NXT Explained

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					                              NXT EXPLAINED


                                           Table of Contents

1  The potential beneffits of NXT technology ................................................ 2
 1.1   Commercial ....................................................................................... 2
 1.2   Architectural....................................................................................... 2
 1.3   Performance ...................................................................................... 2
 1.4   Design considerations ....................................................................... 2
2 Introduction ............................................................................................... 3
 2.1   Quick Comparison ............................................................................. 3
3 Detailed explanation ................................................................................. 4
 3.1   What is sound? .................................................................................. 4
 3.2   How big is sound? ............................................................................. 4
 3.3   Auditory system ................................................................................. 4
4 Sound sources .......................................................................................... 7
 4.1   History ............................................................................................... 7
 4.2   Piston type Sound source .................................................................. 7
 4.3   NXT flat panel .................................................................................... 9
 4.4   Summary of advantages for NXT panels ......................................... 10




By: Jan Hawrot 6ec93fab-3a7a-4af0-a9ba-eec5c4f845a8.doc                                       Page 1of 10
                  NXT EXPLAINED


1       THE  POTENTIAL                BENEFFITS             OF        NXT
        TECHNOLOGY
1.1       Commercial
1.1.1       Because of the lightweight and simple design and construction
            of an NXT panel, volume production will offer a competitive
            solution. In its current form, the NXT panel can be used as a
            direct replacement for ceiling, wall cabinet, projection and
            suspended ball type speakers. Longer ranges and bigger areas
            can be covered by adding together smaller panels or designing
            bigger ones.

1.2       Architectural
1.2.1       The slim and lightweight design will allow the NXT panel to
            become part of the building rather than a carbuncle on it. The
            superior performance allows the NXT panel to be introduced
            into acoustic environments otherwise prohibitive to conventional
            speaker designs.

1.3       Performance
1.3.1       Distributed mode speakers offer superior performance making
            improvements in performance without over burdening the
            budget. Potentially, architects and designers can be freed up
            from all the constraints placed upon them by conventional
            speaker design philosophy.

1.4       Design considerations
1.4.1       Conventional sound system design is been re-defined in order
            to embrace the benefits offered by NXT. In most circumstances,
            complex speaker designs; horns cabinets and arrays will be
            superseded by NXT panels. The use of NXT technology solves
            a myriad of boundary problems thus making design easier,
            more aesthetic and ultimately better performance perceived by
            the listener.




By: Jan Hawrot 6ec93fab-3a7a-4af0-a9ba-eec5c4f845a8.doc        Page 2of 10
                        NXT EXPLAINED

2       INTRODUCTION
2.1           Quick Comparison
The table bellow contains a brief comparison between NXT and conventional
piston speakers. At this point, no explanations are offered, however, if you
wish to read on after the table we have done our best in simple terms to
explain how we hear and the physical influences affecting sound. We hope
that you will then have a better understanding of why NXT works.


 PISTON TYPE SPEAKER                                   NXT FLAT PANEL
Heavy and bulky, usually round                  Light weight and thin, can be virtually any
                                                shape.
Requires a large strong rigid heavy Does not require any enclosure, only
cabinet, usually wood or high density requires a light weight suspension frame
plastic or even metal
Is not efficient at converting electrical Is 3 to 6dB more efficient at converting
signals into sound waves                  electrical signals into sound waves
Except bass frequencies, requires               Except bass frequencies, only requires
several speakers of progressively smaller       one panel to cover 8 octaves (1st octave
size to attempt to evenly reproduce the         centre is 125Hz; last octave centre is
full audio spectrum                             16000Hz)
The electrical characteristics are complex      The electrical characteristics are simple
and vary wildly with frequency, require         and constant (resistive) within its
careful crossover design to smooth out          operating range; this makes the panel
the      effects.   Complex       electrical    easier to drive, amplifier circuit not
characteristics require a more complex          required to damp an NXT panels
amplifier drive circuit to cope with            movement
controlling the speaker cone (damping
factor)
Sound radiation is directional as Sound radiation is even in all directions
frequency increases, this happens with and does not vary with frequency, all
all piston type speakers and varies frequencies are present in all directions
according to the cone size. Not all
wanted frequencies radiate in the
required direction
Using directional sound sources of this         The scattered nature of sound radiated
nature    in    areas with        significant   from an NXT panel reacts with
boundaries causes unwanted and                  boundaries to enhance the sound in the
destructive effects in the listeners area       listeners area
Directional sound is affected by obstacles The scattered nature of the sound is not
between the listener and the speaker       greatly affected by obstacles in the
                                           listeners path



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                  NXT EXPLAINED
3       DETAILED EXPLANATION
3.1       What is sound?
3.1.1       Sound that we hear is caused by changes in air pressure; these
            changes can be likened to ripples in the surface of water when
            a stone is thrown in.

3.2       How big is sound?
3.2.1       Sound waves travel at about 340 meters per second; for a
            sound wave to travel the length of a football pitch, it would take
            about 3/10’ths of a second. For example, if you stood at one
            end of a football pitch and shouted the word “Stop!” (Which
            lasts for about ½ a second) the “S” sound of the word would
            reach the far end and be ½ way back to you by the time you
            uttered the last part of the “p” sound at the end of the word.

3.2.2       Any sounds we hear are made up of waves of different lengths
            (frequency, unit is Hz) and sizes (loudness measuring unit is
            the “Bel”; or 1/10 of a Bel is the decibel dB). Long waves
            represent low notes and short waves represent high notes.
            Small waves are quiet and large waves are loud. For us mere
            mortals, the most common sound waves, which we can hear,
            can range from 17m for the lowest notes (20Hz), to 1.7cm for
            the highest ones (20000Hz or 20KHz), as we grow older we are
            less able to hear the shorter waves.

3.2.3       Because sound is made up from waves, a little bit like light,
            when the wave meets an obstacle it is reflected. Most of us at
            some time have played snooker or pool, when the cue ball hits
            the cushion at one angle; it then bounces off at the same angle
            in the other direction. Sound waves behave in a similar way.

3.3       Auditory system
3.3.1       The sound we hear is transferred to our brain by the inner ear,
            by a part called the “Cochlea”. This is filled with a fluid; the
            sound vibrations travel along the cochlea and stimulate about
            30,000 sensitive hairs, which line the inner surface. It is from
            the motion of these hair cells that the brain interprets sound.
            We must not forget the importance of our ear lobes (Pinna),
            they filter the sound according to its direction. Along with the
            brains remarkable ability to “time” the sound over the distance
            between your ears, this and all the other features of our hearing
            system enables us to tell from which direction a sound came.
            Because of the small size of our head and ears, we are only

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                  NXT EXPLAINED
            able to tell the direction of the shorter sound waves; or the
            higher notes. Sounds producing long waves; low notes, appear
            to come from all directions.




3.3.2       It is also a fact that we cannot hear all sound waves at an equal
            loudness. In general, long sound waves; low notes, have to be
            bigger than mid length sized ones for our ear to think that they
            are equally loud. This also applies to short sound waves; higher
            notes. It must be said that our ears are most sensitive to
            medium sized sound waves. The fact is that a note of 1000 Hz
            (waves per second) produces the loudest sensation when
            compared to a wave of the same size but a different length; this
            wave is about 34cm long.

3.3.3       The Haas effect, (after Helmut Haas) in simple terms it
            describes the human psychoacoustic phenomena of correctly
            identifying the direction of a sound source heard in both ears
            but arriving at different times. Provided the sounds arrive
            closely together, we hear them as one and in some cases; this
            helps to make better sense of sound. If the relevant sound
            arrives outside this critical time, we will hear it as a separate
            sound, which in most cases will worsen understanding. In most
            natural listening surroundings that we experience, there are
            always some echoes. If a person speaks to you, most of the
            sound you hear should come directly from their mouth to your
            ear. Some of their voice will also spread out in all directions; if
            this sound never reaches a wall, ceiling or floor, then you will
            hear perfect speech. However in the real world there is always
            at least a floor, a wall or a ceiling. As mentioned before, sound

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                   NXT EXPLAINED
            will bounce off these boundaries like a snooker ball off the
            tables cushions. As with a snooker ball, if you hit it hard
            enough, it may come back to where it started. Sound waves
            work in the same way; the waves bounce from the walls, ceiling
            and floor, some will return to the place of origin, the rest end up
            somewhere in the room. In some places these reflections will
            add to assist the listener, in others, it will totally confuse. For an
            improvement to occur, the bounced (reflected) sound waves
            must be of the same portion of sound and arrive within a given
            time.

3.3.4       It will become apparent in the next sections that because of the
            way our ear works it is vital to create the sound in a manner
            that makes better use of the floor, ceiling and walls; otherwise
            known as the boundaries.




By: Jan Hawrot 6ec93fab-3a7a-4af0-a9ba-eec5c4f845a8.doc             Page 6of 10
                    NXT EXPLAINED

4       SOUND SOURCES
4.1       History
4.1.1       For 80 years, or as long as speakers have existed, designers
            have been aspiring to design a flat thin lightweight speaker. All
            attempts were doomed to failure because they were all based
            on a piston driving a diaphragm.

4.1.2       After many years of failure, finally in 1994 the breakthrough was
            made. After two years of research by Verity Laboratories the
            NXT flat panel was born. The solution to the NXT panel is
            remarkably complex but is now fully understood; this may
            explain why until recently this method of producing sound has
            escaped the designer.

4.2       Piston type Sound source
4.2.1       Imagine a flat thin sheet of material, which you want to use to
            make a speaker. The next step is to make the panel move in
            sympathy with an electrical signal, which represents the sound.
            In order to help to explain what happens next, remember
            Newton’s First law of motion “every action has an equal and
            opposite reaction”. In the case of our speaker, we need to
            create a sound pressure wave. Sound has been compared to
            waves in a pond; this helps to see how sound waves move. The
            sound we want to make is in air, to do this we make alternate
            high and low pressure. As the flat sheet has two sides, when
            one side moves forwards it creates a high pressure, the other
            side of the sheet makes an equal and opposite low pressure.
            When the sheet (diaphragm) moves back to the middle and out
            the other side, the high becomes a low and the low becomes a
            high. This is the basis of all conventional type speakers.

4.2.2       You may have noticed that most speakers are round, Ok, some
            are oval, and come in different sizes. Apart from reasons of
            power handling, the main reason for size differences is that the
            diaphragm of a given speaker is a lot heavier than air and
            therefore can only move at a limited speed. The speed of
            movement of this diaphragm can be directly related to the note
            (frequency) of sound required. For low notes the speed is slow,
            as the notes rise in pitch, the speed increases. Try this
            experiment; hold up a sheet of ordinary A4 paper between your
            fingers with the paper dangling downwards. Now start to move
            your arm (the one holding the paper) backwards and forwards

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                  NXT EXPLAINED
            as if you were trying to waft the paper. As long as your motion
            is slow, the whole of the sheet of paper follows your hand
            faithfully. Now, increase the speed of your movement, at some
            point the paper will start to bend, if you increase the speed of
            your movement further, the paper will eventually start to flap
            and also produce from an otherwise silent process other
            sounds. If this experiment is repeated with smaller or stiffer
            pieces of paper, you should be able to tell that smaller and or
            stiffer objects can move more quickly in air.

4.2.3       The principle explained above (4.2.1) illustrates the main draw
            back of this type of speaker. To enable faithful reproduction of
            the full range of sounds, speakers having different sized
            diaphragms (cones) must be used. For full range
            reproduction, at least two speakers are required.

4.2.4       The speaker cone produces a sound wave at the back and at
            the front, these waves are opposite, in order to prevent them
            from cancelling out, a box is built around one side to prevent
            this. A piston type speaker system requires a large box.

4.2.5       The sound produced by a piston driven cone is not the same in
            all directions. In all practical speaker systems, the size of the
            cone cannot alter; therefore, the speaker will be used to
            reproduce a large range of notes (frequencies/wave lengths).
            Assuming we are using this speaker within its range of notes;
            then only if you listen to it at a point directly in front of the
            speaker will you hear all the notes at an equal level. If you then
            move to a new listening position, say to one side, you will notice
            a vast difference in the balance of notes. The higher notes will
            have been reduced where as the lower notes will seem
            unchanged. This effect is known as “Beaming”. In order to
            prevent this, a speaker system would have to be made from
            many speakers, all getting progressively smaller as the notes to
            be reproduced get higher. The beaming effect of piston
            driven loud speakers causes uneven sound coverage. The
            consequence of this is that when this type of sound
            bounces from the inevitable boundary, it will mix in uneven
            amounts in every different location of the listeners area.
            Sound produced by this source must reach the listener
            directly, without obstruction and without bouncing off a
            boundary, any such modifications to the sound wave are
            likely to cause poor sound quality.




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                  NXT EXPLAINED

4.3       NXT flat panel
4.3.1       Unlike a conventional speaker, the NXT panel does not move
            backwards and forwards, it vibrates microscopically over its
            entire surface. Imagine the panel to be thousands of tiny
            loudspeakers all working to reproduce all the different notes.
            The panel uses both sides, since there is no overall forward
            and backward motion of the whole panel, the sound produced
            from the back and front can add together. The NXT panel
            produces sound in all directions

4.3.2       The vibrating action of the panel scatters the sound in all
            directions. The scattering takes place at the surface of the
            panel and is responsible for full frequency response in all
            directions. Compared to a piston type speaker, the NXT
            panel radiates all notes (frequencies) in all directions.

4.3.3       It would seem at first glance that this effect has no advantage;
            on the contrary, it’s the NXT panel’s biggest advantage.
            Because of the scattered nature of the sound, the sound waves
            reflected from the nearby walls, ceiling or floor add to, and are
            of the same nature as, the direct sound from the panel. The
            scattered nature of the sound works with the boundaries to
            reinforce the sound the listener hears.

4.3.4       Because the size of any one vibrating part of the panel is small
            compared to the nearby boundaries, the listener is almost
            always in the reverberant field of the speaker. A major effect
            of this type of sound field is that the loudness does not fall
            away as quickly as with a piston type speaker, and areas of
            constant sound pressure are easily generated in an
            enclosed room.

4.3.5       The combination of wide dispersion of sound, and the
            constructive use of nearby boundaries, means that even
            coverage of sound for a large number of listeners can be
            achieved with fewer loudspeakers. Fewer NXT panels
            required covering the same area when compared to
            conventional cone type loudspeakers.

4.3.6       A listener positioned close to an NXT panel will only perceive
            part of the panel output. Sound pressure is not deafening in
            close proximity to the NXT speaker and microphone
            feedback is dramatically reduced.




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                  NXT EXPLAINED

4.4       Summary of advantages for NXT panels
4.4.1       Constant impedance, because the panel vibrates rather than
            moves. The electrical characteristics are constant and do not
            vary as with a piston type speaker.

4.4.2       Good acoustic mechanical coupling, this makes the panel
            efficient at creating sound.

4.4.3       The panel does not require a large enclosure; a light
            suspension frame is all that is required. The panel can be hung
            in free space or incorporated into a wall and decorated to suit.

4.4.4       Reaction with boundaries is constructive, reverberant rooms
            could be used to an advantage. The scattered nature of the
            sound means it is relatively constant within the room. The
            obvious “Hot-Spot” associated with piston speakers is greatly
            reduced.

4.4.5       Feedback problems associated with microphones used close to
            speakers is greatly reduced.

4.4.6       A superior transient response ensures faithful reproduction of
            fine detailed sound. The term used to describe a characteristic
            sound produced by any type of speaker system is “colouring”,
            the NXT panel is relatively free from this.

4.4.7       Conventional speakers can be used as microphones, in some
            designs this may be used to breach security; NXT panels
            cannot be used as microphones.




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