Distributed Mode Loudspeaker (DML) is a flat-panel

loudspeaker A loudspeaker (commonly referred to as a speaker or, more fully, a speaker system) is a combination of one or more speaker drivers, an enclosure, and electrical connections (possibly including a crossover network). The speaker driver is an ...

technology, developed by NXT, in which sound is produced by inducing uniformly distributed vibration

modes Mode ( meaning "manner, tune, measure, due measure, rhythm, melody") may refer to: Arts and entertainment * MO''D''E (magazine), a defunct U.S. women's fashion magazine * ''Mode'' magazine, a fictional fashion magazine which is the setting fo ...

in the panel through a special electro-acoustic exciter. Distributed mode loudspeakers function differently from most others, which typically produce sound by inducing

piston A piston is a component of reciprocating engines, reciprocating pumps, gas compressors, hydraulic cylinders and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder (engine), cylinder a ...

ic motion in the diaphragm. Exciters for distributed mode loudspeakers include, but are not limited to, moving coil and piezoelectric devices, and are placed to correspond to the natural resonant model of the panel.

Applications

NXT licenses two classes of distributed mode loudspeaker: SurfaceSound for traditional flat-panel applications, and SoundVu for applications in which sound is produced directly in front of the display (either through a

projection screen A projection screen is an installation consisting of a surface and a support structure used for displaying a projected image for the view of an audience. Projection screens may be permanently installed on a wall, as in a movie theater, mounte ...

which functions as a DML or a transparent DML overlaid on the display). SurfaceSound technology has been incorporated into a number of novel products such as school equipment, portable folding cardboard speakers (SoundpaX, an OEM product manufactured by a number of different companies), and high-end musical

greeting card A greeting card is a piece of card stock, usually with an illustration or photo, made of high quality paper featuring an expression of friendship or other sentiment. Although greeting cards are usually given on special occasions such as birthday ...

s. Aside from projection screens, SoundVu has been integrated into computer and mobile phone displays. NXT also licenses the Balanced Mode Radiator (BMR), a hybrid technology that blends DML technology with that of traditional pistonic-action loudspeakers. According to NXT, the resultant speakers feature the low-frequency performance of a traditional loudspeaker, but with a wider directivity and shallower profile, as well as the

mid-range In statistics, the mid-range or mid-extreme is a measure of central tendency of a sample defined as the arithmetic mean of the maximum and minimum values of the data set: :M=\frac. The mid-range is closely related to the range, a measure of ...

and

high-frequency High frequency (HF) is the International Telecommunication Union, ITU designation for the radio band, band of radio waves with frequency between 3 and 30 megahertz (MHz). It is also known as the decameter band or decameter wave as its wavelengt ...

performance of a DML. The two types of BMR offered are: the Audio Full Range (AFR), a

full-range A full-range loudspeaker drive unit is defined as a driver which reproduces as much of the audible frequency range as possible, within the limitations imposed by the physical constraints of a specific design. The frequency range of these drive ...

optimized circular speaker; and the High Aspect Ratio Panel (HARP), a long and thin form factor for use in narrower spaces. DML exciters are compatible with traditional amplifiers. Initial testing by researchers at the

Delft University of Technology The Delft University of Technology (TU Delft; ) is the oldest and largest Dutch public university, public Institute of technology, technical university, located in Delft, Netherlands. It specializes in engineering, technology, computing, design, a ...

concluded that DML panels are good potential candidates for use in

wave field synthesis Wave field synthesis (WFS) is a spatial audio rendering technique, characterized by creation of virtual acoustic environments. It produces ''artificial'' wavefronts synthesized by a large number of individually driven loudspeakers from elemen ...

applications, as they are light and can be placed close to walls.

Purported advantages and disadvantages

Advantages

*Broad frequency range (100 – 18000 Hz for 0.6m² panel). *The air radiation resistance is small and constant with frequency. This means that directivity is not affected by size of speaker. *Bipolar (radiates sound in 2 directions), but may be made forward directed. *Flat, don't require enclosing, may be produced in different shapes, may be decorated etc. Some DML units are designed to be plastered into walls and completely hidden. *Low cost of materials relative to traditional loudspeaker designs.

Disadvantages

*Problems radiating low frequencies. Increase in size makes it possible to radiate sound with lower frequencies. *Low directivity and slow fading may lessen

stereophonic sound Stereophonic sound, commonly shortened to stereo, is a method of sound reproduction that recreates a multi-directional, 3-dimensional audible perspective. This is usually achieved by using two independent audio channels through a configurat ...

impression. Still, listening from an off-center position gives some imaging of phantom sources as the other speaker can be heard with its full spectrum, but with extra delay due to the listeners local position.

Business history

NXT created intellectual property for surface transducers. HiWave Audio was created in late 2010 as the rebirth of NXT. Tectonic Elements was founded following the acquisition of HiWave Audio by FLAT Audio Technologies.

References

External links

Understanding the balanced-mode radiator, James Lewis, 30 November 2012Analysis of Flat Panel Speakers, Luke Humphry, King’s College Cambridge 2007Analysis of Flat Panel Speakers, Luke Humphry, King’s College Cambridge 2007 (final draft)
{{DEFAULTSORT:Distributed Mode Loudspeaker Loudspeakers