AC, Speaker Polarity?

Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=60851
Printed Date: July 12, 2025 at 3:10 PM

Topic: AC, Speaker Polarity?

Posted By: 349517
Subject: AC, Speaker Polarity?
Date Posted: August 06, 2005 at 11:34 PM

Hey guys, this may be a dumb question but here it is: If when working with AC power you dont have one wire that's always positve and same for neg then why do car speakers have one postivive and one negitive when the amp is putting out AC?

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Jim
Best Buy MECP Mobile supervisor in store 820
jimmyb3rddegree@hotmail.com

Replies:

Posted By: DYohn
Date Posted: August 07, 2005 at 12:05 AM

In general laymen's terms, loudspeakers are polarity marked in the "forward drive" direction for the voice coil. When a positive electrical signal is placed on the positive terminal, the voice coil drives the speaker cone "forward." The marking is for ease of setting up and building systems, as it is important to understand the electrical polarity of the voice coils so you can ensure your system is all "driving" in the same direction. You want the speakers all moving "forward" together or else the sound pressure waves they create can cancel each other out. But as long as all speakers in a system are in electrical phase, it really does not matter which terminal you use as positive as long as you use the same one on all of the speakers. Was that clear at all?

Now in some crossover designs and some loudspeaker enclosure designs, the electrical phase becomes inverted by the system and you have to wire one or more speakers out of phase with the others, but that is another topic for another night. Cheers.

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Posted By: 349517
Date Posted: August 07, 2005 at 7:52 AM

That clears it up a little but how about this. How can you make + and - on a speaker when its not always what polarity.

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Jim
Best Buy MECP Mobile supervisor in store 820
jimmyb3rddegree@hotmail.com

Posted By: geepherder
Date Posted: August 07, 2005 at 8:47 AM

The polarity on the speakers will give you a starting point. If you have one speaker's cone pull in, while it's counterpart's cone pushes out, you'll get cancellation- that's why it sounds like there's no bass. This way, as long as they're all connected the same way- with the same starting points, it'll sound fine.

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My ex once told me I have a perfect face for radio.

Posted By: DYohn
Date Posted: August 07, 2005 at 9:56 AM

349517 wrote:

That clears it up a little but how about this. How can you make + and - on a speaker when its not always what polarity.

With a Sharpie? posted_image

Like I said, a + signal on the + terminal will ALWAYS drive the cone forward. The fact that the polarity changes is why it's called alternating current, and without that you will have no sound.

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