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Hi
My Altec 288C have genuine 24 ohms aluminum diaphragms.
I made impedance measurement with an Altec 1005B tar filled at 630 hz. The results I had with both drivers is 141 ohms !!! (seems really high)
Here what I've done to measure the impedance.
I placed a 1000 ohm pot in series with the 288C. I injected a 630hz sinewave to feed the amp with driver and looked at the ac voltage across the pot and the driver. I adjusted the pot so I had the same voltage across the pot and the driver. Last, I measured the resistance of the pot to get the results.
AC voltages were taken with my Fluke 24. I tried another multimeter and it was the same.
As 141 ohms seems high, does it mean I can't measure correct voltage at 630 hz with my multimeter or 141 ohm is normal ?
Thanks
Follow Ups:
The JBL 2370/2426H measures 3.3Ω DC, but hits about 10X that on the horn with AC.
Impedance goes way up at resonance.
I don't think meter inaccuracy would matter. You're just looking for the same reading across both the pot and speaker. The same inaccuracy should show up in both places rendering the reading totally useful for your purposes.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Hi Tre'
How will impedance increase at resonance when Xc=Xl=0? Z should be purely R no? Just trying to understand. Thanks.
Abe
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