JBL 2450 with Truextent vs TAD 4001?

[neskor]

I need your help.
Still deciding what is best thing to do.
Anybody had a chance to compare JBL 2450 loaded with Truextent diaphragms vs TAD 4001?
What you will choose?

[cosmos]

I need your help.
Still deciding what is best thing to do.
Anybody had a chance to compare JBL 2450 loaded with Truextent diaphragms vs TAD 4001?
What you will choose?

We did not listen to the Truextents in 2450, they were in either 2441 or 2445. However, when compared to TADs, I'd give them a slight edge. Others in the group might give the Tads the nod, but in any case, it was close. Very close. I don't think you could lose with either combination.

[Mr. Widget]

I've heard both, but not at the same time... so I can't make a useful comparison. As cosmos said, I don't think you would be making a mistake with either assuming the TADs are up to spec and the Truextent's are properly installed in the JBLs.


Widget

[neskor]

I had some bad experience buying old and (ab)used Alnico drivers.
Unfortunately there is no recharge service in my country :(
Maybe is better and safer to go with neodymium magnet.

[Mr. Widget]

Maybe is better and safer to go with neodymium magnet.If you don't have the drivers yet, and you choose the JBL route, you can safely go with ferrite. They are larger and heavier, but they also are less costly. I would go with the 2446 if I wanted a 2" throat.


Widget

[pos]

Guido recommends the Radian 950PB driver which is supposed to be better thanks to its 5-slit phasing plug. He also sells 950PB drivers with truextent diaphragms installed :bouncy:

I am running truextent 16ohms diaphagms in 2450 cores and I really like what I hear and measure, much improved over Ti and Ti SL diaphragms. They require some compensation in the high tho: if you want to run them with a passive filter it would probably be much easier to use a Ti SL diaphragm or a TD4001...
What you get with the truextent is a very efficient mid/high band, and a really well behaved (but rolled off) top end. The milar surround certainly has much to do with this.

[neskor]

What you get with the truextent is a very efficient mid/high band, and a really well behaved (but rolled off) top end. The milar surround certainly has much to do with this.
My plan is to use 2405 above 10KHz

[4313B]

Guido recommends the Radian 950PB driver which is supposed to be better thanks to its 5-slit phasing plug. He also sells 950PB drivers with truextent diaphragms installed :bouncy:
Very tempting! Too bad it has the wrong brand name stamped on the back. :rotfl:

[neskor]

I have some plots of JBL 2450j with Truextent diaphragm from German magazine.
Is it ok to post results here or is that forbidden?

[Mr. Widget]

I have some plots of JBL 2450j with Truextent diaphragm from German magazine.
Is it ok to post results here or is that forbidden?As long as you realize any copyright infringement is by the poster not the Forum.


Widget

[neskor]

Here it is.
I hope nobody will sue me :D

[spkrman57]

If you don't have the drivers yet, and you choose the JBL route, you can safely go with ferrite. They are larger and heavier, but they also are less costly. I would go with the 2446 if I wanted a 2" throat.
Widget


I have Be diaphrams in my 2446's mounted on 500Hz tractix Edgarhorns and use them on top of my 2226's and they sound great, at least to my ears! I used to have them on my 350Hz Edgarhorns shown in my avatar.

Regards, Ron

[Guido]

Here it is. I hope nobody will sue me :D Obsolete!! These measurements where taken with the first run of Truextent diaphragms. Due to a problem with the fixation of the VC leads these had k2 issues as can be seen. k2 is way to high. The newer diaphragms behave much better!

[neskor]

Obsolete!! These measurements where taken with the first run of Truextent diaphragms. Due to a problem with the fixation of the VC leads these had k2 issues as can be seen. k2 is way to high. The newer diaphragms behave much better!
Good to hear that! :D

[maxwedge]

Obsolete!! These measurements where taken with the first run of Truextent diaphragms. Due to a problem with the fixation of the VC leads these had k2 issues as can be seen. k2 is way to high. The newer diaphragms behave much better! How do you tell if you have a fist run? Just measuring them? I bought a pair 3/11 and they sound good to me.
Edit: I see the article is 6/10 so maybe I got a gut set.:D

[pos]

Truextent should do a recall for such a problem.

I think Guido told me once that diaphragms with serial number below 700 might have the problem.

[Mr. Widget]

Truextent should do a recall for such a problemThe way they explained it to me was that it was only a problem in certain drivers. Ultimately they made a change in production so that their diaphragms would fit more drivers, but I believe, that for those who bought the very early diaphragms, if the diaphragm fit your driver, you are good to go.

Guido, do you have any more info on this?


Widget

[ivica]

I had some bad experience buying old and (ab)used Alnico drivers.
Unfortunately there is no recharge service in my country :(
Maybe is better and safer to go with neodymium magnet.

I think that 2446 -"motor" would be cheaper and appropriated solution, while the diaphragms would be another "story". At the end I think that desired horns would be of great influence to the total sound experience. Old 2311 with 2308 would be a good starting point if the speakers are intended for "home listening" but, with some kind of mid-bass support (such as: 2122, 2123, 2202,....).

http://audioroundtable.com/forum/pdf.php?th=16472
Upper link very interesting for reading.


Using 2405 (or something the same) would be "a must" in any case

[4313B]

The way they explained it to me was that it was only a problem in certain drivers. Ultimately they made a change in production so that their diaphragms would fit more drivers, but I believe, that for those who bought the very early diaphragms, if the diaphragm fit your driver, you are good to go.
I had one pair that absolutely would not fit into some 2441 cores. They fit just fine into some 2445 and 2446 cores.

[edgewound]

I had one pair that absolutely would not fit into some 2441 cores. They fit just fine into some 2445 and 2446 cores.

That's probably due to the later ceramic units having a relief machined into the top plate where the voice coil leads rise up the terminals.

The alnico drivers don't have that feature....which makes fitting new diaphragms more of a challenge.

[1audiohack]

The first ones of these I got my hands on, serial numbers in the 300's would not run rub free in the 2441's I had either, noway, nohow. Having carefully measured half a dozen of these I can tell you that the concentricity is much better on the later assemblies and as hard as it is to measure something so fragile and flimsy as a voice coil the later ones are about 0.010" smaller overall. There should be no problem if they don't rub, either they do or don't. The early ones went, measured, run and sound fine in the 2450's.

[Mr. Widget]

The first ones of these I got my hands on, serial numbers in the 300's would not run rub free in the 2441's I had either, noway, nohow. Having carefully measured half a dozen of these I can tell you that the concentricity is much better on the later assemblies and as hard as it is to measure something so fragile and flimsy as a voice coil the later ones are about 0.010" smaller overall. There should be no problem if they don't rub, either they do or don't. The early ones went, measured, run and sound fine in the 2450's.Good God man... How many Be diaphragms do you need!
:applaud:


Widget

[Guido]

That's probably due to the later ceramic units having a relief machined into the top plate where the voice coil leads rise up the terminals.

The alnico drivers don't have that feature....which makes fitting new diaphragms more of a challenge.

That exactly WAS the problem with Alnico core JBL's and Radian 950PB. The newer ones fit fine.

[pos]

But the graph with high distortion in the article is with a 2450 driver which has the machined ribs for the VC leads!

[Mr. Widget]

But the graph with high distortion in the article is with a 2450 driver which has the machined ribs for the VC leads!Good point... could be a less than stellar diaphragm or installation.


Widget

[Guido]

could be a less than stellar diaphragm

Yep, this was one of the first dias. In fact a beta version. See the lower impedance. It was also fixed later.

[Elac310]

I do happen to have the magzine article/test mentioned earlier, with the comparison JBL original vs JBL with Truextent Dia.
I also do happen to be fluent in German.

What was interesting was that the test concluded that the JBL driver with Truextent was better in all respects, DHT-wise, frequency response extension and linearity-wise etc. Not quite obvious to me, but I'm not an engineer.
I don't dare imagining what the conclusion would have been with a proper diaph mounted...

[ivica]

I do happen to have the magzine article/test mentioned earlier, with the comparison JBL original vs JBL with Truextent Dia.
I also do happen to be fluent in German.

What was interesting was that the test concluded that the JBL driver with Truextent was better in all respects, DHT-wise, frequency response extension and linearity-wise etc. Not quite obvious to me, but I'm not an engineer.
I don't dare imagining what the conclusion would have been with a proper diaph mounted...

Here are my measurements with JBL 2450SL (1.5 inch) driver with its original Ti-SL diaphragm, and Be ( truextent) diaphragm, with JBL 2332 horn (1.5 inch).
It is 'visible' that over 10kHz Ti diaphragm has become more 'nervous'..
But over 12kHz either Be diaphragms has started to 'shake', it is visible in non-smoothed blue curve.

Non-smoothed curves are windowed with 8ms long window in order to eliminate first reflection from the sealing.
Smoothed curves are 1/3 octave 'averaging'.

In my opinions UHF driver used over about 10kHz would be good suggestion.
( JBL 2405, or Beyma TPL150, or Beyma CP21/F).

Measuring THD (distortion) up to 10kHz did not make too many differences between them.

[speakerdave]

I used the 2450 in my stock 4345. Mounted on the 2311 the wide part of it fell just aft of the dog box. I was using a factory dusted diaphragm. I thought it sounded really good. With the truberyl there should be additional refinement. Used 2450's have been available steadily on eBay for quite a while, now for $449. If you are planning on new diaphragms anyway, that might be a good way to go, but the total investment would be over $2k. The 2450 has a more recent phase plug and throat design than the 2445.

[Champster]

Here are my measurements with JBL 2450SL (1.5 inch) driver with its original Ti-SL diaphragm, and Be ( truextent) diaphragm, with JBL 2332 horn (1.5 inch).
It is 'visible' that over 10kHz Ti diaphragm has become more 'nervous'..
But over 12kHz either Be diaphragms has started to 'shake', it is visible in non-smoothed blue curve.

Non-smoothed curves are windowed with 8ms long window in order to eliminate first reflection from the sealing.
Smoothed curves are 1/3 octave 'averaging'.

In my opinions UHF driver used over about 10kHz would be good suggestion.
( JBL 2405, or Beyma TPL150, or Beyma CP21/F).

Measuring THD (distortion) up to 10kHz did not make too many differences between them.



This is an interesting thread, but it strikes me as odd that there seems to be a reluctance to accept Ivica's several posts that adding a 2405 resolves the breakup issues in all of these 'phrams. Especially when a pair of 2405's costs less than 1 Truextent 'phram.

Can someone explain please explain this?

[Ian Mackenzie]

This is an interesting thread, but it strikes me as odd that there seems to be a reluctance to accept Ivica's several posts that adding a 2405 resolves the breakup issues in all of these 'phrams. Especially when a pair of 2405's costs less than 1 Truextent 'phram.

Can someone explain please explain this?


It requires first further reading for best interpretation ..that of how a compression driver diaphragm functions.

http://www.audioheritage.org/html/projectmay/technology/435be.htm

"However, it was recognized that there were compromises with the new diaphragms. Titanium does not have the internal damping of aluminum and thus has marginally higher distortion levels. The diamond surrounds, while extending frequency response, do so at the expense of transient response. Further, due to its lower stiffness, titanium goes into breakup at a lower frequency.

This issue of breakup is worth elaboration. Ideally, a dynamic loudspeaker diaphragm should act as a piston, with all points in uniform motion. However, since diaphragms are not infinitely rigid, there will be a condition at which the forces acting upon it cause oscillating deflections resulting in different points on the surface moving in different directions. Under this condition, the diaphragm is said to be in breakup, and there is an attendant increase in distortion. Both aluminum and titanium compression driver diaphragms are in breakup for much of their response. On a large format driver, the breakup modes for aluminum diaphragms occur as low as 7000hz, and for titanium diaphragms, as low as 4000hz."

The short answer is that about a certain frequency the diaphragm no longer operates in piston mode. This in fact applies to any direct radiator.

TI as a material was introduced following the aluminium for strength and at the time and the diamond surround was introduced to extend the response .

The TI diaphragm were in break up mode in fact at a lower frequency than the aluminium explains why the Be alternative are so much superior with break up mode at 15khertz or higher.

So with then Ti and diamond surround you have a relatively noisy diaphragm compared to Be that has a much higher break up frequency and no requirement for a diamond surround.

The response graphs are of very limited value to expose the true operation of the diaphragm.

Laser imaging and other approaches are far more resolving of the small movements (vibrations across) in the operation of the diaphragm.

In relation to the addition of the 2405 there are a number of variables, the specific driver, the phase plug and horn geometry that ultimately determine the accuracy and extension of the system above 10000 hertz.

JBL has adopted the diffraction of their bi radial horns to not only extend bandwidth, but also polar response at high frequencies. In vintage systems the horns that had neither extension nor a wide enough polar response at high frequencies to be useable.

JBL maintains the UHF driver in the K2 systems was provided to satisfy the marketing department as in those systems it is introduced at over 15,000 hertz.

[Champster]

thank you Ian for such a thoughtful and complete overview. I'm leaning more toward breaking the bank and getting Be diaphragms or maybe just TAD CD's.... Don't they all use Be as their default material?

Has there been any analysis over the breakup issues between 1" and 2" throat CD's?

The reason I ask is that is makes some sense that smaller diaphragms (made from the same material) might compare more favorably in smaller sizes? Obviously there are output reductions to go along with the smaller size, but if minimizing breakup (i.e. cleaner sound) is the issue of this thread, then is smaller better???

Thanks,
Paul

[Robh3606]

Look here for the comparison of different materials used for the diaphragms in a large format driver 4"


http://www.audioheritage.org/vbulletin/showthread.php?30412-Truextent-White-paper-for-Large-Format-Diaphragms&p=305351#post305351

Rob

[Ian Mackenzie]

To be pragmatic it depends on whether you have the competency to deal with the additional complexity of a super tweeter which is not trivial.

Some people use a Tad 2002 a upper HF on a conical horn and cut it over at 4000-6000 from a large format horn like the Living Voice system and then a Tad 703 UFH on a diagonal

Have a look at some of the Radian Be equipped drivers before you leap too far.

I would keep it real simple to start.

Spend money to buy no compromise drivers that allow as simple a set up as possible, aka the two way Iconic principle.

Don't try to over engineer or aim at theoretical perfection on paper.

The intent of the Be material is resolution and neutrality, the simplicity buys you coherent imaging.

Efficiency delivers spatial dynamics.

See how that goes then augment either end of the spectrum as required.

This is the cook book approach to the 66000.

Given the physical scale of the drivers you will find the displacement of the point sources vertically or laterally a serious issue in terms of integration if you start of too complex

[Champster]

Look here for the comparison of different materials used for the diaphragms in a large format driver 4"


http://www.audioheritage.org/vbulletin/showthread.php?30412-Truextent-White-paper-for-Large-Format-Diaphragms&p=305351#post305351

Rob

Thank you Rob for posting that article. They make a good argument that Be is a superior material to the previous materials. However, the ribbed Ti driver does appear to be a worthy competitor from 1khz - 4khz. Which makes me now understand why, as Ian says in the previous post and I've read elsewhere, that some use the 2" CD for 3 octaves (from ~500-800hz to 4khz) and cross over to a 1" CD from 4khz - 20khz and avoid the UHF driver altogether.

I find it interesting that JBL now appears to have chosen Magnesium diaphragms (476Mg CD and 045Be-1 UHF) in the K2 S9900 (http://www.jblsynthesis.com/downloads/products/prod_93_634484024579847476_JBL-K2 speakers_092209.pdf). Mg instead of Be. Could it be that Be is yesterdays news in diaphragm technology? Read Christo's comments here (http://www.audioheritage.org/vbulletin/showthread.php?35621-DIY-2235h-2206h-1446j-and-2405h-Build-Thread/page2) about his side by side comparison of a 4344 (Be TAD CD) and the K2 S9900.

[Mr. Widget]

Thank you Rob for posting that article. They make a good argument that Be is a superior material to the previous materials. However, the ribbed Ti driver does appear to be a worthy competitor from 1khz - 4khz. Which makes me now understand why, as Ian says in the previous post and I've read elsewhere, that some use the 2" CD for 3 octaves (from ~500-800hz to 4khz) and cross over to a 1" CD from 4khz - 20khz and avoid the UHF driver altogether.

I find it interesting that JBL now appears to have chosen Magnesium diaphragms (476Mg CD and 045Be-1 UHF) in the K2 S9900 (http://www.jblsynthesis.com/downloads/products/prod_93_634484024579847476_JBL-K2 speakers_092209.pdf). Mg instead of Be. Could it be that Be is yesterdays news in diaphragm technology? Read Christo's comments here (http://www.audioheritage.org/vbulletin/showthread.php?35621-DIY-2235h-2206h-1446j-and-2405h-Build-Thread/page2) about his side by side comparison of a 4344 (Be TAD CD) and the K2 S9900.Mg is considerably less expensive to manufacture and offers performance that approaches Be. For cost no object performance Be is the material of choice and TAD's vapor deposition technique while less durable than the Be foil used by TruExtent and JBL when over driven, is sonically the best example of Be.


Widget

[Ian Mackenzie]

I think its a marketing positioning thing that they want to keep the current TOL SOA drivers and materials exclusively for the TOL SOA models like the new 67000.

[Mr. Widget]

I think its a marketing positioning thing that they want to keep the current TOL SOA drivers and materials exclusively for the TOL SOA models like the new 67000.I imagine that is part of it, but as an example of the cost of the material, when I toured Materion, the manufacturers of the Be domes for JBL and manufacturers of the TruExtent diaphragms, they recycled the Be material to the gram... with aluminum and magnesium the raw material isn't so dear.


Widget

[Champster]

Mg is considerably less expensive to manufacture and offers performance that approaches Be. For cost no object performance Be is the material of choice and TAD's vapor deposition technique while less durable than the Be foil used by TruExtent and JBL when over driven, is sonically the best example of Be.


Widget

Widget,
Your website is really well done!

Good point on the cost to manufacture. I suppose that has a lot to do with it. Silly question, but does TAD make a diaphragm that fits the JBL CD's or do you just have to buy the whole TAD CD to get there?

Thanks,
Paul

[ivica]

This is an interesting thread, but it strikes me as odd that there seems to be a reluctance to accept Ivica's several posts that adding a 2405 resolves the breakup issues in all of these 'phrams. Especially when a pair of 2405's costs less than 1 Truextent 'phram.

Can someone explain please explain this?

Hi,
I want to emphasis here that I have done measurements with and Be ( truextent) diaphragm, not JBL Be (476) 'dusted' diaphragm. The main differences between that is in the diaphragms suspensions. In JBL Be model it is used Be-"diamond shaped" suspension, while on Be ( truextent) diaphragm a kind of "semi rolled" polymer material is used as a suspension. So may be diaphragm to suspension interaction can produce such driver behavior.

I have done some measurements with 18-sound 2060A (3-inch -VC diaphragm) but over 12-13kHz a kind of "diaphragm shaking" has been visible.

Regards
Ivica

[Champster]

I think its a marketing positioning thing that they want to keep the current TOL SOA drivers and materials exclusively for the TOL SOA models like the new 67000.

Is there a new 67000 being introduced with Mg? I just looked at their webpage (http://www.jblsynthesis.com/downloads/products/prod_233_634927282032470382_JBL Synthesis Everest DD67000 Speaker Info Sheet CES-2013.pdf) and it shows the 67000 with Be diaphragms and the K2 S9900 (http://www.jblsynthesis.com/downloads/products/prod_93_634484024579847476_JBL-K2 speakers_092209.pdf) has conflicting data on its information sheet. One place it says the tweeter is Be another place it says it is Mg.

To further extent your marketing hypothesis Ian, I read somewhere that they Marketing and Engineering Depts argued over adding the tweeter. Marketing wanted it for the Japanese market, and Engineering didn't feel it added anything to the system acoustically and drove the cost to manufacture up. So they compromised and filtered it in above 20khz, which I would argue is above the frequency most of their customers (older folks) that can afford these can even hear.62027

Paul

[Robh3606]

Hello Paul

I have a pair of 476Mg's that I measured on PTH1010 waveguides. Take a look at where they drop off. It's no wonder that they cut in at 20K. Also notice how clean they are up above 10K. The measuerments are 1/12 octave so minimal smoothing. Take a look at the CSD as well. Very clean where other drivers have noticeable break-up issues. Not your farthers large format compression driver to say the least.

Rob:)

[ivica]

Hello Paul

I have a pair of 476Mg's that I measured on PTH1010 waveguides. Take a look at where they drop off. It's no wonder that they cut in at 20K. Also notice how clean they are up above 10K. The measuerments are 1/12 octave so minimal smoothing. Take a look at the CSD as well. Very clean where other drivers have noticeable break-up issues. Not your farthers large format compression driver to say the least.

Rob:)

Hi Rob,

With such measurements, it become clear why 476 drivers are so worthy. It seams that PTH1010 horn perfectly pairs with 476 driver.
Have You tried it with PT-H90 ?

Regards
Ivics

[Champster]

Agreed. Beautiful graphs!!!! Wish I could buy a pair but I suspect the woofer is equally advanced with its dual spiders mechanism....

[Robh3606]

Hello Ivica

Never tried them. Going way back I used to use 2344's with aquaplased 2426's. When the 2435 showed up on Ebay I grabbed a couple of pairs purchased the ferro recharge packs and had 4313B aguaplas them for me. I looked at what was available with a 1.5" throat and decided on PTH1010's. They were a drop in replacement for the 2344's in both radiation pattern and size.

The 2344's worked really well in my room and as expected so did the PTH1010's. I have a tendency to stick what I think works and just take time to get it dialed in. I don't jump around all that much. My active main HT speakers have not changed in years and are not likely to as they are my original reference system. That's where my original pair of PT's reside. I purchased a second set for a latter project that got broken down taking out a pair of aquaplased 2435's to go into my Arrays. Fortunately I decided to keep the second set of PT's for a rainy day.

The closest thing I have are the Array horns which the 2435/435Be's do really well on. I would expect the 476's to work there as well. Maybe some of the other guys can post some measurements. I know 4313B did some measurements on that waveguide with 476Be and they were impressive to say the least. Might be in the DIY 1200 Array thread.

Rob:)

[ivica]

Hello Ivica

Never tried them. .............
I would expect the 476's to work there as well. Maybe some of the other guys can post some measurements. I know 4313B did some measurements on that waveguide with 476Be and they were impressive to say the least. Might be in the DIY 1200 Array thread.

Rob:)

Hi Rob,

I have seen 4313B picture of 476 & PTH90 horn,

http://www.audioheritage.org/vbulletin/showthread.php?33151-DIY-1200-Array&p=344169&viewfull=1#post344169

but never seen any measurements. May be on some other post (if any)?
May be long throat of the PT-H90 horn would not allow High-frequency dispersion of the 476 driver, but on the other side a kind of
"soft dispersion slot shape horn throat" would improve horn dispersion.



Reagrds
Ivica