Zero impedence vs. infinite impedence

[tomzarbo]

On another forum I posted a response to someone who wanted to do away with their center dash speaker and was contemplating just pulling the wires off of it, covering them, and letting the amp do what it will.

This is a car with small factory amps for each speaker, in this case the mono center speaker (Bose) between the two front door speakers.

I said that I wouldn't do it that way myself, just pulling the wires off the speaker, I would rather address the amp issue by turning it off, pulling the fuse, etc.

I assumed that it would result in the amp seeing zero impedence, and it may not like it and get hot, or go into protection mode, but I got called on it by someone who said it would be infinite impedence. What is that exactly? Would someone care to enlighten me?

TomZ

[Jeff B.]

On another forum I posted a response to someone who wanted to do away with their center dash speaker and was contemplating just pulling the wires off of it, covering them, and letting the amp do what it will.

This is a car with small factory amps for each speaker, in this case the mono center speaker (Bose) between the two front door speakers.

I said that I wouldn't do it that way myself, just pulling the wires off the speaker, I would rather address the amp issue by turning it off, pulling the fuse, etc.

I assumed that it would result in the amp seeing zero impedence, and it may not like it and get hot, or go into protection mode, but I got called on it by someone who said it would be infinite impedence. What is that exactly? Would someone care to enlighten me?

TomZ

If they pulled the wires off and connected them together this would short circuit the amp and the load would be zero impedance. However, if they pulled the wires and taped off the ends as they described then you have an open circuit, which is essentially and infinite load to the amp, or no circuit at all. The person who called you on it was correct, and it should not be an issue for the amp at all. You are warning against a short circuit, when in fact, they have an open circuit.

[MSaturn]

If there's no completed circuit, you could think of it as analogous to unplugging a computer. It no longer draws current; the amplifier will not overheat or get angry. It would be ZERO impedance if you connected the wires - a short circuit.

[tomzarbo]

I'll have to go back and admit that I was wrong. I'm used to doing that. :)

TomZ

[benchtester]

A well designed amp shouldn't have any problem with infinite impedance; however a poorly designed amp could oscillate. It would be safer to pull the fuse or power. Alternately they could connect a resistor across the leads.