Up-grade Kit for JBL 4310
Copyright 2018 © Troels Gravesen

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Except for the tweeter, the 4310 is identical to the L100 Century speakers, thus a short presentation here.

In 1968 JBL launches the first 3-way studio monitor, the 4310, later to be replaced by the 4311 model. Read history here. The 4310 differs from the later domesticated L100 Century by having the LE20 tweeter, although I have seen images suggesting the L100 Century actually first had the LE20 tweeter, which later was replaced by the smaller LE25. LE20 really didn't do much above 10 kHz as can be seen from my measurements here. The LE25 made some 15 kHz albeit a quite ragged profile above 10 kHz. With the successor LE26, JBL finally got control of the treble range and most LE26 tweeters do a smooth frequency response to around 16-17 kHz. Treble is - trouble!

Everything written about the L100 up-grade kit goes for the 4310 and can be found here. Only difference is the tweeter being LE20, thus requiring a modified crossover for the tweeter section.

 

 


From the JBL history website. To the left, encircled in red, are the drivers going into 4310, bass 123a, midrange LE5-2 and tweeter LE20.

 

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LE20 tweeter.

 

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Bass and midrange section are identical to L100 and the LE20 not being particularly sensitive takes no attenuation resistors, just a standard 3rd crossover. By doing so, we can lift the response above 10 kHz as can be seen from simulation. Crossover values come with the kit.

 
Crossover simulation.

 

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Above the level 3 kit.

Jantzen Audio does not sell drivers in case you miss some.
Replacement drivers must be found on eBay.

All kit and component prices may be subject to change and are always to be confirmed by Jantzen Audio Denmark.

Download Complete Kit Sale Presentations (pdf file):

All technical questions to troels.gravesen@hotmail.com

All questions regarding purchase of kits, please mail Jantzen Audio at contact@jantzen-audio.com

 

CROSSOVER-LAYOUT
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Crossover wiring:


Make sure to check your LE20 polarity to make connections correct. Read this.