The effect of materials employed in drivers re loudspeaker performance

[phoenixdogfan]

I noticed in one of Amir's speaker reviews a newer member made an allusion to driver materials having some salutary influence on the reproduced sound of a speaker. All things being equal, I wonder how true this assertion really is. I know it's a great marketing point for some of the companies making and marketing five and six figure designs, but if those materials really made a difference, how would they not be revealed in measurements? Moreover, do those materials make a differnce justifying the price premium the designs employing them command?

Maybe some of the members with a better technical background can weigh in on this. Do things like Beryllium tweeters make an audible difference, and lead, for example to an inherently superior tweeter over, say, a silk dome or even an aluminum or magnesium dome. Perhaps rise times are shorter with the Beryllium, but does this feature translate to better sound?

Same question is also raised for ceramic or graphene midranges and woofers. Does employment of these materials, make for audibly superior drivers? And, if so, where does that show up in the measurement set?

I myself rather suspect that the engineering that went into the design far outweighs any small advantage afforded by a particulular material used in either the cabinet or the driver. I think the materials needed to make superior drivers are widely available and reasonably priced and, if used by a designer who knows what he (or she) is doing will yield results every bit as good as diamond coated Beryllium tweeters, ceramic midranges, and graphene nanofiber woofers, or exotic epoxy cabinetry.

Anyone care to weigh in on this?

 

[ahofer]

A couple of videos on Harbeth's claims here. He tends to start from the *very* beginning, so if you don't want the lecture on forming/molding, skip around.

https://www.harbeth.co.uk/usergroup/threads/the-unique-harbeth-radial-bass-midrange-drive-unit.2472/

 

[mansr]

The ideal driver membrane has zero mass while being perfectly rigid. As that isn't possible, some compromises must be made, and here materials do differ measurably. One important aspect is resonance which should be well above the intended frequency range of the driver.

That said, is a beryllium tweeter that much better than a cheaper aluminium model? I'd say that's debatable. Even with the same material, the design can make a significant difference. A badly designed driver made with an expensive material is still going to perform poorly.

 

[thewas]

Different materials have different dynamic, modal and break up behaviour, although all other details of a loudspeaker chassis (like its motor, spider, basket etc) also play a measurable role to its behaviour and in the end we listen to the total of those choices.
A good loudspeaker designer tries to use the chassis as much as possible in regions where their behaviour is a linear as possible, so if possible away from break up frequencies (unless intended like with balanced mode radiators).
If appropriate good chassis are used so that their distortions are under the hearable thresholds, we mainly hear their frequency response and individual directivity behaviour.
If we take those two parameters out of the game by equalising them to the same FR and listening to them anechoically so only on-axis sound matters, then different materials don't produce a different sound as shown in this work:
https://www2.ak.tu-berlin.de/~akgroup/ak_pub/abschlussarbeiten/2010/RotterAndreas_MagA.pdf

I electronically translated its conclusion to English:

Summary
The present study examined the popular opinion that the subjective sound impressions of tweeters are clearly related to the drive principle, the diaphragm material used and the geometrical extension of the diaphragm. For this purpose, six typically in tweeters used in the current loudspeakers, which can be both in the transducer principle, its geometry and in the sound-generating material of the diaphragm.
In order to exclude typical discoloration of the sound image due to interaction with the surrounding room as well as with the baffle of a loudspeaker cabinet, all drivers were placed in a quasi infinite baffle in an anechoic environment. In order to avoid discoloration of the sound image, which solely from the driver-specific distortions of the amplitude and phase response all drivers were tested using a digital crossover based on FIR filters for one point in space equalized. The goal of the compensation was a linear amplitude response in the range from 2 kHz to 22 kHz with maximum deviations of ±1 dB and a linear phase response. After successful equalization of all drivers, they were used in combination with
binaural impulse responses are recorded by a compensated bass-midrange driver. The Measurement of the BIR was performed in positions relative to the drivers, which are a left and right corresponded to a right speaker in a typical stereo arrangement. In order to enable a dynamic simulation of the loudspeaker pairs in a later comparison, the BIR were plotted in a radius of typical head movements.
In a final listening test, the two virtual pairs of loudspeakers were compared, which showed the greatest deviations from each other in the analysis of the binaural data. On the basis of the binaural, dynamic simulations of the loudspeaker pairs, ten test persons were asked to find out whether there was any difference at all, which could be determined by the subjective sound image exists between the tweeters. The result of the experiment allows the conclusion that there is no longer any perceptual difference between the tweeters.
In conclusion, it can be stated that in the case of excluded interaction with the room and the baffle, with drivers linearised axially in amplitude and phase, there is no longer any difference in linear operation between loudspeakers with different transducer principles, different diaphragm materials or diaphragm expansions exists. The common vernacular can thus, at least under these conditions be considered disproved.
Further binaural measurements and simulations can now be performed to evaluate the effects of other parameters such as the directional characteristic and the resulting driver-specific interaction with the space. Likewise the differences can be examined, which result from
driver-specific interactions with the baffle or resulting from non-linear operation of the tweeters.

 

[carlob]

Reposting from the Harbeth Monitor 30 review thread:

This is Harbeth patent for their Radial cone: https://worldwide.espacenet.com/pub....com&locale=en_EP&CC=GB&NR=2269511B&KC=B&ND=5

and text here https://worldwide.espacenet.com/pub...rue&FT=D&date=19940209&CC=GB&NR=2269511A&KC=A

Also interesting this post in the HUG and the attached graphs: https://www.harbeth.co.uk/usergroup...ve-unit-and-crossover-issues.2215/#post-44546

 

[Pio2001]

As far as I understand, the spinorama measurement tells us most of the story. But these materials can have an indirect influence on it : a better material can allow a driver to work properly at frequencies that could not be reached by the same driver if it was made of cheaper materials. Which allow to setup the crossover frequency higher, or lower, which in turn allow a better control of directivity, which shows up as better spinorama results.

 

[Ron Texas]

There's always silly putty...

 

[mhardy6647]

Luddite that I am -- I still like paper for cones.

 

[Xulonn]

As far as I understand, the spinorama measurement tells us most of the story. But these materials can have an indirect influence on it : a better material can allow a speaker to work properly at frequencies that could not be reached by the same speaker if it was made of cheaper materials.

I am curious to see if speakers with various cone or driver membrane materials measure differently - and by how much - based on Amir's Klippel tests. There is a good list of speaker cone and membrane materials at THIS Aussie website, but it doesn't go into detail about sonic performance of various materials.

Unfortunately, there is so much data from each Klippel speaker test, that I wouldn't know where to look for clues. As with subjective evaluations in general, it will be interesting to see where there are correlations between test results and listening tests published elsewhere - or between ASR member impressions and the test results. Relating that information to cone/membrane maters is a whle 'nuther dimension.

However, it will take someone with a better memory for detail than me to spot relevant information. I will be interested in comments and analyses of such findings.

 

[Pio2001]

I am curious to see if speakers with various cone or driver membrane materials measure differently

Sorry, I meant driver, not speaker, in my previous message.
It's a bit confusing for me because the french word for "driver" is "loudspeaker" (haut-parleur), while the french word for loudspeaker is "enclosure" (enceinte).

For example, Igor Kirkwood replaced the original tweeter of the Yamaha NS-1000X with a Focal beryllium tweeter. He says that just swapping the tweeter brings nothing (it even destroys the sound of the speaker if you don't make a new mount for the new tweeter). The goal is not for the tweeter to sound better, but to lower the frequency of the crossover from 6000 Hz (original) to 2000 Hz, which the original tweeter could not stand.
https://www.homecinema-fr.com/forum...e-ns1000x-2s-griesinger-by-ohl-t30082891.html

 

[Putter]

Quotes from Ken Kantor on Audiokarma

No one will believe me, but I have to call it like I see it: I am convinced that how a driver is used, and how it fits the system requirements, has at least as much to do with tweeter sonics as the make and model. There are tweeters that I have come to like a lot over the years, but this has mostly to do with consistency, reliability, ease of use, cost-performance and well-thought out specs, as anything. Just as with cars and drivers, and chefs and food, average tweeters in the hands of a pro will almost always sound better than expensive, fancy parts in the hands of a someone without training and experience.

I used to judge various amateur speaker building contests, and got to listen to the best efforts of both first-time and well-known amateur designers, year after year. Submissions invariably used very well-regarded drivers, yet it was very rare for any of the judges to find a submission that would make it on the market at any price.

I'm not meaning to be snobby. Anyone can learn to be a great speaker designer. But, you have to learn, and you have to try dozens and dozens of different designs. Most importantly, you have to hone the skills to listen very quickly, analytically and brutally, and understand exactly how to correlate listening to engineering, without philosophical biases.

If you think that the finest drivers make the finest systems, you aren't paying attention!! Ingredients are only a start.

I will never cease telling people, who will never cease to disagree:

Experiment after experiment has shown that driver materials have no characteristic sound.

Paper doesn't sound woody.

Metal doesn't sound harsh.

Plastic doesn't sound, eh, plastic-ey.

Silk doesn't sound silky.

It is ALL confirmation bias and imagination. End of story.

Beginning of, "But, even my wife can hear that my metal domes sound metallic, you idiot!!"


He is certainly an authority on the subject which doesn't of course guarantee you have to agree with him. I tend to like hard domes because of all the reviews saying they're metallic sounding with no real proof (I'm a bit of a contrarian), the fact that they were developed after paper domes, and because they seem to be found on higher end speakers.

 

[gene_stl]

I have been listening to Beryllium domes since 1977. But I think it is more important that the system is quad amped.
There are numerous good ways to skin a cat.

Why would you want to wreck the original excellent Yamaha design by lowering the crossover frequency? You could replace the NS1000 tweeter with one from the NS500 (see left image) which was a two way system and crossed over lower. The Yamaha drivers are vapor deposited Be whereas I am sure the Focals are made with formed sheet metal.

When I built these I was very pleased to see that Martin Collums said that the Yamaha Be domes were the lowest distortion he had ever measured.
This was in his book "High Performance Loudspeakers" by Pentech Press later reprinted by John Wiley. Multiple editions. My copy escaped.

I was even more pleased to see that when I looked through Floyd Toole's wonderful book (3rd Ed) on page 453 he shows spinoramas for a bunch of vintage speakers from back in the day. The only one that performs wonderfully (if I am interpreting the graphs correctly) is the Yamaha NS1000.

If you quad amp using a Pioneer D-23 which bristles with knobs you can control the crossover frequencies, the slopes, and the level (shelving) of each driver without reducing the amplifier's damping and control of the diaphragm. You also don't waste a huge percentage of the power warming high level crossover components. The newer paradigm for this is the DSP inputs of modern professional amps from Crown and many others, or speaker management systems like the Drive Rack or Behringer that can make a speaker do anything you like within its limits.

Polycrystalline Diamond as used in the B&W and Thiel Accuton drivers is the ultimate Audiophile absurdity. Madisound now has a pair of diamond Seas tweeters for $7100+ per pair. But the mass and density of diamond is not that great. Furthermore synthetically produced polycrystalline diamond is not expensive to produce. Eventually some nice Chinese producer will figure this out and the price of these will come way down. I probably would not mind Diamond tweeters and midranges if I could not get Beryllium. But in another life I am a gemologist. They are making synthetic diamond as substrates for semiconductors. Synthetic diamond jewelry and tweeter diaphragms are just a little side show to bring in some overpriced cash from the main event.
Peerless has some corundum tweeters:Parts Express Peerless Corundum tweets at $53 and $64 each. This is realistic pricing because most folks don't realize that corundum is what ruby and sapphire are. These materials are also almost free and have good characteristics for making spikkers.
Ceramics too which is a huge subject.Tang Band ceramic one inch Tweeter $34 Ceramic is essentially polycrytalline corundum (although it can be any number of things but alumina is the same Aluminum Oxide as corundum.

There are sooo many ways to skin a cat.

 

[phoenixdogfan]

I suspect speaker enclosures are another marketing absurdity. There is almost certainly a point where, with respect to audible resonnances, it is possible to achieve with good design for a modest amount of cost a cabinet that is not creating those resonnances. And all the heroic measures (Wilson's "X" material, Magico's aluminum boxes with "tensioned baffles", Panzerwood, carbon fiber, and constrained layer damping) will, if it is possible to demonstrate where that sweet spot is, prove to be nothing more than ridiculous and costly overkill. And since those materials are unfamiliar, probably ridiculously overpriced as well.

 

[dshreter]

A related question - how much of a speaker’s sound is its frequency response shape, vs distortion or harmonic response? On most speakers that have a well measuring frequency response, is distortion a negligible component of the sound?

 

[amirm]

A related question - how much of a speaker’s sound is its frequency response shape, vs distortion or harmonic response? On most speakers that have a well measuring frequency response, is distortion a negligible component of the sound?

Frequency response is just about everything. Speakers vary so much in that department that everything else gets lost in the equation.

Of course at the limits of what a speaker can play back, distortion goes through the roof. So that is a case where distortion matters more than frequency response.

 

[kschmit2]

The ideal driver membrane has zero mass while being perfectly rigid. As that isn't possible, some compromises must be made, and here materials do differ measurably. One important aspect is resonance which should be well above the intended frequency range of the driver.

Maybe the graphene drivers in this kickstarter project will be a step in the right direction. They have Klippel plots acquired by Warkwyn Labs (see under "The Data - Third Party Tests"). Only time will tell though.

 

[milezone]

The ideal driver membrane has zero mass while being perfectly rigid. As that isn't possible, some compromises must be made, and here materials do differ measurably. One important aspect is resonance which should be well above the intended frequency range of the driver.

The goal is a material that generates resonant modes which are outside the frequency range of the driver -- or ideally the audible range. Every driver has specific frequencies where resonant modes occur. This is determined by material, cone shape, and driver design. Certain manipulations of material and driver geometry can help break up and or nullify these resonant modes. High modulus high self damping materials (e.g. graphene versus a rubber band) materials like beryllium, titanium, certain carbon or glass fiber reenforced materials are best suited for speaker drivers. All the while striving for the lowest moving mass possible.

 

[gene_stl]

Somewhere buried in my basement are a pair of DuKane Ionovac tweeters which are zero mass, ozone producing, massless tweeters. Of course I would be willing to bet that the primitive RF amp built into them to drive them has more distortion than a diaphragm based tweeter. They are on horns.
If anyone wants to buy them they are for sale. I inherited them from a Manhattan project scientist who was an audio nut. I am afraid to light them.

There once was a similar system which eliminated the ozone by emulating a HeliArc welder. You had to show your devotion to your stereo by having a big Helium tank associated with it. Of course now Helium has gotten very expensive and may even be restricted due to being a limited resource. In some research locales they have helium scavenging systems. You probably could substitue Argon which is cheap and plentiful for Helium. It would probably have a warmer sound.

 

[Xulonn]

SDuKane Ionovac tweeters

About that horizontal dispersion problem...

 

[gene_stl]

Talk about an item that is ripe for "modding".