19 August 2013|
Q: I’m writing to get some help with the charging system in my Chevy Cavalier. I have a new battery and the stock alternator. The car has 78,000 kms on it. My stereo is powered by a JL e4300 for the mid range and tweeters, and a Kicker ZX500.1 for my Kicker Comp R 12s.
About a month ago my battery died. When I bought a new one, all my friends said I needed a high-output alternator. But my Dad says a high output alternator will fry my cars computer and accessories. I want to make sure my new battery lasts a long time and I’m properly charging my amps. What should I do?
Jason from Edmonton
A: Well Jason, you actually have several questions here, so let’s start at the beginning. First thing to remember is batteries don’t last forever. You don’t say how old your car is, or how old the battery was, but it’s pretty normal to replace your battery every three to five years. Here in the desert southwest we seldom get more than three years from even the best batteries, because of the heat. Since you have used the new battery for a month, I’m going to assume that the Cavaliers charging system is working okay.
High output alternators designed for street-driven vehicles produce more current (amperage) than stock alternators. The voltage is still regulated to the usual 14.4V, so there is no chance the high output unit will do any damage to your electronics. The additional current is available on demand, for example when you have your headlights on, the blower on high, or a deep bass note hits and you have the volume turned up. The alternator simply puts out enough current to keep up with the demand, no more.
Frankly, unless you have something else in your car that’s drawing a lot of current, like a set of halogen driving lights for example, the stock alternator should be able to keep up with your audio system demands quite well. So, if I were in your shoes, I’d keep my connections clean and tight, make sure the ground cable from the battery negative to the car chassis is at least 8-gauge copper cable, monitor the voltage of the charging system and just enjoy your ride. Eventually, that stock alternator will wear out – that will be a good time to decide if you want (or need) to upgrade to a high output unit.
Q: Hi, I’m a big fan of the magazine, and read every issue cover to cover. I never thought I’d be writing to you, but here goes. I have a 2009 Mustang and I want to add an amplifier for a subwoofer. The trouble is, the amp and woofer I have only uses RCA inputs, but my head unit doesn’t have RCAs. I think I need a line output converter (LOC) adapter piece to get RCA outputs, that much I have figured out. My question is, what type of RCA cables should I run from my radio to the back of the car? Are the expensive ones worth the money, or can I buy cheaper ones online and be ok?
Scott M. via email.
A: Hi Scott, thanks for the question. We’re glad to hear you enjoy the magazine. My answer might just surprise you. If it was me, I would not run RCA’s from the radio to the amplifier. I would run ordinary 18-gauge primary wire that I had transformed into a twisted pair by
putting one end in my vise, and the other end in my drill. Or, if you don’t want to be bothered with twisting your wires, you’re still better off with regular zip-cord speaker cable instead of RCA, then put the LOC device as close to the input of the amplifier as possible.
If it was me, I’d do away with the LOC completely and build my own voltage divider, but we’ll save that for another time.
The reason I would run the primary or speaker cable (instead of RCA) over the noisy chassis of your car is because the speaker wires carry a higher voltage signal, and are in a balanced configuration coming out of the radio. This setup will give you much greater immunity to radiated noise problems, and save you money on signal cable to boot. Generic speaker wire is much cheaper than decent RCA cable.
For some reason I will never quite understand, everyone thinks the LOC has to go in the front of the car behind the radio. This is completely wrong. If you must use an LOC, it should go right at the input of the amplifier, so you can take advantage of the excellent noise avoidance properties of the already existing amplified output. And if your LOC has gain controls on it, make sure they are wide open. Signal level matching should be adjusted at the amp, never at the LOC. Good luck with your system.
Q: I recently got a new car, and swapped my dual voice coil Alpine Type S subwoofer and PDX amp out of my old car. I also switched from a sealed to a custom vented box with Plexiglas. The system used to have killer bass, but now there is hardly any, and the woofer cone doesn’t bounce like it used to. I’ve checked all my power and grounds, and the RCAs. I even plugged my iPod into the amp, but it made no difference. Is this because of the vented box?
Erick via email
A: Erick, I don’t believe your problem is with the new woofer box, I think you have the woofer wired wrong. Specifically, I’d bet money that you accidentally wired your woofers voice coils out of phase with each other. This is easy to check, simply pull one wire off of one coil. Then if the woofer has output, that is the problem. You need to reverse the polarity of the wiring to one of the coils to get your bass back. Hopefully you have not damaged the coils by overheating them while trying to get the woofer to play. Good luck with the fix!