Discover the difference of the Tectonic Flat Panel Speakers.
If you are at this page, you are looking for more detailed information than that provided by our marketing materials and the Tectonic FAQ’s. The following collection of white papers detail the concepts, designs and math that embody our Resonant Mode Loudspeaker patented technologies as applied to Distributed Mode Loudspeaker applications.
These documents explain the science, performance and behaviors of our core technology; the Distributed Mode Loudspeaker (DML). While these materials are not specific to Tectonic Plates, we are the only company to utilize this technology for large-format sound reinforcement.
The following collection of papers starts with a technical overview provided by NXT® describing the basics of DML technology. Library contents continue on with a collection of published AES Papers describing the specific operation, characteristics and benefits of DML transducers and systems. Included are additional documents from other entities that have experimented with and documented DML characteristics and performance.
Click on the PDF links at the end of each abstract to view.
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"Much of the past 70-plus years of loudspeaker development has revolved around identifying, understanding and then suppressing diaphragm resonances and their resulting coloration and ‘smear’ What we will describe here is an entirely different approach which, rather than attempting to eliminate transducer resonances, encourages and exploits them."
Audio professionals are understandably wary of an idea that so comprehensively inverts the conventional wisdom. But if you read through this description of our technology we are confident you will understand why we at NXT believe this innovation actually brings major benefits to both loudspeaker users and loudspeaker designers.
A theoretical model of the distributed mode loudspeaker (DML) is presented, and compared to that of a conventional, mass-controlled loudspeaker. Electro-mechanical modeling results are compared to real measurements of example DMLs. The implications of uniform directivity and diffuse radiation to room interactions are discussed.
The principles of a new class of acoustic radiator (DML) are described and the counter-intuitive result for broad, band, frequency independent acoustic radiation established. It is demonstrated that a low-loss panel with optimal modal distribution produces a flat power response. A simple mechanical model is presented to calculate the mean velocity within the panel as a function of frequency and intrinsic properties.
The unique signal generation and radiation characteristics of Distributed Mode Loudspeakers (DML) suggests that they should find effective application in Sound Reinforcement and Public Address / Announcement systems. In particular, their reduced boundary Interaction, diffuse and wide radiation properties should be of benefit. This paper reports the results of theoretical modeling studies, site and laboratory measurements. It is shown that the Distributed Mode Loudspeakers can be successfully employed in such situations, but that traditional sound system assessment techniques may need revising and extending in order to adequately deal with this class of loudspeaker.
The Distributed Mode Loudspeaker’s performance is analyzed with reference to its radiation mechanism. In particular the effect of the wave propagation type, shear or bending, over the frequency range is examined. The paper shows that a flat frequency response is possible, but only under certain conditions.
A Distributed Mode Loudspeaker (DML) operates by introducing bending waves into a panel, which has specified mechanical properties. Although the dimensions of the panel will affect the bandwidth, the sound radiated from such a panel will be diffuse in nature, and the directional characteristics should be substantially independent of its size. Both the theoretical justifications as well as some practical comparisons are given.
DML Scaleable Directivity.pdf
A method involving the evaluation of the Cross-Correlation Function has been developed to describe the diffusivity of direct sound radiation. The dependence of the spatial correlation of the radiation field on sound source properties and frequency has been investigated. This work has highlighted the diffuse nature of the sound field of a Distributed Mode Loudspeaker vs. the correlated output of a conventional cone loudspeaker.
DML Diffusivity Properties.pdf
The degree to which radiation from a loudspeaker is diffuse may be quantified by a spatial correlation function normalized to the on-axis response. This is true for any loudspeaker type, including the distributed-mode loudspeaker (DML). However, because of the variation in material damping and design-related constraints, correlation commonly varies both with frequency and direction. A modified function, the offset spatial bandwidth of correlation function, is introduced as a means of describing diffuse performance and quantifying its variation over the radiation field.
DML Spatial Bandwidth.pdf
Traditional phase-coherent acoustic radiators are subjected to destructive interference when they interact with their boundaries. A new class of acoustic radiator is discussed, whose radiation is spatially and temporally diffuse; mitigating the problem by producing sympathetic boundary reflections. Results from computer simulations for both classes of radiator are presented, and these are compared to single boundary and listening room measurements.
DML Boundary Interaction.pdf
The diffuse nature of the radiated sound from a distributed-mode loudspeaker is likely to produce a less severe boundary interaction normally associated with early reflections and their related audible coloration. This effect is investigated and comparisons are drawn between specular phase-coherent speakers and distributed mode panel (DML) radiators. Results are presented and supported by both measurement and analysis.
DML Early Reflections.pdf
In AES paper 5215 presented at the 109th convention, both 2-D Finite Element Analysis (FEA) and measurements were used to examine the effects of a single dominant reflection on the radiation of a loudspeaker. This earlier research is extended here by exploiting an analytic 3-D solution to the problem of an acoustic source located in a non-anechoic room. Unlike the earlier FEA solution, this method is mesh-less, potentially providing output at any point in space at any frequency. Application of the inverse Fourier transform allows the method to model time domain results indirectly, thereby providing a complete time and frequency domain description.
DML Modeling Room Interaction.pdf
The unique sound generation and radiation characteristics of distributed mode panel loudspeakers (DMLs) are shown to produce improved intelligibility under given listening conditions. The improvement mechanisms are investigated and are shown to be related to a number of unique features of this new type of radiator, including transient response, synergetic decay, lower inherent distortion, the directivity and the diffuse nature of acoustic radiation.
Acoustic feedback stability is a fundamental limitation of all public address, sound reinforcement and duplex teleconferencing systems. Over the past 30 years, a number of techniques have been developed to help improve the gain before feedback margin. This paper reviews progress to date and demonstrates that a new class of loudspeaker, the distributed mode loudspeaker inherently possesses a number of characteristics which potentially make it less prone to feedback. Initial experiments are reported which show a 4dB improvement in feedback margin without electronic assistance, gains comparable with most other current signal processing techniques.
In the auditioning of Distributed Mode Loudspeakers (DML), listeners have remarked on the position independence of sound quality. This study compares the subjective loudness properties of DML and conventional loudspeakers. Auditory modeling of objective measurements and the results of psychometric experiments to determine the perceived loudness, are presented in this paper. Investigations into the psychoacoustic mechanisms to explain the phenomena are discussed.
The distribution of the acoustic field from a DML class radiator in real room environments has not been fully described to a satisfactory level. Anecdotal evidence (often from experienced listeners) and some limited experimental evidence suggests that the acoustic field radiated by DMLs into rooms does not experience as noticeable a drop-off with distance as is commonly observed with conventional piston class radiators. Listeners have also commented that DMLs appear to provide a more natural and less fatiguing acoustic experience.
Results of a series of subjective listening tests support the hypothesis that diffuse acoustic radiators, such as distributed-mode loudspeakers (DML), lessen the degradation caused by room acoustics on stereophonic localization. In early tests, a pair of DMLs performed at least as well as quality two-way cone-in-box loudspeakers. Further experiments to confirm the hypothesis are reported.
Perceived timbre depends strongly on spectral shape. We compared spectral shape discrimination for a Distributed Mode Loudspeaker (DML) and a cone loudspeaker. Subjects were asked to distinguish between a tone complex with a flat spectral envelope, and a tone complex with a ripple in its spectral envelope, for each type of loudspeaker. The ripple depth was varied to determine threshold. Performance was significantly better for the DML than for the cone loudspeaker.
The complex radiation pattern generated by distributed mode loudspeakers makes a single-point measurement an inadequate representation of the sound field. In this paper we discuss simple multiple-point measurements as appropriate characterization tools. These techniques are used to determine the total power, together with its directivity, and are equally applicable to both distributed mode and conventional cone loudspeakers.
The Distributed Mode Loudspeaker’s polar response is analyzed with reference to its radiation mechanism. In particular the polar response below and above the supersonic plate propagation boundary is examined. The paper shows that a quasi omni-directional response is possible.
DML Polar Patterns.pdf
An experimental investigation is reported into the effects of a porous layer on the radiated sound intensity from distributed mode loudspeakers (DMLs). For an un-baffled panel, the results suggest that attaching an absorbent layer behind the panel leads to a smoothing of the spectra of sound intensity. When a specially developed enclosure was used, an improvement in the low frequency response of DML panel was observed. The inclusion of a porous layer in this enclosure further reduced the fluctuations of the emitted sound spectra, and smoothed the resonance peaks in the low frequency range.
A radiation model of the Distributed Mode Loudspeaker (DML) is investigated and compared to measurements. The approach makes use of the bending wave Eigen Functions and Fourier Transformation to describe the acoustic coupling. The model is implemented into a lumped element simulator, which helps to display the complete system response including exciter and other components.
DML Radiation Simulation.pdf
The usefulness of Distributed Mode Loudspeakers (DMLs) in arrays has been investigated. The design goal is an array that evenly distributes energy over a hemi-disc. A model has been developed to predict trends of DML array radiation and compared with measurements. This model enables the performance of established array technologies to be tested.
The applicability of distributed mode loudspeaker (DML) panels for Wave Field Synthesis based sound reproduction is investigated. For WFS a large number of closely spaced loudspeakers is necessary. DML panels are light-weight and can be placed directly on the walls. Results are reported of a research project to test the objective and subjective performance of these speaker panels.
Conventional pistonic loudspeakers excite the modes of an enclosed sound field in such a way as to introduce modal artifacts which may be problematic for listeners to high-quality reproduced sound . Their amelioration may involve the use of highly space-consumptive passive absorptive devices or active control techniques [eg 2,3,4]. Other approaches have concentrated on the design of the driver used to excite the room. Distributed sources ranging from the dipole  to more complex configurations  may be expected to interact with the room eigenvectors in a complicated manner which may be optimised in terms of the spatial and frequency-domain variance of the soundfield. Recent interest in distributed sources has centred on the Distributed Mode Loudspeaker (DML), and this paper reports an investigation into the interaction of DMLs with modal soundfields. It is shown that large DMLs may be expected to modify the low-frequency soundfield. Producing useful low-frequency control remains difficult but may be achieved in some circumstances.
LF DML Room Excititation.pdf
In this paper we examine methods for digital room correction and loudspeaker equalization as they apply to Distributed Mode flat panel loudspeakers. We present a method that combines LPC inverse filtering and tunable DWT octave-band equalization. Furthermore, we discuss frequency response and time-domain smearing/spread issues and considerations for real-time implementation.
DML – New Approach to Speaker/Room EQ.pdf
A Distributed Mode Loudspeaker (DML) operates by introducing bending waves into a specified panel, so that the radiated sound will be diffuse in nature. By mounting the panel into an infinite baffle, the effects of panel edge diffraction will be eliminated, and the directional characteristics can be easily observed. Measurements of sample panels are compared to theoretical models.
DML Scalability In Infinite Baffle.pdf
Distributed-mode loudspeakers are well known for their unique complex diffuse-dipolar radiation, in certain applications, however, the rear radiation may be a hindrance to the best performance of the system. The present paper investigates the unique behavior of DMLs in closed enclosures of small dimension, offering analytical solutions leading to the prediction of the far-field pressure as well as the impedance response of the system supported by various measurements.
DML Small Enclosures.pdf
True spatial reproduction of sound images over a large listening area can only be achieved by Wave Field Synthesis, which requires a high number of individual loudspeaker channels. This paper describes a novel method to realize such systems in a practical way using multi-exciter distributed mode panels and digital filtering. Explained in detail are filter designs for the reproduction of plane waves, which is required to efficiently transport and render a wave field in a perceptual sense, and filters for the creation of focused sound sources behind or in front of the panels. For MPEG-4 applications, the display of moving sound objects requires special algorithms to generate and interpolate long impulse responses, which are presented as well.
DML Spatial Reproduction Arrays.pdf
It’s not easy to overturn 80 years’ worth of established thinking on how to reproduce sound.
Flat speaker delivers volumes of sound
There has been developed a new class of the loudspeakers, the principle of work of which is based the excitation of vibration in flat panel as a result of which they appear the standing waves. For the production DML loudspeakers are used rigid, light materials with the small mechanical damping.
Research of DML Loudspeaker Properties.pdf