1.5" 2431H upgrade: should the 2435 BE diaphragm be the solution?

[Bruno_du_13]

Hello all,

I am new on this forum. I am found of JBL audio system since 25 years! :)

My system is an active 3 ways with 18" 2268H in vented box, a CMCD-81H 8" for the midrange (350 - 2kHz crossover points), and a 1.5" 2452H for the upper range.
At first, the HF driver was a 2431H Neodynium, but its frequency response was not good above 10kHz. And despite an efficient EQ with the the DP226 FAN, it doesn't sound very good.
So I replace it by a 2452H and it was a lot better.

By now; I would like to improve my 2431H, and I think about the Beryllium diaphragm of the 2435H. I would like to be sure both diaphragms are compatible (2431 vs 2435), and that a 2431 with a 2435 diaphragm is really equivalent to a 2435.

Many thanks in advance,

Regards

Bruno

[ivica]

Hello all, I am new on this forum. I am found of JBL audio system since 25 years! :) My system is an active 3 ways with 18" 2268H in vented box, a CMCD-81H 8" for the midrange (350 - 2kHz crossover points), and a 1.5" 2452H for the upper range. At first, the HF driver was a 2431H Neodynium, but its frequency response was not good above 10kHz. And despite an efficient EQ with the the DP226 FAN, it doesn't sound very good. So I replace it by a 2452H and it was a lot better. By now; I would like to improve my 2431H, and I think about the Beryllium diaphragm of the 2435H. I would like to be sure both diaphragms are compatible (2431 vs 2435), and that a 2431 with a 2435 diaphragm is really equivalent to a 2435. Many thanks in advance, Regards Bruno

Hi Bruno,

why not use UHF driver over 10kHz such as:

jbl 2408-1 or
bms4540 or
jbl 2405 or
faital_pro_hf104

that are intended to be used in such frequency range.

regards ivica

[Bruno_du_13]

Hi Ivica,

I do not want to have a 4 ways system... it would imply to change the crossover, add another amplifier (I want to stay in fully active filtering), and have more phase rotations. And the UHF could not be placed very close to the HF horn in my system.

I can keep the 2452, which is a very good driver, but the BE diaphragm should allow extended HF and better waterfall/CSD due to its excellent damping.

Thanks!

[ivica]

Hi Ivica,

I do not want to have a 4 ways system... it would imply to change the crossover, add another amplifier (I want to stay in fully active filtering), and have more phase rotations. And the UHF could not be placed very close to the HF horn in my system.

I can keep the 2452, which is a very good driver, but the BE diaphragm should allow extended HF and better waterfall/CSD due to its excellent damping.

Thanks!

Hi Bruno,

using active (digital) network, spacial difference between VHF and UHF drivers can be 'time' compensated.

using 4" diaphragm, may be you can reach 15~16kHz, but I think You have to use JBL Be diaphragm, or JBL Aluminum, not Truextent, but here on the Forum lot of members has much, much more experience in that field then me,

regards
ivica

[cooky1257]

Hi, to answer your question yes a 2435 Be will drop into a 2431.
With your XTA 226 you should be able to eq it out to about 15khz with good results-I wouldn't push them further, as I recall the PT's work well with this driver(use the search function i think Zilch did a lot of experimentation a few years ago).
I'm using an XTA 224. My SAM1 horns have the 2435 Be and are good up to about 14khz.
I also use 2452 with Truextent Be on H9800 horns and enjoy good flat clean output up to about 14khz where I let them roll off naturally.
What the Be will give you is lower distortion, less colouration, more clarity and detail, it isn't necessarily a more extended response but it will be of a higher quality.

[Bruno_du_13]

Thank you very much Cooky1257! very interesting.

So no more HF extension... but better quality up to 14kHz.
I will search on the forum for Zilch experimentaions.

Thanks!

[wrager]

Not to mention the truex is a little cheaper than the 2435 phragm, last I looked. As an aside , you could put the SL phragm in your 2452.

[pos]

Hi Bruno,

A 2435 will have the exact same problem at the 2431 above 10kHz. This problem is not caused by the diaphragm itself but by the phasing plug/horn interface.
See Doug Button's comment here: http://www.audioheritage.org/vbulletin/showthread.php?14369-2435h&p=147356&viewfull=1#post147356

In the frequency range you are targeting (the last decade IIRC) a D2430K (D2) would probably be the best solution there is, would bolt directly onto your waveguide, and would also be cheaper than a 3" Be diaphragm :
https://reconingspeakers.com/product/jbl-d2430k-tweeter-for-jbl-m2-5032754x/

FYI this is the driver used in the M2 (http://www.jblpro.com/www/products/recording-broadcast/m2/m2-master-reference-monitor#.VeS12H2iHN0) ;)
And this is a 32ohms driver, which will help reducing any amplifier hiss/noise/distortion problem you might have in an all active setup...
In fact being a dual VC driver, it can be configured as a 8 ohm, 32 ohm, or dual 16 ohm driver, which leave plenty of room when it comes to amplifier choice!

[jerv]

Hi Bruno.

I have a combination much like yours: with the CMCD-81H as a midrange unit and PT waveguide on top of that. Very nice combo.

I have tried various high frequency drivers, including the 2435, the D2 and the 2450SL (much like the 2452).
I am in total agreement with pos above: the 243x units does not work really well with the PT waveguides. This is because of the horn/phaseplug interface, and it will not get better with a Be diaphragm.

The D2 is much better.
But best of all, both when listening and when measuring, is the 2450SL with a Truextent Be diaphragm.

Se my advice would be to keep your 2452 drivers, sell your 2431's, and use the money to upgrade to Truextent :)

[Bruno_du_13]

Hi Pos,

Many thanks for your expertise and your detailed response!
So it's not a good idea to use the 2435 diaphragm. 2000$ saved! :)

For the moment I will go on with my 2452, which are good drivers. The D2430K seems very interesting, I will think about it for a future upgrade...

Thanks!

[ivica]

Thank you very much Cooky1257! very interesting.

So no more HF extension... but better quality up to 14kHz.
I will search on the forum for Zilch experimentaions.

Thanks!

Hi Bruno,

I have done one on-axis measurement 2450SL & PT-H95, so may be can give You some ideas.
Reagrds
Ivica

[pos]

The D2 is much better.
But best of all, both when listening and when measuring, is the 2450SL with a Truextent Be diaphragm.
That is the combination I have, and I plan to compare it to the D2 on the M2 waveguide soon.
I thought the D2 would best the 2450Be in the >2kHz range.
Could you describe the differences you heard once EQed?

[ivica]

That is the combination I have, and I plan to compare it to the D2 on the M2 waveguide soon.
I thought the D2 would best the 2450Be in the >2kHz range.
Could you describe the differences you heard once EQed?

Hi POS,

I think that there is great differences between PT-H95 and PT-F100, especially in the region under 2kHz. PT-F horns have short throat horn part, so LF loading of the driver (without internal horn such as old school 2420, 2440,41,45,46, 50).
I have calculated acoustical impedance of the driver with OSWG horn horn flare,

http://www.audioheritage.org/vbulletin/showthread.php?36154-OSWG-Acoustic-Impedance&p=366503&viewfull=1#post366503

and it can be shown how bad loading of the drivers is present.
I believe that the mentioned is the reason why M2 has about 4cm (almost pipe like throat), and then diffraction slot in the throat, and then fast 'flaring' horn.
For me it would be interesting to seen D2430K driver loaded with PT-H95 horn (not PT-F95/100), as much better LF loading I would expect.

regards
ivica

[cooky1257]

Hi Bruno,

A 2435 will have the exact same problem at the 2431 above 10kHz. This problem is not caused by the diaphragm itself but by the phasing plug/horn interface.
See Doug Button's comment here: http://www.audioheritage.org/vbulletin/showthread.php?14369-2435h&p=147356&viewfull=1#post147356

In the frequency range you are targeting (the last decade IIRC) a D2430K (D2) would probably be the best solution there is, would bolt directly onto your waveguide, and would also be cheaper than a 3" Be diaphragm :
https://reconingspeakers.com/product/jbl-d2430k-tweeter-for-jbl-m2-5032754x/

FYI this is the driver used in the M2 (http://www.jblpro.com/www/products/recording-broadcast/m2/m2-master-reference-monitor#.VeS12H2iHN0) ;)
And this is a 32ohms driver, which will help reducing any amplifier hiss/noise/distortion problem you might have in an all active setup...
In fact being a dual VC driver, it can be configured as a 8 ohm, 32 ohm, or dual 16 ohm driver, which leave plenty of room when it comes to amplifier choice!


Hi Pos,
So are you suggesting that all of the throatless/short phase plug drivers(24**) aren't a good match for the M2 horn too? I ask as looking at the pics of that horn it has a very short throat before the pinch/slot section....

Cooky

[Bruno_du_13]

Pos, Jery: so the D2 or my 2452 with Truextent diaphragm (should it be the same as the 2450 one)? :spin:

For my 2431: try to sell it since more than one year but nobody wants it... :nopity:

[ivica]

Hi Pos,
So are you suggesting that all of the throatless/short phase plug drivers(24**) aren't a good match for the M2 horn too? I ask as looking at the pics of that horn it has a very short throat before the pinch/slot section....

Cooky

Hi cooky,

phase plug 'length', and driver internal horn are two different things.
4" diaphragm drivers such as 2440/41/45/46/50/51 have almost the same phase plug 'length', but 2452 has shorter one. I have no info about 243x types.
M2 horn has about 4cm long throat, so I believe can be used with JBL 1.5" drivers too (2447,2450sl/51/52)

regrads
ivica

[cooky1257]

Hi cooky,

phase plug 'length', and driver internal horn are two different things.
4" diaphragm drivers such as 2440/41/45/46/50/51 have almost the same phase plug 'length', but 2452 has shorter one. I have no info about 243x types.
M2 horn has about 4cm long throat, so I believe can be used with JBL 1.5" drivers too (2447,2450sl/51/52)

regrads
ivica
My intended point was more concerning the 2435 and the 2452's as they are throat-less and feature the shorter phase plug,( the older 2440/41/45 have a cylindrical front throat built in), in the the M2 horn images I've seen I'm not seeing a 4cm throat.......
The 2435H is finicky as to what wave guides it works with because the phasing plug is so short. - Courtesy of Doug Button

[pos]

Hi Pos,
So are you suggesting that all of the throatless/short phase plug drivers(24**) aren't a good match for the M2 horn too? I ask as looking at the pics of that horn it has a very short throat before the pinch/slot section....

Cooky
Hi Cooky

The "problem" only seem to appear on the 2431/2435, and on some horns (PT and 2332 for example)
I did not measure any problem on the 2452 and 2450SL cores, so it is not only a matter of being a throatless driver.
It looks like the snout on the 2432 is an attempt at addressing this problem.

I plan to measure the 2435 on the M2 waveguide and see if the problem remains.
So far from the different horns I had the pleasure to try the 2435 on, only the H9800 behave smoothly enough above 10kHz.

[cooky1257]

Hi Cooky

The "problem" only seem to appear on the 2431/2435, and on some horns (PT and 2332 for example)
I did not measure any problem on the 2452 and 2450SL cores, so it is not only a matter of being a throatless driver.
It looks like the snout on the 2432 is an attempt at addressing this problem.

I plan to measure the 2435 on the M2 waveguide and see if the problem remains.
So far from the different horns I had the pleasure to try the 2435 on, only the H9800 behave smoothly enough above 10kHz.

Thanks Pos,

Informative as always, I've been on the forum long enough to witness more than one mad rush for the next great thing-heck I've participated in 2 of them so I'm holding off the expense of another change from H9800 to M2 just yet.

[Didier]

Hello,
As it seems that the main problem with 2431H and 2435HPL is the throat with some horns,
Did someone compared those drivers to the 2432H?
As pos said, maybe this different core could solve the high frequency problems...?
If yes, it would be also interresting to compare Al, Ti and Be in this driver :D
Didier

[pos]

Hi Didier,

Are you sure the 2435HPL would show this particular problem on your particular horns? (Arai290 3/4 scaled version IIRC?)
In my tests I found the problem was almost non-existent on the H9800 for example.

[Didier]

Hi pos
Effectively I have no idea of what would happen with the 2435 on this specific horn. Maybe no problem;)