Voice Coils & Baskets?

[417 - Alnico]

I have tried to get this nailed down before, have not found the definitive answer.

1. Even though I mainly deal with MI drivers, your help is requested.
I read on the Library Site, in the 1972, 1974, 1975, 1978, & 1982 MI catalogs that The New H series through to the Series II had Copper Voice coils.
Before the B, C, D were fully replaced by the H units, their Voice Coils were Aluminum.
I talked to the guys at GPA and was told that they were never Copper but, copper clad Aluminum. WTH is that? Obviously the wire has PE or Poly insulation on it, as do guitar pickups; I have seen old Paper Former 417's and JBL D-120's were the wire looked like Copper. Even though they were purported to be Aluminum.
I am sure this relates to non MI applications, any opinions or facts are welcome.

2. I have two basket frames the are Ferrite Ceramic powered. They are a nice dark gray color. The dates are 1987 - 1989. I was told these were 917 baskets, yet the cones that came on them were modified 617 Ceiling cones. That is; there were no center duplex cones, just the Aluninum Domes.
The strange thing is, they came from two different sellers, different cities, and were used in a hanging PA above the podium in a Lecture Auditorium.

Do all the post Alnico 12" speaker model cones fit into the same frame. Are their different 12" frames for the various units 414, 412, 417 etc..?
Thanks
Jeff

[Steve Schell]

Copper clad aluminum wire is used in voice coils chiefly to make terminating the voice coil leads easier. It is virtually impossible to solder to aluminum, and the copper coating solves this problem. The wire is only about 10% copper by area, so the weight is nearly as light as pure aluminum. Conductivity is much better than pure aluminum though, close to that of pure copper; possibly another reason it is chosen.

[417 - Alnico]

http://www.lansingheritage.org/image...pro/page14.jpg


http://www.lansingheritage.org/image...-mi/page07.jpg

http://www.lansingheritage.org/image...ro/page_2b.jpg

http://www.lansingheritage.org/image...-mi/page04.jpg

http://www.lansingheritage.org/image...-mi/page04.jpg

http://www.lansingheritage.org/html/...ponents/mi.htm

[donaldpatten]

Jeff
The aluminum wire can be clear anodized for insulation while the copper clad must be enameled or varnished .So the color is a give away.
Don

[417 - Alnico]

Are all the post Alnico, aka, the Ceramic 12" Frames the same?
Do all 12" speaker model cones fit into the same frame?
Are their different 12" frames for the various units 414, 412, 417 etc..?
Thanks
Jeff