ADAM Audio HM2 - Manual (Page 5)

5
A.R.T. Accelerated Ribbon Technology
So far, all loudspeaker drive units, whether they are voice coil driven, electrostatics,
piezos or magnetostatics, act like a piston, moving air in a 1:1 ratio. As the specific
weight of air is much lower than that of the driving mechanics, there is a bad match
between source and load. This is one of the main reasons for the small 1-2% efficiency
of conventional speakers.
All ADAM speaker systems take a completely new approach in kinematics to move air
and overcome this problem.
Based on the original works of Dr. Oskar Heil, who invented his “Air Motion Transformer”
back in 1972, new electrodynamical transducers have been developed. The A.R.T.
tweeter’s and midrange membrane consist of a lamella-like folded diaphragm whose
single folds move according to the alternate current, thus squeezing air in and out (see
Fig. 1).
The A.R.T. principle achieves a 4:1 velocity transformation between driving diaphragm
and driven air, i. e. the air moves in and out four times faster than the folds itself are
moving. This superior “motor” is responsible for the enormous clarity and transient
reproduction and thus their increased efficiency.
Another factor in dynamics is diaphragm area. For practically all drive units, the cone
area you can see is the acoustically active area of the loudspeaker. By folding the A.R.T.
diaphragm into the third dimension as seen from the listener’s position, the acoustically
effective area of the diaphragm is increased by a factor larger than 2.5 (see Fig. 2).
Thus, a smaller movement is needed for a given sound pressure level, enabling the unit
to reach a higher sound pressure level without dynamic compression.
Besides these advantages, the membrane construction in single stripes avoids the
typical break up of stiff domes or cones at higher frequencies and the resultant dynamic
limiting.
Since the A.R.T. membrane is not by a conventional voice coil but an Aluminum stripe
on a very thin Diaphragm, it is extremely light and therefore ideally suited for high
frequency reproduction up to 35kHz. In comparison to magnetostatics and ribbons, the
A.R.T. tweeter offers an above average efficiency of 93dB/W/m, as well as a perfectly
linear impedance of 3.2 ±0.05 Ohms, an equally perfect phase response of ± 1° within
the used bandwidth, a reasonable directivity characteristic and a thermal power
handling that exceeds that of 1” domes by a factor of 2 to 3.
Area comparison between the
unfolded A.R.T. tweeter diaphragm
and a 1” dome tweeter
The A.R.T. Principle: moving the air in a
4:1 ratio instead of a 1:1 piston motion
Fig.1 Fig.2