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Dave G
11-29-2003, 06:56 AM
Does the black spot on genuine replacement diaphragms show negative or positive polarity?

The bigger compression drivers have red paint marking for :confused: amateurs like me.

Dave G
12-03-2003, 12:25 PM
I am surprised, no answer:eek:

I can check with DC input but how many volts and will diaphragm movement be detectable on a ring radiator such as these.

boputnam
12-03-2003, 12:32 PM
I honestly don't know. Data is ambiguous... :yes:

I do know (or think I know... ;) ) that ring movement will not be discernable to naked eye. If you had one o' them "Cricket" polarity tester your troubles would be over.

You might call JBL Pro - since those are "genuine replacement" diaphragms, they should be all-knowing...

Dave G
12-03-2003, 12:45 PM
I haven't phoned JBL in the USA before, might be a bit expensive with me being in UK.

Incidentaly UK JBL has gone over a new distributor, I have been told it would be a nightmare to get service until they are settled. It was hopeless before IMO.

Arbiter Group PLC are no longer distributing products manufactured by
JBL Professional, AKG Acoustics, dbx Professional, Powersoft and Digitech

Please use the following contact details for any enquiries you may have...

JBL Professional
AKG Acoustics
dbx Professional
Harman Pro UK
Cranbourne House
Cranbourne Road
Potters Bar
EN6 3JN

boputnam
12-03-2003, 12:50 PM
OK, I'll go in for ya.

What part number / kit is it?

Dave G
12-03-2003, 01:02 PM
Part is D8R075

Serial J694-30710. I don't think that will be needed.

Actually there is another code on the top of the packaging.

35Z JBF. Plus the barcodes also. Must be for stock tracking and quality control.

Anyway thanks very much bo for the offer. I am in no hurry so wait until you need to contact them for a more essential service query.

I also wonder what the 'SP' in a circle on the underneath of the diaphragm means. Perhaps speaker positive or it might just be a checked stamp.

boputnam
12-03-2003, 02:17 PM
Originally posted by Dave G
Does the black spot on genuine replacement diaphragms show negative or positive polarity?

The bigger compression drivers have red paint marking for :confused: amateurs like me. :yes:

You should be confused, and it is ever so ironic this ended-up in MY lap!

Straight from JBL Tech Support: Old diaphragms were marked with RED on the Negative side. New diaphragms are marked with BLACK on the Negative side. So, both vintages are marked on the Negative connection. This figures, knowing what we know about JBL Polarity Convention. ;)

So, install the new diaphragm with the coloured spot in the same position as the diaphragm being replaced.

*****

You know, with the importance of this, it would be worth noting the position of the original diaphragm: When still installed, is the RED mark on the original diaphragm connected with the Red or Black transducer post?

This is making me feel :barf: And, I'll bet there are a few DIY'ers :confused:

Giskard, you out here today? What ya know about this?

I've got a pair of 2405's at home and two diaphragms for same - you can bet I'm gonna tear into them tonight... :hmm:

Dave G
12-03-2003, 02:54 PM
I'll send a picture in due course. I can assume that the black dot signify a negative pole and should be lined up with the negative post of the 2402. I think these are mid 1990 diaphragms so the will be claased as 'new'

I didn't have the luxury of seeing the old fitted phragm, hence the worry. I have soldered these in as above. I will have two more to do soon, kind of a e-bay/scrapbox colection of 2402.

A problem is another four 2402 which I suspect will have pattern diaphragms fited inside. These do work OK but I will need to confirm that all eight tweeters are firing in the same phase so to speak at some point in the future.:confused:

To add to the confusion I'm pretty sure my home use 075 are not wired as the convention and these are still waxed sealed. They seem to out of phase in comparison.

And is it just me or is everyone else happy to use copy parts for these tweeters. I never found a genuine one yet in all my junk buys.

boputnam
12-03-2003, 03:11 PM
Originally posted by Dave G
1) I can assume that the black dot signify a negative pole and should be lined up with the negative post of the 2402.

2) I'm pretty sure my home use 075 are not wired as the convention and these are still waxed sealed. They seem to out of phase in comparison.

3) And is it just me or is everyone else happy to use copy parts for these tweeters. I never found a genuine one yet in all my junk buys. :hmm:

1) I too think you're OK. Since the JBL Polarity Convention is/was Negative, putting the RED mark to the negative post would give a negative response from the 2402. Consistent. Now, it seems to avoid confusion, JBL are marking that side of the ring with BLACK, to the negative. OK.

2) Do you mean soldered, or wired? If the latter, the Red lead should connect to the Red transducer post. And, out of phase with what/which? You have too many 2402's... :rotfl:

3) Very interesting point. I myself use only factory, but...

boputnam
12-03-2003, 05:45 PM
Hey, Dave...

I cracked-open the 2405's and the Black mark is on the Black terminal. And, the new D16R2405 kit has the same Black mark, and when installed as-is the existing, it will be Black-to-Black.

You sir, are good to go... ;)

Dave G
12-04-2003, 09:40 AM
I had a lucky guess there.

Not sure about 075 and it hardly matters. They are on N7000 crossover with 1234 terminals. I don't think we should go down the polarity road again on these setups as the speaker sounds fine:smthsail: