How much impact does driver material actually make?

[tuga]

But shouldn’t measurable differences correlate to audible ones if the change of material is at all meaningful? I do want to hear the difference in a more exotic driver, not just measure it.

Please do not conclude that I don’t think measurements are meaningful, it’s just that they have to be in service of better sound.

Would you not agree that (all things being equal) a better measuremed performance will result in a more accurate transduction of the signal, regardless of whether there's an audible improvement? Is that not a worthy goal?
And there's a possibility that the improvement might not be audible to many listeners but only to some.

 

[fpitas]

It is possible with stiff cones to make the drivers operate like a piston, ie without resonating, also known as cone breakup, in their passband. Paper and fabric will have cone breakup in the operating range but have more internal damping than metals and can also be doped with a damping layer to make the resonance lower amplitude.
Cone breakup in metals are very narrow band but high amplitude so it is important the rossover has high attenuation by then.
So, in principle the high stiffness materials should be capable of superior performance but are more difficult to exploit well.

Exactly. My SEAS W18s act almost purely pistonic to a kHz or two, but have a horrendous resonance at 5kHz. I cross them at 800Hz LR4 to get that peak down.

 

[fineMen]

But shouldn’t measurable differences correlate to audible ones if the change of material is at all meaningful? I do want to hear the difference in a more exotic driver, not just measure it.

I left out my rant about exotic drivers. As we might have learned already, the difference they make is just shifting sonic signature to something else. If there is one at all. We are all susceptible to prejudice.

What I have found - admittedly by listening examination, is the relevance of intermodulation distortion. Purify as the speaker manufacturer they try to become, acknowledge its importance. But once the IM is found to be relevant, Klippel strongly supports that, this criterion is objectively accessible.

For instance Purify optimizes the shape (not material!) of the surround as to mitigate IM, while the motor is a presumably most sophisticated one, but the cone's foundation is just ordinary paper. We enjoy tweeters with unprecedented performance due to wider surrounds; fabric-made to begin with.

Not the least, we as hobbyists, what do we know especially if we don't use the full spectrum of objective data?

 

[fpitas]

There's a psychological aspect of designing with expensive drivers, in that you feel driven to produce something exceptional sounding.

 

[Killingbeans]

As we might have learned already, the difference they make is just shifting sonic signature to something else. If there is one at all.

The way I see it any cone material will sound the exactly same as long as it's working in it's purely pistonic range and has the same geometry. An audible difference can only come from the breakup modes of the materials paired with its damping characteristics.

You can choose a "soft" material with good inherent damping, or you can go all in on stiffness and try to push the breakup modes as close to the utrasonic band as you can.

IMO, that whole idea of trying to fix everything with "moar stiffness!" seems a little dumb.

I'd rather like to see a lot more R&D put into Balanced Mode Radiators. Geometry has way more potential for innovation than the materials themselves.

 

[MattHooper]

Not being a speaker designer, so not being able to compare different drivers in an "apples vs apples" comparison, I don't know the answer to the question of the thread.

But just anecdotally related: I just received my Joseph Audio Perspective speakers back from being upgraded to the newer Perspective 2 graphene version.

I owned the original (from around 2012) version of the floor standing Perspective speakers. The upgrade involved changing out the older SEAS midrange/woofer drivers and putting in the updated SEAS drivers with the graphene coating:

SEAS Announces New Excel Graphene Woofer Series

With a very discreet announcement on their own website, SEAS Fabrikker has stepped ahead of many other major loudspeaker manufacturers with the commercial introduction of a graphene-coated 5-inch woofer. And the new W16NX003 model also signals the launch of a completely new series of Excel...

audioxpress.com

Apparently the graphene coating itself has as much to do with fighting corrosion as it does adding damping. (And so when Joseph calls their speaker the "graphene" version I think it's more of a catchy name). But as I understand it SEAS updated the motor system and other items for the driver. Joseph Audio
re-did their crossover to accommodate the new drivers in their updated version.

So...can I tell the difference between the old drivers and the newer drivers/new crossover? Well, I've had my Thiel speakers in my system for quite a while (experimenting with various things) so it's been a while since I was listening to my Joseph speakers. And I didn't even pop the Josephs in my system for a listen again before sending them off for the upgrade. Everyone who has heard the new Perspective vs the original have said the same thing: stronger, tighter bass, slightly clearer midrange, essentially the same highs. (Jeff Joseph has said once he tried the new SEAS drivers the most obvious difference was in the quality of bass).

Anyway, whatever differences aside, wow these must be excellent drivers. The sound just had me gobsmacked tonight. The clarity, detail and smoothness was out of this world. Especially the incredible rendering of fine timbral details in instruments. I was listening the Herbie Hancock's score for DeathWish, which at many points is a wacky flow of jutting instruments popping in and out of the score - tons of different types of percussion, wood blocks, shakers, bells, reed instruments/horns darting in and out. The exact timbral charcter of every instrument was so convincing and distinct and popping in to the space with a great sense of "surprisingness" in clarity and aliveness.

As good as my Thiels are, with their proprietary drivers, they don't quite reach the sheer clarity and sophistication I'm hearing from the Joseph speakers.

 

[valerianf]

"As good as my Thiels are, with their proprietary drivers, they don't quite reach the sheer clarity and sophistication I'm hearing from the Joseph speakers."
It could also be the result of the "infinity slope" crossover designed by Joseph speaker.

 

[Chromatischism]

"As good as my Thiels are, with their proprietary drivers, they don't quite reach the sheer clarity and sophistication I'm hearing from the Joseph speakers."
It could also be the result of the "infinity slope" crossover designed by Joseph speaker.

Way too many variables. First thing to check is: is the frequency response the same?

 

[tuga]

The way I see it any cone material will sound the exactly same as long as it's working in it's purely pistonic range and has the same geometry. An audible difference can only come from the breakup modes of the materials paired with its damping characteristics.

But if the weight of the cone is different due to a different material then the motor and surround will also be different so you're now changing three variables.
Impossible to compare cone 'signaures' in my view unless nothing else changes but the cone itself...

 

[anphex]

I kind of like Textreme in this case, at least for Tweeters. It's price/value ratio is stellar and they give Beryllium and Titanium a run for the money.
Increbibly high end extension, great directivity and super low res frequency.
If I'd ever build a speaker, it would probably this bad boy.

https://doc.soundimports.nl/pdf/brands/SB%20Acoustics/TW29TXN-B-8/SATORI-TW29TXN-B-8.pdf

 

[Frank Dernie]

I kind of like Textreme in this case, at least for Tweeters. It's price/value ratio is stellar and they give Beryllium and Titanium a run for the money.

This isn't a personal attack just adding some engineering facts to burst the bubble of some marketing implications I have seen about materials in speaker cone/domes.

I hadn't heard of Textreme, so I looked it up.

It is a trade name of one of the carbon fibre vendors.

The actual performance of any carbon fibre part is every bit as much dependant on weave, fibre orientation and resin content as it is on the fibre mechanical properties themselves.
It is often just the fibre properties which are quoted when talking about carbon fibre and the actual performance of a complete woven component will actually be nowhere near that because of non homogeneous structure, non straight fibres due to weaving and the resin mass. Using unidirectional fibres gets rid of the non-straight fibre problem but is much harder to lay up into 3D curves like a speaker driver.

I would think a tweeter would actually be the driver least suited to having good performance if made from carbon fibre, it could be good but very expensive for mid and bass drivers if properly designed and excecuted.

Carbon fibre is a brilliant material, I have been using it in Formula 1 car parts since 1977 but the name is used nowadays almost as an implication of magic properties it doesn't have and it has even become fashionable in shiny resin rich panels for embelishment - which is a dreadful waste of a good engineering material IMHO.

Next, it is incorrect imply any equivalence between Titanium and Berillium.
Titanium has about the same specific stiffness as aluminium and magnesium (and steel fwiw) so a titanium part the same weight as an aluminium part will not be any stiffer, less so probably because the Ti part will have to be thinner since it is denser than either.
Berillium OTOH has a much higher specific stiffness than these other metals so a piece the same weight will be stiffer or a piece the same stiffness will be lighter. Take your pick.

From its mechanical properties I actually would expect titanium to have the worst breakup characteristics of any metal being used for tweeters.

The only other material with competitive mechanical properties to Berillium is Boron and realistically no Boron manufacturing process could make a speaker driver moving part, fibres are about it - hence its use in cartridge cantilevers.

 

[anphex]

Thank you for the insight! But looking at this specific Satori tweeter the specs look pretty similar for Berilium, so I wasn't being hyped for carbon fiber but for this specific implementation. Weird is, I've seen the Texttreme woofers of SB Acoustics and the performy kind of weird, that's why I always thought it is a high frequency material if tuned correctly due to the weave method.

Look at the wavyness in the mid range here: https://doc.soundimports.nl/pdf/brands/SB Acoustics/SATORI MW16TX-8/SATORI_MW16TX-8.pdf

 

[Frank Dernie]

Thank you for the insight! But looking at this specific Satori tweeter the specs look pretty similar for Berilium, so I wasn't being hyped for carbon fiber but for this specific implementation. Weird is, I've seen the Texttreme woofers of SB Acoustics and the performy kind of weird, that's why I always thought it is a high frequency material if tuned correctly due to the weave method.

Look at the wavyness in the mid range here: https://doc.soundimports.nl/pdf/brands/SB Acoustics/SATORI MW16TX-8/SATORI_MW16TX-8.pdf

I am just pointing out the difference in the basic material properties.
The overall function of the driver depends on the detail design too, for one example damping from the surround, as well as the material used.
Often very expensive materials are used where not needed for function.

 

[fineMen]

From its mechanical properties I actually would expect titanium to have the worst breakup characteristics of any metal being used for tweeters.

I won't participate in the esoteric part of this conversation. Just a question: wasn't titanium introduced by JBL to overcome the problems with their mid/treble compression drivers' surround? The diaphragm was one piece embossed from a single sheet of aluminium, but the incorporated surround broke regularly after a certain period of use. Maybe it became brittle, changing its crystal structure with extended use. Later JBL used the titanium for commercial tweeters also. The compression drivers' domes got later a 'diamond' structure, and as a third step were changed back to plain but with some coating.

An aftermarket supplier, Radian namely, offered an alternative with aluminium for the dome, and polyamid or so for the surround. It was by all means the better solution--had all four versions in my speakers.

 

[Frank Dernie]

I won't participate in the esoteric part of this conversation. Just a question: wasn't titanium introduced by JBL to overcome the problems with their mid/treble compression drivers' surround? The diaphragm was one piece embossed from a single sheet of aluminium, but the incorporated surround broke regularly after a certain period of use. Maybe it became brittle, changing its crystal structure with extended use. Later JBL used the titanium for commercial tweeters also. The compression drivers' domes got later a 'diamond' structure, and as a third step were changed back to plain but with some coating.

An aftermarket supplier, Radian namely, offered an alternative with aluminium for the dome, and polyamid or so for the surround. It was by all means the better solution--had all four versions in my speakers.

No idea why JBL changed anything, they are not a brand we have ever had adequate availability of here, so I have not paid them any attention.

As I wrote, I am just talking about basic material properties, actual engineering use cases should drive the material choices, not fashionable materials for marketing, and mechanical failure of a material in an integrated design would indeed be a normal way to reject a material for that use case.

 

[HarmonicTHD]

I won't participate in the esoteric part of this conversation. Just a question: wasn't titanium introduced by JBL to overcome the problems with their mid/treble compression drivers' surround? The diaphragm was one piece embossed from a single sheet of aluminium, but the incorporated surround broke regularly after a certain period of use. Maybe it became brittle, changing its crystal structure with extended use. Later JBL used the titanium for commercial tweeters also. The compression drivers' domes got later a 'diamond' structure, and as a third step were changed back to plain but with some coating.

An aftermarket supplier, Radian namely, offered an alternative with aluminium for the dome, and polyamid or so for the surround. It was by all means the better solution--had all four versions in my speakers.

There is nothing esoteric about specific material properties eg specific stiffness (eg GPa x m3 / kg) etc. Undergrad ME students learn about it in their first semesters.

The material itself is seldom the silver bullet which solves all problems as marketing wants us to believe so they can differentiate their product in a market of increased commoditization. As many manufacturers showed (speakers, amps), it is the engineering which counts to integrate the components to a well performing end product. The sole focus on components (speaker materials, DAC chips, GA transistors) is not leading automatically to a better performing product. @fpitas gave a perfect example (few posts up) of a good engineering decision.

 

[Frank Dernie]

eg specific stiffness

Actually this example is the one which is fairly esoteric!
Most engineering metals have the almost identical specific stiffnesses so Berillium (and Boron) which do not are esoteric

Non-metals are all over the place, particularly composites

 

[HarmonicTHD]

Actually this example is the one which is fairly esoteric!
Most engineering metals have the almost identical specific stiffnesses so Berillium (and Boron) which do not are esoteric

Non-metals are all over the place, particularly composites

Correct.

I perceived that the OP meant the concept of specific stiffness is esoteric, which it is not among MEs.

Personally I would not describe Advanced Fiber Composites as esoteric either, because their behavior is well understood as you probably know better than anyone else ;-) (I did my PhD way back then, collaborating with Boeing and Northrop Grumman investigating composites, but then switched fields, so I am certainly not up to date).

Boron yeah maybe esoteric especially in the context of speakers.

But I think we don’t need a definition of esoteric either to have a meaningful conversations among engineers we just refer to the materials in question directly. What do you think?

 

[djw.cloud]

Why wouldn't the material make a difference?

When we see smooth FR charts, they're smooth because we have digitally applied smoothing. In reality, there are thousands of peaks/dips that I imagine are a function of the driver itself, including the diaphragm material (i.e not a function of the room). For instance, take a simple swept sine wave starting at 500H (TOP), with 1/12-octave smoothing. This is what we're used to analyzing:
View attachment 91236

But in reality, this is what the actual swept sine wave FR "curve" looks like (same as above, but without smoothing):
View attachment 91235

Or perhaps someone is aware of evidence that the unsmoothed response doesn't matter?

It amazing that half this forum will attach themselves to smooth graphs, and declare that as scientific truth.

 

[Frank Dernie]

Correct.

I perceived that the OP meant the concept of specific stiffness is esoteric, which it is not among MEs.

Personally I would not describe Advanced Fiber Composites as esoteric either, because their behavior is well understood as you probably know better than anyone else ;-) (I did my PhD way back then, collaborating with Boeing and Northrop Grumman investigating composites, but then switched fields, so I am certainly not up to date).

Boron yeah maybe esoteric especially in the context of speakers.

But I think we don’t need a definition of esoteric either to have a meaningful conversations among engineers we just refer to the materials in question directly. What do you think?

No I was being cheeky, your original point is spot on.
Material choice - or component choice - is simply part of the overall engineering decision making process in producing an effective overall product.
Getting hung up on material or component type is a mistake and a distraction and is mainly used by marketing people to try to distinguish their product from others and sell as a "must have".
It is bollox, good engineering is about fulfilling the requirement and being reliable at a sensible cost, over-engineering is pointless too IMO.