I’ve used low-power amps and subs in the past, but now I’m thinking about stepping it up. I’m considering a single 12” sub with around 500-600 watts. Can I run that on a stock electrical system, or will I need upgrades? I drive a 2006 Infiniti G35, does that help?
You’ll need to make a few assumptions, and you can adjust based on your car’s specs. For example, let’s say your alternator is rated for 100 amps. Subtract about 40 amps for other vehicle systems, and let’s assume the voltage drop is around 13.8 volts. Now, using the formula Watts = Amps x Voltage, here’s how you figure it out. A Class D amplifier is about 85-90% efficient, while Class A/B is closer to 65%. So, 100A - 40A = 60A, and then 60A x 13.8V = 828 watts. Assuming 90% efficiency for Class D, that gives us 745 watts RMS. Based on that, your alternator should be fine for an 800-watt RMS system. You might need to adjust if you have other amplifiers for speakers. Just remember, your car’s alternator won’t put out max power when idling. Also, make sure your grounds are solid because a poor ground can affect performance. If your car has body panels that aren’t grounded well, consider grounding directly to the frame or battery.
Great explanation, thanks for breaking that down!
Awesome info, you really nailed it! This is how it works!
I have a 2004 Volvo S60 with a 120 amp alternator. I’m running 1,000 watts on my subs and 600 on my front speakers, and I still get a steady 13+ volts, so you should be fine.
It can vary based on your car’s make and model. I had a Nissan with a similar alternator and big 3 upgrade with 0/2awg wiring. Even with that, I saw my voltage drop to 11.2V during heavy bass hits.
It’s a good idea to check the amp rating on your stock alternator. Some cars come with powerful alternators that can handle 1,000-watt systems. But if you go above 1,500-2,000 watts, you’ll need some serious upgrades, like a high-output alternator. At the very least, do the ‘big 3’ upgrade. Clean the ground connections and make sure they’re connected to bare metal for the best results.
The quality and efficiency of your amplifier matter a lot. I’ve run three JL Audio RD amps (1000w, 600w, and 400w) on my 98 BMW and 96 Buick Roadmaster with no issues. I didn’t even need any wiring upgrades, just good power and ground cables. The ‘big 3’ is still a good idea, though—it’s a cheap upgrade that can prevent problems later on.
1,000 watts is fine. Once you go over 1,500 watts, you’ll want to look into electrical upgrades, especially if your car is newer than 2000.
I’m running a JL Audio 1500 watt amp on 2 Rockford P3 12s in my '23 Ford, and I haven’t had any electrical issues. Check the amp rating of your alternator, though—mine is on the lower side and I haven’t had any problems.
It really depends on your car’s electrical system. If you have an older car with a small engine, you might only have a 65-75 amp alternator, which won’t handle much power. But if you have something like an old police car with a 170 amp alternator and auxiliary battery, you should be good. My car runs fine with my JP13 setup.
I’m running an 800-watt amp for a 12-inch sub, along with a 360x4 amp for my door speakers. It’s on a stock alternator, and if I turn up the volume to max, my lights dim a little during heavy bass hits. But it’s nothing too bad, you should be fine.
How long is a piece of string? It really depends on your setup!
Thanks to everyone for the help!
I have a 97 F150 with a 130 amp alternator. I’m running 2,000 watts for subs and around 450 watts for other speakers. I only get minimal light dimming and my voltage stays above 13.4 volts.
In my old Camry with a stock 80 amp alternator, I was running a Sundown SAZ1500D and two SAX 100.4s. I added a Diehard Platinum battery (made by Odyssey) and dedicated power and ground runs to the trunk. No issues at all.
A lot… more than you need to worry about.
I’ve seen people run a few hundred watts and others run over a thousand watts.
I have a Kia with a 4-cylinder engine. Nothing too crazy, but I run a 600-watt amp and a 1500-watt amp, and I crank my music. I don’t have any capacitors or upgrades, and I’m good. Just check your car’s alternator output and look at some online graphs to make sure you’re safe. I had a 2004 G35 Coupe with a 1,000-watt amp and no issues. Just get an efficient amp.
It depends on whether the sub amp is rated for RMS or peak power. A 500W RMS sub draws about 42 amps, while a 500W peak sub draws closer to 10 amps. Both will pull a few extra amps to keep the caps charged. Drawing 40+ amps on a 120-amp alternator can cause the battery to not fully charge, which could shorten its lifespan or leave you stranded needing a jumpstart.