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RE: JBL 2405 and 077

Posted by seancuster71@gmail.com (P) on April 25, 2025 at 18:52:11

In Reply to: RE: JBL 2405 and 077 posted by Inmate51 on April 22, 2025 at 15:14:01:

I have several the brand is fluke One desktop model 8808A and several handheld one handheld is a 117 the others I don't remember. Can't go wrong with a fluke. Funny thing is I've never use a multimeter for anything audio lol besides biasing an amplifier.

And why is everybody fixated on how to check a speaker's polarity when a speaker does not have a fixed polarity?

If you take a three-way system and you reverse the polarity of the Tweeter the mid-range and the woofer putting all positive wires on the negative terminals and all the negative wires on the positive terminals will the speaker be out of phase? Will the speaker measure different?
The answer is the speaker will not be out of phase and it will measure exactly the same as if it were wired normally.

What if you didn't have an expensive multimeter and you just had a little cheap multimeter, but you had no battery could you still check the polarity of say a woofer? Yes, you could. A speaker's voice coil moving inside a magnetic field creates voltage just like a moving coil phono cartridge would.

So if you take a woofer put the red lead from a multimeter to the positive Black lead to the negative put the multimeter on DC millivolt setting. Now push the woofers cone down the meter will read voltage and show a negative symbol. When the cone comes back up it will show voltage and a positive symbol. This is a very easy way to check polarity with a woofer or a mid-range. Cone moving up or forward means positive polarity.

You could also check the polarity of any type of speaker with any multimeter if it's in the cabinet hooked to your amplifier and playing music. When your cone moves it creates DC voltage this is called back EMF electro motive force. And if you set any multimeter to DC millivolts you should be able to measure the polarity even though the amplifier is feeding the speaker AC due to the back EMF being DC.

Speaking of amplifiers delivering AC current AC current has no fixed polarity which means your amplifier is just like your speaker and has no fixed polarity. The black and red outputs on an amplifier are not to Mark the polarity that's not there it's to keep the speakers in phase. Same with a speaker.

I'm not an electrical engineer I'm not a speaker driver designer I don't even know what all a multimeter can be used for. But I do know this if a simple post about how to check a speaker's polarity caused the response that it did. Then this post telling people that think amplifiers and speakers have fixed polarity. That they actually don't have fixed polarity should be fun times.

This post is made possible by the generous support of people like you and our sponsors:

Atma-Sphere Music Systems, Inc.

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