems
The installation of complex car hi-fi systems requires knowledge of electronics and the cables and connections used in the automotive sector, such as CAN bus or ISO 10487 . According to the applicable law, additional electrical installations must be secured no later than 30 cm behind the car battery, otherwise the vehicle's operating permit may expire. Cable fires can result from incorrectly selected cable cross-sections. Differential voltages in the vehicle ground cause ground loop problems; further interference fields can arise, for example, from the starter , the alternator or the ignition distributor of the engine. These can have a negative impact on the sound of the system. In the professional sector, therefore, multi-shielded audio cables are used and these are laid separately from the power cables. High voltages can also overload the alternator or malfunction of the on-board electronics ( airbag , ABS ).
The vibrations can cause roaring in the body panels. Attempts are made to counteract this by attaching bitumen mats, glass fiber reinforced plastics , insulating materials or changing the types of connection.
hazards
In general, distraction when operating the radio while driving can increase the risk of accidents. A complex car hi-fi system can also endanger road safety: it is possible that traffic noises, such as horns or special signals, are not heard if the volume is too high. Excessive volume can also lead to noise pollution, which can be punished as an administrative offense. Speakers that are mounted on the rear shelf of the car can pose a safety risk, as can improperly secured subwoofer boxes in the trunk, as they could be thrown forward in the event of an accident.
Web links
Individual evidence
- ↑ Car radio: Significantly overpriced! - Mobility. In: Spiegel Online . June 7, 2001, Retrieved June 10, 2018 .