I have a few 2420 driver and one of the diaphrams looks different than the other 2??
I have a few 2420 driver and one of the diaphrams looks different than the other 2??
That looks like the phenolic diaphragm the 2470 and 2461 drivers were furnished with. Don't throw it away; they are not made any more and some people like them.
Check the 2470 data sheet in the library for some information on performance:
http://www.lansingheritage.org/html/...-comp/2470.htm
I have three of these drivers and all have different DCR. The one in the photo is 11.3 and the other two are 6.5 and 3.8.
Don't think this would be the case.
Seems more to me that the 16 ohm impedience should go with the 11.3 ohm dcr, and 8 ohm impedience with the 6.5 ohm dcr. If the 16 ohm impedience is for the 6.5 dcr and 8 ohm impedience for 3.8 ohm dcr, how does the 11.3 ohm dcr fit in?
This is confusing to me as well...at soundspeakerrepair.com the "8 ohm" replacement for a 2420 (JBL-2425-8) notes that JBL specs this model as "JBL's DCR 3.2 +or- 8%"; the "16 ohm" version (JBL-2425-16) notes "JBL's DCR 6.4 +or- 8%".
Has anyone actually measured the AC impedance of these different diaphragms? I have "8 ohm" LE85's and "16 ohm" 2420's (all original diaphragms form the early to mid 70's) and they all measure 6.2-6.5 ohms DCR. So, the listed driver impedance changed arbitrarily, however the diaphragm was identical.
It seems that the 11.3 ohm rating is actually an average AC impedance for the 16 ohm version. See the 2420 curve in post #7 here: http://www.audioheritage.org/vbulletin/showthread.php?t=5213.
Also see this post on 2420 voice coil DC resistance:http://apollo.csd.net/vbulletin/showthread.php?t=2303
Thanks to 4313B:
D16R2420 5.9 - 7.0 ohms
D8R2421 2.9 - 3.5 ohms
D16R2421 5.9 - 7.0 ohms
D8R2425 2.9 - 3.5 ohms
D16R2425 5.9 - 7.0 ohms
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