Truextent Beryllium replacement diaphragms

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more10

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Joined 2011
Only 5208C and 5210 can be fitted with Truextent diaphragms. All other have 3 inch voice coil. But, the 450PB is not their best one inch driver. However, all their one inch drivers have the same mounting, so it should be possible to mount a 465PB or a 475PB on these coaxes.
 
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Dave Zan

Member
Joined 2010
LineSource said:
The Altec forum measurements(fig 1) match data from several other sources. Aluminum and Titanium diaphragms have break-up modes between 10KHz and 15KHz, but beryllium does not typically break-up until above 18Khz, and usually only above 20Khz. This SPL data shows the more extensive break-up of titanium over aluminum diaphragms.

The general viewpoint on the Altec forum is that a beryllium diaphragm has little value with a 2" exit compression driver because the 4" mechanical diaphragm plus phase plug frequency limit is below 10Khz, especially when distortion is also considered. Aluminum diaphragms typically do not start break-up until above 10Khz.

The general viewpoint on the Altec forum is that the $400+ expense of a Be diaphragm is probably only justified for a 1.4"-1.5" CD to remove Al/Ti 10K-15Khz break-up distortion, or marginally valuable for a 1" CD to avoid break-up distortion until over 20Khz(example: TAD 2001). High frequency boost compensation can now extend a flat response to near 20KHz.
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Do you mean Lansing Heritage forum? Best to credit the author properly so the correct person can take responsibility for any errors.;)
The notes appear to be incorrect. The 2450SL is not aluminium, it's Ti. So the subsequent discussion based on this chart's results about Al versus Ti. is pointless if so.
I do think that you are correct that the 1.5" exit CDs are the way to do it. Better in several ways despite the sentimental attachment to "classic" 2".

Best wishes
David
 
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JoshK

Member
Joined 2004
more10 said:
I sent a message to Materion using their web form , asking for information on Truextent for Radian and Altec drivers with 1,75 inch voice coils.

I got an answer within 24 hours. They will release a diaphragm with 1,75 inch voice coil for Radian drivers in january 2013. I really hope this is not confidential :).
Click to expand...

Hey, that is pretty cool news. I've been very interested to see what a Be diaphragm would do for a 1" CD.
 
Legis

Legis

Member
Joined 2009
I finally got my pair of JBL 2446Js, these things are quite huge:yes:. I will be playing them for awhile with the original phrams, but at some point Truextent is the natural course of action. I bet they will sound wonderfull in a right horn, they sound quite good even without a horn.

2446J and 8"

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An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.
 
pos

pos

Member
Joined 2008
rephase.org/
Another measurement for those interested, comparing a 2452H (ribbed titane) and a 2450SL+Truextent, both on the same PT-F95HF waveguide.

3rd distortion is plotted, and is lower that the titanium diaphragm as you can see.
A small distortion peak can be seen just above 7kHz. As it is 3rd distortion it does happen just above 21kHz, which corresponds to the big response peak (breakup mode). That 21kHz breakup also clutters the impulse response (ringing), but is of course rather benign at this high a frequency. EQ would get rid of the response peak, but not of the 3rd distortion peak (but who can hear that sort of thing anyway). Reticulated foam on the other hand would probably take care of both, so it would be interesting to try...
 

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Dave Zan

Member
Joined 2010
Legis said:
I finally got my pair of JBL 2446Js, these things are quite huge:yes:. [/IMG]
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May I ask what you paid for them?

pos said:
Another measurement for those interested, comparing a 2452H (ribbed titane) and a 2450SL+Truextent, both on the same PT-F95HF waveguide.
Click to expand...

Thanks for the data, several surprises.
I am surprised that breakup seems to occur at the same frequency for the Ti and the Be. Very different stiffness to mass ratio so this seems unlikely. Could this be a measurement anomaly? due to a resonance in the microphone perhaps. Or a real anomaly but due to a resonance elsewhere in the driver, maybe a cavity mode?
The lower distortion is also a bit of a surprise. I expected similar pistonic response in the lower frequencies. Perhaps the polymer suspension really is as superior as TrueExtent claims. Very nice for you anyway.

Best wishes
David
 
pos

pos

Member
Joined 2008
rephase.org/
Dave Zan said:
I am surprised that breakup seems to occur at the same frequency for the Ti and the Be.
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Not sure what you are referring to here.
The Ti ribbed diaphragm has two main breakup modes that show on the frequency response and CSD around 12khz and around 17khz.
The Truextent has its main breakup at 21khz.

The lower distortion is also a bit of a surprise. I expected similar pistonic response in the lower frequencies.
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At it is 3rd harmonic distortion it happens at 3 times the frequency it is reported at, so it looks like it is due to breakups (more spread with the Ti diaphragm, both because of the ribs and the diamond surround I think).
 
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Dave Zan

Member
Joined 2010
pos said:
Not sure what you are referring to here.
....
The Truextent has its main breakup at 21khz.
Click to expand...

There is also a substantial spike in the Ti. curve at the same frequency and the associated spikes in the 3rd harmonic distortion at 7 kHz. Seems a bit of a coincidence. You mention a CSD so perhaps it is clearer on that.

At it is 3rd harmonic distortion it happens at 3 times the frequency it is reported at
Click to expand...

Yes of course, but there is a substantial difference even below 4Khz where neither the Ti or Be have breakup modes below 12 Khz.

Best wishes
David
 
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pos

pos

Member
Joined 2008
rephase.org/
Dave Zan said:
There is also a substantial spike in the Ti. curve at the same frequency and the associated spikes in the 3rd harmonic distortion at 7 kHz. Seems a bit of a coincidence. You mention a CSD so perhaps it is clearer on that.
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Yes I think it is a coincidence, and the peaks are not exactly at the same frequency.
On the CSD you clearly see two ringing traces at 12 and 17khz for the Ti ribbed idaphragm.

Yes of course, but there is a substantial difference even below 4Khz where neither the Ti or Be have breakup modes below 12 Khz.
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They both have breakups bellow those that we clearly see on the frequency reponse.

This is particularly true for the Ti ribbed diaphgram: the entier >5khz range is cluttered with small partially controlled breakups, due to both the ribs (that give a boost in this range compared to a normal Ti diaphragm) and the diamond surrounds (that allow some extention in the UHF). It seems to show in the distortion measurement also...

In comparison the Truextent Be is much smoother in this range, and does not attempt to control the dome breakups that occure above 15khz. And neother does it rely on parasitic resonances of the surrounds to extend its reponse up high. And it shows, as it drops quite a bit in the UHF (despite the higher mass breakpoint), but nothing that a good EQ cannot compensate...

It is similar to the TAD TD4001 vs TD4003 comparison.
 
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