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What kind of equipment would be needed to measure the impedance curve of a speaker? They are Klipsch CF=3 and I cannot find one on the web. I am guessing it's elaborate stuff, but I'm curious anyway, a friend has some stuff.
Bob
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Spend $99 and get DATS at Parts Express. That will give you an impedance curve, provided you also own a computer.
Quick, easy, and accurate. I used to do it the "old fashioned" way, described by John Ellison below, but that requires a signal generator, frequency counter, amplifier, precision resistors, and a volt meter. DATS is an all-in-one package that interfaces with your laptop to show you the graphs, and it ALSO gives you Thiel-Small parameters.
I used a signal generator to provide discrete frequencies to my power amplifier and I monitored voltage across each speaker and a precision 1-ohm, 2.5-watt series resistor using a two-channel AC millivolt meter. I made the precision resistor by placing ten 10-ohm, quarter-watt 1% resistors in parallel. Then, I connected the 1-ohm resistor in series with the speaker and I measured the voltage across the speaker and the resistor simultaneously using the two-channel AC millivolt meter while setting the frequency generator to third-octave frequencies between 20-Hz and 50-kHz. I maintained 0.5-volts RMS across the resistor at all measurement frequencies and recorded the voltage across the speaker. The voltage across the resistor was equivalent to the current through the speaker. Therefore, impedance could be calculated by dividing the voltage across the speaker by the voltage across the resistor. I did this in a spreadsheet and made a graph of the impedance curves. Of course, each speaker was measured separately.
Edits: 03/17/15
That is fairly low load, is the phase rather gentle? Otherwise, what a load for an amp.
I'd call it a 3-ohm speaker. Yeah, the phase is rather benign. The dotted line in the following diagram is phase response.
good work and great explanation
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