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November 2011 Randy’s Electrical Corner

Posted in How To: Electrical on November 1, 2011
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Speakers can be hard to understand. It’s hard to see what makes them work and hard to see what went wrong when they stop working. Lucky for you guys I’ve blown up more speakers in my time than Carter had pills and I’ve figured out a few tricks along the way.

A long time ago some cars and Jeeps use what is called a common or floating ground stereo system kind of like the way we wire power in our Jeeps today. The speakers only had one wire running to them. Now I’ve never dealt with these systems aside from just removing them and replacing them with the later two-wire setup. Those early systems were often meant for one speaker and came attached to AM radios.

I like having more than one speaker and like listening to music so I put in more speakers. When installing speakers, there are some important things to remember. The first thing to remember is polarity. Just like in your Jeep the speakers have a plus and a minus side (Editor’s note: positive and negative). Unlike the Jeep, you won’t automagically start a fire if you wire up the speakers wrong. However you might as well not put in new speakers if you are going to wire them up wrong

Another thing speakers have like a Jeep is a suspension. Now, you can’t go getting new springs for it and installing a long-arm lift, but just like the Jeep the suspension is important. If you don’t have the right bumpstops or shocks in your Jeep you will just bounce around and possibly cause damage to the Jeep. The same idea for speakers but it has to do with the air in front of and behind the speaker. It is actually called acoustic suspension. If you can separate the air behind the speaker from the air in front, you can prolong the life of your speakers and possibly get better bass sound out of them as well. Just as with a Jeep with no shocks or bumpstops, if the speaker has nothing to dampen it from moving too far or too fast, it can get damaged.

Sound is measured in decibels (dB) and for every extra dB a stereo cranks out, it requires a doubling of power. Speakers have a rated sensitivity in dB at 1-watt of power input at a range of 1-meter. So a speaker that has a 90 dB sensitivity rating will be as loud at 1-watt as a speaker with an 87 dB rating will be at 8 watts. It doesn’t sound like much, but when you consider most stereos are only capable of 15 or 20 watts per channel, it matters in your loud Jeeps.

I like Kicker speakers. I’ve had good luck with them over the years and they tend to last a long time in Jeeps. I’m not just talking about the big subwoofers either. Kicker makes smaller full-range speakers that sound good and last a long time. You see, because of the exposure that Jeeps normally see, whether it is from accidentally leaving the top down or windows out in a rainstorm to tracking mud, snow, and dirt in off the trail, the interiors of Jeeps see a lot of abuse. Then you factor in mud tires, soft tops-a-flapping, and the Jeep stereo is turned up louder than stereos in a certain red El Camino I have done a lot of work on. So there are some things that I look for when buying speakers, and Kicker has always come through.

Jeep must have had fun through the years on purpose. I can’t figure out why else they would change the speaker wire colors every year. Or at least it seems that way to me. So one of the first things I do is test the factory speakers for polarity and write the results down. Shown here is a Kicker DS693 but the process is the same for factory speakers. I use a battery and using a couple of pieces of scrap wire, I pop it. You hook the positive of the battery to one terminal on the speaker and the negative to the other terminal. If the speaker cone moves in, you’ve got it right. If it moves out, you have the polarity reversed.

Anyway, enough of me yabbering. On to the fun.

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Crutchfield Corporation
Charlottesville, VA 22911
Stillwater, OK 74076
4WD Hardware

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