My new 4430 system

[grumpy]

no Be in that format that I'm aware of.

I'd (personally) go with the Al unit I mentioned already, unless you like to regularly stress the system loudness capability (then Aquaplassed Ti, but that again is DIY or commissioned).

[Earl K]

Ultimately, I would think you would want an 8-ohm diaphragm (D8R2421 or perhaps a dusted Ti version),
as I believe the system was already limited in the level matching between drivers given the HF EQ required <<SNIP>>

Usually I'd agree Grumpy, but it's worth noting that Zilch showed ( more than a couple of times ) that a healthy diaphragmed le85 ( & I accept that most 2420's are likely not that healthy being a "PRO" device ) can out-perform the equivalent ferrite magnet type driver ( ie; 2425/6J ) above 3K .



Seems to me ( from the above traces ), that above 10K, the le85 ( maybe 2420 ) has 3db extra UHF to play with ( which ought to negate the gain advantage of using the lower impedance [ "H" version ] driver ).

( just speculating )

[badman]

Nope, one for each driver/filter. Look again at 4313B's schematics to apppreciate the need for two batteries. There are two in the biamp implementation.

Why is that? Because, with a single battery, it's (-) connection must be common to both filters and amplifiers.

If you are biamping using one amp per channel, (I forget if that's "horizontal" or "vertical,") that may not be an issue, if it's permissible to common the output "grounds," but, using separate amps for HF and LF, particularly different types, it's asking for trouble....

Miss you buddy. An alternative solution to our departed brother's is to use half the resistor value on both + and -, and use individual resistors per connection point. Since the R values are high, you'll be able to use the same battery across multiple filters without worries of crosstalk or amplifier loading.

[grumpy]

Fair enough. My personal swing is 2421A diaphragms are $125 (at the moment) and available new
(no passive mods required). No harm in trying the 2420, particularly in that some folks seem to prefer
the tangential vs diamond surrounds. In all of this, I'd want to be able to verify the result with measurements.
My 4430's did not sound their best until the adjustments were effected to match L/R responses.

[berga12]

Fair enough. My personal swing is 2421A diaphragms are $125 (at the moment) and available new
(no passive mods required). No harm in trying the 2420, particularly in that some folks seem to prefer
the tangential vs diamond surrounds. In all of this, I'd want to be able to verify the result with measurements.
My 4430's did not sound their best until the adjustments were effected to match L/R responses.

This is an interesting input...

where Can I find 2421A spares JBL originals?

thank you a lot.

[grumpy]

google D8R2421 (?)

I see $125-$199 USD