ASoN
Meeting – May 6, 2012
Acoustic 3D – 3 dimensional acoustic hologram speakers
Introduction:
At the May meeting, we got an early look at radical new
loudspeakers from Australian company Acoustic 3D. Although when I say “new”,
they have been over 20 years in development, and incorporate innovative
thinking and application of a field of mathematics known as fractals. Think
chaos theory, clouds, snowflakes, and the famous Mandelbrot set. (I’ll leave it
to interested readers to google.)
These speakers promise to virtually eliminate the effects of listening
room acoustics, including echo – previously considered difficult if not
impossible. The goal is to “make every
spot a sweet spot” i.e. all listeners should hear the same thing, regardless of
location, and of course, to provide an accurate 3 dimensional image.
Inventor, mathematician and acoustician Joe Hayes, together with
esteemed loudspeaker designer Brad Serhan, presented a small speaker system,
currently on sale, known as the Emergence 2.1,
and an early prototype of a larger speaker known as the 7 2 or 7 squared.
The first speakers are based on fractal dispersion algorithm lenses
which create a 3D sonic field. This lens, which sits above the upward-facing
driver, at about 45 degrees, looks like a series of channels or slots machined
into a short length of aluminium or plastic (presumably), and acts to disperse
the sound waves in accordance with the mathematical theory stated above.
The latter speakers use an array of 49 x 2” drivers arranged in a
square, hence the name. They also have a tweeter array of 49 dome tweeters
similarly arranged, although being a prototype these were not yet fitted. Seven
channels of amplification and digital signal processing are used to create the
required sound field, again according to the above theory, as well as allowing
the sound to be tailored and compensate to an extent for some of the driver
limitations.
Equipment:
As the Emergence 2.1 are not designed for a room as large as the main
listening room, these were set up in the foyer.
Closing my eyes, I could imagine a much larger loudspeaker, and the
sound did indeed fill the room, with impressive image size and surprising
depth.
In the main room, we had the 7 2’s with source from a computer.
Brad was using feedback from listeners to tune the DSP (digital signal
processors) in the 7 2’s, and made considerable improvements in a surprising
short time – aah! the power of DSP!
The overall opinion was that these speakers sounded “ a bit PA (public
address) “, and in my words “lacked the finesse of what audiophiles are used
to”. But it must be remembered that these were prototypes, and did not have the
tweeters fitted, so the midrange/woofers had a difficult job to do.
Some felt this was due to the use of DSP and Class-D (switching)
amplifiers, but I doubt it. Despite popular opinion (not based on fact) to the
contrary, some class-D amplifiers in my experience, sound amazingly clean and
detailed. They don’t suffer from crossover distortion, for starters, although
they do have to overcome other issues.
Conclusion:
While there are some loudspeakers in commercial use using arrays and DSP
to “steer” the sound without having to physically move the loudspeaker,
Acoustic 3D are taking the technology to new heights, and attempting to
accomplish much more: the removal of the listening room!
(Steering is accomplished by applying a time delay to various drivers –
this has the same effect as moving them. For example, as sound travels at 345
metres per second, if we delay the sound by one thousandth of a second in the
DSP, it’s as if we moved that speaker back by 345mm.
This idea was originally used with radar antenna arrays in the 1940’s!
Although then they were dealing with radio waves travelling at the speed of
light, so an extra metre of antenna feed cable had the same effect as moving
the antenna a metre (approx).)
The Emergence 2.1, which use a sound lens rather than DSP, is especially
ingenious – and effective.
I believe that these speakers are just the forerunners of some very
exciting things to come, using DSP, and that they help cement the place of DSP
in high end audio.
Watch this space !!!
Many thanks to Joe Hayes and Brad Serhan for a most interesting and
exciting session.
