Ring Radiator Comparisons

[andychris]

Hello

I can get a pair of 2402 alnico with silver diaphragms,,, could you tell me if those diaphragms seem JBL original ? Ans silver diaphragms, is it a fine diaphragm because I've never heard one ?

Thanx

62175

[ivica]

Hello

I can get a pair of 2402 alnico with silver diaphragms,,, could you tell me if those diaphragms seem JBL original ? Ans silver diaphragms, is it a fine diaphragm because I've never heard one ?

Thanx

62175

Hi andychris,

It seems (to me) to be JBL original.
I have very good experience with 2405 "sliver-like" diaphragms,
but I have no experience with 2402 "sliver-like" diaphragm.

reagrds
ivica

[gibber]

Hello

I can get a pair of 2402 alnico with silver diaphragms,,, could you tell me if those diaphragms seem JBL original ? Ans silver diaphragms, is it a fine diaphragm because I've never heard one ?

Thanx


Hi andychris,

your fram seems original, but the bullet part of the horn seems to have been taken from the ferrite rather than alnico version.

My ferrite-sourced bullets (on the right) show the same outside removal of material at the wide end (near fram) as the one in your picture. Despite removal of material, they measure 43.8mm across -- half a millimetre more than the old bullet taken down from a 1970's alnico 2402 at 43.3mm shown on the left :

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(note the machined entry into the scew-hole on the '70 bullet)


Side note: i would never have noticed it without having read this GREAT thread: my 2402H bullets have the 2405-fram layout, i.e. plane area at the bottom side of bullet is 36.6 mm instead of the '70s bullet's underside plain area being 35.6 mm across -- a whopping whole millimetre !

Ralph

[gibber]

Most people recommend the 2405 over the 2402 due to its wider freq. range....

But is their a lot happening above 15khz in reality ?
And is the usual individual aged above 30 still capable of hearing these frequencies anyway!?

This weekend i will visit a friend to give quite a full brace of varieties a go: He was lucky enough to get hold of a pair of cat-eyes and on the ETF.14 auction he got himself a pair of "extended-horn" bullets made from brass. These things exude luxury, will see if they live up the the hype (and will check whether their bullet's underside is machined for 2405 or 2402 frams :dont-know: )

Ralph

[toddalin]

Most people recommend the 2405 over the 2402 due to its wider freq. range....

But is their a lot happening above 15khz in reality ?
And is the usual individual aged above 30 still capable of hearing these frequencies anyway!?


The difference in what is heard is not so much what is above 15K, but what is actually happening in the 8-9K region. The 2402 have a much deeper dip in this area than the 2405, and the ear readily hears this difference as a loss of detail.

[gibber]

The difference in what is heard is not so much what is above 15K, but what is actually happening in the 8-9K region. The 2402 have a much deeper dip in this area than the 2405, and the ear readily hears this difference as a loss of detail.


Time domain effects might have an influence on listener preference, too. But i would actually suspect that the 2402 horn is better in that respct than the later designs due to no folding / slotting / etc. after the initial compression*). The 2403 could be as good but is second in my book since it sports the same phase plug as the 2405-fram versions of the 2404, so some extra complexity for the sound path.

Back to the frequency domain effects -- i fully concur that the 15 kHz behavior is likely of secondary importance compared to the 9 kHz aberrations. So big Q is, are these dips due to the 2402 horn or are they a consequence of the much-larger 2402 fram? 1Audohack's post #195 (http://www.audioheritage.org/vbulletin/showthread.php?6368-Ring-Radiator-Comparisons&p=302857&viewfull=1#post302857) showed Bode plots of the 2402H-5 vs the normal 2402H version, but doesn't resolve the issue coz both of his tweeters do not seem to suffer much output loss at 8..10 kHz (the larger fram just a little bit at 8 kHz, but far away not only in severity from the 9.5 kHz dips in MrWidget's post that started this thread).
You mentioned the dip of 2403 to be almost as bad as 2402 in this respect and Grumpy's post #150 (http://www.audioheritage.org/vbulletin/showthread.php?6368-Ring-Radiator-Comparisons&p=264114&viewfull=1#post264114) points to a possible source, as off-axis responses show a relative level increase for that frequency range, meaning in turn that the on-axis response might be weak at same frequency if we assume relatively flat power response into the room. That said, Grumpy's findings are more in the area around 8, not 9.5 kHz ...

The weekend's coming, will be interested how the audition turns out -- Ralph




*) anyone remembers Fostex 725 that did away with the initial compression?

[toddalin]

So big Q is, are these dips due to the 2402 horn or are they a consequence of the much-larger 2402 fram?

The weekend's coming, will be interested how the audition turns out -- Ralph




*) anyone remembers Fostex 725 that did away with the initial compression also?


Primarily because of the bigger fram.

IIRC, when I put the 2405 fram in the 2402, the dip largely went away and the result was pretty much like the 2405 tweeter with the 2402 dispersion. (JBL did make some 2402s with 2405 frams.) You can use a elastomeric filter (rubber band) too further smooth out the >10K response and even push it beyond that of the 2405 while adding to the dispersion of the 2402 at the cost of dB. This really turns the 2402 into a "super tweeter."

But, you can also put the band on a 2402 with the 2402 fram, kill most of what's below 9K and extend and smooth the response above that. You won't get it as high or as much volume as with the 2405 diaphragm, but if you have an RTA and a rubber band (the ones used on asparagus work well), it's fun to try.

Push the rubber band over the "nose cone" evenly around using a wooden stick, paint brush handle, etc., while running white noise though it and watching it on the RTA. Just before the ring closes up, the slot gets very narrow and you will see the frequency range change as the lower frequencies drop way. Physics says, the narrower the slot, the greater the dispersion, and we confirmed this. If you go too far, a pin can pull it back out.

[Dr.db]

The difference in what is heard is not so much what is above 15K, but what is actually happening in the 8-9K region. The 2402 have a much deeper dip in this area than the 2405, and the ear readily hears this difference as a loss of detail.


Thanks a lot, I missed out on your previous post. Thanks for posting again!

[gibber]

Short report on what turned out only as the beginning of that listening comparison. We had quite a bit of preparations to do, so there will be a second date. The tweeters were passively added @ ca 7kHz (3rd order 1u/.3mH/1.5u) to a 8" vintage die-cast frame Grundig paper cone full range w/o whizzer cone or even dust cap. Contenders are a bronze horn flare waiting for a motor and
1) pr gray ferrite 2402H-5 w/ 2405 fram; 2) pr blue fram 077; 3) pr yellow fram 2402H; 4) pr 2402 w/ 2405 yellow frams; 5) pr 2404H w/ yellow 2405 frams; 6) pr Coral H100; 7) pr 076; 8) pr 2405; 9) pr silver fram 2402H.

Also a pr of Beyma Cp21F, a single Beyma Cp21 alnico w/ vintage fram & single 2402 / orig. fram

Auditioned were only 3/5/7/8. No level adjustment was used so far, will do once the measurement gear is used. Classical, Jazz and Pop were tried; #3 and 5 produced something that can only be likened to a kind of "grey" hiss alongside the music. Sound was veiled in comparison to 7/8. The latter two markedly differed from each other only very high up with the cat eyes having quite a bit less in highest overtones or cues to the "mechanics" of music-making such as the soft string squeak you can often hear, etc. No clear winner here: 076 a little more recessed/relaxed, 2405 a little more revealing. As toddalin predicted: surprisingly similar sound given the two very different horns ...

to be continued

[gibber]

Well, sorry for long quiet period. In the end it was four weekend dates and the best part of a day at an amateur audio meeting, so it took some time to get a clear picture ...

Here's a few measurements that my friend and i wanted to make in order to shed some light on the time-domain related arguments made in this thread, ring radiators first :


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[gibber]

Here's an interesting effect (sorry for the X- and Y- axis jumping a bit) in that the 077/2405 shows a double peak at the beginning of the response train :

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[gibber]

We used a 22cm "fullrange" unit made by Grundig in the 50's. These speakers came with various frames (made from sheet metal or diecast) and magnets (mostly alnico types). The one we used had a thin diecast frame and a chunky alnico ring magnet (so not inside the coil as that is ca 25mm only). That alnico ring was somewhere between round and square outside and had recesses for the bolts that hold the magnet on the basket.

The version we had at hand is one with a surprisingly high resolution capability. The thin paper cone has no dustcap or dispersion dome (just an open pole piece) and is subjectively very "fast". As bit of a "forwardness" was observed, we tamed it by a simple strip of sticky tape. The unit was used without a filter and rolls off by itself. Crossover for the tweeters, as mentioned in an earlier post here, was 3rd order at ca 7kHz. Resistors were used in parallel/series to ensure roughly comparable levels.

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Attached is the frequency response of the mid-bass, the sound is much less rugged than the response might make you think. Response shown is of the 22cm with a 10cm "Sachsenwerk" cone tweeter added at nom. 7kHz:

65154


We used a baffle for most of the tweeters. The baffle had a strong effect on axis for wide-dispersion designs only. Not used on baffle were 2404H, Coral H100, HH/Multicell HF200, and TOA HT371, although the latter is a wide-dispersion design and was shown to benefit from a baffle when doing measurements after the listening test. Here's two Bode plots showing the effect of the baffle on a 2405 slot, first one with the baffle, the second plot w/o :

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Missing in the previous post, here's the pulse resp for 076 #2 :

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[gibber]

My friend and i took the two enclosures/X-overs/baffles plus the equivalent of two L100s in tweeters to an audio gathering and demo'ed the setup there. Since we offered it, a number of people turned up and listened to the bass-mid with various tweeters of their choice.

Some interesting comments were made, of which i will list some here:

1) the JBL's were regarded the most "dynamic-sounding" of the field (the non-JBL types are mentioned elsewhere in this thread).
2) especially the two JBL slots 077 and 076 (the cateye is a slot, just a little less extreme than than the 077/2405) were commented on as being best in speech intelligibility. Fostex T825 and 2404Hs (and a makeshift 2404 alnico version) did not find so much applause.
3) among the nominally same-type JBL diaphragms, large differences (sound & later also measurement) were observed.
4) among the various types of JBL diaphragms (best ones of each chosen), the 077/2405 was preferred over 076/2403 and 075/2402 frams. We even put together a cat eye with 2405 frams and it was rated as better than the original by the audience.
5) using a good pair of 077/2405 frams makes the choice between 076 and 077 really difficult. Even listeners on the very side did not prefer 077/2405 over the cateye with 2405 frams (but did over the standard cateye). The ring radiator (alnico or ferrite) was deemed slightly inferior to these slots even if it had 2405 frams installed.
6) the longer/large diameter bronze horn was installed instead of the normal 2402 front pieces but was not found superior with this 7kHz/3rd order configuration -- perhaps it's real advantage is extending the 2402 towads lower frequencies.


Admittedly, this listening test might be flawed in that each tweeter pair was only combined with that very pair of Grundig full-range at hand, so take the above with the usual grain or two of salt.

We tried to also find out if a preference ferrite vs alnico exists, but as outlined elsewhere, the parts are not easily exchanged between the two. A 2404 (no "H") was put together and tried vs 2404H but results seemed to indicate there is no difference. The 2402H we had with us came with inferior frams compared to the 2402 alnicos (as measured later) and hence were deemed inferior in this comparison. And while we look at diaphragm quality variance in a ring radiator, this certainly was previously stated for the slots...

The on axis response of the 2405 is indeed more linear and a bit more extended (but really, how cares about extension above 17kHz ??), but if you look at unit to unit matching all these consideration become moot anyway...

Fostex T825s at this event were considered very smooth, a little too polite for most, but very neutral and well resolved despite a apparent lack of top-end sparkle. Listeners to the extreme side of the room did again not necessarily favour this slot radiator over the non-slots such as the Goto tweeter. I wonder how Fostex T845 might have fared, as they seem to be very close in construction to 077/2405s...

The Goto, despite the hype, fared well but not better than the 2405 or the 076 with 2405 fram. Reason as before was the better portrayal of dynamics and superior intelligibility of speech and song with the JBL 2403/2405, while the Goto like the T825 did offer slightly better resolution and "refinement".

All in all, this event's results were in contradiction to my predictions as outlined previously in this thread. Although the 077/2405 did show funny time domain behaviour as expected, the listening panel did not prefer bullets w/ 2405 frams but judged otherwise.

Ralph

[pos]

Hello Ralph

Thanks for these interesting measurements and listening comparisons.
This double spike in the 2405 IR is also something I measured on all of mine.

What diaphragms did you try in the 2403 core?

[gibber]

What diaphragms did you try in the 2403 core?

One blue & one silver 2405 fram, if i recall correctly. And actually, not in the "2403 core"; we took quite a bit of trouble to make it happen. The cateyes were never opened before (sealed by 076 typesticker on back). So in order not to break that seal, we removed the elliptical horn from the front and used the same pieces of metal taken from a buttcheek in order to build up a cateye with proven quality 2405 frams.

[script56]

While on the subject, I'm wondering how 075 diaphragms are used for 076 replacements. The original 076 has pointed diaphragm and 075 has hole for metal bullet

[JeffW]

While on the subject, I'm wondering how 075 diaphragms are used for 076 replacements. The original 076 has pointed diaphragm and 075 has hole for metal bullet

The pointy part is the phase plug. Remove it and there's a hole just like the 075.

[script56]

Oh. Ok. I bought some 076 horns (without driver). I was going to try to attach them to a 075 magnet assembly, but I guess it won't work.

[JeffW]

Oh. Ok. I bought some 076 horns (without driver). I was going to try to attach them to a 075 magnet assembly, but I guess it won't work.

It should work, I think all of the motors are the same. (http://www.audioheritage.org/vbulletin/showthread.php?23869-075-2402-076-2403-2404-077-2405&p=239652&viewfull=1#post239652) You'd just need the 2403 phase plugs.


To my knowledge, all of the motor assemblies are interchangeable from a mechanical standpoint. The ferrites probably have a little more flux level than the alnico’s but that is all. The main difference in them is the horn or bullet or whatever is mounted on the front side. Any diaphragm can go in any body. Results will vary.

[script56]

Yes that's the problem. Any idea where to find them?

[JeffW]

Not a clue. Don't see many people parting those out, but the 2404 phase plug looks pretty similar. Maybe somebody can compare those.

[gibber]

Not a clue. Don't see many people parting those out, but the 2404 phase plug looks pretty similar. Maybe somebody can compare those.

Hi Jeff, we did exactly that. There are plenty of those parts on eBay right now, just look for '2404H horn throat and phase plug'.

Problem is that even if the cone and the first part of the horn are shared between 2403H and 2404H, the elliptical end section of the cateye horn is difficult to get.



Yes that's the problem. Any idea where to find them?

eBay had quite a few of them listed in previous months ... same seller as the one that has the buttcheek phase plugs.
Or buy some cheap ferrite tweeters (no matter which type) with challenged cosmetics, if alnico is difficult to get right now.

Ralph

[gibber]

Measurement distance was 1m, mic and preamp were Behringer. Speakers were fixed to baffle openenig by sqeezing in some pieces of cardboard alongside the horn throat.

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[gibber]

Here's a few shots that show the setup and help to put the Bode traces with / without baffle into a clearer context :

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[gibber]

Following in the next posts are the Bode plots corresponding to the pictured ferrite/alnico JBL tweeters and some non-JBL types.

First, the 2405 (#1 sample) mounted on a small baffle as per the picture in the previous post
Second, the same 2405 sample, but naked on top of box aligned with front face of that speaker
Third, #2 sample of 2405
Fourth, fifth -- the 2404H pair without a baffle -- a meas. with baffle was not done for 2404H

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[gibber]

Here's five rings, some original some with slot (2405) fram.
When viewing watch sample variation, but also keep in mind that the 2405 fram sounded much better than the std. fram despite nice response graphs from all :

First a standard 2402H (sample #1)
Second, std. 2402H (sample #2)
Third we have alnico 2402 with 2405 diaphragm (#1)
Fourth, another sample of the above
Fifth, a ferrite 2402H with 2405 disphragm ex-factory. Metal parts are a wee bit differently machined (see elesewhere) to accomodate the 2405 fram into the ring radiator design.

No difference due to magnet type was found from any of the plots.

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[gibber]

Some non-JBL types were measured and listened to also. The HH was also sold under the Multicell brand in Europe; the sample later turned out to have quite some damage to it's diaphragm, but sounded and measured very good nevertheless. Wonder how good that thing gets when reconed. Perhaps the best value in the field ...

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Also very good, but a bit tame at times was the Goto tweeter type SG16. This is the smallest magnet Goto offers for their super lightweight aluminium supertweeter coil/membrane. Larger magnets with this diaphragm are reported to sound and measure very similar to the SG16. The agile moving parts have very fine resolution as a result. Perhaps resolution will increase with larger magnet size even more.

The larger magnets are also available with Beryllium diaphragm. Deep-pocket territory ...

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A very finely resolving slot tweeter is available in the unusual hemisherical design of the Fostex T825. The fram is quite small and perhaps because of this, resolution and dynamis are similar to the Goto tweeter. Very wide dispersion as in 2405, while neutrality was also really nice. Below is an overlay of the on-axis and 30° plot.

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And here a tweeter from category unobtanium - a mint sample of Coral H100. Quite a bit more dynamic sounding than the small Goto, and at the same time offering the highest resolution of the whole field. This tweeter is so ruthlessly revealing that we tried a different source after first listening resulted in the panel not liking it all that much despite the wealth of detail and examplary neutrality. It simply tended to sound a wee bit hard-edged, even harsh before the change of source.
Only recommended for top-notch setups, go for cateyes or slots otherwise and enjoy a more forgiving sound with nevertheless same or better subjective dynamics at slightly reduced resolution if your setup isn't in the super-league.

65791

[gibber]

Here we're back in Lansingland with two samples of Don Keele's babies in standard (D8R2405-equipped) configuration :

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What remains to be done?

Well, first, there's the need to retry a quick experiment we did with using a slot tweeter fram in a 2403/076 motor. During the tests it became more and more clear that larger magnets coupled to smaller frams are the best combination in tweeters unless you want them from 2 or 3 kHz up. Given the info i read earlier in this thread namely that all JBL models of a given period had identical magnets, it seems safe to assume the cateye as the most balanced sounding JBL expansion would benefit from using 077 instead of the heavier/wider 076 frams.

And then, there is the surprise tweeter from TOA ... in the listening comparison it already scored well, but although we might have guessed it, its tiny slot must be coupled to a baffle just like a 2405 -- but little did we know that the HF371 cannot do without a 2.5 kHz trap: listening was before measurement, hence needs to be repeated.
(last pic shows response with a rudimentery baffle to the sides, not at top/bottom of exit; watch how the usable range smoothens out and the peak at 2.5kHz up even more)

Should be fun comparing the two.

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[Earl K]

Great Thread !

Lots of wonderful contributions in here!

Thanks!

:)

[alnico500]

https://www.youtube.com/watch?v=w6tYFX6DJ6w