When it comes to ensuring that your car audio amplifier is making the most power possible, nothing is more important than properly sized, high-quality power wire. Can an amplifier produce 2,000 watts of power if fed with 4 AWG wire? What factors affect the size and quality of wire needed for an audio system? There’s a lot of confusion around wiring, so let’s look at some considerations and test the power production capabilities of an amplifier when fed with differently sized cable.
Power Wire Quality
Make no mistake: If you stick with the name brands, you will most likely get what you expect in terms of power wire quality. Stinger, Wirez, Rockford Fosgate, T-Spec, Connection by Elettromedia and several others offer premium cabling that follows industry standards for strand content, copper quality, conductor diameter and jacket materials. All of these requirements are outlined in the ANSI/CTA-2015 Mobile Electronics Cabling Standard.
The biggest red flag is an amplifier installation or power kit that refers to cable size using the word gauge instead of AWG (American Wire Gauge) to describe the wire size. A 4-gauge amp kit is likely nowhere near the quality of a 4 AWG amp kit. To comply with the American Wire Gauge standard, a wire must be constructed of copper, so copper-clad aluminum isn’t an option. Likewise, the conductor itself must have a certain number of strands in a certain number of groups and a specific cross-sectional area. If you’re shopping for a power kit to have a car audio amplifier installed, don’t look for the best value, look for the best performance – the longevity and reliability of your audio system depend on it.
Why Does Power Wire Size Matter?
If you’re a regular reader of BestCarAudio.com articles, then you know that car audio amplifiers can draw significant amounts of current. It’s not uncommon for a moderately sized amplifier to want more than 100 amps of current to drive subwoofers. The problem with high current requirements is that cable resistance wastes a lot of energy in the form of a voltage drop and, subsequently, heat. When current passes through a resistance, a voltage is produced across that resistance. Lower quality and smaller diameter power wire has more resistance and as such, more voltage is present across the ends of the wire. This means that less of the voltage from your alternator and battery will arrive at your amplifier. Less voltage at the amplifier means it will produce less power for your speakers.
Let’s say we have a high-power amplifier that’s rated to produce 1,000 watts of power. If the amp has an efficiency of 85% at full power, and our electrical system can supply 100 amps of current at 13 volts, everything should be fine. What if we cheap out on the power wire and buy an inexpensive, undersized 4 AWG amp kit to feed the amp? How much voltage do we lose between the battery and the amplifier power terminal?
A high-quality, fully CTA-2015-compliant 4 AWG conductor with a length of 15 feet would result in 0.4 volt being dropped across the cable with 100 amps flowing through it. This means we only get 12.6 volts to the amplifier. What if we use an inexpensive copper-clad aluminum cable? I’ve tested a dozen of these kits in the past, and they vary SO much from brand to brand that it’s almost frustrating. The worst kit I tested had more than three times the resistance of the best kit, and the best was still nowhere near as good as a full-copper cable. So let’s say we have three times the resistance. Now we’re only going to get 11.8 volts to the amplifier. Clearly, the amp won’t make as much power. How much less? Let’s test it!
Does Low-Quality Power Wire Affect Amplifier Power?
I have a large subwoofer amp in my lab that I use to break in speakers and subwoofers. It makes more than enough power at 4 ohms to meet my needs and doesn’t mind driving a 1-ohm load. For this test, we want to look at how much power the amplifier produces when fed with different qualities of power wire. We’ll make three measurements. The first will be the reference configuration with 15 feet of good-quality 4 AWG wire on the connections between the amplifier and the power supply distribution block. Then we’ll see how much power the amp can produce when I use 15 feet of low-quality 4-gauge cable on the positive feed.
Amplifier Power Production Versus Cable Quality
I set the amplifier up and wired it to my bank of load resistors. Then I increased the output until I saw 1% total harmonic distortion on my audio analyzer. With 15 feet of full AWG-spec, all-copper wire in the system, the amp produced 950.5 watts of power, with 13.8 volts at the amplifier power terminals. I repeated the test with 15 feet of low-quality, copper-clad-aluminum power cable to the positive connection, then reset the sensitivity control on the amp and measured power again at 1% THD. This time, the amp produced 911.65 watts with 13.12 volts at the power terminals. A difference of 39 watts in the output really isn’t much to get excited about unless you’re competing to see who has the loudest stereo. The difference in SPL is a theoretical 0.18 dB.
So where did that energy from the power supplies go? It was turned into heat in the wire. The problem with wires getting hot is that their resistance continues to increase. Our little test showed just over 56 watts of heat energy being wasted in the wire. What happens if we let the amp play for a while? I fired the amp up again and let it play for 10 minutes at the same input level, and then I measured the power output again with the hot wire. The amp’s output dropped a few more watts to 907.4, representing a full 0.20 dB drop in output. The wire was generating 60 watts of heat.
Speaking of hot, just how hot do you think the wire got? It started at 70.5 degrees. In the 10 minutes that I let the amp play, the wire temperature climbed to 170.7 degrees. It would have kept climbing had I not stopped. If you want to see a soft jacket on a 4-gauge power cable, heat it up to 170 degrees!
What Have We Learned About Power Wire Size and Quality?
If you’re going to draw massive amounts of current with a big amplifier, the quality of the wire you use matters in terms of getting the most voltage possible to an amplifier. The use of undersized or low-quality wire will not only starve the amp, but it will heat quickly, exasperating its inadequacy. When it’s time to have an amplifier installed in your vehicle, make sure your installer is using full AWG-spec power and ground cables that are all-copper with no aluminum. Your amplifiers will be much happier for it!