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mulanee
10-07-2009, 04:17 AM
Hi,
Recent owner of JBL 4312 , I plan to bi amp them with 2 NAD 2100.
Can I envision to substitute the 2 ways plugs by a 4 ways.
No addition of external crossover.
Is it easy to realize?

BMWCCA
10-07-2009, 08:57 AM
I'm no expert but since the 2213H woofer runs full-range in the 4312 anyway, just isolate the woofer leads from the cabinet connections and connect the woofer directly to another amp. As long as you can control the level of the amps individually, or if you use identical amps, it should work fine. I have no idea if it will offer an improvement in sound but it can't hurt to try. Let us know what you find.

http://manuals.harman.com/JBL/HOM/Technical%20Sheet/4312%20ts.pdf

Frenchie
10-09-2009, 02:29 AM
hello
I think med/high impedance will grow when the 2213h will be disconnected.

4312 = 8 ohms

2213h = 8 ohms

crossover+med+high = ??? ohms

BMWCCA
10-09-2009, 07:08 AM
hello
I think med/high impedance will grow when the 2213h will be disconnected.

4312 = 8 ohms

2213h = 8 ohms

crossover+med+high = ??? ohmsSince the 2123H doesn't run through the crossover at all, how could it make a difference? They're already essentially in parallel, so it would seem for the system to be rated as 8-ohm, the 2123 must be 16-ohm already (even though the specs say otherwise) and the upper range running as 16-ohm to get the box impedance to 8. Or, I suppose, the upper-range drivers could be showing a load through the network of 24-ohm to get a combined 8-ohms.

Regardless, I can't see how a higher individual impedance would affect bi-amping as long as both amps have attenuators to balance the output. I also said I don't see how there's any advantage to it since the woofer is still running full-range. You might as well just use one more-powerful amplifier instead of bi-amping unless the point is running one of those high-zoot tiny tube amps on top. :dont-know

I can only assume the ignorance in both the original question and my replies have kept any intelligent contribution out of this thread? Bueller?

But then I already claimed no expertise at this. :D

jcrobso
10-09-2009, 07:52 AM
All speakers are 8 Ohm! The crossover is a 8 Ohm 6db per octave! All of the filters are high pass at two different frequencies. Note the 8 Ohm L pad in the high sections.
Bi amping involves the use of a electronic crossover before the amps. Each amp will only get a certin band of frequencies.
If you want to do this OK, but don't worry about the impedance.