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View Full Version : checking 2405s tweeter frams



robertbartsch
10-30-2009, 10:44 AM
I bought a pair of alnico 2405 slots recently for a steal. They were used in SR applications and the diaphragms have been changed at least once as evidenced by a hole in the rear decal of each driver.

The seller claimed the untis were maintaned by a pro sound company who used only JBL OEM diaphragms. I removed the horns and the units appear to be OEM based on some other dead OEMs I have lying around.

Anyway, is there anyway to assess the condition of the current frams or should I assume they should be replaced and the cores re-maged?

Other than an Ohm tester, I don't have access to other test equipment.

Beowulf57
11-03-2009, 07:32 AM
Do you have a way to listen to them with an 8K-10K crossover?

robertbartsch
11-03-2009, 10:17 AM
Yeh, I could swap the SR 2405 units with some passive 075s that are crossed at 7K in another system, I suppose.

The frames have black felt-tip writting on them; one says, - "JBL 2405 10.8.85." The installation solder points look a tad primative so I know the frams are not factory original for the cores I have.

How are the graphs that often appear in posts here made? Is this with a studio quality mic and some PC software?

Beowulf57
11-03-2009, 06:32 PM
The 2405 should be fine for testing with a 7K crossover. As far as I know, yes...a microphone and PC software, although I have also seen audio spectrum analyzer pictures posted. As an easy first check, I would simply hook them up in place of the 075's and see what the sound was like.