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View Full Version : Biamping a pair of L300 Summit?



Bebo
12-03-2006, 05:34 PM
Just tonite ( Im' writing from the other side of the ocean) I read, on this forum, something about biamping the L300's. I own a pair of Summit, but my JBL's fan friends, always discouraged me into trying to do it.
Our common friend Wiking, that's much than a pretty good expert and a serious person, told me that's pratically impossible to do it in a polite way, with the risk of destroyng the fantastic balance of these loudspeakers.
Can you tell me something about it, and eventually your personal experiences?

Thank You very much

Bebo

Rolf
12-04-2006, 08:48 AM
This should not be a problem, but you have to get an electronic crossover and fix the internal on or build new internal crossovers witch is the best.

Of course you might also use a 3way electronic crossover and use 3 power amps.

I guess somebody with more technical know how will climb in here soon.

Robh3606
12-04-2006, 09:52 AM
Hello Bebo

JBL didn't have problem biamping 4333's so I don't know why you would have a problem with L300's. You would need an active 5234/5235 crossover with the correct cards. You would also have to modify the crossover which I would not reccomend. I would build new ones to go with the biamp set-up. The schematics are readilly available here on the sight as links.

http://www.jblproservice.com/pdf/Vintage%20JBL-UREI%20Electronics/JBL-5235%20manual.pdf

http://www.jblproservice.com/pdf/Network%20Schematics/3133A%20Network.pdf

http://manuals.harman.com/JBL/HOM/Technical%20Sheet/L300A%20Summit%20ts.pdf

Rob:)

Mr. Widget
12-04-2006, 10:25 AM
Rob is right, but there are two very real issues.

First, the N333 networks use JBL tapped autoformers that are NLA (no longer available) so you would need to work up an equivalent network. (Giskard may have done this for the N333/3133) You would need to do some searching here.

Second, even with the correct networks and correct filters in your active crossovers, to properly balance a multi-amped system, you need to take great care fussing with the amp settings and phase to make sure you haven't taken a step backwards.

Once properly set up though, you will have a system that is superior to your stock single amped L300s.


Widget

Robh3606
12-04-2006, 12:16 PM
Hello Widget

Take a look at the biamp switch positions in the posted schematic. The tapped inductor for the 2420 is switched out. The 2405 uses a standard inductor. Giskard also has an equivalent crossover without them.

Rob:)

Mr. Widget
12-04-2006, 02:21 PM
Hello Widget

Take a look at the biamp switch positions in the posted schematic. The tapped inductor for the 2420 is switched out. OK... I admit it... I haven't looked at that schematic in quite a few years.:D

Still, point number two... properly setting up a bi-amped system isn't trivial...

However with patience and care they can be quite rewarding.


Widget