2311 Horn Frequency Question

[Chas]

I am thinking about dropping in a pair of 2440/2311's into my DIY 4333's. I note that JBL used the 2311 horn in the 4350 and 55 monitors at a crossover freq. of 1.1 -1.2 Khz depending on the model. I want to initially run mine at 800 Hz, but can't find any specs on the 2311 horn.
I know I will have a large efficiency difference compared to the 2420's, but I'm hoping the L-pad's can be used to compensate.

Does anyone know what the recommended low freq. cutoff is for a 2311?
Charles.

[4313B]

Low enough. JBL used the H93/2311 in the "legendary" S22 system. Basically an L300/4333 with the LE85/2420/H92/2312 replaced with the 375/2440/H93/2311. What a killer! Let us know what you think!

*****

BTW, your "warranty replacement parts" shipped via USPS yesterday ;)
I missed the boat by 2 minutes on Saturday :( Sorry!

"I know I will have a large efficiency difference compared to the 2420's, but I'm hoping the L-pad's can be used to compensate."

Not really.

*****

Here's something -

http://lansingheritage.org/images/jbl/catalogs/1976-comp/page9.jpg

The Pro Catalogs in the Library might be worth looking at too. There is an old catalog of the exponential horns somewhere as well.

[Mr. Widget]

In the 60's and 70's JBL used to rate the 2307 with 2420 and the 2311 with 2440 as essentially identical in effeciency and bandwidth to 10KHz. (The 2420 is obviously more extended in the top end.) They even reccommended the same crossovers whether you used the 2420 or the 2440.

Widget

[Chas]

Thanks guys. It's hard to believe the effeciency would be the same. My guess would be at least +3 dB for the 2440.

Giskard, I am looking forward to the parts. Are there any tricks to installing diaphragms in 2440's? I am guessing they drop in and get tightened, then do a sweep test. Simple as that?:banghead:
C.

[boputnam]

Originally posted by Giskard
I'll send you the destructions. Ha! I too, have a copy of them! Quite the ticket! :yes:

[Chas]

Um, no. Not as simple as that.

Are we talking about a need for manual dexterity here?:D

I suppose there is some way to center the voice coil, also clean the gap?
Charles.

[4313B]

A

[4313B]

B

[4313B]

Professional Series Acoustic Lens Family (http://lansingheritage.org/html/jbl/specs/pro-comp/horn-lens-series.htm)

The 2391 is the 2307/2308 combination otherwise known as the HL91

The 2392 is the 2311/2308 combination otherwise known as the HL93

[speakerdave]

I've looked into this and have noted in the literature that the 2440 is rated at 118 and the 2470 at 117 dB in that same era. I'm assuming that is close enough for the 2470/2307 to be workable as a substitute in the 4350 system for the 2440/2311 even when using the 3107, which does not provide adjustment for the midhorn relative to the 2202.

David

[4313B]

It depends on the efficiency of the horn/lens/cd combo. All the exponential horn/lens are ~ 108 dB sensitivity.