As stated before, check the amps rating on your alt. Also, find the total RMS watts (basically the true wattage of an amp). Use appropriate gauge of wiring (don't skimp on this!). Look into the "Big 3" (google that real quick). Umm, other than that make sure you have good grounding locations and fuses for the amps. You should be fine if the above measures are addressed. I, myself am running a Hifonics 1606d sub amp and JL Slash 300 4v2 totaling (off manufacturer's RMS ratings) above 1400 RMS watts. Even before i did the Big 3 my lights and other car electronics did not dim or fail. After 2 years with this system my OEM alternator and battery check out in the green ('07 Mazda 6 i sedan)
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