Enjoying an In-Car Sound System?
October 22, 2009
My car is my favorite place to listen to music. An In-Car system delivers surround sound as if one’s entire body is inside a pair of headphones, each deep rumble of the drums can be aurally heard as well as bodily felt. Tweeters can be aimed at the ears and large Woofers can be accommodated at the rear producing an amazing sound.
However, a running automobile is also a hazardous environment for the electronics in the car, particularly the In-Car Sound System. There a lot of vibration, high temperature and high electrical and radio interference. Eliminating such noise is our topic for today.
An automobile has a multiple spark plugs radiating rf, an alternator that’s producing electricity, a battery storing DC and large number of cables connecting various electrical components. If not maintained properly, all these items can result in interference that the In-Car system will not only pick up but also amplify. The AM band on an automobile is particularly susceptible to inference, inherent in the nature of AM Itself and that’s why most In-Car systems do not have any AM band. FM on the other hand can maintain excellent signal to noise ratio due even in highly noisy environments.
Alternator Noise
When the engine spins the alternator around, the alternator produces an AC voltage that is converted to DC and used to charge the car’s electrical system.. If a small amount of AC voltage leaks into the system it can be heard as a high pitched whine. Frequencies change accordingly to the engine’s RPMs. Since the alternator noise is high frequency pitched, it can be heard from mid range speakers and tweeters.
Engine Noise
Most engine noise can be traced to the following:
We discuss these factors in detail below:
B+ Power Cable / Power Cable: The correct-sized power wire should be used to meet for the current (amperage) demands of the installed system. At least 8-gauge power cable is preferred for each amplifier, although 4-gauge is recommended if there are 2 or more amplifiers. A 4-gauge cable provides the headroom to add more amps later without having to re-wiring.
NOTE: The B+ cable MUST be fused 18" and be attached directly to the vehicle’s battery using a high-quality battery adapter. Install the fuse holder using water tight contacts.
Ground Cable: All ground cables should be and the same exact size as the power cable and less than 18" long. A high quality the battery-to-chassis cable will lower the ground path resistance and provide a better grounding. It is always preferred to use a single grounding point to the chassis so that ground loops are eliminated. It’s better to employ a distribution block for this. Clean the chassis scraped of any paint and secured the ground connection with a non-anodized screw and star washer.
RCA Cables: Signal Cables need to be located away from any power cabling ( eg the power cable for the amplifier or any factory wiring) . Run the remote turn-on with an additional ground wire, and ground it to the exact same spot to where the amplifier is grounded. Power cables should be run down the opposite side of the vehicle from your RCA Cables. The RCA cables should be a high-quality type or twisted-pair cables.
Vehicle Charging System: The car’s alternator or battery may also contribute to noise. If the alternator is starting to fail, it will cause noise through the audio system. A failing battery can add noise, but this is less common. To be sure, please take your vehicle technician and test the battery and alternator under load. If your alternator is not adequate for the total power loads in the automobile then its better to install a higher rated unit.
High Resistive Connections: All power or signal connections need to be firm and tight. Loose connections with high resistance result in noise. A simple check up of all connections will cure such noise.
Conclusion: It is easy to ensure that an automobile does not mar your enjoyment of the In-Car sound system. Most car manufacturers ensure that their product is satisfactory in this respect, but as vehicles age, their ability to avoid inference may degrade. That is where you would find this article useful.
All power or signal connections need to be firm and tight. Loose connections with high resistance result in noise. A simple check up of all connections with cure such noise.
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