Hard Audio - Ceramic Speakers

Hi Gang,
One thing I think about both as a listener and speaker builder is ceramic drivers, such as the famous Accutons. I'm talking true ceramics, not sandwiches here. I'll include here hard diamond drivers as well, not vapor deposited diamond dust.

Some of what I've seen is super impressive in terms of specifications, and design far beyond merely the dome materials.

I've never ever been moved though. For whatever reason, every ceramic speaker I've heard sounded cold, clinical, pure without power.

What are your experiences? Have you heard ceramic speakers that made you really feel you had experienced something great?
I think the Raidho's are great. I have the D3.1's. Raidho uses a particle accelerator to fuse a diamond coating on the ceramic driver. 
@erik_squires, "every ceramic speaker I’ve heard sounded cold, clinical, pure without power."
That’s mostly how I’ve heard it, though not universally. Not only the Raidhos, but I’ve also heard what I remember may have been a Mastersound at a long ago Stereophile show in NYC that beguiled me. Lumen White products certainly come across as the poster children for what you’ve described.
Crossover topology carries so much weight, as much as the drivers. So if I designed around such drivers, and my preference would not go in that direction, I’d have that at the forefront of my mind. For me, that means series crossovers beginning with a zeta value of 1.2, and experimenting up to 1.5.
A final thought, people don’t realize the (literal) brittleness of ceramic drivers. Yes, just like any other ceramic such as a plate or cup. I’ve seen more than a few loudspeakers that feature them shatter in transport. And these drivers obviously cost a lot, so replacement is less than fun. Speakers have it hard enough at the hands of UPS and FedEX, so please keep that in mind
Hard rigid solid drivers may be pistonic but they also vibrate internally. This is a FACT.

They sound terrible to anyone with a discerning sense of timbre. They simply aren’t musical at all even if the articulation can be impressive.

Those who just listen to the impulse response may prefer these type drivers. They can use cheap drive motors because they are light and efficient. However if you try to listen behind the action you will easily hear the splashy sound these drivers tend to make and it can be extremely fatiguing. Like everything, some designs are better than others and some even approach but do not surpass the best soft domes or pulp/paper/woven fabric designs.

That said - sandwich of rigid cones with an internal viscous damping layer are much better but they quickly start weigh as much as or more than conventional drivers and therefore require big drive motors.

They lack power because of cheap drive motors and small voice coils. Also the splashy hash created after the transient means the transient no longer stands out as it does with damped drivers.

Simple analogy - a tight bass drum head creates a booooom sound. Place a blanket inside or an Evans EQ kick drum muffler and suddenly the kick is transformed into a more transient canon shot - basically the resonance head has now become damped - it produces the initial explosive force of the batter on the head and then rapidly goes quiet and the kick drum sounds extremely dynamic and punchy. A speaker is not a musical instrument so the extra resonance from rigid drivers is a curse for critical listening even though the sound may appeal to some - it sounds a lot like jitter or poor quality digital sound and some like this splashy or etched sound.
@shadorne I think you are right about the sandwiched ceramic drivers, the new Revel Performa3Be speakers are quite low in sensitivity, officially rated at 86db. I bought one a pair of M126Be however I noticed they need noticeably more more power than other similarly low sensitivity speakers.

What do you think is better, pure ceramic or beryllium for a midrange? From what I understand, beryllium is a metal that bends, but is also isn’t internally well damped, wouldn’t it have a similarly splashy sound to a pure ceramic driver? What is the materials science reason behind both hard (ceramic) drivers and beryllium (a metal that bends) both having internal damping issues?

And what would you consider your ideal midrange driver material?

The big advantage of harder materials is they don’t suffer from cone breakup and therefore have a broader operating frequency response. This translates to tweeters that go up an extra third of an octave or so.

Ideal mid range is about 3 inch in size in order to avoid beaming at the upper end of the frequency range. Pulp/paper woven fabric and doped fabric work well. Rigid Sandwich with constrained layer damping are good. Polypropylene and magnesium are some of the stiffer materials that are damped internally. There is no “best” as it depends on overall design and application. The whole idea of internally damped is finding a balance between pistonic behavior over a useful bandwidth up to breakup and no timbral coloration of the cone at useful SPL levels.

Many agree that ATC 3 inch dome is close to an ideal mid range. It was developed more than 30 years ago. It plays very loud with a quality and clarity similar to Quad electrostatic speakers in the mids. Certainly if you care only about mid range at modest volumes then electrostatics are a great choice. In the case of electrostatics the entire super light diaphragm is amplifier controlled (no voice coil) so damping of the cone can be achieved electronically. Large SoundLabs are the bee knees in electrostatics.
Are the Accuton ceramic midrange drivers pure ceramic or are they sandwich type?

I found this paper regarding Harman's CMMD drivers that were used in the Infinity line for quite a while:  https://www.excelia-hifi.cz/infinity/data/ceramic-metal-matrix-diaphragms.pdf

The new DCC cones in the Revel Be speakers reportedly take the CMMD design and improve upon it.  
I think the original Accuton were pure ceramic but they used dampening rubber dots to tame the materials tendency resonance. In recent years the dots have disappeared so perhaps damping is on the inside of the cone where you can’t see it?

Accuton are very good drivers.
Harman’s CMMD look very good on paper. The fact folks are still working on this problem shows you how pesky it is!

ATC solution to breakup (bending) of softer materials was to use a dome shape supported by a large 3 inch voice coil. They also had to use a massive 20 LB drive motor to get the necessary SPL out of such a small dome. Finally a 3 inch voice coil in a 3 inch dome is going to suffer from rocking motion - so ATC use a double spider to maintain alignment. So ATC solution works brilliantly to overcome the highly damped softer cone material issues however it comes at a huge cost - a very expensive transducer.

These newer designs that concentrate on fancy cone material structure look promising to be more cost effective but can they be mass produced with consistent quality? Will they last? And do they work better and as reliably as the “brute force” ATC massive drive motor style approach to dealing with softer damped materials - Time will tell.

Whatever the solution - internally damped drivers are absolutely critical to SOTA speakers.
Maybe I'm just fussy, but as far as I can tell, those Infinity drivers are basically anodized aluminum drivers. That is, they make aluminum drivers and then using acid and current (I think) they transform the outer layers. This is essentially what Calphalon does for it's cookware, no? 

And yes, Accuton are considered technically among the best drivers made. Certainly based on measurements and low distortion this seems to be the case. And yet... I'm happier with paper cones from Scanspeak. Kind of why I started this thread. :) The engineer and music listener in me do not reconcile well when it comes to these particular drivers.


Give me some kind of paper woofer and a silk dome tweeter any day.

Yes, I believe the coating is Aluminum Oxide, which is a ceramic material.  I'm not sure how they apply it, or what the difference is with the new Revel drivers.  

The benefits of paper drivers and soft dome tweeters are that their breakup nodes aren't nearly as nasty as metal drivers.  The downside is that their breakup nodes occur at lower frequencies.  

Still, breakup nodes are only an issue if you're running drivers into the extremes of their range or using shallow slope crossovers.  If you're building a 2-way or 2.5 way speaker with a first order crossover, it's something you need to worry about.  If you're building a 3-way using 4th order crossovers you'll have a lot less to worry about with regard to breakup nodes, unless you just picked the completely wrong drivers for your project.
I've never ever been moved though. For whatever reason, every ceramic speaker I've heard sounded cold, clinical, pure without power. 

Funny we purchased the Auccuton drivers and just plugged them into an old pair on Infinity Kappa speakers and then compared them to my old Vandersteen model 5 speakers.  We felt the Auccuton drivers were faster, had better clarity and were just as musical.  No modifications, just put them in and let them play.  Go figure. 

Do you think a pure diamond driver would be able to avoid the pitfalls of a ceramic driver? I understand Accuton makes 5.5" diamond domes for the La Assoluta Tidal speakers. 

The great expensive of making a driver like that must be worth it, no?
The great expense may be worth it for marketing purposes alone.  I’ve never heard the speaker, maybe the diamond midrange is something special, but the B&W diamond tweeters don’t sound any better than the beryllium domes or RAAL or Aurum Cantus ribbons, or Legacy AMTs I’ve heard IMO. 
The Marten speakers used to be thst way very neutral a bit too cool, ,but they changed the crossover parts I believe to Mundorf s best Silver Gold oil
That changed their sonic voice to much richer and involving 
The crossover is the Heart of the speaker..

From what I read on DIY sites the B&W diamond tweeter isn't considered anywhere near the same class as the Accuton or Seas diamond tweeter.

Yikes, at $7,100/pair for the Seas or $3,700/pair for the Accutons, those had better be something amazing.  Given that most of us can't hear much beyond 14khz or so once we're nearing 40, I think I'll take a pass on those.

FWIW I did think the Accuton ceramic midrange sounded excellent on the Salk Song3As.  Salk is using another fancy midrange in the Song3 Encores, a magnesium cone with a bunch of holes drilled into it and some sort of (polymer I believe) backing made by Eton, which didn't sound bad, but the room those were in at Axpona wasn't set up as well as the room with the Song3As, so probably not a fair comparison.  
Hi Erik,

I´ve heared a couple of speakers using Accuton ceramic and diamond

It seems to me, that especially the cross-overs are essential for a
natural sound.

A few companies are really producing bad, harsh and unnaturally
sounding speakers (to my ears) using (Accuton) ceramic chassis.
Marten, Gauder and Raidho were not bad. The only company which
produces speakers which are able to "sing musically" (to my ears)
is Tidal Audio.

Diamond tweeters like the one in B&W measure equally well compared to the Excel Millenium soft dome. So world class. Extremely delicate.

Don’t know much about the diamond midrange. Diamond is usually half a human hair in thickness. It might be very fragile if overdriven. Diamond is in a different league from ceramic. It is so rigid that any internal resonance may be entirely outside the audible band.

Regarding your views on hard drivers & ringing, what do you think of the Floyd Toole school of thought on this? On AVS he routinely cites his research (which is from the 80s), claiming no one can hear ringing and FR represents the full picture.

If you take Toole’s beliefs to their logical conclusion, the company he is with (Revel) is wasting their time as their entry level Concerta line has just as good FR measurements as Performa or Ultima, and things like using Ceramic drivers like on the Performa3 have no performance gain to using a driver that rings like aluminum or titanium, and by offering these things at a higher price they are merely selling to the market.

I asked Floyd why a company like Sennheiser would create something like Helmholtz Radiator to suppress time domain ringing when they could have simply changed the FR response of the driver, and he gave the impression that it’s done merely for marketing and FR response is all that matters.

IMO Toole’s beliefs on this seem weird considering we’ve known for decades people can pass double blind tests when comparing amps that used and didn’t use excessive negative feedback (and caused a spike in IMD distortion) even with ruler flat FR.

Dr. Toole has a wealth of knowledge and far more experience than most experts. I trust what he says to be true. I think frequency response is primary but I can’t believe he would say that this is all that matters. After frequency response and harmonic distortion measurements then even dispersion response and finally waterfall is very important. Stereophile show off -axis dispersion and waterfall plots on most speaker tests.

Furthermore, we know that concert hall reverberation and room RT60 are very important to our enjoyment of music. Sabin studied this extensively. Anyone who says spurious artifacts and poorly damped resonances (easily visible in a waterfall plot) aren’t important is ignoring a very important aspect of SOTA design.

One interesting fact about any unusual bumps in the frequency response is that they are often an indication of some undesirable resonance that will be even more evident in a waterfall plot and visible in the impedance curve too. So flat frequency response is indeed the most important indicator of a good speaker - even transducers should have a flat smooth response across their useful bandwidth and any unusual wiggles usually indicate trouble.

What he has said is, if two speakers have the same response but one speaker has a rise of x db at a particular frequency caused by ringing, and the other is completely free from such artifacts, all you have to do is remove that 3db of output via EQ, and the two speakers will sound exactly the same, and that no one can hear the independent effects of time domain ringing outside FR in a double blind test.

If harmonics and ringing are inaudible from the fundamental frequency then a sufficiently advanced room correction software should be able to make any speakers sound exactly the same on-axis.
Dr. Toole has said that EQ can help for room effects, but it can't fix a poorly designed speaker.  Frequency response is important, but you can't just look at on-axis.  A smooth and predictable off-axis response that mirrors on on-axis response (though with a more downward slope as you move further off axis due to directivity of the tweeters) is just as important as a smooth on-axis response, and EQ often doesn't fix problems in off-axis response.  

So, proper EQ can help make a good speaker sound even better in a room, it can't fix a speaker with fundamental design flaws.

As far as the various levels of Revel speakers go, while all are designed to exhibit the best on and off-axis response as possible at their various price points, there are benefits moving up the line. 

Moving from Concerta2 to Performa3 (and now Performa3 Be) to Ultima2 you get greater bass extension, greater power handling, greater dynamic range capability, less dynamic compression, less distortion at extreme dynamic levels, etc (plus of course the intangibles like more nicely finished cabinets and such).

Playing material without much bass content at a lower volume the Concerta2 F35 should sound remarkably like the Ultima2 Salon2.   Change the material to something with deep bass content and a very wide dynamic range played at reference levels and the differences will become apparent.  

The new drivers in the Performa3 Be offer more dynamic headroom, lower distortion at extreme volume levels, and stronger motor structure/better cooling to decrease dynamic compression.
AFAIK, damping the FR damps the ringing as well. Something about this is how minimum-phase devices work.

It’s not intuitive. We believe that a passive or active EQ would affect the frequency but not time domain, but I’ve read otherwise.

In rooms, the same principle works, with some help from bass traps. 


In theory, with everything equal and no other speaker distortion mechanisms then Dr Toole may be correct: pure ringing at the fundamental can be removed with a notch filter it. However, in practice speakers are not perfectly linear and have limited operating range and other forms of distortion - so the speakers won’t sound the same -  so in practice it is far better to have a speaker with a flat response to begin with then to compensate using electronics. 

The kind of ringing that is of most concern is that from wobbling modes from energy within the cone diaphragm itself. This sounds splashy or dirty and is not necessarily harmonically related to the music.
I also want to point out that many, many drivers have break up modes / ringing in the top end of their usable range. Dealing with this is not all that difficult or new. 

How it is dealt with in crossover design depends a great deal on the next component up the frequency spectrum. Low pass filters may put the ringig 20-30dB or more down in response making a specific notch filter irrelevant. All the fans of the Focal inverted domes have ultrasonic ringing which they don't seem to complain about very much either. :) 

And sometimes we deal with the resonance by designing speakers not to be toed in. :) 


Kharma Grande Ceramique loudspeakers uses a 7 inch ceramic midrange and in my opinion still among the best. I have had them for a decade and they still blow me away

Interesting they are made with Focal Tweeters, and another, non-ceramic woofer. :) 

I wonder if they add color? :) 


A while back, I had a chance to audition a host of some very nice, current model, speakers among them was the little Raidho, C-1.2s. At first listen, I was very impressed with their quick, dynamic and micro detailed presentation, but after a half hour of listening to various tracks of jazz, pop and band, at somewhat moderate volume levels, I began to get a bad case of listening fatigue. Hands down, for long, enjoyable sessions of listening (at a fraction of the cost) I would choose the Vandies, Maggies or even my little Gershmans, JMO.....Jim

I've never ever been moved though. For whatever reason, every ceramic speaker I've heard sounded cold, clinical, pure without power.

 Boy there are quite a few makers that use ceramics that sound utterly fantastic IMO.Personally most of them I love and would own.

@shadorne Aren’t planar and electrostatic drivers also technically "ringing" due to the fact that the driver’s have to absorb all of the transient energy without a voice coil? Planar/electrostatic drivers all tend to have much worse impulse response than a good dynamic driver as it keeps moving for a while after the initial transient. Would you say the ringing/excessive decay in those types of driver’s are just much more benign than the internal ringing of a hard ceramic/metal driver?
The old accuton midrange C90-6-079 used in a lot of commercial offerings sure conveys a cold and dry sound especially when playing violins.  The newer C90-6-724 delivers a marked improvement right out of the box.  Requires a slight attenuation if you are swapping out a 079. 
Also the 10khz peak (at least they admit it) needs a notch filter to mitigate. But overall musicality and transparency without the old “splashy” sounds as some have opined makes it a worthwhile investment. 
I bought  XTZ Devine Delta speakers. They have MTM configuration. All 3 drivers are accuton ceramic drivers. They sound as clean and real as electrostatic speakers without all the drawbacks. In comparison, I demoed 5000$ Dynaudio , 8000$ B & W And 8000$ Sonus Fabers. Only Sonus Fabre came close in sound quality. I am not an audiophile or a musician. The way I judge a speaker is I like to close my eyes and be able to fool myself that the singer or musician is there with me.
If anybody wants to listen to them in person, I can arrange a demo for you. I live in Las Vegas.
Martens are a great example of well done ceramic drivers, with Accuton drivers they are very nuetral ,that is why the Cover parts are crucial. They use Mundorf Silver Gold oil caps which are better then most out there.
   My used Avalon Acoustics Eidolons snatched me off the audio merry-go-round just in time to enjoy retirement. I'm guessing its the whole package not just the drivers.
   It turns out most of the electronics that were to solve my dissatisfaction actually worked very nicely through the Eidolons.   

Hey @m-db so what electronics did you end up pairing those Eidolons with?

@audioman58  Interesting!! I'll have to see if I can have a listen sometime.