E120 production line - when did it start?

[Krischu]

When did JBL start the E120 production line? Somewhere in the 70ies?

[edgewound]

The use of ferrite motors for low frequency drivers other than compression drivers started in 1979 I believe.

For sure the E-Series was in 1980, and I think 1979 was a transitioning year due to the world cobalt supply shortage from Africa making alnico too expensive to produce.

[Krischu]

Thanks a lot! Just curious, does ceramic (ferrite) require more mass/volume/material than alnico to obtain the same magnetic field strength? (That would explain why the E120 magnet is so much heavier than the D120 one).

[Rolf]

Thanks a lot! Just curious, does ceramic (ferrite) require more mass/volume/material than alnico to obtain the same magnetic field strength? (That would explain why the E120 magnet is so much heavier than the D120 one).

Yes. If I remember correctly a woofer with 5.9 kg alnico used 8.5 kg ferrite. (2231)

[edgewound]

Thanks a lot! Just curious, does ceramic (ferrite) require more mass/volume/material than alnico to obtain the same magnetic field strength? (That would explain why the E120 magnet is so much heavier than the D120 one).

Yes, you're correct. Ferrite is not as powerful as alnico magnets, but is much less expensive to produce. I'm no expert on magnets but I think the ratio of ferrite to alnico is something like 5 to 1 to get the same relative magnet strength.

On top of this, the E-Series magnet was even a little bigger yielding about 1dB additional output in the midrange. D/K Series alnico gap flux is listed as 1.2T whereas the E-Series is 1.35T.

The E120 is actually a more accurate driver throughout it's range. Some prefer the warmer (less midrange) tone of the D/K120...not to mention it weighs about 6 pounds less.