Ring Radiator Comparisons

[Mr. Widget]

This thread will show the on and off axis response of all four of JBL's ring radiator tweeters. There seems to be some confusion over these so here is a mini background. All four tweeters can use the same diaphragms and have the same motor structure. There is an alnico and ferrite version. After having measured several of each tweeter in both motor types I am certain that there is a fair amount of unit to unit variation, but not due to magnet type.

The first model of this series was the 075 "Bullet Tweeter". There is also the Pro variant the 2402 and the ferrite version, the 2402H. This model has a the heaviest diaphragm of the three and is capable of operating over the widest frequency range. It also has the most focused dispersion pattern.

The next model offered was the 077 "Slot Tweeter" and it's Pro variant, the 2405. Later there was the ferrite 2405H. This model has the lightest diaphragm and offers the widest dispersion pattern and produces the highest frequencies.

The third model offered by JBL was the 076. There was also a Pro variant offered, the 2403 in alnico and the 2403H in ferrite. It was originally designed specifically for the L220. It uses a unique diaphragm. I believe that it has a moving mass that is between the 075 and 077.

The final model offered by JBL was the 2404H. It uses a mini butt cheek bi-radial horn. It uses the 2405 diaphragm, but is usable down to much lower frequencies than the 2405.


Here is an on axis plot comparing two brand new 2402Hs.

[Mr. Widget]

This plot shows the off axis performance of a 2402H.


On axis is in Red
15° off axis is in Blue
30° off axis is in Green
45° off axis is in Purple

[Mr. Widget]

Here is the plot of a 2405.


On axis is in Red
15° off axis is in Blue
30° off axis is in Green
45° off axis is in Purple

[Mr. Widget]

Here is a plot of the 2403H (076 Cat Eye)


On axis is in Red
15° off axis is in Blue
30° off axis is in Green
45° off axis is in Purple

[Mr. Widget]

Here is a plot of a 2404H.


On axis is in Red
15° off axis is in Blue
30° off axis is in Green
45° off axis is in Purple

[Mr. Widget]

Here is a comparison we did between a pair of 2404Hs. One was labled 2404H and the other 2404H-1.

[Dr.db]

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!?

[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!?

No, I don't agree. Most people recommend the 2405 over the 2402 due to the much more linear response at ~9kHz (even if they don't know it). Most of us have no problem with ~9 kHz and the drop out in the 2402 is substantial compared to the 2405. The ear really picks up on this on ride cymbols, etc., but also in vocal intelligibility.

[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 )

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 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 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 :