Ring Radiator Comparisons

[RKLee]

can anyone advise me if it is practical to use a simple first order xover on these @ say 3.5 K
.
.

I am NOT an expert at this. I am just regurgitating from a JBL brochure, but JBL recommends a xover of 3.5K with a 2nd order xover, ie 12db octave, rather than a 1st order for their 075/2405 tweeter. I would suspect that you could damage 075/2405 because it was not really designed to reproduce sound loudly below 3.5Khz

[Rudy Kleimann]

After doing a lot of research a couple of years ago here, on the JBL pro website, and anywhere else I could find (including the local JBLPRO service dealer) a couple of things became evident:

All of the old ring radiators used the same magnet structure, except the old ones are AlNiCo and the newer ones (from about 1976 on) were ceramic-ferrite. All four designs use uniquely different phase plugs and corresponding horn throat/bell assemblies. The only other difference was the mounting flange: early ones have a round neck with a circular clamping ring to mount it to the cabinet baffle board, and the later ones had integral mounting flanges that use through-bolts to hold it on the baffle board.

Originally, these diaphragms were made of an alloy JBL called "duralumin" in the old JBL catalogs, but that name has been dropped. Supposedly, this alloy was obtained by recycling the skins of WWII airplanes, and the supply was eventually exhausted. Newer diaphragms are referred as simply "aluminum". Different material or the same? Who knows? Some aftermarket diaphragms are made from Titanium, with uniquely different properties and sound, according to some. Those who have heard them parallel their impressions regarding the sound difference to those about JBL's dome compression drivers equipped with aluminum or Titanium diaphragms.

JBL makes three slightly different diaphragms for these older ring radiators (075/2402 "bullet", 076/2403 "cat-eye", 2404 "baby-butt", and 077/2405 "slot") All are interchangeable, but with slightly different performance and reliability advantages.


All of these ring radiators have the same impedance, about 12 ohms, regardless of the part number having an 8 or a 16 in it as the impedance. The same is true of the drivers- some are marked 8 ohms while others were marked 16 ohms. All the voice coils are the same.

the D8R075 diaphragm material is apparently a little thicker. It's total effective mass is a little higher. Its HF extension is not as good as the others, but it is much more durable. It is the diaphragm of choice for high-level playback for a HP crossover frequency of 2.5-3.5KHz or higher. This is the standard replacement diaphragm for some "-1" variants of the 2404H. This is also noted on some of the exploded diagrams of certain production models that used a 2404H or a 2404H-1 The metal plate in the center and edge of the diaphragm on these are almost always golden in color.

The D8R076 is uniquely for use in the 076/2403 "Cats-eye" tweeter. The center and outer diaphragm plate is almost always blue in color. Not much else I can say about this driver or diaphragm except that they are a cult clssic JBL driver and ungodly expensive -if you can find them to buy.

The D16R2405 is a lighter, thinner diaphragm with better HF response than the D8R075, but are more easily damaged from overexcursion and metal fatigue at high levels when crossed over lower than about 7KHz. Don't know if the inner and outer rings have any coloration other than silver to them at all. They are the replacement diaphragm for most 2404 "baby butt" and 2405 "slot" drivers. Exceptions include some 2404H-1 which used the D8R075. It is good reccomendation to use the D16R2405 in appliocations from 7KHz up, and the D8R075 for applications starting above 3-3.5KHz (as in 2-way systems), with a little UHF rolloff characteristics in the D8R075.

To minimize the risk of damage and get the cleanest response, all of these really should be crossed over at a minimum slope of 12dB/octave. 24dB/oct is really much better in all ways.

Note: be oh-so-careful not to allow the phase plug to twist even a slight amount during tightening down onto the diaphragm and magnet assembly, or the phase plug will put twisted wrinkles in the diaphragm like the tires on a drag car launching from the starting line, resulting in the death of perfectly good -and expensive to replace- diaphragm.

[johnaec]

...twisted wrinkles in the diaphragm like the tires on a drag car launching from the starting line, resulting in the death of perfectly good -and expensive to replace- diaphragm.

Aw, c'mon now - we all know "it makes no difference to the sound...".

John

[subwoof]

In about 2 weeks I will do a "mechanical" thread of all the ring radiator mechanical variations over the many years. braclets, horns, throats, clamps, magnets, etc. Even the LE30 variant.

note: the ferrite's were sold beginning in spring 1982. I bought bullets for 2 club installs that year and the january ones were anlico and the april ones were ferrite.

One thing to note - I kept a bag full of bad diaphrams and the color of the outside and inside ring has NEVER been consistent with ANY of the models over the years.

I have silver and gold bullets. I have gold, blue and silver slots. Some with part numbers, some without. Thick leads and thin leads. OEM models and on and on.

With ONE exception. A large group of factory 2403's came in some years ago and the outsides were silver and the insides were blue. Those were the ONLY bi-colored ones I have seen in 30+ years.

I was going to make a hanging mobile of them and title it "blow me" but the wife nixed that idea even though it was in the shop...;(

sub

ps - see avatar.

[Rudy Kleimann]

Good to see you chime in, subwoof. Looking forward to that thread. Will you PM or email me when you post the thread?

BTW- do you have any of the ring radiators used for ultrasonic railroad crossing, traffic signal controlling, or military variants (or information about them) to post?

I always wondered if the colors were kept consistent as a means of identification of the variants of the diaphragms, apparently not, according to your experience.

I do know that the D8R075 D8R076 and D16R2405 diaphragms are different, and it's not the impedance. It's the thickness of the diaphragm or perhaps the size of the inner support ring, corresponding to the diameter of the phase plug?

[subwoof]

I will have *some* parts and pix of the tideland signal / and general railway variants.

As far as thickness, I have examples of each - maybe even a 1950 era bullet with the old alloy..? I have yet to see official comment / docs from JBL on this though. Nobody knows anymore. All the old timers have retired.

Maybe I will get them measured at cornell ( next door ) when I find the right contact.

As soon as the borrowed 2403's get here, I will post. Expect odd humor, it might be ale-influenced.

[Rudy Kleimann]

Actually, a lot of my information came from this site- I did a whole lot of reading researching this about three years ago. I may not remember correctly WHERE I read all this, but I do know it is verifiable fact since I had heard contradictory information from "authority" sources including the local JBL service center and I was determined to find the truth for my own sake. Since I own a couple 075 AlNiCo drivers, a 2404H, a 2405 AlNiCo, and a couple 077/2405H ferrites, I wanted to know details for properly designing a passive crossover and was baffled by the whole impedance controversy surrounding the driver labels and the diaphragm part number nomenclature.

IIRC, Widget posted the impedance details, including his own measurements (with the aid of Zilch) of at least 4 variations and combinations of drivers with 8 or 16 ohm labels and different diaphragm part numbers.The weights of the diaphragms was a common denominator in one of the many threads about ring radiators and diaphragms. In that thread, someone had known part number dia's and weighed them, measured DC resistance, and measured the thickness of the inner and outer mounting rings. I think someone provided a measurement spec for the thickness of the diaphragms... and someone else may have verified that the free air resonance was different between the part numbers. Zilch nailed the "-1" variant of the 2404 in a JBL Cabaret Series cabinet he had at the time that used a D8R075 as the diaphragm, and the exploded diagrams on jblproservice.com listed it as a 2404-1 and a replacement diaphragm part number of D8R075. Other threads here, and some deep reading in JBL tech notes and the JBL PRO Service manual (which either giskard or subwoof emailed me) confirmed this.

Do search for 2-3 year old posts by Widget, Zilch, Steve Gonzales, 4311B (aka Giskard and that oriental princess whatever ), and myself containing or pertaining to ring radiators, D8R075, and D16R2405.

I'll dig up my notes next time I'm at my own house and can fire up the right PC where I have all these notes saved. In fact, your new thread will be just the impetus I need to do it

And now, back to business -Weller 107* over rocks

It's been a long day...

Rudy

[Mr. Widget]

Widget posted the impedance details...

Yep... post #51 in this thread.

Quite a while back I was at a friend's house measuring some of his other gear and realized he had a mint collection of these drivers... I already knew from other comparisons and posts by Harvey Gerst and Robert G among others that JBL wasn't really labeling some of their drivers as consistently as we might wish.

Here is the comparison between four original slot tweeters:

http://www.audioheritage.org/vbullet...2&postcount=51

Widget

[Rudy Kleimann]

I re-read this thread after my last post... apparently my memory is holding up pretty well (better than my eyes lately) Anyway, didn't you and zilch have another thread that also discussed these (and other) drivers? Seems that is where the whole bit about diaphragm weight, thickness, resonant frequency, and F.R. came up, as well as Zilch and the 2404-1 with the D8R075 diaphragm spec'd for it in the Cabaret Series speaker system. Do you recall?

Also worth noting is another thread discussing labels with 8 or 16 ohm impedance ratings on early drivers (woofers in this case) with the same DCR and same recone kits. Harvey Gerst commented that it was (most likely) due to following popular trends at the time and output transformer taps on tube amps (some didn't have 8 ohm taps, only 16 or 32 ohm) of the day- the drivers were actually the same, only the labels changed as 8 ohm drivers became more popular to match up with 8 ohm output taps on the amps of the time.

As you demonstrated, all of the ring radiators tested were closer to a nominal 12 ohms impedance in their operating range, and pretty consistent among the aggregate.

I just put my GF on a plane and am house/dog-sitting at her place tonight. I hope to get by my house tomorrow and open up my JBL notes on these ring radiators to add my documentation to Subwoof's new thread on this. I especially hope to find the JBL documents regarding the Duralumin alloy from WWII aircraft skins and the applications details regarding the D8R075 and D162405 diaphragms to corroborate my story here.

Rudy

Waiting for Spring and warm water...

[Allanvh5150]

The use of duralumin is interesting. Duralumin is the old name for an alloy of aluminum, or aluminium as we call it, with copper, magnesium and manganese. It is roughly equivalent to the modern spec AA2024 aluminium. The stuff was originally made for airships if my memory serves me correctly. Later on it was used for aircraft. It is a lot harder than normal aluminum, but is more corrosion prone. To improve the corrosion qualities there is a pure coat of aluminum applied to the faces of the sheet. This stuff is used in the aircraft industry today and is commonly called "alclad". Chances are the modern aluminum diaphragms are made of the same stuff.

Allan.

[Zilch]

Four of us participated in the Widget Works "Ring Radiator Test Fest," as I recall: Infredible, Johnaec, Widget, and me. We all brought stuff, so there was an abundant sample...

[hjames]

Four of us participated in the Widget Works "Ring Radiator Test Fest," as I recall: Infredible, Johnaec, Widget, and me. We all brought stuff, so there was an abundant sample...

Would that be this 8 page long thread?

Horn/Driver Comparision


Used the following horns:

1) PT-F1010 - 100° X 100°, 6.5" X 12"
2) PT-H1010, 100° X 100°, 12" square
3) PT-F64, 60° X 40°, 6.5" X 12"
4) SF-95, (Sound Factor), 90° X 50°, 1" thread-on throat, 6.5" X 12"
5) P-Audio PH-230, 100° X 100°, 2342 Clone, 1" bolt-on throat, 9" Square

And used these drivers:

1) 435Be 3" Beryllium Diaphragm 1.5" exit from JBL Consumer
2) 2435HPL 3" Beryllium Diaphragm 1.5" exit
3) 2431 3" Aluminum Diaphragm 1.5" exit
4) 2418 1.75" Titanium Diaphragm 1" exit
5) 2426 1.75" Titanium Diaphragm 1" exit
6) LE85 1.75" Aluminum Diaphragm 1" exit

[johnaec]

... 4311B (aka Giskard and that oriental princess whatever )

That would be 4313B .

John

[johnaec]

Would that be this 8 page long thread?

Horn/Driver Comparision

Nope. The meeting Zilch mentions was exclusively for testing ring radiators. We *may* have also tested the 035Ti for comparison - I'd have to go back over the thread...

John

[Rudy Kleimann]

...and controversy

That would be 4313B .

John

That would be him. But, what was her name?

I just stick to the name I got in the beginning...

Whatever the name, the man has got his data right. Just don't be an idiot and piss 'em off

and suffer at the hands of the master