component system total load?

Just look on the box they came in

Jason

mattbarlow wrote:

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I have a question...

When component sets are hooked up to a crossover, what is the impedance for the whole set?

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Honestly, it is going to depend on the component set you are asking about. Each individual driver, as well as the crossover itself will all combine to determine the overall impedance the amp will see.

Which component set are you referring to?

EDIT: you could also just test it with a multi meter...

greenbroncoguy wrote:

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EDIT: you could also just test it with a multi meter...

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Actually you can't.  The total load on the amplifier is dependent on the crossover and will change with frequency.  An "ideal" crossover will never place less than the lowest impedance of one speaker on the amp, but some can load the amp with both speakers in parallel.

The earlier suggestion about reading the manual (or the box) was much more correct.

DYohn] wrote:

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QUOTE=greenbroncoguy]

EDIT: you could also just test it with a multi meter...

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Actually you can't.  The total load on the amplifier is dependent on the crossover and will change with frequency.  An "ideal" crossover will never place less than the lowest impedance of one speaker on the amp, but some can load the amp with both speakers in parallel.

The earlier suggestion about reading the manual (or the box) was much more correct.

[/QUOTE]

Well, this holds true for speakers as well - total impedance will change with frequency on them also, correct? But you can still meter a speaker to see if it is a (rated as)2/4/8 ohm. So why couldn't you do this same thing for a component set, just take your resistance reading at the crossover input with the drivers connected to the crossover? This would give you a general idea of where you would be at.

For example, usually if you measure a speaker that is rated at 4ohms, it will be somewhere around 3.4 or something IIRC, at least for all the ones I have checked like this. I realize the impendance of the driver will only be this at a few frequencies, but at rest aren't the drivers usually pretty close to what they are rated at?

Resistance = The opposition  of electrical current in a DC circuit.  (Ohm meter) 

Impedance = The opposition of electrical current in an AC circuit.  (Output of an amplifier)

As DYohn stated if the crossover is properly designed the amp will see only one speaker at a time and never go below the impedance listed on the component set. 

greenbroncoguy wrote:

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Well, this holds true for speakers as well - total impedance will change with frequency on them also, correct? But you can still meter a speaker to see if it is a (rated as)2/4/8 ohm. So why couldn't you do this same thing for a component set, just take your resistance reading at the crossover input with the drivers connected to the crossover? This would give you a general idea of where you would be at.

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Yes, a loudspeaker's impedance changes with frequency but no, the DCR is never the same as the impedance.  Since a crossover is a frequency dependant filter, reading it with a multimeter will result in reading only the DCR of the crossover components (and of whatever may be connected to the woofer output) and will not give you a good idea of the actual load placed on the amplifier at varying frequencies.  Measuring the DCR of a loudspeaker is generally useful only to check if a voice coil is blown, not to determine the impedance characteristics under normal operation.

i am an idiot wrote:

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As DYohn stated if the crossover is properly designed the amp will see only one speaker at a time and never go below the impedance listed on the component set. 

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Ah, this is where my confusion lied; I was under the impression that reading the inputs of the crossover would give you a reading of the summed resistances of both drivers connected and the crossover itself.

Thanks for the correction guys.

-Matt

i am an idiot wrote:

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Resistance = The opposition  of electrical current in a DC circuit.  (Ohm meter) 

Impedance = The opposition of electrical current in an AC circuit.  (Output of an amplifier)

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So are both futile, or just resistance?

To really confuse the conversation, the nominal impedance written on the side of the box is usually just a rounded number and the actual nominal impedance of different "4 ohm" speakers will vary.  That's partially why some speakers will sound louder than other speakers on the same amplifier.