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 "I
found the sound of these drivers thoroughly beguiling. They show
marvellous mid-to-treble delicacy, focus and coherence and possibly the
most natural voice-band presence I've encountered, with quite exceptional
fingers-up-the-spine realism."
-Paul Messenger, HiFi Choice, 2005
"Unique" has
almost become a tired old cliché in the world of high end AV. Every man
and his passive crossover are claiming "unique this" and "unique that".
The sad truth is that 99.9999 (yes six nines!) of all the loudspeakers in
the world are all using exactly the same, fatally flawed, 100 year old
technology that does not work! Pistonic motion (cones, domes, ribbons and
panels, yes including Quads!) and passive crossovers (inductors,
capacitors and resistors) were first used in audio in the early 1900's!
They didn’t work then and they still don’t work today and here's the two
reasons why.
Timing, Timing
and Timing & Speed, Speed and Speed .
Please be patient, read on and allow us to explain this radical but true
statement. Just before we start the explanation you should know that
Overkill Audio do not use any passive crossovers in any of our
loudspeakers and we have eliminated conventional pistonic motion drivers
from 90% to 100% (depending on model) of the entire audible frequency
range. Our unique technology is unique!
OK, here we go with the explanation,
hold on to your preconceptions cause this is really going to put the
hungry cat among the fat pigeons!
Timing first;
The human (and all the other land based
mammals) ear does not care what a sound is, what a sound sounds like or if
a sound is pleasant or unpleasant. All that matters is where a sound is
coming from in three dimensional space. All mammals ear brain
mechanisms were developed to locate prey or flee from predators. In
mammals the primary trigger for the fight or flight response is aural.
When our primate ancestors detected a noise they instantly bolted in the
opposite direction, away from the source of the noise. They may
have been 10 meters into their flight response before they correctly
identified the sound and realised it was as a false alarm… like a falling
coconut. Or they may have identified a snapping twig as a predator was
about to strike, then they looked back and thought that was close! Natural
selection ensured the survival of the creatures with the most accurate
spacial location hearing mechanism not the most accurate tonal
identification mechanism. So how does this well documented and accepted
science & biology affect you and I in today's audio world?
To answer that we must first take a brief
look at the mechanics of our ears and how they work, how they don't work
and how fast they work.
Fact, our ears do not use pistonic motion!
Our ears use a rippling (or bending wave)
principal to decode sounds. The outer ear channels sound waves (a series
of compression and rarefactions in the air) down the ear canal onto the
centre of the ear drum (imagine dropping a small pebble into the centre of
a calm pool of water) which then ripples in response to this sound energy
hitting its centre. Various tissues & tiny hairs and nerves located all
around the edges of the ear drum (imagine how a spider detects the
movement of struggling prey in its web) convert this movement, Kinetic
energy, into electrical energy, and these impulses are then sent to the
brain for decoding.
Now speed; The ear drums response time is critical.
How quickly the ear drum starts and stops the rippling motion determines
the accuracy and effectiveness of our ears. Mother nature addressed this
mechanical limitation by evolving the fastest possible energy conversion
system, the rippling or bending wave ear drum motion. Pistonic motion is
far too slow. The reason the ear drum does not work like a cone
loudspeaker driver (a mass on the end of a spring) is because it would be
in constant oscillation as it wobbles in and out never having enough time
to settle back to its neutral or starting point. This would send a
constant stream of "ghost echoes" to our brains which would be impossible
to decode quickly and accurately.
Our ears are incredibly sensitive and
specialised devices which are designed to detect where sounds are located
(spacial information) in a fraction of the time it takes to identify what
a sound is (tonal information). The point to note here is that our hearing
mechanism is ultra sensitive to time domain distortions. So the
fundamental prerequisite in order for any loudspeaker to reproduce life
like accurate sound is that its response time (speed) has to match or
exceed that of the human ear.
Someone with average hearing can detect
time domain errors down to an incredible 25uS (twenty five
one-millionth's of
a second) or even less if your hearing is very good. The very best ribbon
drivers covering 2KHz & above settle in an average of 100uS, the best dome
tweeters have a settling time of between 140uS and 180uS, ultra fast
midrange units need over 450uS to settle in the 500Hz to 2KHz band and a
typical high end 12" bass driver can continue to oscillate and resonate
for nearly a second after the initial musical note or impulse stops.
Our Prey head units cover the entire 300Hz
to 30 KHz band with a blindingly fast rise time of 13uS and they do so
without any of the ghost echoes and distortions caused by sluggish
pistonic drivers slow settling times. The Prey cover 90% of the audible
frequency range with both rise and settling times that average over
twenty five times faster than the very best pistonic drivers. Even
more startling is the fact that our drivers are so fast, their 13uS rise
time is undetectable by the human ear, even a very good one! How is this
possible I hear the sceptical voice cry?!
We have developed and refined the worlds
only true rippling or bending wave loudspeaker system incorporating linear
phase (time and phase coherent) digital crossovers and a genuinely unique
cabinet material, our Self Damping Compound (SDC). Our secret combination
is the combination! All full range loudspeaker systems are a combination
of three equally important components; the driver, the cabinet and the
crossover. No one has ever succeeded in finding the secret combination
before. No one. We have pushed back the boundaries with original ideas and
innovation, applied precision engineering and craftsmanship and above all
listened to the music. In a world obsessed with measurements and
statistics its easy to forget that it is more important how music sounds
than how it measures.
Now lets take a closer look at the
beautiful Prey cabinets.
There has been a great deal of R&D invested
in the material science, construction techniques, shape and finishing of
the Prey. We are delighted with both the sonic and aesthetic results,
proving to be vastly superior to the more commonly used casting or
injection moulding techniques.
We do not view a loudspeaker cabinet as a
passive box. Regardless of its material & construction techniques, a
loudspeaker cabinet must be viewed as an active component which is equally
important to the overall sound as the driver and crossover.The cabinet is
an active energy conversion system, its job is to contain and convert
energy, it must deal with the sonic back wave produced by the drivers it
houses. Remember that the back wave disappearing into the cabinet is just
as loud as the sound flowing into your room!
Our goal was to create a beautiful looking,
acoustically inert loudspeaker cabinet to house our rewired Manger
drivers. We used creative engineering solutions to convert the kinetic
(sound waves) energy of the back wave into heat energy by utilising
proprietary viscoelastic materials and techniques.
We have achieved our design goals in great
style!
MDF, ply wood, hard wood, phenolic resin or
plastic simply can not approach the energy conversion characteristics of
our unique 16 layer Self Damping Compound (SDC). The combination of
skilled craftsman, 40 hours of labour, natural and synthetic materials
results in an unequalled performance that forms the cornerstone of all
Overkill Audio loudspeakers.
In acoustics
the most important law of physics is,
"for every action there is an equal and
opposite reaction", so for all the musical sound you hear
filling your listening room there is exactly the same amount of sound
energy bouncing around inside the speaker cabinet! How can you convert
this sound into heat before it bounces back out through the driver
diaphragm out of phase!?
The only answer is…. “two Prey”!
We tried the conventional solution of
stuffing the box full of various sound deadening and absorbing materials,
this simply killed all the dynamics and life in the music. “Baby and
bathwater” spring to mind!
We gave a demonstration to an extreme (cost
no object) DIY speaker builder who spent over £3,000 on finishing and CNC
machining two large solid Mahogany "eggs" to house his Manger drivers.
When he compared them with the Overkill SDC Prey he “demoted” his mahogany
eggs to rear speaker duty and bought a pair of Prey as his new two channel
stereo reference.
Previous commercial designs (Audio Physics
Medea and Mangers Zero box 103) used the drivers with passive crossovers
and shallow slopes of 12dB per octave to 24dB per octave. They also
crossed over very low i.e. 150Hz to 180Hz.
We have taken advantage (with a huge 15 fold increase in crossover cost!)
of the advances in Digital Signal Processing (DSP) and we now use linear
phase (not Butterworth or Linkwitz Riley) crossovers at 300Hz..
Our DSP based crossover has three major benefits.
First a massive decrease in
distortion as the driver is now completely free of all the X-max consuming
"hard work" below 300Hz.
Second a massive increase in power handling and dynamics as all the
power band below 300Hz is now handled by ultra fast custom
designed 10 inch and 12 inch drivers perfectly suited for active
amplification.
Thirdly the mid and high frequencies now
soar and blossom as never before. This simply was not possible when the
driver was forced to handle all the power down to 100Hz. Please remember
that in reality, a typical 12dB per octave passive crossover at 180Hz,
still allows over 50% of the current and voltage to pass straight through
at 100Hz!
Our DSP also has the major advantage of full real time EQ and room
correction which allows us to tailor every system to both the listening
environment and sonic preferences of our clients. The Prey are designed
with flexibility in mind, using our 96dB linear phase crossover, they can
be crossed over as low as 250Hz. We recommend 300Hz as the best all round
choice for most situations with the option of 350Hz or even 400Hz for
SPL’s up to 118dB!
The timeless teardrop shape sits perfectly
on its polished alloy stand, looking equally at home in an art gallery as
in any listening room or home cinema.
The classically curved Encore bass / low
midrange cabinet with its sumptuous real wood veneer and piano black gloss
makes a heavenly combination with the Prey.
The cool and contemporary Angels & Dark
Angels featuring acrylic and Moonstone make a truly iconic 21st
century design statement.
The Prey are the crowning glory on the
Finale speaker system and here they really do command respect both
visually and sonically. This is as good as it gets.
Product specifications;
Frequency response - 200Hz to 30KHz
Sensitivity – 91dB
Power handling – up to 500 watts depending
on crossover.
Max SPL – Up to 118dB depending on
crossover.
Weight 19Kg. Shipping 27Kg.
Maximum diameter 335mm.
Depth 450mm
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