BackstageAn Engineer's Perspective

Legacy Audio Dual Air Motion Tweeter (AMT): Continuing the Pursuit for Perfection

"I have always been a proponent of low mass, high acceleration drive elements. The acceleration capability of the loudspeaker’s diaphragms ultimately determines the overall transient or waveform tracing capability of the loudspeaker. The recent AERIS loudspeaker development gave me the opportunity to tool LEGACY’s new Dual Air Motion Tweeter System.

LEGACY Audio has enjoyed the benefits of low mass ribbon drivers since 1984. I have a collection of ribbon tweeters from the world over and always loved the way good ribbons reproduced the swishing sound of brushes on a snare- and the simple honesty in the reproduction of strings without imparting an edgy ringing effect found in most tweeters. There’s just something right about the sound – like a C12 mic capsule. However, ribbons typically exhibit moderate power handling and are limited in their low frequency range. The benefits of further increasing the dynamics to natural levels and extending the frequency range of such ribbons would be considerable, musically.

To build a better speaker, one MUST first acknowledge that loudspeakers are dreadfully slow by nature. Their responsiveness lags the electrical waveforms settling time by orders of magnitude; logically so, if one contrasts the mass of an electron to the mass of a speaker diaphragm. Speakers are also extremely inefficient--wasting more than 98% of their input power in the form of heat and out-of-phase motion.

For these two reasons I have been working with speaker motors with magnetic field strengths as high as 2 Tesla (60,000 times the field strength of our planet Earth) to overcome these limitations. With such field strength, greater levels of articulation are possible at the lower limits of a transducer. For example, the reproduction of a simple strike of a heavy anvil will reveal tones that are richer, darker and more complex than otherwise possible.

In constructing the new Dual Air Motion tweeter, it was necessary to accordion-fold sixteen square inches of Kapton into the 4” long, 1” wide chamber. Neodymium again was employed to provide the flux density required. But the solution was made even more elegant by mounting the new 4” ribbon on the same faceplate as its complementary 1” AMT ribbon super-tweeter. The results were more uniform dispersion and tremendous attack. Treble now had weight instead of tizz. A natural fullness in the treble is exhibited-- reminding us why we love high-end audio so much."

-Bill Dudleston, Chief Designer, Founder of Legacy Audio

LEGACY’s new Dual Air Motion Tweeter System extends bandwidth and dynamics due to premium grade Neodymium magnetics and Kapton diaphragms stable to 750 degrees Farenheit.

The AMT System is featured in Whisper XD, AERIS, Focus SE and Signature SE speaker systems.

*Kapton is a registered trademark of DuPont.


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