The Car Audio System Nobody Would Build - Part 41

The significant current consumption of the audio system required the auxiliary battery to have considerable storage capacity. I intended to both compete and perform critical listening with the engine off, relying completely upon the auxiliary battery for power. A large 4D marine battery typically weighs about 135 pounds and has a capacity of about 200 ampere-hours ("A-hr"). My system, at maximum output, would drain this battery in about 35 minutes, if the engine weren't running. At half the output, the system would be expected to play for about 50 minutes, and substantially longer at even lower levels of system output. Using an inductive current measuring device, I determined the current draw to be about 6 amps with the system idling. Because of the significant demands placed on the battery, I chose a large, 4D marine-grade, deep-cycle battery manufactured by Lifeline Batteries, which employs absorbed glass mat technology.11

The purpose of this article was to stress the importance of matching the amplifiers to their loudspeaker systems to achieve maximum sonic performance. Selection of the appropriate amplifiers determined the power consumption of the system, which in turn, influenced the size and type of power cables, alternator, and auxiliary battery selected. The importance of often overlooked components in the musical signal path such as interconnects, loudspeaker cables and audio connectors was also discussed. Finally, this article emphasized the importance of component selection, since each component in the playback chain can only maintain or degrade, not enhance, the performance of a musical playback system. Next month, we'll begin the fabrication process.

Table 4. American Wire Gauge specifications for common conductor sizes.