Ring Radiator Comparisons

[Rudy Kleimann]

Thank you, Steve! Another GEM for the LHS Archives!

Thanks also to LHS member 1audiohack. You have resolved most all the pertinent questions regarding ring radiators IMHO. Grumpy has also been a help too, along with many others including Widget, 4313B (Giskard), Subwoof, Zilch, and many others... a lot of input from many members. that's what makes this site so great!

The only thing that I want to add is that there is a distinct difference between the AlNiCo motors and "Tops" i.e. horn parts, and the Ferrite versions of the same:

1: The AlNiCo magnets have the guide pins, and corresponding holes in the "tops" that bolt on to the magnet assemblies.
2: The AlNiCo magnets are smooth across the top, where the Ferrite magnets have a machined recess of approximately .015"-.017" across the face of the magnet to accept and align the diaphragm.
3: The pole piece is aligned with the outer portion of the top plate in both the AlNiCo AND the ferrite magnets; meaning the diaphragm sits "flat" in either magnet- the diaphragms' inner clamping ring and outer clamping ring sit in the same plane on either magnet: the top of the pole piece is aligned with the diaphragm seating surface on both magnet versions.
4: the "Tops" are machined accordingly to mate with their intended magnets: the AlNiCo magnets mate up with "tops" that have a recess for the diaphragm that is approximately .035" deep, and the ferrite magnets mate up with "tops" that have a diaphragm recess that is approximately .015"-.017" deep.

IIRC, diaphragm clamping rings measure approximately .040" in all cases, I did these measurements last summer and was in regular communication with 1audiohack during the course of our measurements and other sleuthing regarding the distinctions among the various incarnations of JBL Ring Radiators.

I measured this on my AlNiCo 075 and 2402, and compared it to a pair of 2405H as well as the magnet for a 2404H-1 that I have. I used a machinists' straightedge and feeler gauges to measure the diffeneces, and I feel confident in my findings. I believe that 1audiohack would support me on this as a viably accurate method.

That being said, I feel that anyone concerned about "bastardized" combinations of parts could use this method to validate a proper combination...

[1audiohack]

These just in, whats missing?

[1audiohack]

I am glad I got all my drivers built last year, from a quality standpoint the future does not look promising from here.

[JeffW]

These just in, whats missing?

Polarity dot?

[1audiohack]

Zactly.

How do you like the voice coil to diaphragm glue job not to mention the gap in the former?

This stuffs not ready for prime time yet here it is. Sad.

[4313B]

from a quality standpoint the future does not look promising from here.

We've been over this ad nauseum. I get the impression that alot of you guys think JBL was joking when they said it was going to be a real problem moving out of Northridge.

The end of June 2010 was the end of JBL as we know it. Alot of people seem to be in denial which I think is kind of tragic.

[toddalin]

Will be a real shame when the cheap aftermarket units have better quality (sound???) than the new, more costly OEMs.

[1audiohack]

I get the impression that alot of you guys think JBL was joking when they said it was going to be a real problem moving out of Northridge.

I didn't, I rebuilt literally every driver and speaker I had and some more to spare when the word came out. I've been through this before with other suppliers.

There has been a lot of speculation, I didn't want to start it all up again but this is proof.

[ratitifb]

The end of June 2010 was the end of JBL as we know it.

Those have done stock don't have to regret

[Rudy Kleimann]

You missed it- how long could N.O.S. last- and who has access to it?

I have a couple of friends I made at JBL in their service and in their Engrg. Tech. Support depts. that I'll have to look up and forward these pics to them. One in particular was critical of the move, yet spoke of the quality increasing quite well down in ole' Mexico.

I'll have to bust his chops' er eyes. with these pics.

Hod forbid if the Chinese outdo us and the Mexicans- I'll forward these pics to Congressmen too.

Remember this in upcoming Elections-

[ratitifb]

Sorry but i prefer the VC quality from my "old" stock

[1audiohack]

You know there are people in Mexico with fine motor control, in just about every tourist town there is someone who will write you name on a single grain of rice with a pen for a buck. Did they try to find one or two of them to wind coils? Nope. They got the stucco guy that winds them with chicken wire and cement and leaves you a window or two in the process. QC? Obviously non existent. I hope these don't just get looked at and sent back out to someone else, I hope.

This has managed to stay a fairly technically oriented thread so this is the last of this from me, back on to the 2402H-05.

[1audiohack]

Remember a while ago there was a whole bunch of "nonsense" about attempting to use a D16R2405 diaphragm in a 075 / 2402? Shims, spacers, elastic bands and all?

This is how the JBL factory did it.

The bottom of the phase plug is the same outside diameter, as the standard 075 / 2402, 1.720" and the "shroud" on the bottom of the phase plug is the same depth as all the 075 / 2402, 077 / 2405, 076 and 2404's (both variations) I have measured, 0.040".

What is different is the inner flat area diameter, it is 1.450" rather than the standard 1.400" bullet. Since the outer diameter of the bullet is the same and the inner flat area diameter is different the angle of the shroud is increased to some degree.

Don't mind the dings and burrs huh?

[1audiohack]

It's a D16R2405 for sure.

[1audiohack]

Here is a performance comparison.

That's a pretty damn fine performance for a bullet. From a 5kHz to 20kHz average it is 3dB down at 4878Hz and 19,122Hz!

The top chart is magnitude (white) and phase (red) of the 2402-05, the bottom chart is magnitude of the 2402-05 in white and an 075 in yellow. Both charts have zero smoothing applied, all measurments taken at 1 meter on axis.