2402/2405 Diaphr

[4313B]

Originally posted by Guido
JBL Data somtimes confuse

Well it's a combination of factors First would be the old standby - "JBL continually engages in research related to product improvement. New materials, production methods and design refinements are introduced into existing products without notice as a routine expression of that philosophy. For this reason, any current JBL product may differ in some respect from its published description but will always equal or exceed the original design specifications unless otherwise stated." Other factors could be typing errors and incorrect data. I have to admit that I have discovered conflicting data and incorrect data among JBL's documents over the years.

Originally posted by Oldmics
As you know reverse engineering is a job really based upon the tools available for the research. My little shop trying to second guess JBL-I don't think so.

Good point.

[Düse]

Thats what I found

2402H and 2404H-1 use D8R075 0,0015" diaphragm

2404H and 2405H use D16R2405 0,0010" diaphragm

Of course they are interchangeable

JBL Data somtimes confuse

..i have orderd a original jbl D16R2405.. the DC Resistance is 7,2 Ohms
messurement the same built in or not.

[1audiohack]

Both the D8R075 and the D16R2405 are formed from 0.0022" aluminum alloy.

That's what I measure.

Are you sure about that? I read somewhere that the difference between the D8R075, and the D16R2405 was the moving mass, with the 075 being the one with the most mass and the 2405 having the least mass.

Right

It comes from a service bulletin ( # 231183 ) that describes the difference between the regular 2404 and the 2404H-1 ( as found in the 4612 ). The published statement is; the replacement of the regular D162405 diaphragm with a D8R075 ( giving a 2404H-1 ) enables a lower cross-over point that's 1000 hz lower than whats recommended for the typical 2404H .

Right

I've bought in the past from a guy 2 2405. I wondered, why they sound different. i opened them and i saw that the dias looked different. at one the aluminium dia was wider ( 1 or 2 mm ) than the other.

Right, good eye.

If the service manual that Earl is quoting from, recommends that the lighter weight 075 diaphragm can be used at a lower crossover point. How is this possible? How can a diaphragm that has less density be subjected to a greater operating range on its low frequency reproduction end where a greater number of non-linear vibrations are prevelant?
Or am I just splitting hairs over 1000 Hz?

-

The 075 assembly is lighter because the stationary rings are of different dimension, the outer ring has a larger I.D. and the inner ring has a smaller O.D. creating a larger radiating area. With the same 0.0022" material, this gives more moving mass than the 2405 and a lower spring rate equating to a lower FS. The lower safe frequency operating range is due to the fact the bending moment at the suround termination points are reduced by the longer distance edge to edge.

It might be that the 2405 ( 077 ) is "purer" aluminum stock while the 2402 ( 075 ) is built wth a sort of Duraluminum alloy. These 2 alloys will have different Fs points. These two alloy distinctions used to show up in older JBL literature. The two alloy types would have different "fatigue" points .
- And it might be, that we are looking for a "higher" Fs to work within the 2404 horn. Apparently (I've never measured this ) - a properly loaded/constructed horn will "lower" a drivers' Fs. So ; the softer / thicker 2405 may actually have an Fs that drops "too" low when the horn is added. This Fs shift or "unloaded" condition might drive the need for a higher crossover point .

I don't think so.

As a note the 2404H1 and the 2404 have different phase plugs, the plug in the H1 is smaller. Be sure of what you have and carefull if you mix parts.

[Allanvh5150]

Ummmmmmmm..............why doesnt someone just measure the thickness of an old diapragm and compare the two?

[Oldmics]

Good stuff there hack

That question has bugged me for awhile.

Appreciate the input.

Oldmics-Old but never too old to learn !

[1audiohack]

I did measure them, 11 of them, old ones, new ones, blue rings and gold rings, 075's and 2405's, with a Mitutoyo ball mic, they all measured 0.0022" within 0.0001".

[Earl K]

The 075 assembly is lighter because the stationary rings are of different dimension, the outer ring has a larger I.D. and the inner ring has a smaller O.D. creating a larger radiating area. With the same 0.0022" material, this gives more moving mass than the 2405 and a lower spring rate equating to a lower FS. The lower safe frequency operating range is due to the fact the bending moment at the suround termination points are reduced by the longer distance edge to edge.

Good Info ( for this ancient thread ) .

To Paraphrase ( your findings ) ;

- The "2402 bullet" ( when compared to the " 2405 slot" ) has a larger diaphragm / "radiating area" ( the most important part of the complete assembly ) .
- This larger diaphragm results in a lower Fs which allows a slightly lower crossover point .

>< cheers

[Allanvh5150]

So there does seem to be a lot af variance between .010 and .022. I do not have any old 2405's laying about so I cant do any measuring. I do know that one upon a time I checked this out and the 05 was noticably thinner and with a blue ring.

Allan.

[subwoof]

Please read again what was posted. in engineering quickspeak he said that the *tolerance* was within 0.0001

That means 0.0021 to 0.0023


" I did measure them, 11 of them, old ones, new ones, blue rings and gold rings, 075's and 2405's, with a Mitutoyo ball mic, they all measured 0.0022" within 0.0001"."

[Go Dawg Go]

Hey fellas,

New to Lansing Heritage...

I have been playing around with 2402's and 2405's for a while. I recently replaced my 2402's with aftermarket diaphragms and they sounded horrible. Joined Heritage to find out why? Poking around the internet and conversations with my friends at Orange County Speaker, I was told the diaphragms are indeed not interchangeable and a shim needs to be made from tape to offset the dimensional differences in the center phase plug seat (pole piece). Basically, the diaphram is bottomed out on the pole peice and doesnt permit proper excursion affecting efficiency and life of the diaphragm. I was also told there is no after market diaphragm for the 2402/075, just OEM. Anyone who says there is at this time is mistaken???
Attached is a "you tube" video which explains the offset and shimming. I just installed the tape shim on one of mine and I will let you know the outcome..

http://www.soundspeakerrepair.com/DWP_JBL_2404_1.asp

Tab down to the JBL-2404-Video Instruction

Thanks

Bob

[4313B]

Here is JBL's final response on the whole ring radiator thing:

075/2402, 076/2403, 2404, 077/2405

[toddalin]

Hey fellas,

New to Lansing Heritage...

Poking around the internet and conversations with my friends at Orange County Speaker, I was told the diaphragms are indeed not interchangeable and a shim needs to be made from tape to offset the dimensional differences in the center phase plug seat (pole piece).
http://www.soundspeakerrepair.com/DWP_JBL_2404_1.asp

Bob

Eric Sundra at OCS actually has a plastic shim that I made and gave him when I was testing the 075 with the 2405 diaphram.

[Rudy Kleimann]

So, Toddalin (and others in the know), how does the 2405 dia measure/sound in an 075/2402 driver?

Has anybody measured the frequency response of an 075/2402 driver with a 2405 diaphragm in it?

Would you dare say that this hybrid results in more extended UHF response than an 075 diaphragm in the 075/2402 driver?

I have pondered and researched this very question numerous times over the years, scouring JBL documents and everything I could find on the ring radiators on this website. I have learned a lot about these drivers and diaphragms, but never could get to the answer of this question. I always "knew" that the differences between the two diaphragms would end up being simple and straghtforward, but never had one of each to measure myself. Lacking sufficient test equipment and the funds to bankroll such an experiment, I have been hoping for all this to come out from the efforts of others more fortunate than myself...

I own an old pair of "bullets" that I'd like to use for UHF on a pair of long-throw 55* PA cabinets (horn-loaded 2012 from 300Hz and 2447/2383 crossed at 1250Hz). The coverage pattern of the bullets seem acceptable for this application, but I wasn't gonna go to all the effort of re-engineering the crossover and making cabinet mods unless I would get better response than the stock 075 would do, hoping to get all the way out to 20K.

[toddalin]

So, Toddalin (and others in the know), how does the 2405 dia measure/sound in an 075/2402 driver?

Has anybody measured the frequency response of an 075/2402 driver with a 2405 diaphragm in it?

Would you dare say that this hybrid results in more extended UHF response than an 075 diaphragm in the 075/2402 driver?

I have pondered and researched this very question numerous times over the years, scouring JBL documents and everything I could find on the ring radiators on this website. I have learned a lot about these drivers and diaphragms, but never could get to the answer of this question. I always "knew" that the differences between the two diaphragms would end up being simple and straghtforward, but never had one of each to measure myself. Lacking sufficient test equipment and the funds to bankroll such an experiment, I have been hoping for all this to come out from the efforts of others more fortunate than myself...

I own an old pair of "bullets" that I'd like to use for UHF on a pair of long-throw 55* PA cabinets (horn-loaded 2012 from 300Hz and 2447/2383 crossed at 1250Hz). The coverage pattern of the bullets seem acceptable for this application, but I wasn't gonna go to all the effort of re-engineering the crossover and making cabinet mods unless I would get better response than the stock 075 would do, hoping to get all the way out to 20K.

If you are going to cross over to the tweeter at over 7,000 Hz, its a big improvement! It extends the HF and takes some of the 8-9kHz dip away. The dispersion in the verticle plane is actually better than the 2405.

Additionally, you can add an elastomaric band to the 2402/075 as a filter to slightly increase its dispersion and further extend and smooth the UHF even beyond that of the 2405/077.

Grumpy was present for this testing and we used his computer (CLIO I believe) to capture the data. Angles/distances were maintained using a length of string and protractor.

Yes, I had posted pics here, but they were pulled from the thread at the time and you will have to go elsewhere on the web to find them, if they still exist.

If I were to use 2402/075s in the home, I definately would have used the 2405 diaphrams with the shims. But at the time I came across three 2405s with original diaphrams and the owner traded me straight across for three LE175s, two HL-91s (no lenses), and a potato masher I had on the shelf.

[grumpy]

Grumpy was present for this testing and we used his computer (CLIO I believe) to capture the data. Angles/distances were maintained using a length of string and protractor.

Fuzzmeasure ...

0º on-axis
15º
22.5º
30º
45º

(do note that this was for -one- -specific- -modified- driver, spacer and 2405 dia...
no rubber bands)