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.