2470 Franken drivers

[ivica]

http://www.jblpro.com/pub/obsolete/A...ns_Family1.pdf

The above link to Jbl data sheet

The curve above is on axis

In use the compromises are listener position in the vertical plane is critical hence my comment it’s not CD.

The curves don’t tell you everything. See comments below.

The 2405 is required with the 2307/2308 in practice.

In terms of a single driver application the 2344 bi radial horn wins

It does a lot of things well and it’s diy friendly.
But mass break of the diaphragm is the limiting factor ultimately.
(THD rises quickly above the mass break up frequency due to the boost of the CD EQ for the 2344)

But it works in spite of the facts.

In comparison setting up the passive voltage drive and adjustment of the Lpads for the 2307/2308 is critical for optimum performance. But done precisely the addition of the 2405 has the alluring subjective piston range quality.

Hi,
I have 2420 with Ti diaphragm with 2312 and 2308. Its HF response is quite usable, and dispersion in the room (7x4m) is OK, I have to say without any beaming at HF, but its LF response is not something that I have to say 'enjoyable', so I have exchange such combo with 2441 (Radian) with 2311 and 2308 (usable up to 10kHz), but I have to put 2405 as UHF driver. I have to say that 2405 is very nice driver, especially A-version with JBL 'blue' diaphragms.
I can imagine that with 2441 using JBL Be (476 diaphragm, or JBL AL-2441 diaphragm) can be properly EQ up to 15kHz.
2441&2311&2308 is much better , especially in lower frequency range then 2420 & 2312 &2308. I can imagine that 2420 (2470 motor) &2307&2308 is very much the same
I have no experience with 2344/A horn

regards
ivica

[Ian Mackenzie]

Hi Invica,

Can you post some measurements?

Below is a link to some solid Jbl data on directivity of the Jbl 4331 system and the 2307.

See a fig 4 , figure 12.

As you can see the vertical polar reduces to 45 degrees above 5000 hz then falls away.

The impact of this is the height of the horn/lens assembly must be exactly at ear height much like your head in a vice situation. Just something to be aware of.

I don’t mind sitting still in my favourite chair listening to an album with a glass of Knobs Creek Bourbon if it sounds good....Lol (the good stuff)

The whole EQ of a room and power response thing was the intent of the bi radial approach in studio situation with the document below.

I won’t elaborate on that because it’s a big topic. But it can invite challenges in the diy space like CD equalisation and room curves and it goes on and on.

Depending on your own preferences and scenario this may be relevant.

http://www.cieri.net/Documenti/JBL/D...)%20(1983).pdf

Below is the raw driver response (top) and the EQ with the schematic posted in the link previously.

The raw driver is 110 dB at 1 khertz and 105dB at 10 khertz.

The equalisation gives 100 dB at 1 khertz and 10 khertz.

The lower curve is flattened and extended a bit and the crossover slope.

That’s the difference between just trying it casually and setting up the driver to perform its best. You of course need something to do reliable measurement with.

Again my acquplas dusted diaphragm being a tad more mass may not extend as much as the factory 2425 Ti diaphragm.

You may be able to do this with your drive rack

[ivica]

Hi Ivica,
Can you post some measurements?
Below is a link to some solid Jbl data on directivity of the Jbl 4331 system and the 2307.
See a fig 4 , figure 12.
As you can see the vertical polar reduces to 45 degrees above 5000 hz then falls away.
The impact of this is the height of the horn/lens assembly must be exactly at ear height much like your head in a vice situation. Just something to be aware of.
I don’t mind sitting still in my favorite chair listening to an album with a glass of Knobs Creek Bourbon if it sounds good....Lol (the good stuff)
The whole EQ of a room and power response thing was the intent of the bi radial approach in studio situation with the document below.
I won’t elaborate on that because it’s a big topic. But it can invite challenges in the diy space like CD equalisation and room curves and it goes on and on.
Depending on your own preferences and scenario this may be relevant.

http://www.cieri.net/Documenti/JBL/D...)%20(1983).pdf

Below is the raw driver response (top) and the EQ with the schematic posted in the link previously.
The raw driver is 110 dB at 1 kH and 105dB at 10 kH.
The equalization gives 100 dB at 1 kH and 10 kH.
The lower curve is flattened and extended a bit and the crossover slope.

That’s the difference between just trying it casually and setting up the driver to perform its best. You of course need something to do reliable measurement with.
Again my acquplas dusted diaphragm being a tad more mass may not extend as much as the factory 2425 Ti diaphragm.
You may be able to do this with your drive rack

Hi Ian,

You can see some of my measurements in the:
http://www.audioheritage.org/vbullet...with-2311-Horn

And if we are talking about the 2308 dispersion ( with 2307, 2311, 2312 ) JBL horns it is evident that its horizontal dispersion is respectable, reaching +/-45 deg ( I think just a few of known horns have such good results), but its vertical dispersion over 10kHz is almost less then +/-10deg (that is not so huge results,and is much LESS the 2405/2), but it has to be emphasized that from the seated position to standing position with the distance of about 3m from the speaker totally changed angle in the vertical plane would be about 15deg (that would correspond to +/-7.5deg), so even i such situation (without 2405) 2308 combo can be acceptable solution ( such as 4331 )

[GoldcountryJim]

Found the information! It was page 3 of the same paper. Should be a fun weekend!

http://www.lansingheritage.org/image...ens/page03.jpg