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legarem
02-26-2011, 04:27 AM
Last night I changed the diaphragm in my JBL2405 Alnico with original D16R2405 JBL diaphragm
They are 16 ohms diaphragm. The measured DCR is 6.4 ohms for both tweeters.
As I use them over 11khz (6db high pass filter) I measured the impedance of each tweeter to know exactly the cap needed to use. I had a big surprise when I measured the impedance at 10 khz.

One tweeter measured 8.9 ohm and the other mesaured 7.5 ohm.

Why is there such a big difference ? Can it be related to the magnet power of each tweeter ?

Any help to give me an explication is welcome.

Thanks

ratitifb
02-26-2011, 06:28 AM
take a look @ http://www.audioheritage.org/vbulletin/showthread.php?6368-Ring-Radiator-Comparisons&p=62922&viewfull=1#post62922 ;)

The modulus of driver impedance you measured is in the frequency range showing pic and valley and understand that different production runs exibit "slight production differences" as Widget said ...

Remind you that 16 ohms = 8 ohms = same diaphragm

http://www.audioheritage.org/vbulletin/showthread.php?23869-075-2402-076-2403-2404-077-2405

legarem
02-27-2011, 06:04 AM
My problem is resolved

I had a rubbing diaphragm

As it seems, the 8 and 16 ohm diaphragms have near the same impedance at 8 ohm. Why they call the D16R2405 a 16 ohm diaphragm ?