Provided by HOW To Church Sound Workshops.

 
Few things can affect the quality of a sound as speakers being out of polarity.

You can lose bass response, cancel your vocals and cause general phase mayhem in your sound system.

There are may ways to determine polarity, however here’s a cheap and easy solution to test for proper wiring inside your speaker cabinets before you install them up on the wall and without running any audio signal through them.

See Figure 1 for Thumper, my trusted polarity signal injector.

Once you build Thumper, you just hook a speaker cable from its phone jack to whatever cabinet you want to test.

A brief push on the momentary push button will inject a 9-volt positive signal into your speaker cones.

You should then see all the woofers pop out just a bit. If one speaker pops in while the others pop out, you have big wiring problems inside the cabinet.

If all of the speakers pop in, then the input jack on the speaker cabinet or the cable itself may be wired in reverse. You already know how to solder from a previous column, so get fixing.

Figure 1.

Click on the image to the left for a bigger graphic. You can build Thumper from junk parts or go to Radio Shack for a little plastic project box, quarter-inch phone jack, 9-Volt battery clip and SPST (Single-Pole/Single-Throw) Normally-Open (N-O) momentary contact switch.

An exact part mounting plan isn’t critical — as long as everything fits inside the case it should work.

I usually put a small piece of foam under the battery to keep it from rattling around or sliding inside the box. But just make four solder connections, and you’re done.

Thumper works great on speakers both large and small, and the 9-volt output only dumps a 10-watt pulse into your speakers, so it’s safe to use.

What’s not to like? If you build Thumper, let us know in the comments below!

Mike Sokol is the chief instructor of the HOW-TO Church Sound Workshops. He has 40 years of experience as a sound engineer, musician and author. Mike works with HOW-TO Sound Workshop Managing Partner Hector La Torre on the national, 36-city, annual HOW-TO Church Sound Workshop tour. Find out more here.