You are correct.

With speakers, resistance varies with frequency, so the rated impedance is
usually referred to as "nominal" impedance, or functional average of the
load on the amp.

DC resistance is as you said, merely the resistance of the voice coil and
usually lower than the nominal impedance. It is safer to design low
impedance systems around the DC resistance as then you have some fudge room
on the load the amp sees and the actual impedance will be higher than the DC
resistance.

-- FLINT

"Denny B" wrote in message
...
Is it possible to measure Impedance with an ohm meter.
For example can you measure the Impedance of a 4 ohm
car speaker with an ohm meter?

When I tell people they cannot measure Impedance with an
ohm meter, you need an impedance meter and the impedance
must be measured with the speaker in operation, with a signal generator
supplying a fixed frequency, this always leads to disagreements
with the person who demands an ohm meter to measure what he calls
Impedance, when I tell him an ohm meter can only measure the resistance
of the coil there is always disagreement.

I tell them Impedance is AC resistance and what they measure
with an ohm meter is DC resistance. Disagreement here again.

Will somebody take me up on this and clarify the situation.

Thanks in advance
Denny B

On Wed, 16 Jul 2003 22:57:36 -0600, "Denny B"
wrote:

Is it possible to measure Impedance with an ohm meter.
For example can you measure the Impedance of a 4 ohm
car speaker with an ohm meter?

When I tell people they cannot measure Impedance with an
ohm meter, you need an impedance meter and the impedance
must be measured with the speaker in operation, with a signal generator
supplying a fixed frequency, this always leads to disagreements
with the person who demands an ohm meter to measure what he calls
Impedance, when I tell him an ohm meter can only measure the resistance
of the coil there is always disagreement.

I tell them Impedance is AC resistance and what they measure
with an ohm meter is DC resistance. Disagreement here again.

Will somebody take me up on this and clarify the situation.

Thanks in advance
Denny B


Hello,
That's easy; you're right and they're wrong. Although impedance can be
calculated by using an AC voltmeter to measure the signal voltage and
an AC ammeter to measure the current, then dividing the voltage by the
current.

""Denny B" wrote in message


Is it possible to measure Impedance with an ohm meter.

Only at DC.

For example can you measure the Impedance of a 4 ohm
car speaker with an ohm meter?

Ironically, most speakers have a nominal impedance that is about the same or
a tad more than their DC resistance. A 4 ohm car speaker will have a DC
resistance that is close enough to 4 ohms to convince most people.

When I tell people they cannot measure Impedance with an
ohm meter, you need an impedance meter and the impedance
must be measured with the speaker in operation, with a signal
generator supplying a fixed frequency, this always leads to
disagreements with the person who demands an ohm meter to measure
what he calls Impedance, when I tell him an ohm meter can only
measure the resistance of the coil there is always disagreement.

You're right. They are wrong, at least in theory.

I tell them Impedance is AC resistance and what they measure
with an ohm meter is DC resistance. Disagreement here again.

You're right. They are wrong, at least in theory.

Will somebody take me up on this and clarify the situation.

The ironic part is that the DC resistance of most speakers is close to the
nominal impedance.

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begin On Wed, 16 Jul 2003 22:57:36 -0600, Denny B f wrote:
Is it possible to measure Impedance with an ohm meter.
For example can you measure the Impedance of a 4 ohm
car speaker with an ohm meter?
no. An ohmmeter uses a dc test signal.