Designer's Notebook: EVO = Distributed Intelligence
Intelligent loudspeakers mean imagination becomes
creation
LSMAG! has long championed the notion of intelligent, interactive loudspeaker systems. One of the first fully integrated system to grab our fancy is JBL’s EVO. What follows is a general description from JBL of how EVO advances the notion of dynamic, real time control of a professional sound system.
The first thing to understand about EVO is that its raison d’ętre (reason
to be) is no different than many of the products we use around us on a
daily basis. It is through the application of technology that we make
our lives easier.
Forget about the obvious one for a second, the home computer, but look
at the humble digital watch, automatic transmission, TV remote control
and the digital camera, to point out a few.
The digital camera, that’s an interesting one. The application of technology
has evolved the product to a level that brings consistently good pictures
into the grasp of any level of user.
It focuses for you, pops up the flash when needed and enables you to look
at what you’ve just taken immediately, so if you’ve cut someone’s head
off you can erase and take it again. Think back to your options not that
many years ago. Without laboring the point, I think you get the picture
(pun intended).
GOALS & FUNDEMENTALS
EVO is designed for small and medium sized venues such as schools, houses
of worship, meeting rooms, pavilions. The goal of this combination of
technologies is to simply provide a speaker that manages itself and is
intended for end-users that want or need a level of equipment self-reliance.
Typically, these sites require quality audio, but do not provide a high
level of on site service or expertise. EVO takes over some of those duties.
EVO will maintain its own audio quality by continuously adjusting itself
for consistent audio, even suppressing feedback automatically when needed.
EVO also tunes itself to its environment, both for frequency response
and delay settings between speakers. And if something does go wrong, the
onboard diagnostics tells the operator what the problem is. From a day-to-day
standpoint EVO is simply easy to set up and easy to use.
The fundamental principle behind an EVO system is ‘Distributed Intelligence’.
This is a term used to describe the de-centralized design architecture
of the system, where the main processing power has been distributed to
each EVO Intelligent Speaker. With each EVO speaker processing its own
functions, the need for a complex system of communication across the EVO
network is greatly reduced.
This means that no specialized network cabling is required. All network
data transmission is via the XLR audio cables (see ‘Distributed Intelligence’
in the following Technology Sidebar). Each EVO Intelligent Speaker may
be directly connected to a single rack space central hub, EVOi.net. EVOi.net
coordinates functions and serves as an end-user interface (i.e. button
panel to access each EVO Speaker’s functionality).
EVO Intelligent Speakers perform their own individual optimization for
their own unique acoustic environments and performance situations such
as feedback control, thermal management and performance in half or full
space environments. (see Figure #1) All the performance data is communicated
back through the network to the EVOi.net.
This design architecture is not unlike that of an automobile, where each
component (fuel injection, braking system, etc) is controlled by a localized
processor but all report back to a microprocessor behind the dash, communicating
functionality to the driver via the instrument panel.
Figure #1: EVO Loudspeaker System Control
HOW DOES IT WORK?
Figures #2 and #3, display typical EVOi.sys physical and processing set-up.
EVOi.324 speakers are installed and aimed to a position approximately
2/3rds into the listener area. They have been backward engineered to provide
a 1:3 Throw Ratio (see side bar “Throw Ratio”). XLR cabling is used to
hook up the EVOi.324s to the outputs on EVOi.net.
The system measurement microphone is then placed at approximately the
position both EVOi.324s are aimed and connected to the EVOi.net. Once
connected, the system is now instructed to tune itself to the room. This
is done by pressing the Auto EQ “Setup 1&2” button.
Each EVOi.324 proceeds to tune itself to its specific acoustic environment
(see side bar “Auto EQ”). For larger rooms or listening areas that require
delays, up to two additional EVOi.324s can be connected to the EVOi.net
and tuned in a similar manner.
Once tuned these can then be automatically delayed and level adjusted
to match the rest of the system. This software routine is also programmed
into each EVOi.324 and is initiated by pressing a button on the EVOi.net.
Each software routine only takes a few moments and like the digital camera
analogy, if you don’t like the picture you’ve just taken, you can erase
it and do it again. Once set up, the settings can be protected so that
buttons are not accidentally pushed by the operator.
Figure #2: EVO System Components
PRE-EMPHASIS
EVOi.net provides access to sophisticated operator routines in the EVOi.324s.
One is a set of pre-emphasis EQ curves that can be applied to the whole
system to tailor the performance for specific programs: speech; live music;
pre-recorded music.
The design goal was to take away the classic scenario of a novice operator
with a 32-channel dual band graphic equalizer causing a subsequent call
to the contractor to set it up again. A second routine is also performance
related, where two different types of anti-feedback routines are programmed.
The first, ‘Fixed Anti-Feedback’ is used to achieve more gain before feedback
with the set number of microphones open on the stage. With one press of
a button the operator slowly rings out the system.
Six filters are available to address the feedback that occurs and they
are then set until cleared. The second, ‘Live Anti-Feedback’, is a routine
that when initiated sets an additional six filters loose, roving the entire
bandwidth of the system and attacking feedback when discovered.
These can be cleared by the operator or left on to be automatically dropped
after a pre-set time period. If all six are used up and feedback persists
then the oldest filter clears and attacks the newest problem.
STATUS DATA
The last piece of information EVOi.net provides the operator is a continual
report on how the EVO system is working. Every few seconds, the EVOi.net
will communicate with the EVOi.324s connected to its outputs; a health
check of sorts.
The EVOi.324s will respond by reporting their condition. This is not dissimilar
to the automobile. If an EVOi.324 reports a fault or change of operation
(i.e. it is a replacement EVOi.324), then a diagnosis code is sent to
the operator via a series of flashes of the annunciating LEDs.
Setup data is stored in both the EVOi.324 and the EVOi.net, so that if
either is replaced, data can be uploaded or downloaded as required. Also,
as on any computer, there is the equivalent of a ‘Ctrl + Alt + Del’ function
to access a factory default re-set. The entire flow of data, audio and
commands is shown on Figure #3.
EVOi.net also provides a communication channel for future EVOi.324 speaker
control via a PC. Now that all the processing is located in the individual
speakers it is only a matter of designing software to make the system
do things that, until now, the industry has only dreamt about.
Figure #3: LoudspeakerSystem Electronics
WHY DID JBL DO IT?
JBL did it to make high quality audio more accessible to a greater audience.
A single loudspeaker is quite a simple device relatively speaking, however
the correct application of it is not. There are so many other elements
involved that need to be addressed to achieve good sound, e.g. selection
of amplifiers, crossover, cabling, location of the equipment, etc.
For fixed installations in many smaller and mid size venues (fewer than
500 seats), the installation results can vary wildly. In this level of
installation there is a growing demand for high quality audio. By designing
these elements into a system solution JBL reduces the complexity of the
task to achieve that.
Also, as a pro audio industry, we have not really addressed the cosmetic
appearance of our sound reinforcement offerings, such that great efforts
are made to hide the elements. With EVO, great lengths were made to produce
a solution that blended quite easily with other fixtures, especially lighting.
The whole EVOi.324 package was engineered to achieve favorable cosmetic
result.
The size, the utilization of Class-D amplifiers, switch mode power supplies,
paintable SMC material, the use of innovative new NDD transducers, the
structural and thermal use of aluminum, the application of F.A.T. to facilitate
horizontal mounting while maintaining even pattern control, are the nuances
of EVO.
All of these features were developed to accommodate a particular focused
application, providing a solution to those tackling these installations
for the first time; or to those that require a simple solution to be economically
effective for these applications.
It is the beginning of a new way to achieve customer satisfaction providing
consistent results in the hands of many. Like many innovations, EVO is
designed to simplify our lives. Have you ever wondered what the reaction
was upon the introduction of the first automobile automatic transmission?
TECHNOLOGY SIDEBAR
Distributed Intelligence
JBL’s Distributed Intelligence is fundamentally the utilization of sophisticated
technology operating transparently that makes highly complex systems very
simple. The key to this de-centralized architecture design is a reliable
data communication system.
The EVO system utilizes a BiDat (Bi-directional Data-over Audio Transceiver)
communication system. The basic principle behind Bi-Dat is FSK (frequency
shift keying), where EVOi.324 ‘receive’ digital messages in a serial bit
stream are communicated as f0 = 256kHz (0) and f1= 180kHz (1) and ‘send’,
back to EVOi.net, are f0’ = 75kHz (0) and f1’ = 88kHz (1). Two points
to note are that:
1.) It is extremely important in the design that any combination of f0, f1, f0’, f1’ or harmonic of them, combined with the DSP sampling frequency of 96kHz is greater than 20kHz.
2.) It is a closed network and a direct connection, via the audio cable, is required between EVOi.net and the EVOi.324s.
Throw Ratio
The Throw Ratio is a simple guideline to describe the acoustic performance
and coverage of the EVOi.324. It is a ratio of the height the system is
positioned above the listening area to the distance out into the listening
area within the optimum coverage area.
For example, installed 20ft(6.1m) above the stage, expect optimum acoustic
performance and coverage out to 80ft(24.4m). Taking the target application
of a 2FxEVOi.324 system it was determined that a uniform coverage pattern
of 80° x 80° and equivalent 1w/1m performance of 10dB would result in
this 1:3 Throw Ratio.
Auto EQ
Once instructed via the button on EVOi.net, EVOi.324 generates its own
MLS (Maximum Length Sequence) test signal. This signal sounds similar
to noise. It allows for the efficient calculation of the response of EVOi.324
and its acoustic environment.
An MLS consists of pseudo-random numbers that are sent as audio to the
EVOi.324 output. The internal DSP then calculates the frequency response
of the system in the room based on the measured input from the microphone.
The Fast Fourier Transform (FFT) technique used for this calculation is
a mathematical technique used in many measurement systems to convert an
impulse response into a frequency response. The resultant measurement
is next compared to the internal target response. Six parametric filters
are then applied one at a time to adjust the response to match.
Enhanced Total Thermal Management System
Heat is not a loudspeaker’s friend. As the transducers get hot they behave
differently and can lose 50% or more of their performance. The ETTMS maintains
a balanced thermal environment.
Thermal modeling programs in each EVOi.324 are used to prevent thermal
overload and also maintain tonal balance, compensating for power compression.
The extensive structural use of aluminum is not only to support the components
but to also behave as a thermal window, known as Thermomaster.
F.A.T.
F.A.T. stands for Filtered Array Technology. Each of the low frequency
transducers is independently controlled for magnitude and phase response,
resulting in smoother power response and constant coverage.
EVOi.324 Electronics
Size and weight were design goals. The board is a unique combination of
Class-D amplifiers, a switch mode power supply and the EVO ‘brain’, the
DSP board. All of the digital functions are synchronized at a sampling
rate of 96kHz, derived from the DSP portion.
The Class-D amplifiers provide a very efficient solution to heat dissipation.
The switch mode power supply aids in the reduction of weight as the use
of a large toroidal transformer is not necessary.
NDD
Patented Dual coil Dual gap Neodymium Differential Drive transducers are
1/5th the weight of conventional ferrite transducers. The reduction in
weight aids the total ease of installation design philosophy.
SMC
Sheet Molding Compound is a thermal set composite material with ultra
high wall stiffness, which results in a very high strength to weight ratio.
It is also compliant to complex mold shapes, a requirement for accommodating
architectural pleasing designs. SMC is also easily painted.
September/October 2001 Live Sound International