Radian 951Be vs 18sound ND4015BE

[Iamimpossible]

Thanks Pierre, Arez, Walter

I did reach out to 18sound in regard to ND3be and they said all their be diaphragms are polymer surround just the ND3be is slitly higher percentage although all are over 90%.

 

[Arez]

Both the TD-4001 &4003 spec sheets list the same magnetic flux density of 20,000G, yet the SPL of the TD-4003 is rated 2 dB higher at 112dB

Yes, a completely different motor structure, with Neo magnets. You will see that the TD-4001, 2001, 2002 all have a more tradiitional Alnico magnet structure, like older JBL's. With the huge Alnico ring magnet, and all the structure infront of the diaphragm, necessitating the longer internal throats. Whereas the 4003, has a shorter throat, with a deeper back chamber, while the driver is about equal length.
The diaphragm was redesigned, the surround was changed, the DP-40003 has the "banana connectors" that plugs into the diaphragm assembly directly, just like the TD-2002 does. A lighter weight diaphragm helps raise efficiency. Never saw a number on the DP-4003.

The DP-4001 is just under 1 gram.
The documents attached gives some data and insight into the mfg. process and material properties.

The strongest magnet is in the Neo TD-4002:

Sound Pressure Level 110 dB/W (1m)
Total Magnetic Flux 246.000 Mx
Magnetic Flux Density 21.500 G

A 4" Be foil diaphragm from Materion are "substantially" heavier.
JBL 476 4" is listed with 2,1 grams mms.
The Be foil is a thicker, heavier and more ductile material (Why they do not shatter, like the stiffer and thinner TAD's). Which also gives the more damped top end response from the foil diaphragms.

From these which use polymer surround diaphragm?

I forgot to add them but the Radian 1245-8/16 Be diaphragms, will also fit the following 1,5" and 2" drivers.

DAS ND10, DAS ND8, DAS K10, and DAS K8.

Have you heard or seen comparisons of the newer 4003 design used on comparable horns to the older TAD designs?

Not really i'd say. The TH-4003 is 39mm exit, finless, 70x30 Apaxial, and with a resonance absorber in the horn.
The phase plug is different and so is the throat and exit angles as shown below. So even with the different exit diameters it would require a custom throat adapter to use a comparable horn, which would give a mismatch in the throat.
The diaphragm, phase plug, motor sturcture etc. are all improved in the 4003, along with the 39mm exit for better HF dispersion. It does not have the beryllium half surround resonance of the DP-4001 that keeps it 'flat to 18k. So the driver is better behaved in the top octave, with lower distortion. Although it is still a 4" diaphragm, but the nastyness in the top octave is fairly well damped.
It is a improvement in just about every area, provided you can live with the TH-40003 or get made custom horns/waveguides that fits the driver and it's throat.

I think the TD-4001 is better compared with the 2" drivers like: JBL 2450H, 2440/41, Sony SUP, GT sound GSU, DAS ND/K8 etc.
The 2450H with a Truextent diaphragm performs decently as shown.

I guess a 4002 used without the adapter, could be tried on the TH-4003, but there will still be a throat mismatch.
The TH-4002 was not for sale normally i believe, and the TSC cinema horns for the 4002 is hard to find.
As shown below:


Throat angle [deg]
Equiv. Fc (Exp) [Hz]
Equiv. Fc (Hypex T=0.7) [Hz]
Equiv. Fc (Hypex T=0.6) [Hz]

TAD TD-4001, TD-4002.
49.2 mm.
10
217
290
320

TAD TD-4003.
39 mm.
8.5
225
300
340


JBL 2450 H/J.
49.2 mm.
10
217
290
320


https://josephcrowe.com/blogs/news/tad-td-4003-on-es-450-biradial-no-2184


https://zero-distortion.org/tad-4003-dual-woofer-flh-leifs-system-norway/

Audioheritage.org has several threads, concerning the subject Wiget's system fx.

https://forums.melaudia.net/showthread.php?tid=11748&page=10

 

[Iamimpossible]

Thanks Arez this is really informative.

I often see tad drivers that have or need replacement diaphragms (commonly radian). Is it because they are more fragile do to less mass?

 

[Arez]

I often see tad drivers that have or need replacement diaphragms (commonly radian).

Yes that is not uncommon to see, the prices of replacements are rather high, those that are even available.
And yes Radian 1292 alu diaphragms for the 4001/4002.

Is it because they are more fragile do to less mass?

The material is much stiffer, and thinner. The material itself is not as ductile, so it shatters instead of deforming.

Same principle that applies to a knife, you heat treat the edge to the desired hardness. The harder it is the more easily it chips the edge (or shatter). Instead of the edge bending, and 'rolling the edge over" when being abused.
Beryllium is a metal like most metals it behaves similarly.

https://www.twi-global.com/technica...enite-martensite-bainite-pearlite-and-ferrite

https://www.sciencedirect.com/science/article/abs/pii/0022508864901237


So yes they are more fragile, it has to do with the thickness and manufacturing process, heat treatment and how that affects the material etc. Tad uses a vapour deposition method, it is explained in the attached document in previous post, with pictures of different grain structures.
Same as with other Japanese Beryllium diaphragms, like Yamaha, Goto, Linear Technology (modified TAD's), ALE, etc.
The material is sourced through NGK Berylco, which has a Japanese department. So not Materion/ Brush Welleman, unlike most other manufacturers.

 

[Iamimpossible]

Yes thank you.

What I was asking is, would the truextent equivalent be more robust as it's thicker?

 

[jawen]

Ye

I really appreciate your great knowledge of all different hifi-things Arez.
Appreciated from Sweden !

/John

 

[Arez]

What I was asking is, would the truextent equivalent be more robust as it's thicker?

Yes they are more robust by default, more because the material is more ductile /softer so it does not break/shatter easily.
Sorry if i was not clear enough. Also the thickness matters ofc.
The polymer surrounds will also not shatter or fracture from fatigue like a Be surround can.

What kills a TAD diaphragm is a ruptured surround, or being overdriven to the extent that the diaphragm hits the phase plug and shatters.
They are not made to be abused, which should also be indicated by they're power ratings.

They are also used in large part by people who try to run them as low as possible in frequency, preferrably with 1st order xos, or even without protection caps etc.
Those things does not help when the diaphragms are relatively 'fragile to begin with.

It should also be evident by the intended use a TAD 400x was not designed specifically for maximum output, maximum power handling and light weight, which is PA manufacturers priorities in general.
Modern PA drivers 18S etc. also have a much higher power handling, heavier voice coil, more cooling area, looser tolerances, materials especially selected for heat resistance, etc. to keep thermal limits much higher.
And a Foil diaphragm tends to deform instead of shattering, due to it's much higher ductility, so it does not fail in a spectacular way usually.