The 4315's

[johnaec]

Well the "A" version used "ferrite" 12", and 5" magnet structures - These were sold right when the big alnico / ferrite conversion was changing the industry so who knows...

Hmmm - I thought I saw a scan here at one time listing the drivers in the various 4315 series that showed the A still using Alnico, but with a different crossover. I guess I'll open one up one of these days to see what's in it...

John

[Don McRitchie]

My understanding is that the original 4300 series dates from 1974 and carried no suffix (with the exception of the 4310/11 and 4320/25 which were introduced earlier). 1976 saw the introduction of the "A" series which had enclosure and network changes, but the drivers were mostly the same Alnico versions as the originals. The "B" series dates from 1979 and was introduced as a result of the ferrite driver conversion. There are likely are exceptions to this, and the 4315 may be one. However, based on the above, I would nominally expect the 4315A to contain Alnico drivers.

[mech986]

JBLPro website (www.jblpro.com) list brochures for the 4315 and 4315B. The 4315A is not mentioned as having a marketing brochure so it may have been a short lived model. (you can find this under "product guide" then Vintage Products) - or see this link:

http://www.jblpro.com/pages/obsolete.htm

However, this page under Customer Service, Support info, Systems Reference Charts, listed under Studio Series (the 4xxx series) lists all the drivers, networks, etc. that went into building this series' speakers. The 4315 series is listed on page 2, the B model using likely redesigned networks which then had to cope with the new ferrite magnet drivers. The 4315 and 4315A had the Alnico magnet woofers.

http://www.jblproservice.com/pdf/Sys...r%20Series.pdf

Here's the JBL version of the schematic for the 3114 crossover of the 4315:

http://www.jblproservice.com/pdf/Net...%20Network.pdf

and here's the 3114A crossover of the 4315B:

http://www.jblproservice.com/pdf/Net...%20Network.pdf

Hope this is of some help.

Regards,

Bart

[4313B]

The 4315A and 4315B are identical except for the alnico versus SFG ferrite drivers. Both used the 3114A network. If I remember correctly, some early versions of the 4315 with the dual ports had black baffles. I've had both the 4315A and 4315B versions. The B version is usually pretty easy to spot from a distance with the 8-inch having the terminals facing straight down and the 5-inch having the black aluminum dome.

Bypassing the capacitors is highly suggested.

[johnaec]

Thanks, Mech986 and Giskard. From that info, it looks like these are 4315A, since they have a single port and the paper dome on the 2105. I'll probably open one up anyway just to have a look-see. And in the near future I'll probably be looking for advice on bypass surgery...

Thanks again - John

[johnaec]

OK - I opened one of the 4315's today and am sure they are 4315A. LF is 2203A, and I noticed all the serial numbers, including the crossover, have the first part of the SN stamped in, with the suffix "A" screened on at the end.

I also discovered one of the clamps was hosed when I loosened it - the other 7 are fine. I imagine whoever last tightened them broke the first one when he torqued it down, then did the rest correctly. See the pic in the Marketplace forum - 'anyone have a spare?

John