Trinnov Reveals Details of WaveForming Redefines Low Frequency Reproduction

Trinnov WaveForming vs DIRAC ART

Hot on the heels of DIRAC’s
announcement regarding their Active Room Treatment (ART) approach, Trinnov has
introduced their WaveForming technology, which presents remarkably similar
claims and capabilities. The close timing of these two announcements and the
resemblance of their claims might lead one to assume that Trinnov is imitating
Dirac. However, the reality is that Trinnov, like Dirac, has been diligently
developing this technology over an extended period. In fact, research into the
realm of room correction, specifically delving into more advanced forms of
Multi-input Multi-output (MIMO) correction, has been an area of interest for decades.
To gain a comprehensive understanding of how Trinnov’s WaveForming technology
differentiates itself from Dirac ART and why it represents cutting-edge
technology, continue reading. For those who prefer a more concise format, we
invite you to watch our recent YouTube video.

Trinnov WaveForming Technology Explained with Arnaud Laborie

Let’s begin with a general overview
of what MIMO (Multi-input Multi-output) signifies in the context of room
correction. While we have touched upon this topic previously, it is crucial to
recognize the inherent complexity of room acoustics. Oversimplifying both the
issues and their solutions only leads to further confusion among non-technical
audiences. We start by acknowledging that room modes are a part of a highly
intricate problem. They arise as sound waves emanating from the source
(speakers and subwoofers) reach the walls, bounce off them, and traverse back
through the room, intersecting with other reflections in the process. It
typically takes several cycles for our auditory system to perceive tones,
especially considering the length of a cycle at frequencies below 100 Hz.
Consequently, we can primarily discern bass frequencies that have undergone
multiple reflections and have intersected with themselves numerous times
throughout this journey. These phenomena give rise to what we refer to as room
modes or standing waves. As these waves propagate, they create interference
patterns within the room. Although we can attempt equalization to mitigate
these issues, it is important to recognize that we can only address the peaks,
not the dips. Furthermore, this corrective process introduces a trade-off,
where improving one location exacerbates the problem elsewhere. Equalization
alone offers only a partial solution. What we truly require is sound field
stabilization, necessitating a reduction in spatial variation that contributes
to the formation of standing wave patterns. The “multi-input” aspect
involves employing multiple microphone positions to obtain data from various
locations within the room. “Multi-output” refers to the speakers we
intend to equalize. In traditional systems, we typically rely on either a
single measurement (SISO) or multiple measurements (MISO) of the room to
develop a correction filter for each individual speaker. While we may consider
the interaction between multiple speakers, such as those in a bass management
system with subwoofers, the correction is still limited to a single speaker or
speaker system. We rectify the problem after it has manifested and base our
corrections solely on a single speaker (for the purposes of this discussion, a
bass-managed speaker and subwoofer combination is considered a single source).
MIMO fundamentally alters this approach by incorporating not only multiple
measurements (required to thoroughly sample the room and comprehend its behavior)
but also multiple speakers to address the problem. This represents a
significantly more powerful approach.

What Does DIRAC ART Do?

 

In the case of DIRAC
ART., all room sources are leveraged to address the issue of reflections. While
I primarily discussed standing waves earlier, it’s important to note that we
encounter various other problems beyond just standing waves. One such issue is
speaker boundary interference effects (SBIR). These problems are all a result
of reflections, which can be quite bothersome. DIRAC tackles the bass problem
by incorporating subwoofers, LCR speakers, side surrounds, rear surrounds, and
even top layer ATMOS speakers into the correction process. DIRAC takes the
approach of optimizing the correction given the available sources. However,
DIRAC does not provide explicit guidance on speaker selection, nor does it aim
to prevent the problem from occurring in the first place. That being said, it’s
worth noting that all these approaches, including DIRAC ART, perform better
when implemented alongside specific design strategies. Employing multiple
sources strategically positioned in the room can yield improved results.

Another challenge to
address is the utilization of speakers as active absorbers in these approaches.
These speakers are fed specially processed signals designed to fully cancel out
the incoming wavefront when it reaches the absorber speaker. However, there is
a drawback to active absorbers. Since the active cancellation originates from a
sound source, a portion of the cancellation signal becomes unwanted noise in
the room, akin to added distortion. This noise propagates across the room,
introducing another element to cancel out. Consequently, the pure active
cancellation method can be considered imperfect. Although there are techniques
to mitigate this issue and reduce the artifacts associated with active
cancellation, alternative methods exist that offer superior outcomes.

For instance, the cancellation
method achieves optimal results when employed with arrays, necessitating an
accurate mapping of the 3D sound field and precise alignment of the speakers.
While exact inch-level placement is not required, speakers do need to be
positioned relatively precisely to maximize effectiveness. Simply placing four
subwoofers in the corners will not suffice. In fact, they cannot even be placed
on the floor. The idea of hoisting an 18″ subwoofer and mounting it in the
middle of a wall might already be causing nightmares for some.

How is Trinnov WaveForming Different from DIRAC?

One approach to
mitigate acoustic issues is to prevent the creation of problematic reflections
altogether. If reflections are the primary concern, the key is to avoid
generating them in the first place. This is where waveguides, specifically
controlled directivity speakers, come into play. By exerting control over the
sound direction, we can minimize undesired sound dispersion. However,
subwoofers, due to their long wavelengths, function as omnidirectional
radiators in monopole configurations. Past efforts have been made to control
subwoofer directivity with varying degrees of success, primarily focusing on
reducing room interactions and mode formation, especially in relation to SBIR
effects. Many passive approaches have struggled to narrow dispersion
sufficiently across a wide frequency range, limiting their effectiveness in
significantly altering room mode formation. This is where Trinnov’s WaveForming
technology, supported by modern DSP and beamforming capabilities, plays a
critical role. Trinnov leverages properly positioned subwoofers on the front
wall to narrow dispersion, bending the low-frequency radiation and confining it
to specific areas. Moreover, not all reflections are detrimental; Trinnov’s
technology intelligently recognizes beneficial wall reflections while avoiding
unfavorable ones, a concept known as “Room matched bass steering.” We
can envision the room itself as a waveguide, with Trinnov optimizing bass
propagation within this waveguide-like environment, minimizing distortions from
the floor, ceiling, and side walls. However, this leads us to the next
challenge: the pesky back wall.

All rooms exhibit longitudinal
modes, which are reflections generated by sound waves traveling the length of
the room, bouncing between the back and front walls. These modes tend to
produce some of the most problematic and lowest-frequency resonances. While
beamforming and waveguide technologies can address certain modes, they are
insufficient to solve the issues arising from the back wall alone. An
alternative solution is required. This is where Trinnov distinguishes itself
from other approaches. If we consider the subwoofers on the front wall as
launching sound into the room, Trinnov incorporates an additional set of
subwoofers on the back wall, designed to capture and cancel the soundwaves,
preventing the formation of longitudinal modes. In practice, the rear array may
not completely absorb 100% of the reflections to avoid introducing undesirable
artifacts. Hence, a portion of the reflection may bounce back towards the
front, but it can be further canceled out by sending a signal to the front
array. This integrated approach is referred to as “Multiple Source
Multiple Controller,” utilizing all speakers in the system to address the
challenges posed by the back wall.

What is an MSMC?

 

 

MSMC,
or Multiple Source Multiple Controller, is a comprehensive approach that
combines both preventative and curative methods of correction to achieve
optimal performance. By leveraging the steering method and active cancellation,
MSMC effectively addresses the most challenging acoustic issues while avoiding
the creation of problematic conditions in the first place. This concept
originated with the introduction of Double Bass Arrays (DBAs), which have long
been recognized for their ability to produce superior bass in room
environments.

The core principle behind DBAs is
the formation of a planewave instead of a spherical wave. Typically, sound
radiating from a speaker propagates as a spherical wave, which allows for
reflections to occur. However, a planewave extends uniformly to all boundaries,
much like a sheet of bubble attached to the edges of a wand before it is blown
into a sphere. Similarly, the bass wave in a room adheres to the walls, floor,
and ceiling without significant reflection.

MSMC
relies on sound design principles to prevent the formation of acoustic
problems. While beamforming a narrow bass beam that specifically covers the seating
area (rather than the side walls) is one viable approach, the planewave method
offers the best solution. Moreover, a planewave can be easily canceled out by
an opposing planewave with equal and opposite power. The traditional approach
to DBAs involves applying simple DSP techniques, such as sending an inverted
signal to the rear array with an appropriate delay matching the room’s length.
However, DBAs tend to work effectively only in perfect rooms and struggle when
the room deviates from ideal conditions, such as incorporating a riser or
having a non-rectangular shape. DBAs are also highly sensitive to misalignment.

Keith Yates, a prominent advocate of DBAs, has highlighted
the challenges associated with their implementation. His team often had to meticulously
model the room and iterate solutions for extended periods to determine the
optimal placement and DSP processing for each individual subwoofer. While it’s
true that Trinnov may be out of reach for many enthusiasts, optimized DBAs pose
an even greater challenge for a broader audience.

This is where MSMC shines. While it
can utilize DBAs, it offers the distinct advantage of automatically determining
the optimal DSP processing for each signal sent to the subwoofers, resulting in
optimal performance. There’s no need for time-consuming iterations or
specialized software like COMSOL. Previous approaches would require starting
from scratch if significant changes occurred in the room. However, this is not
an issue for Trinnov, as its assumptions are based on the actual
characteristics of the room, allowing for reassessment and adjustments as
needed. Whether it’s adding more subwoofers, using different ones, changing
seating arrangements, or relocating the theater, Trinnov’s MSMC adapts
seamlessly to the evolving environment without complications.

The impact of this
technology is truly revolutionary. The MIMO (Multiple Input Multiple Output)
approach is the only way to achieve such remarkable results. While I appreciate
the bass optimization methods popularized by Welti and Geddes, they were only
capable of reducing spatial variation to a certain extent and were not
universally effective in all room environments. The challenge escalated with
larger seating areas, making it increasingly difficult to achieve satisfactory
results in every chair. Moreover, certain rooms presented insurmountable
obstacles, with destructive interference dips that could only be resolved
through extensive speaker and listening position rearrangements.

Trinnov’s WaveForming
technology eliminates these concerns. By adhering to proper woofer layout
principles and utilizing the new algorithm, the outcome is nearly perfect bass
reproduction in nearly every seat. Although I use the term “nearly”
cautiously due to the novelty of this technology, it has the potential to
deliver flawless bass performance in every seat, given the appropriate setup.
The main limiting factor lies in the number and placement of low-frequency (LF)
sources in the system. As the ratio of sources to wall size decreases, the
spacing between the sources increases, resulting in poorer performance at the
upper end of the system’s bandwidth.

In my personal theater, measuring
approximately 15.5 feet in width and with a ceiling height of 9.8 feet, I have
found that two woofers surprisingly perform well. However, to achieve optimal
results in the 50Hz to 150Hz range, an additional layer of woofers is necessary
due to the height of my ceilings. Configuring three or four woofers in a
triangular or square layout would significantly reduce variability in the upper
bass range. This brings us to the crucial aspect: the layout and quantity of
subwoofers.

Do I REALLY Need More Subwoofers?

Firstly,
I must debunk a myth that seems to be circulating regarding both Dirac ART and
Trinnov WaveForming. There is a notion that these technologies are merely
strategies to sell more subwoofers, or that the number of subwoofers required
for success is so high that only the ultra-wealthy can afford them. This is
simply untrue. Due to the novelty of this technology, we currently lack
sufficient deployed systems to fully comprehend their capabilities. What I mean
is, in practice, we have discovered that things do not need to be as perfect as
expected. The end results often surpass expectations, even with fewer than
optimal woofers and improper placement. Hence, it is incorrect to assume that
achieving good results necessitates using 12 woofers in the front and rear (24
in total) or even 6 in the front and 6 in the rear. While these configurations
would yield excellent outcomes in large rooms, they miss the point. In many
average-sized theaters, mounting just two or three woofers at the midpoint of
the front wall and two at the midpoint of the rear wall can yield highly
favorable results. With a total of only 4 or perhaps 5 woofers, exceptional
outcomes can be attained. However, it is crucial to avoid placing the woofers
on the floor or at the extreme edges of the wall. They should be positioned on
the wall or potentially on stands. Additionally, achieving satisfactory results
with a single woofer is challenging, so a minimum of two woofers is required as
at least two sources are necessary to manipulate LF (low-frequency) waves
effectively.

Interestingly, the output benefits
are primarily derived from the front array. If, for instance, three woofers are
installed on the front wall and two on the back wall, an additional 9dB of
output can be achieved compared to a single woofer. The rear wall array does
not contribute to the output; its purpose is solely for curative correction.
However, based on comments made by Arnaud and our understanding of the
underlying physics of this technology, Audioholics believes that this statement
is not entirely accurate. Below 20 or 25Hz, no correction is needed as all
rooms essentially function as pressure vessels, with the subwoofers uniformly
affecting the room’s pressure. In this scenario, we can provide a different
type of signal to the subwoofers, allowing them to collectively work together
to enhance output. The advantage is that we can use smaller woofers. As long as
the woofers produce any output at 20Hz and below, even if it is minimal, they
can contribute collectively. In the example provided earlier, with five
subwoofers, we observe a transition from an additional 9dB of output to roughly
14dB of extra output. This effect is applicable only at the point of uniform
pressure, but it aligns precisely with where it is most needed.

Do I Still Need Room Treatments?

Let’s address the next myth.
Contrary to popular belief, Trinnov does NOT claim that this technology renders
room treatments obsolete. On the contrary, room treatments are now more crucial
than ever. The truth is, bass traps are not particularly effective. They
exhibit inefficiency, and active methods like MSMC are far superior in dealing
with bass damping. However, this technology does have its limitations. Beyond
those limits, traditional passive absorbers are essential. The challenge lies
in achieving the right balance between active absorption and passive
absorption. It is not sufficient to simply hang panels on the wall and consider
the job done. The result would resemble the figure below.

Instead, careful selection of
absorbers is necessary, with a focus on critical concentration of absorption at
the crossover region. WaveForming does not abruptly cease to function at a
specific frequency, just as passive absorbers do not have a hard cutoff. A
2″ absorber, for instance, can effectively work down to 300Hz, but its
efficacy gradually diminishes below that point. At 125Hz, its absorption
coefficient is approximately 0.2, which is relatively low. Nevertheless, with
sufficient surface area, it can still contribute to overall absorption. This
overlapping region is crucial, and using 4″ absorbers may be necessary to
enhance LF absorption within the 100Hz to 150Hz range. The challenge arises
from the remarkable effectiveness of this new technology. To achieve a suitable
overlap, we may require a greater area for LF absorption than for mid/high
frequency absorption, considering that absorbers become less efficient as
frequencies decrease. This implies that specialized bass absorbers, optimized
for maximum efficiency within the 100Hz to 150Hz range, can provide significant
benefits. Keep in mind that this technology can
operate well above 80hz, but in practice will be limited by the spacing of the
woofers in the array and crossover point selected for them. Ultimately, this
technology reduces the need for bass traps specifically designed for the 20Hz
to 80Hz range and beyond. However, it is essential to
acknowledge that such products are either extremely rare or non-existent (and
it is worth noting that there are few laboratories and no standardized methods
for measuring absorption at such low frequencies).

This
technology is poised to revolutionize the design of speakers and home theaters.
The inclusion of LF sources on the wall has become a compelling proposition,
necessitating the development of optimized on-wall or in-wall subwoofers
capable of delivering impressive output. The current market offerings in this category
are scarce and inadequate, requiring true home theater subwoofers that meet the
demands of this technology. Size is a critical consideration as well, as
excessively tall in-wall boxes would impede practical installation of 4, 6, or
12 subwoofers on a typical wall. Furthermore, the incorporation of full-range
speakers throughout the room offers tangible benefits by increasing the
availability of LF sources in strategically advantageous positions. Notably,
the front wall emerges as the most vital area for significant LF source
placement, making full-range main speakers an invaluable asset. Consequently,
both speaker designs and room layouts must undergo substantial changes to
optimally support this paradigm shift. Placing subwoofers on the floor near corners,
a conventional approach, is no longer optimal. The Trinnov system, in
particular, derives limited benefits from side-wall LF sources. While it can
utilize them, they are not necessary. The optimal location for
the woofers is spaced at 25% and 75% points of the front and rear walls. Many individuals perceive the need
for large, unsightly subwoofers as a hindrance to achieving high-performance
home theaters. However, with this technology, we have the opportunity to
effectively conceal them behind screens and rear treatments, enhancing both
performance and aesthetics. As we embrace this new era, we stand on the
precipice of transformative advancements in speaker and home theater design,
reshaping the possibilities of immersive audio experiences.  

Conclusion

In conclusion, the advent of
Trinnov WaveForming technology represents a seismic shift in the world of home
theater design and how we approach low frequency mode control. By leveraging
advanced algorithms and sophisticated signal processing, this groundbreaking
technology offers unparalleled control over low-frequency sound reproduction.
The implications are vast and profound. It empowers us to reimagine the
placement of LF sources, urging the integration of optimized on-wall or in-wall
subwoofers capable of delivering truly unique bass experiences. No longer
confined to conventional subwoofer locations, we can strategically position
these woofers on the front and rear walls, harnessing their collective power
(and that of the Trinnov technology) to achieve remarkable output and accuracy.
Furthermore, the synergy between this technology and full-range speakers
positioned throughout the room unlocks a wealth of sources in strategic
locations, truly enveloping listeners in a rich and captivating sonic
environment. As we embrace this paradigm shift, both speaker designs and room
layouts must evolve to fully support the transformative capabilities of Trinnov
WaveForming. With the ability to conceal subwoofers behind screens and rear
treatments, we not only elevate performance but also elevate the aesthetic
appeal of our home theaters. The future of immersive audio experiences beckons,
and the allure of Trinnov WaveForming technology compels us to embrace this
revolution in our own home theaters. It’s time to embark on a new era of audio
excellence, where every movie, game, and musical piece resonates with a depth
and clarity that transcends imagination. The possibilities are limited only by
our willingness to embrace the cutting edge.