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Distributed Mode Loudspeakers generate sound in a fundamentally different way than traditional loudspeakers.
Conventional loudspeakers use uniform pistonic behavior, whether it’s a cone or dome, or some form of planar magnetic or electrostatic device; usually a ribbon or an electrostatic driver. In other words, traditional loudspeakers are air pumps that create sound waves by moving large volumes of air.
The primary goal of the transducer engineer using a conventional design is to make sure the diaphragm does not have any anomalies, i.e. that it does not “break up” in its pass band. However, diaphragm break up is inevitable. The secondary goal is then to move the frequency of this break up as high as possible so that when it does occur, the crossover filter has significantly reduced its level.
We use bending wave modes in our Distributed Mode Loudspeakers (DMLs), which are designed to break up and not just move as a uniform piston. This break up, i.e. “modal behavior” is very intentional and highly engineered to produce a “diffuse sound source,” which correlates at the human ear.
The acoustic differences, both the traits and benefits, are also fundamental. Conventional drivers are either a point-source or a line-source with fixed-size radiators, and as such they “beam” (exhibit a narrowing pattern at higher frequencies) and have strong (destructive and constructive) interactions with room boundaries. DMLs are a diffuse sound source and are highly resistant to disruptive room interactions, especially within the human vocal range, i.e. they are highly intelligible —even in bad acoustic spaces.
The bending waves in a DML panel are dispersive, meaning that the bending wave speed varies with frequency. This ensures that the primary radiation center automatically adjusts its size to provide wide angle output well beyond that of an equivalently sized piston driver.
There are many other benefits from DML applications including high-resistance to microphone feedback, very low distortion, higher relative acoustic efficiencies, low drop-off front to back, a flat form-factor and more.
Traditional loudspeakers “pump” while DMLs “radiate.” The fundamental difference is that all other flat panel speaker systems use uniform pistonic behavior; usually a ribbon, conical or an electrostatic driver.
There are many benefits from DML applications, besides a flat form-factor, including high-resistance to microphone feedback, very low distortion, higher relative acoustic efficiencies, low drop-off front to back, and more.
DMLs are not like any other flat panel technology on the market—don’t let the slim form factor of other speakers fool you.
Electrostatic Loudspeaker (ELS)
An electrostatic loudspeaker (ESL) is a loudspeaker design in which sound is generated by the force exerted on a membrane suspended in an electrostatic field. This is a highly resistive device, requiring high voltage amplification, and the design is inefficient compared to DMLs.
Ribbons and Planar Magnetics
Planar magnetic transducers typically consist of two main components: a diaphragm with circuit and magnet arrays. The “planar” in planar magnetics refers to the magnetic field that’s distributed in the same plane (parallel) to the diaphragm. Planar magnetic diaphragms, thin and lightweight, are suspended in the magnetic fields created by the magnetic arrays.
Other Flat Panel Systems
There are hybrid systems, in a flat panel configuration, which are not electrostatic, planar-magnetic or DML based. For example, (-)-Array offers a product that is configured as a flat panel, using conventional drivers and horns. It’s very complex.
(-)-Array (flat panel, conventional mid-high + compression drivers + DSP)
“The (-) uses twelve 8-inch cone drivers with 2.5” voice coils for low-mid frequencies, powered by six power amplifier channels. The mid-high frequency section uses five 1.75” voice coil compression drivers mounted on 1”x 4” constant directivity waveguides. The drivers form an array exactly in the center of the speaker.
It all comes down to surface area.
Tectonic DMLs are physically bigger in area than conventional drivers. As an example, the Tectonic DML has approximately five times the radiating area of a 12″ driver, therefore the DML’s total movement need only be one fifth of that to shift the same amount of air.
Imagine a 12-inch bass driver being driven quite hard so that it moves +/- 5mm back and forth. This will produce high SPLs. So we can ask; how much does a DML need to move to shift the same amount of air?
A bit deeper:
The radiating area of a 12″ driver is about 0.05m^2. The radiating area of the Tectonic DML is approximately 0.25m^2. If the 12″ driver is moving +/- 5mm, a DML only needs to move +/- 1mm to shift the same volume of air. For the DML to produce the same SPL as the 12″ driver, it only needs to move about a fifth as much.
However, the surface of a DML does not usually move as a rigid piston and the comparison shown above is only true for lower frequency operation of the DML. At higher frequencies, the surface of a DML is undergoing complex vibrations with multiple regions moving with different phases, so the total net radiating area is reduced (although both sides of the DML are now contributing). But remember: we are no longer comparing a DML with a 12” bass driver because a 12″ cone cannot radiate above a few hundred Hertz. In the mid-range, a conventional speaker system is likely to use one or two 3” drivers, each having a radiating area of around 0.0033m^2. (Compression drivers / horns take over from there.)
Comparing these drivers with the radiating area of a DML (0.25m^2 x2 = 0.5m^2 for both sides remember) we can see that this is equivalent to 0.5/0.0033 = 150 midrange drivers. So even if just a portion of the radiating area of a DML is contributing to the on-axis output, there’s easily enough area to provide sufficient output.
Tectonic loudspeakers’ superior intelligibility is a combination of several technical and performance characteristics:
Tectonic loudspeakers generate virtually no 3rd-order harmonic distortion
Pistonic-based transducer designs – cone drivers, compression drivers and horns – by nature of their design, produce odd-order harmonic frequencies (distortion) that are near and can even exceed the amplitude of the original signal source at sound reinforcement output levels. Odd-order harmonics are both unpleasant sounding and mask intelligibility. Tectonic Plate odd-order harmonic distortion is so far below the original input signal as to be nearly immeasurable.
The Tectonic DML has a nominal bandwidth of 100Hz – 20kHz (+/- 6dB)
(A large-format ribbon transducer/wave guide takes over from there to above 20kHz.) There are no passive or active crossover points in the DMLs critical vocal/instrument range that could introduce phase, frequency or delay errors. No external DSP or signal processing is required throughout the pass-band of a DML.The PL-11NR can operate full range without any crossover.
The random and diffuse acoustic radiation characteristics of Tectonic loudspeakers are minimally interactive with reflective room boundaries
Thus, secondary acoustic arrival reflections are not a correlated secondary sound source and do not decrease intelligibility by way of echoes or slap-back.
Tectonic loudspeakers create an extremely wide coverage pattern and very long throw
This provides stereo or surround imaging to nearly every location in a given venue for nearly the same audio experience to all areas.
Collectively, these attributes provide a superior level of intelligibility over existing loudspeaker systems.
Yes … and no.
Yes. Tectonic loudspeakers are extremely forgiving when it comes to room placement and coverage, minimizing room interaction and the need for acoustic treatment. Installation and rigging needs are significantly less than required for line arrays and trapezoidal flown or ground-stacked enclosures.
The Tectonic loudspeakers inherent feedback resistance, full band-width frequency response from 80Hz – 20kHz (including HF ribbon driver,) and no complex DSP needs makes for minimal processor requirements. We have found, from extensive use of the Tectonic systems in a wide array of settings, that there is little house EQ needed to accommodate specific venues.
We currently recommend the Symetrix Radius for simple crossover, limiting and system EQ tasks. That’s all the Tectonic system needs. (Note: The Tectonic system requires our own factory-locked settings for crossover points and power protection. By-passing these settings will void the Tectonic Warranty.)
Tectonic loudspeakers are highly resistant to feedback and allow for fairly extreme speaker placements and the flexibility to add open mics in front of the Plates. That having been said, some feedback situations can occur, requiring adjustments in staging and level management.
No. The Tectonic system is merciless in representing the rest of the signal chain and any problems that may exist that other speaker systems do not reveal. This has been verified at several demonstrations in major venues where poor electronics, bad microphones, unknown DSP plug-ins, internal routing errors, word-clock issues etc. were discovered. It is a reality of a low distortion, revealing speaker system.
Furthermore, the traditional cues to the sound operator that the system is being pushed too hard are not generated by the Tectonic loudspeakers Typical symptoms include excessive 3rd-order harmonic distortion and voice coil bottoming-out. The Tectonic system cannot produce these effects, so the system just goes until it doesn’t. It’s an easy fix—just use your dB meter until you ‘re-calibrate’ your ears.
A note about SPL/dB meters: Pointing an SPL meter at the Tectonic loudspeakers is not an accurate measurement of excessive system output, as the DMLs are not producing a pistonic audio energy wave into the room; ie. not producing sound pressure that a meter is expecting to measure. SPL meter readings of the Tectonic loudspeakers typically read about 3 – 7dB less than actual system output depending on room size. Bottom line—the ‘experience’ will measure surprisingly less than what your ears tell you is happening. This is agood characteristic; just remember this when taking your first readings.
We provide processor files for Symetrix, Lake, Rane, Powersoft, Ashly and many other leading DSP system controllers that include limiting parameters to keep excessive system drive from occurring. That having been said, operator orientation is strongly advised. (Please contact us if we don’t have the settings you’re looking for.)
The wide directivity and diffuse characteristics provide slightly better “drop-off” performance in enclosed rooms than with traditional loudspeakers.
For all speakers that provide room sound there is a measurement called the Critical Distance. This is the point where the level of direct sound equals the level of the reverberant sound in the room.
The more directional a speaker is, the further away from the speaker the Critical Distance occurs. The Critical Distance changes from about 30” (75cm) for an omnidirectional source to over 6.6’ (2m) for a more directional one.
Traditional sound reinforcement speakers have always tried to avoid sending too much energy off to the sides, top and/or bottom of a venue because the waves from these speakers are phase coherent and they can create unwanted reflections bouncing off the walls, floor etc., which obscures intelligibility.
Focusing coverage increases the Critical Distance, meaning that more of the audience is in a region where the sound falls with the square of distance. Putting the audience in such a region means that those at the front will experience significantly higher sound levels than those at the rear – this is not ideal.
Line arrays and steerable column loudspeaker systems, by design direct the audio energy only at the audience, as much as possible. The way that these systems increase throw is by increasing the relative volume of the speaker elements that are aimed at the farthest locations, e.g. the top boxes in a line array are receiving more relative power than the boxes located in the lower part of the “J” array. This allows similar sound levels reach the front and back audiences.
This is the opposite of how real instruments radiate sound into a room, so the effect is not natural.
Enter the DML
DMLs have wide directivity and therefore give a much reduced Critical Distance. This means that after the first 3’ (1m) or so, the drop-off in level is closer to a linear slope. Basically the balance between the direct and reverberant fields is much smoother with an omni-directional source such as a DML.
In other words, as you walk away from a DML you are already almost certainly in the reverberant field (after the first 3’/1m or so) and so will experience a much slower drop off. The initial region (direct sound field) is less intense because the DML is radiating its sound over a wide angle, not ‘firing’ it in a specific direction like a traditional system.
The near omni-directional nature of DMLs would cause significant intelligibility problems if it wasn’t for the fact that DMLs are predominantly diffuse sources. This means that all the energy going into driving the reverberant field is not bouncing around and causing interference. It’s actually doing what the sound from real instruments does.
It’s all back to the diffuse characteristics of the DML.
Feedback is reliant on the looping signal encountering itself in a well-defined way. If the waves coming off a speaker (wavefronts) are ‘coherent’ then it’s easy for the signal to encounter itself at just the right time to generate feedback. It’s a bit like watching a kid on a swing. You can quite easily work out the best time to push him because the motion is so clearly defined. This is because the cone moves rigidly, as one.
For a DML the wave fronts are not coherent, as different parts of the DML are moving in different directions, so the wave fronts arriving at the mic are not in a simple order. It’s a bit like trying to push 10 kids all swinging at random—it would be pretty hard to work out how to step in and push them all so that they suddenly all swing together in unison.
Usually feedback occurs at a specific frequency that is often the loudest individual frequency in the speaker’s bandwidth.
For a conventional speaker there are usually two loud frequencies; the first mode, (or more correctly the zero-th mode), which is the fundamental mass-spring resonance of the system, and possibly the first break-up mode at the upper end of the drive unit’s pass band. Whichever frequency the feedback locks to, it can often be one of these.
The response of a DML is intentionally designed to have as many modes (resonances) as possible, such that any energy prone to a feedback loop to lock into a specific mode is greatly diminished because there are so many of them. The energy is spread across these multiple modes and no single mode is strongly excited into feedback.
The Critical Distance to generate feedback is the distance from the source at which the direct sound level equals the reverberant sound level. For more directional speakers this distance is further from the source (speaker). For more Omni-directional speakers this distance is closer to the source. For feedback to occur, the mic should usually be within the Critical Distance to ensure a strongly correlated feedback path.
DMLs have wide directivity (more omni-directional) dispersion so the Critical Distance is closer, therefore the mic can be brought closer to the speaker before feedback ensues. Conventional speakers with narrower directivity push the Critical Distance further away from the speaker, therefore feedback occurs from much further out.
In most cases, this results in a much greater “gain before feedback.” There are other factors that can reduce this that must be considered, such as type of microphone (dynamic or condenser) and pattern (Cardiod, Omni). However, in the worst case scenario, we find that Tectonic loudspeakers are no worse than traditional loudspeakers and in most cases are much better.
It’s all about those Diffuse Waveforms again.
Tectonic DMLs propagate audio energy in a fundamentally different way than traditional speaker designs; whether it’s a ubiquitous cone or dome or some form of planar magnetic or electrostatic device.
All of the above mentioned designs rely on a uniform pistonic action that delivers an energized column of air into the performance space, with energy and coverage based on driver size and frequency response. The result is relatively high-energy sound waves meeting the boundaries of an enclosed space in a highly correlated manner that reflect directly back in as a correlated wave front that arrives a bit later at the listener’s ear and, depending upon the difference in arrival time, is perceived as an echo or ‘slap-back.’
Each pistonic driver, in its own frequency range, has its own audio energy and coverage characteristics. Reflected audio wave fronts are coherent only for each driver and will be additive or subtractive to the full bandwidth audio; creating areas of unequal audio energy, phase, and frequency anomalies.
Tectonic DMLs propagate audio energy as a non-pistonic energy source, such that audio energy, while initially pistonic enough to create a stereo image, is predominantly diffuse and random. Audio energy produced by a DML that bounces off of a reflective surface is equally diffuse, random, and therefore non-disruptive. Reflected audio energy is not simply correlated to the source audio, and therefore not perceived as an echo or ‘slap-back’.
Absolutely—and in most cases, much better than with traditional loudspeakers.
First, please consider that in most cases, while most traditional loudspeaker systems may in fact be “wired” in stereo, they are not intended to be utilized in stereo. Most sound systems have a singular loudspeaker (or array) designed to cover a seating area. Much care has to be taken minimize overlap and interaction between the loudspeakers, as well as the room. Unless a system has been designed with “stereo shading” loudspeakers (loudspeakers that cover all seating areas from from the left and the right) it is effectively a mono sound system. If you “pan” a particular channel to one side or the other, you are effectively “removing” the sound from the opposite side. The only place where true stereo happens is in the center-most position.
Enter the DML: The panels can produce highly directional sounds, including stereo and surround imaging. This is true for listeners far off axis, including positions on the outside of a stereo outside panel. There are no sweet spots where a listener needs to sit to hear differential acoustic information coming from the panels to create a stereo image. All seats receive stereo directional cues.
There is a relatively small component of pistonic energy that is produced by a DML, right at the beginning of the panel’s excitation. This gives the ear just the cue it requires to locate the source and, with two speakers, to create a stable stereo or surround image. When the remaining energy arrives it does not conflict with the initial component because the remainder is the diffuse output, containing none of the echoes or interference that a conventional speaker produces.
Additionally, since the panels have little drop off (i.e. long throw) and stable wide coverage, the distance from any given panel does not adversely affect the imaging capability. This means that a person sitting in the corner of a venue, either in the front or in the back, can hear stereo and surround events.
The economic advantage for Tectonic loudspeakers is realized in the cost of ownership and use; compact form-factor, reduced power and processing needs, minimal room treatment needs, transport and rigging savings, etc.
The Tectonic loudspeakers are designed for sound reinforcement use in a range of sizes, from small rooms to large stadiums., both fixed install and portable. They are designed to replace traditional line-array solutions for these larger applications.
In real world comparisons, Tectonic has found that fewer speakers are needed to cover the same space as competitive line arrays. We also believe that the Tectonic solution does this with superior acoustic performance.
For example, a 5×5 (10 Plates total) system can typically cover an audience up to 7,500 seats or more depending on the configuration of the venue. This same coverage, employing a line array, may take up to ten boxes per side (20 boxes total), or more. Plus, this type of venue can require fill speakers to augment the highly directional coverage of a line array.
Another example – for smaller venues – would be a simple 1×1 Tectonic system (one panel on each side of a venue), supported by an appropriate subwoofer configuration. This simple install can support 50 to 500 seats, or more, depending on the configuration of the space, and can be mounted employing floor stands or a simple VESA compatible (flat screen TV) mount.
Compared to large-format line arrays, Tectonic loudspeakers are compact, lightweight, quick and simple to rig. The integral rigging system and wide variety of quick-pin interconnects allows complex hangs to be assembled and raised right out of our ‘Toaster’ four-plate road cases.
Two Tectonic ‘Toaster’ cases containing four Tectonic loudspeakers each can easily cover 3,500 – 5,000 seats.
The electrical impedance of a Tectonic DML is predominantly resistant over almost all of its bandwidth, presenting a much friendlier load to amplifiers than almost any other speaker type; with greatly reduced amp and A.C. power needs. Due to the efficiencies of the Tectonic loudspeaker design, A.C. power and amplifier demands are significantly lower; typically two 110v 20A outlets for 5,000 seats.
While Tectonic loudspeakers scale extremely cost-effectively in larger touring operations, smaller venues gain a very cost-effective solutions as well. For Example. two PL-11-NR’s with one or two LS-212 subwoofers can cover a room with 500 seats or less quite well, from either an installed standpoint, or a very flexible portable configuration. In addition to coverage economies, unique room shapes such as very wide rooms can be covered with the same configuration, benefitting from the 165 degree coverage. Tectonic’s minimal room interaction can be a great benefit for portable configurations, where the user is not at luxury to adjust the acoustics of the room in any way.
EASE™ is a predictive software solution that can measure the output of a point source speaker and provide a fairly accurate prediction of its behavior in a modeled 3-D space. The key to its abilities is that it’s measuring a device where audio energy is emitting form a single point. Ease allows designers to virtually “place” loudspeakers, and adjust minute details of the coverage angles to minimize room interaction and loudspeaker-loudspeaker interaction. DMLs mostly eliminate the room interaction component leaving only the coverage angle. Simple modeling applications such as SketchUp can be used if finite analysis is needed. Otherwise, in most cases, the 165 degree coverage of the DML is very easy to place effectively, eliminating the need for costly room modeling.
A DML is a different class of acoustic radiator with a highly complex radiation characteristic that’s not supported by EASE, etc. The DML behaves as a highly complex array of multiple point sources at once; all radiating with a pseudo-random phase distribution across the surface of the panel. There is no one point to measure.
Point source-based predictive software tools are currently not able to cope with the highly complex phase distribution across the panel’s surface and diffuse radiation characteristic of a DML. When we’ve tried in the past, the software just gives a nonsense result, as one would expect. A new generation of software needs to be developed that can understand a bending wave device and provide meaningful information as to its characteristics in a given space.
While predictive software is helpful in creating a speaker system design for a space, with a DML it’s far less critical. The audio energy produced is very broad, diffuse and un-correlated, unlike the very focused and correlated energy from a pistonic device. The net effect is that a DML does not react strongly with reflective room surfaces. The need to use predictive software to keep speaker energy away from reflective surfaces is much less critical for a DML than for a coherent source.
Furthermore, the DML’s 165⁰ horizontal and vertical coverage pattern greatly diminishes the need for precise aiming. It’s an audio fluorescent tube vs. a spotlight.
In traditional speakers, pictonic vibrations of the cone diaphragm produces the sound. In Tectonic loudspeakers, the sound is produced by complex bending wave vibration patterns.
BMRs create superior off axis performance over conventional, equivalently sized, drive units.
A fundamental challenge associated with conventional speaker technology is that when the wavelength of the sound becomes approximately the same as size as the cone circumference, the speaker performance starts to power beam. Beaming is a phenomenon where a mismatch in speaker size verses driven frequency causes a loss of 12dB of sound power per increasing octave. Because the wavelength of sound gets smaller with increasing frequency, power beaming effects will occur at and above a certain frequency. Power loss starts at the most off axis angles and moves inward. This means that multiple drive units are needed to deliver the full audible frequency spectrum in a typical room environment. Added cost and complexity are often the result of this.
BMRs use controlled breakup of the radiating diaphragm to elongate the usable pass band of the speaker. At frequencies with modes the diaphragm is segmented into smaller radiating areas. Smaller radiating areas reduce the effect of power beaming. Masses are placed at specific locations on the diaphragm to utilize the desirable impacts of modal behavior. This is the “balancing” at the core of the technology. Frequencies where piston motion of the driver would have beaming effects are now supplemented off axis from bending modes within the diaphragm.
Two-way systems consist of 2 different drivers, each reproducing a different frequency band. These two drivers blend together at the systems crossover frequency, where ideally both speaker outputs sum to create a flat response through the transition. This crossover frequency in conventional driver systems is generally dictated by the limited low range capabilities of a tweeter, and the breakup of the low range driver as it reaches the top of its useable frequency band, and often lands between 1kHz-3kHz.
This range is an especially troublesome area for any abnormal phase or timing issues that may arise from a crossover, as the human ear is exceptionally sensitive to this area due to its association with the voice and speech intelligibility.
BMR drivers combat this issue by having a functional frequency range that spans the entire vocal range, and allows a crossover at a lower, less sensitive area. This is accomplished again by the balancing of desirable modal behaviour which supplements higher frequency behaviour with modal output. This also gives the low frequency woofer in the two way system a significant advantage, as it can now be optimized entirely for the low end of the system, as opposed to having to supplement the mid range as well.