CEDIA Discoveries—Adam Audio Introduces Mid-Priced Speakers with Heil-Type Drivers

Just a simple question: Any clue about how these designs actually sound?  Or at the very least, which are the alleged technical merits of them compared to conventional designs?  As published, this note looks exactly like a paid insertion.  We the readers deserve a better treatment.

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Thanks for your ample reply, sincerely.
I fully agree that the environment in such an Open-Booth kind of Expo makes it absolute insane to try to even HEAR the sound of a certain pair of loudspeakers among the pandemonium of multi-cacophonic chaos...
But what I would enjoy and appreciate would be to read something a little more informative about this products.  As far as I know, Heli's AMT was briefly used back in the 70's in a limited number of designs as a tweeter-only application,and then almost fade away and continued to be produced in a very limited scale.  When I read that now it is also used as midrange driver in the top Classik model, inmediately I wonder HOW did they achieved that, and what kind of behaviour does it have...  which crossover points is it used, etc.  That was the kind of info that I was left wondering about when I finished reading your short article.  OF course it is great to be informed about any new approach in audio reproduction, but would appreciate it much more if it is more informative.
I completely agree with you in clasifying the Heil in a separate category in its own, because it achieves a very different acoustic coupling to the air compared to a ribbon... in theory it shines as a brilliant, elegant engineering solution!   But the few examples (ESS) I was able to listen to back in those days, had some marked shortcommings; Later on I was subscribed to the very dedicated "Speaker Builder" magazine, and tried their published design, with mixed results; I was able to get a better low end range (for a tweeter), but had other problems (like what a friend called "Slinky-the-toy" effects, that are produced when you try to build a long strip of AMT, and then observe the accordion diaphragm visibly altering its motion like the popular "Slinky" spring toy, where you can see waves traveling up and down along the vertical axis at certain resonant frequencies, most probably caused by a lack of uniformity in the flexural modulus of the hand made diaphragm interacting with the unavoidable lack of uniformity of the magnetic field produced by the assembly of separate magnets, which were selected and installed by hand!  (Home-made Electrostatic panels were certainly easier than DIY Heil's).
Another thing that piqued my interest was what kind of "further development" of the famous ‘Air Motion Transformer' by Oskar Heil is being touted in these new speakers.  Believe me, the original commercial development of the AMT by ESS was somewhat dissapointing.  I wonder if by the use of more modern materials and manufacturing processes the promise is finally met, but I guess the changes must be bold.
Finally, in addition to the advantages you already mentioned in your reply, there is another that is perhaps more important: the ability to quicky damp the motion of the diaphragm as soon as the signal ceases, because the air inside the pleats performs as a very good damper. Any lightweight tweeter diaphragm can start fast when reproducing a transient, but very few of them can STOP as fast, usually ringing for a minimum of 2 to 3 or more complete cycles... The Heil instead is silent in one to one-and-a half cycles, which reproduces the sharp clicking sound of certain instruments like castanets, better than even an electrostatic transducer usually do.  Other instrument where the Heil AMT performs excellently are the Cymbals when those are clamped with the fingers as in certain small Jazz groups, or the "Hi-Hat" when closed and struck with the drumsticks, or the Rim shots of the snare drum (where the tweeter has to reproduce the sharp high-SPL strike, and the separate mid-range has to reproduce the mid and low frecuency resonances of the snare drum heads (drum diaphragms). Other practical benefits are the almost resistive nature of the voice "coil", and some times the dipole sound radiation could be desirable.
Thanks again for arousing my interest in this almost forgotten principle.
Alfredo M. Claussen, Mexico City MEXICO.
 

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