Hard Audio - Ceramic Speakers

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.

@exfoliate

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.

@exfoliate   

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.

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.

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.

@exfoliate

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.

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.

@trelja
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.