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How much impact does driver material actually make?

Frank Dernie

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A fallacy introduced by BBC research in the late 1960s ignoring off axis radiation and intermodulation urging for cost savings and not the least for innovation as such as to justify the expenses ... .



... but if one uses membranes of 5mm diameter ... ;)
A 5mm diaphragm would make the breakup problem easier to deal with but power handling and loudness less so :)
 

fineMen

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There are small-ish 3 ways, mind you most of my speakers are indeed fairly large 3-ways.
In order to activate a book shelf sound-wise I designed a 3-way of just 9 liters internal volume, sealed bass alignment, using:

- 7inch bass up to 350Hz, e/q to f-3 60Hz/0,5 plus room gain
- 3inch mid up to 2,2kHz
- 1inch tweeter

The whole was linear down to 33Hz in-room without any complaints regarding available spl with even highly demanding music (e/g The Residents).
THD was kept below 0,3% / 0,1% H2 and H3 respectively @86dB. The midrange intermodulation was turned down by 40dB as verified with an alternative setup using the 7 and 1 inch drivers alone.

This may read as some what-about-ism. But once the quality of cones in regard to break-up is problematized, the alternative should be of interest.
 

tuga

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It is actually not difficult to understand why different cone/dome materials may sound different as long as you do not use static thinking to try to understand dynamic behaviour.
There are other things radiating sound too, like the surround, in ways not exactly the same as the excitation signal sent to the driver, anyway.

There is an excitation signal sent to the speaker which causes the driver to move, ideally in an exact motion copy of the electrical input.
At low frequencies the accuracy of driver movement is more dependant on linearity of the magnetic and electrical circuit and the linearity of the suspension (surround and spider) once the displacement is small enough for these to be working in a reasonably linear part of their range the cone/dome will follow the signal accurately up to the point where structural resonances in it start producing inaccuracies. This is the point where the cone/dome material must be influencing the sound it is no longer a question of whether it is or not but by how much.

There are two principle ways of dealing with this inevitable product of physics, one is to damp the resonant peaks to an "acceptable" level, the other is to only use the driver in its non-resonant range then cross it over to a smaller driver with its first resonance at a higher frequency.

In the frequency range before any resonance I can't think of any reason why one cone material could sound any different to any other, maybe somebody else can?

Once in a frequency range where resonant effects are influencing output I can't think of any reason one cone material would sound the same as another, it is pretty well not credible.

So what effects the resonances and their amplitude? Cone/dome shape and the mass, material stiffness and internal (and external if applied) damping.

For most of my lifetime there have been no practical and affordable materials with mechanical properties allowing operation with entirely resonance free radiation.

There are other interesting effects, one is to use the fact that thigs resonate by cleverly exciting a lot of the higher modes so there are far more but much smaller peaks. NXT and BMR drivers exploit this.

I suspect things like ribbon, AMT and Lineaum tweeters actually radiate in ways nothing like the "static thinking" explanations we have all seen!

As an aside, I have often seen it mentioned that objects in different materials sound different when struck as an explanation of why they would sound different in speaker drivers but, of course, when you strike an object it resonates and that is the frequency region loudspeaker material choice is trying to avoid, so is a false argument as long as used below any resonance, but true in the resonant radiation range, depending on damping.
One thing that might be worth exploring is a test of levels of IMD of different cone materials operating over the same bandwidth and see if some types are better with a narrow passband whilst others work well when reproducing a wide range.
 

tuga

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A fallacy introduced by BBC research in the late 1960s ignoring off axis radiation and intermodulation urging for cost savings and not the least for innovation as such as to justify the expenses ...

They were doing Directivy Index graphs in 1958... I think that you might be wrong on that one.
 

tuga

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But the relevance wasn't understood.
I have several of their published notes so I’ll have a look.

But directivity is not particularly relevant when listening nearfield in a treated room.
 

fineMen

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I have several of their published notes so I’ll have a look.

But directivity is not particularly relevant when listening nearfield in a treated room.
And finally it would be entirely irrelevant in a vacuum ;)

To link the studio work to the conditions found at people's homes is a major but more contemporary achievement. Back in the day only few could afford a full fleshed stereo system. That made 'stereo' an iconic status symbol like the smart phone is today. We know about the hilarious exaggerations that came with it. Of the few only a minority would accept room treatment and so forth. Despite the fact that if room acoustics wasn't considered tightly the playback wasn't that true to the source--with said speakers. Again, it was about bass and well maintained vinyl with not too much klicks and pops ...

By the argumentation already given I personally suspect that a discussion of cone material is obsolete. The overwhelmingly more promissing alternative is to depart from the mantra of the late 1960s and come back to 3-, even 4-way designs regardless the size. E/g the previously described 3-way mini outperforms a Purify loaded 2-way for a 10th o the cost.
 

Hayabusa

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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?

Here is my unsmoothed response of the tweeter section of a electrostatic speaker, at least a little bit less wild :)
 

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Hayabusa

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fineMen

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the matching distortion and estimated noise levels
I was asking if the nasty thousends of peaks 'n dips would possibly originate in the noise of the measuring set-up. Environment, microphone, amplification ... a rhetorical question of course ...

What could I do to debunk the myths about the 'material' question that was raised by the advertizing, addressing just and only uneducated still undecided customers? An informed customer would know about the contribution of the no-stiffness surround/suspension, the workings of a cross-over, ... noise in measurements ;-) ... and what the desired final outcome of all the effort is. Your pleasure, not idealistic perfection.
 

Hayabusa

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I was asking if the nasty thousends of peaks 'n dips would possibly originate in the noise of the measuring set-up. Environment, microphone, amplification ... a rhetorical question of course ...

What could I do to debunk the myths about the 'material' question that was raised by the advertizing, addressing just and only uneducated still undecided customers? An informed customer would know about the contribution of the no-stiffness surround/suspension, the workings of a cross-over, ... noise in measurements ;-) ... and what the desired final outcome of all the effort is. Your pleasure, not idealistic perfection.
The nasty peaks and dips are just a summation of thousends of 'point' sources putting their energy in one point: the microphone membrame.
 

fpitas

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I was asking if the nasty thousends of peaks 'n dips would possibly originate in the noise of the measuring set-up. Environment, microphone, amplification ... a rhetorical question of course ...
Not in my setup, at least. I reduced the effect from my horn drivers very substantially by using a series resistor. Same measuring setup in both cases.
 

fineMen

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The nasty peaks and dips are just a summation of thousends of 'point' sources putting their energy in one point: the microphone membrame.
Not in my setup, at least. I reduced the effect from my horn drivers very substantially by using a series resistor. Same measuring setup in both cases.
Nice contradiction ;-)

I was thinking of the discrete (as opposed to regular algebra) mathematics. Do you understand it in the details? What is left once the the marketing blurb from the manufacturers is dismissed? Do we have any information?
 

Ra1zel

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The only other material with competitive mechanical properties to Berillium is Boron
What about diamond? Seems quite optimal for tweeters considering nothing has higher specific stiffness

Either way foccusing on dome/cone materials is probably not very productive at this point. I like things like for example Bliesma with their very thin surrounds (look at SB tweeter then Bliesma) and other innovation like that (purifi constant area surround)
 

dped90

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Much of my source material (uncompressed CD track rips; no SACDs or vinyl), are 60s pop, r&b and soundtracks, which were often victims of excessively applied compression. And some tracks during multi-vocal passages and when orchestrations get busy sound “congested”; possibly due to poor miking/baffling (??). So, while not outright crappy (??), much of my music was certainly less than pristinely recorded and/or mastered, even though almost all were issued by major labels.

Therefore, how enjoyable or "listenable" would beryllium drivers, especially like https://josephcrowe.com/blogs/news/...river-test-review?_pos=3&_sid=e989429b4&_ss=r make much of my recordings?

Ditto this beryllium https://www.usspeaker.com/radian 745neoBepb-1.htm , though which doubtless Pierre had perfectly EQed? See posts #15,266, 15,276. https://www.diyaudio.com/community/threads/beyond-the-ariel.100392/page-764

Might you instead recommend the "neutral" sounding Yamahas JA6681B aluminum, with beryllium support "fingers".


Or the perhaps more likely the "warm" sounding B&C DMC50 paper cone?
https://www.diyaudio.com/community/threads/critical-midhorn-build.172704/page-5
https://forum.audiogon.com/discussions/horns-and-2in-drivers/post?postid=1779050#1779050

And @ 17:29 to 25:01here?
 

Chris Brunhaver

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Much of my source material (uncompressed CD track rips; no SACDs or vinyl), are 60s pop, r&b and soundtracks, which were often victims of excessively applied compression. And some tracks during multi-vocal passages and when orchestrations get busy sound “congested”; possibly due to poor miking/baffling (??). So, while not outright crappy (??), much of my music was certainly less than pristinely recorded and/or mastered, even though almost all were issued by major labels.

Therefore, how enjoyable or "listenable" would beryllium drivers, especially like https://josephcrowe.com/blogs/news/...river-test-review?_pos=3&_sid=e989429b4&_ss=r make much of my recordings?

Ditto this beryllium https://www.usspeaker.com/radian 745neoBepb-1.htm , though which doubtless Pierre had perfectly EQed? See posts #15,266, 15,276. https://www.diyaudio.com/community/threads/beyond-the-ariel.100392/page-764

Might you instead recommend the "neutral" sounding Yamahas JA6681B aluminum, with beryllium support "fingers".


Or the perhaps more likely the "warm" sounding B&C DMC50 paper cone?
https://www.diyaudio.com/community/threads/critical-midhorn-build.172704/page-5
https://forum.audiogon.com/discussions/horns-and-2in-drivers/post?postid=1779050#1779050

And @ 17:29 to 25:01here?
That's beryllium copper (which has good spring properties and fatigue resistance) about 97% copper and 2% beryllium, which is nothing like pure beryllium.
 

Descartes

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Used to have diamond tweeters on B&W but now have plain aluminum tweeters on KEF and honestly I prefer the KEF sound if there is such a thing!
 

Chris Brunhaver

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Used to have diamond tweeters on B&W but now have plain aluminum tweeters on KEF and honestly I prefer the KEF sound if there is such a thing!
Well, there are multiple variables here dictating that. It appears that the B&W drivers are quite good and most of the issues are elsewhere in the design/ID.
 
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