Alnico 075´s differences?

[Ingvar Ahlberg]

I´ve got two old 075 units, one all aluminium, small connectors no mounting ring. One black hornbody, larger connectors and standard 4-bolt mounting ring. They do sound very different with the older one much smoother and seemingly more extended in the top while the black one is edgier and rolls off earlier at the top.
Are there any differences in magnetic structure or in horn? Is there any way to "reverse" the newer one to match the other?

[spkrman57]

It might be easier to see what we are dealing with.

Also, there might be a difference in diaphrams(8 or 16 ohm - 2404 or 2402 diaphrams)

Need more info to help out here.

Regards, Ron

[Ingvar Ahlberg]

Tried to attach picture, trying again.

[Ingvar Ahlberg]

One more pic. The badge on the older one has come of and is astray somewhere in the workshop, but it´s 8 ohm and as far as i recall 2402 membrane.

Gratefull for any help Ron!

Best Regards
Ingvar

[Lancer]

The number of 075 variants is staggering and beyond the scope of this forum.

SOP is to replace any 075/2402 diaphragms in pairs with the latest available.

[spkrman57]

I personally could only think of having it professionally disassembled and see which diaphrams are inside.

And make sure the phase plugs/pieces are the same between both of them.

Most of that is beyond my feeble limitations.

Ron

[Mr. Widget]

I would second Lancer's suggestion that for stereo hi-fi use both be re-diaphragmed. Ideally you would have both recharged as well.

I would speculate that the "older" one which is a domestic model has seen an easier life than the 70's era pro 2402 model you have there. In a PA or musical instrument application, it is quite possible that it has been abused or simply worn out. In addition, I see that the 2402, has been re-diaphragmed already. It may no longer have a JBL diaphragm in it or it may be improperly installed.


Widget

[Rolf]

Ideally you would have both recharged as well.
Widget

Why would you do that Widget? As far as I have read, and been told (on this forum and other places) the need for recharging on midrange and high frq compression drivers is not needed. They will never loose the power.

I can understand if used for PA, but in a studio or home? Is there possible to stress them in this use?

Rolf

[Mr. Widget]

I would do it as it isn't that expensive, and is the only way to be certain the magnets are 100%. It is highly unlikely that the power sent to one of these UHF devices would ever be a problem for the magnet, but dropping them is also a problem. A PA/Musical instrument driver can have a pretty rough life.


Widget

[Ingvar Ahlberg]

Thank´s everybody for all input! I´ll start with changing diaphragms, i suppose the best would be to use the 077 version? They will be used domestically and indoors for smaller linedance gigs.

[Rolf]

I would do it as it isn't that expensive, and is the only way to be certain the magnets are 100%. It is highly unlikely that the power sent to one of these UHF devices would ever be a problem for the magnet, but dropping them is also a problem. A PA/Musical instrument driver can have a pretty rough life.


Widget

I understand Widget. For a moment I thought I had to take my drivers to the "doctor".

Rolf