Since launching its X1 system, Berlin-based pro audio company HOLOPLOT has claimed its stake in the pro audio industry with its science-based, software-driven, hardware-enabled Matrix Array sound systems — especially in the immersive audio space. However, not all applications require a fully immersive sound design to engage an audience. Unfortunately, stereo sound produced by conventional systems only provides the best results for a portion of the audience. HOLOPLOT achieves a more even coverage across the entire audience area by precisely steering and shaping sound, a feature that helps improve levels and clarity, while allowing for widened “sweet spot.”
Changing Expectations
Invented in the 1930s, stereo is still the go-to sound reproduction method for theaters and live performance spaces alike, where the focus point is a frontal, centrally positioned stage. However, venues have become ever larger to accommodate bigger crowds, while audiences — accustomed to listening on headphones and very capable home hi-fi setups — now expect better audio from live entertainment, and conventional stereo sound has some very exposed pitfalls.
“True stereo imaging is only achievable within the so called ‘sweet spot’,” says HOLOPLOT projects lead Gareth Davies. “This is due to the psychoacoustic phenomenon of phantom sources. This phenomenon lets a sound source appear to emanate from a point between two speakers in a stereo configuration and is subject to the same sound arriving at both ears simultaneously and with the same intensity. Anyone not positioned in the sweet spot in the middle of a venue perceives the audio as coming from the loudspeaker closest to them. This causes a disconnect between what we see and what we hear.”
So where do we go from here?
Let’s start with beamforming. It’s not a new concept, but thanks to a combination of ingenious hardware and software design, HOLOPLOT has mastered beamforming technology in the pro audio space to a degree that makes it suitable for even the largest applications with high-SPL volumes.
3D Audio-Beamforming allows HOLOPLOT systems to precisely control the direction and shape of wavefronts. Each Audio Module can produce up to 12 beams, each of which can be EQ’d and tailored to taste via 24-band parametric EQs. Consequently, this enables HOLOPLOT to shape and steer beams in both the horizontal and vertical axes over large distances with laser-like precision.
“All of a sudden, the problems caused by unwanted reflections or other audio anomalies are gone,” says Davies. “Sound can be directed exactly where it is required. HOLOPLOT’s Beam Optimization Algorithms ensure uniform coverage and spectral consistency across the whole audience area, giving engineers the ability to mix for the desired level at the FOH position without having to consider whether it’s loud enough at the back.”
This powerful combination of traditional techniques and existing ideas with new scientific theory lets HOLOPLOT technology take sound control to a new level.
Matrix Arrays for a Better Stereo Experience
Deployed as a stereo system, beams from the left and right Matrix Arrays reach every seat in the house, overcoming the loss of energy in the uncontrolled horizontal axis experienced with conventional sound systems (see Fig. 1). This results in a better stereo mix perception.
“As mentioned above, it’s not possible to extend true stereo imaging outside of the natural sweet spot,” Davies continues. “This applies to any left/right audio deployment. If, however, it can be achieved that the sound level of the left and right array does not change with proximity, you can extend the stereo sweet spot. Our Matrix Arrays generate a much more even coverage thanks to proprietary compensation algorithms that compensate for level loss over distance. This allows us to expand the zone in which both arrays can be perceived at the same intensity, maintaining the integrity of the stereo mix.”
This HOLOPLOT stereo concept works for venues and audiences of small to medium size. Once audience sizes increase, the imaging naturally suffers. For conventional systems, mixing engineers often resort to mixing in mono, and audiences usually perceive that mix from the sound source closest to them. Additionally, “spill” from the neighboring array interferes with the mix, all contributing to a less natural listening experience.
A HOLOPLOT system addresses larger audience sizes differently, as Davies explains: “When a system is scaled up, the beam opening angles need to be widened in order for them to cover every seat in the house. But if we continue increasing the horizontal beam width, we run into problems with the arrival times for off-center listening positions. To mitigate this,” Davies continues, “we taper the beams to reduce the problems of arrival times, limiting the beam opening angles from becoming too great. Where these issues are the most prominent (closest to the stage), front fills are deployed using a downmix of both main arrays to reduce the problem of extreme steering angles, arrival times and loss of uncontrolled high frequencies as you get closer to being off-axis to the beam.”
Getting into the Zone
If an audience area is so large that the distance between two hangs of Matrix Arrays on either side of a stage is too great, this can cause echoes due to the delayed arrival time of the sound from the left and right sources. Splitting up the coverage zone keeps the signals from each array separate, minimizing “cross-talk” for dual-mono use, which significantly improves clarity and intelligibility.
“We’ve created a unique solution that uses 3D Audio-Beamforming to define target zones to mitigate loss in audio imaging caused by extremely large coverage areas,” Davies notes. “By dividing the coverage area into zones, we prevent unaligned arrival times of the beams from the left and right arrays. Using defined zones at the front and to the extreme sides of the coverage area, we’re able to taper the gain to ensure that outside of the alignment zone (within 50ms) the audience will only experience a mono summed mix, resulting in clear, echo-free sound. This is a feature unique to HOLOPLOT and can only be achieved using 3D Audio-Beamforming.”
To help make the decision when zoning is the appropriate approach — as opposed to the beams from both arrays able to naturally reach every seat — HOLOPLOT applies the laws of the Haas effect. “This dictates that if the arrival times of sounds from two audio sources differ by less than 50 ms, equating to approximately 17 meters, they are perceived as a single auditory event. This is regularly exceeded with stages getting wider to accommodate large-scale productions, meaning that if the difference exceeds 50 ms, they are perceived as separate events,” Davies continues. “A difference greater than 50 ms results in a clearly audible echo, especially in close proximity to the stage, so zoning should be considered to prevent this.”
Using HOLOPLOT simulation tools, anticipated delay spread across the audience zone can be assessed. The results of the simulation dictate where problematic times of arrival are likely to occur. This then informs where the audience area should be divided into sections to allow for better control of the level and the mix that goes to these zones (see Fig. 2).
One Tool
Done well, stereo sound can accurately represent the sound stage. The precision and flexibility of a HOLOPLOT Matrix Array sound system will significantly improve the audio for stereo systems. 3D Audio-Beamforming greatly improves the sweet spot and allows FOH engineers to mix stereo content as intended by the artists, rather than having to compensate for the shortfalls of a conventional system in their mix. For the audience, a better localization tied to the stage, combined with better intelligibility and audio quality means less listening fatigue and more meaningful connection to the content.
“At HOLOPLOT, we’ve created flexible tools that allow you to tackle age-old problems, regardless of size or shape of your venue. Our technology truly transcends the space between the creative and functional uses of a sound system, all thanks to our beamsteering capabilities. It not only improves stereo sound, but additionally gives venues and engineers added immersive capabilities, enabling them to offer more diverse shows and content,” concludes Davies.
For more info about HOLOPLOT technology and Sound Control capabilities, visit www.holoplot.com.
