2420 voice coil DC resistance?
A quick one, I hope. What are the correct DC resistance ranges for the voice coils in 16 ohm vs 8 ohm 2420 or other 1'' compression drivers that accept the current 2421 replacements (which are available in either 16 or 8 ohm versions, D16R2421 or D8R2421).
Reason I ask is that I recently purchased a pair of nominally 16 ohm 2420's on eBay, not with original wax seals. Upon opening them I found the aluminum diaphragm in one was damaged. I took both to A Brown Soun, authorized JBL Pro repair facility in Bay Area. I asked for both to be checked out and the bad diaphragm to be replaced with an aluminum version.
I had measured the DCR of both prior to bringing them in. One was 5.2 ohms, the other 5.4 ohms. The repair shop called me a couple weeks later and quoted me the price to install a new JBL diaphragm (which was about what I had expected) and said the other one was fine.
Then the guy said he would be ordering the 8 ohm part. I said, aren't they 16 ohm drivers, it says so on the label? He said no and that he had measured them himself, that I should have the 8 ohm to match. I said OK, since I haven't built the crossover network for these yet and figured I would compensate.
Today I get them back, and the new diaphragm measures DCR of about 2.5 ohms. I haven't installed these to test acoustic performance, since I haven't even built the cabs yet. But I am really questioning their statement and choice of parts. Thought i would consult the experts here before I go back to them.
Thanks in advance for the advice.
Re: 2420 voice coil DC resistance?
Here it is again:
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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Is this a genuine JBL Diaphragm???
Here's an update on my 2420 diaphragm replacement situation with A Brown Soun.
When I called them to discuss the impedance difference last Monday, they quickly offered to order a new 16 ohm diaphragm from JBL and replace the wrong one ASAP. I called yesterday to see if the new one had come in. First they said it hadn't, then they said it had, and I could come over and they would install it on the spot. That's what I did, they apologized for the mixup and I left, reasonably happy.
I tested DCR yesterday and it comes in at 6.0 ohms, on spec for a D16R2421, but not by much. This morning, I thought I would have a look inside. Upon removing the cover, the newly installed diaphragm seems to be aluminum, but it has diamond shaped stiffening bumps around the outside edge, not the spiral shaped ones I know JBL used to use. Also, there is some sort of coating around the edge, which I don't recall JBL using in the past. Pictures are below.
In the group's considered, non legally binding opinion, IS THIS THE JBL D16R2421 PART, OR HAVE THESE GUYS TRIED TO PULL A FAST ONE ON ME BY USING SOME AFTERMARKET P.O.S.? Note I paid over $280 for the part and installation the first time around.
I sure hope this is genuine JBL, or the ZILLA part of my persona may emerge up in San Rafael....
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Getting a bit off topic...
Well, if it's Dragons we're talkin', watch out, this bad boy guards the dark crystal (tweeter). Courtesy of my daughter, who appeals to his sweet tooth with the ice cream cone...
And John, appreciate the suggestion, but I'm not sure I want to push it with A Brown. I owe you a PM...