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Hey everyone.
I took this diaphragm out of one of my 288Bs.
I'd like opinions from the members here if they think it is a genuine Altec one or not.
It has the shorter voice coil necessary for the 288B and its top plate, but the material seems different to other Altec diaphragms I have.
What made me remove it in the first place was the DCR measurement of 2.9.
Thanks
Nat
If it's not genuine, it's the best counterfeit i've ever seen.
Looks to have taken some water or other liquid at some point, possible that this could affect the color of the aluminum.
something don't sound right though it should have more DCR then 2.9
Maybe a short in the windings?
Off the bat i agree, but what's the possibility that this is a genuine replacement with a 4 ohm coil from say 1960's vintage?Quote:
Originally Posted by Altec Best
Does anybody know if/when 4 ohm replacememnts were available?
If the coil is partly shorted, i would think this would be audible as well as sport a pretty erratic impedance curve if swept with WT3 or similar analysis.
All i can say for certain is that to me it "looks" genuine, but i have some reservations about it's exact vintage.
What puzzled me was the apparent date markings of 25 85, or 5 25 85 on the rim, but no other Altec numbers, such as a 391xxx or a part number.
The lead wires also look, well, odd compared to say 20221s.
I can believe a 4 ohm dia from 1985, but by then they all should have been the new style.
I haven't run it up to see if it works, that I will do.
I'll also take a look at the other 288B and see exactly what is on the underneath of it.
I'm not keen on removing dias unless absolutely necessary.
Nat
I took the other diaphragm out of the 288B.
It also has the short VC for the top plate issue.
It does have a 391xxx number, that being the only difference I can see to the other one.
It does have a DCR measurement of 12.2.
I'm still puzzled by the first one, want to say it is genuine, just not 100%.
Nat
Well, ran it up, and as far as i can tell, no issue.
Maybe one of those things.
At least I don't need to scrounge up another B type dia.