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Design Notes 3: Sound Lab “The Complete White Paper”

Design Notes 3: Sound Lab "The Complete White Paper"

Writer’s word: Each product comes with an Proprietor’s Guide to familiarize the client with its operations. These paperwork are sometimes written in a dry type and to the purpose. However every so often, we come throughout huge sections in Guide that reads like a clean presentation of concepts and juicy description of sensible applied sciences, and if we’re fortunate, even a narrative on the challenges confronted by the engineers and designers in bringing the idea to fruition. ‘Design Notes” is a brand new collection created to function the informative and properly written documentary inside these Manuals to the readership, to supply information and viewpoints that we consider will profit and even entertain us. All supplies are reprinted by permission.

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Sound Lab Electrostatic Loudspeaker

“The Full White Paper”

Thanks in your curiosity in Sound Lab. This paper is designed to introduce you to our technical philosophy, and it’s our hope that it’ll reply any questions that you might have relating to our merchandise.

Sound Lab has been in enterprise since July 1, 1978. The founders of the corporate, Dr. Roger West and Dr. Dale Ream, shared a perception that electrostatic transduction was probably the optimum know-how for loudspeakers. Over the intervening years, the corporate has efficiently addressed many main issues of electrostatic speaker know-how. As well as, our preliminary objective was, and stays, to get rid of as a lot as potential something that might detract from the purity of the reproduced sound. Particularly, it has been desired to develop a loudspeaker incorporating the next attributes:

1. Really full-range electrostatic know-how having excessive reliability, broad dynamic vary, good sensitivity and wonderful bass response.
2. Single-membrane know-how from which the complete audio spectrum is radiated, offering good time-alignment.
three. Excellent part response by eliminating using spatially separated a number of drivers to cowl the audio spectrum.
four. Dipole topology to remove enclosure coloration.
5. Line-source topology to offer uniform response over all the listening space from wall to wall and from flooring to ceiling, and to scale back wave interference patterns by eliminating flooring and ceiling reflections.
6. State-of-the-art electronics using toroidal audio transformers to protect delicate nuances inherent in music, high-grade polypropylene foil capacitors with low dielectric absorption and high-current functionality, army grade resistors, iron-core inductors, and a regulated bias provide for secure sensitivity.
7. Wide selection equalization controls to offer a flat response in nearly all listening rooms.
eight. Furnishings grade esthetics that may grace nearly any room décor.

We really feel that we’ve efficiently glad our preliminary objectives.

The electrostatic speaker artwork was in its infancy when Sound Lab began enterprise again in 1978. Thus, by default Sound Lab is a analysis and improvement laboratory in addition to a manufacturing facility because of its formidable objectives, which require that the know-how base of the corporate essentially continues to develop. A robust patent and trademark base has resulted from this continued effort. From the attitude of a buyer, nevertheless, this might trigger some uneasiness because the product they elect to buy may probably turn out to be out of date if its know-how is outmoded. To allay this worry we have now established a coverage that any product that we manufacture may be introduced as much as the current technical degree at an inexpensive value.

Our merchandise are meticulously handcrafted piece by piece. Every operation is rigorously completed and checked to make sure that it’s appropriately manufactured. Batch processing and mass manufacturing methods couldn’t insure the person high quality of every product that we manufacture.

The next sections present an in-depth consideration of the technical rules upon which our merchandise are based mostly.

1. How Do Electrostatic Audio system Work And What Are Their Benefits?

This part describes the fundamentals of electrostatic speaker know-how. The next materials is taken from a superb article written by Jacob Turner entitled: “Why Electrostatics?” The article offers a great tutorial on electrostatic audio system and why they’ve determined benefits over different speaker applied sciences:

“Because the latter half of the nineteenth century (circa 1871) the copy of sound by means of electrostatic transducers has stirred the artistic imaginative and prescient of professional engineers and idle dreamers alike. It’s an fascinating reality of historical past that no different single gadget within the audio gear hope chest has loved such an in depth and extended courtship between engineer and Audiophile because the electrostatic transducer.

Early makes an attempt to embody this implies of sound copy have been solely marginally profitable partially due to the shortage of appropriate supplies and processes.

What’s the glamour of the electrostatic precept that gained it such prolonged, devoted consideration? Why has the electrostatic transducer remained the usual of excellence by which different acoustic units are so typically measured?

The reply to those questions lies in at the very least three areas, which can be mentioned within the following order:

1. Some peculiarities of the listening to course of

2. The character of the acoustic medium: air

three. The operational options of electrostatic acoustic units as associated to the above and to dynamic acoustic transducers

The current improve of exercise within the extremely elusive space of psycho-acoustics guarantees to contribute considerably to a extra profound grasp of the complexities of man’s notion of his sound setting. A number of current research have been carried out in regards to the sensitivity of regular adults’ ears to totally different ranges of harmonic distortion. The outcomes recommend that comparatively excessive ranges of harmonic distortion (odd and even order) are imperceptible within the presence of regular musical program, whereas fairly small modifications in amplitude and phasing are readily ascertained. Amplitude modifications have been described as altering the tonal high quality of this system, whereas part displacement e.g. bass and treble of not more than 5 levels degraded the readability and definition of musical transients and upset the homogeneity of the stereo picture between two main frequency bands.

Different research have identified that the inherent transient nature of musical and speech sounds dictates a excessive degree of transient constancy as a prerequisite of top of the range acoustical transducers. The importance of those observations insofar as electrostatic transducers are involved can be pursued a bit later.

One other very important hyperlink within the chain is air, which has the next main traits of conduct which might be germane to our matter. Air is very compressible, that’s, the quantity of air strain (variety of air molecules) in a given area might be elevated or decreased past its regular situation. Air, then, may be stated to be like a spring, a way for storing power; a compliance. Air additionally has weight or mass. Ten kilos of air are simply as heavy as ten kilos of potatoes. Air is, subsequently, like an inertance, which opposes an motion or drive; an inductance. Air may also be randomly excited, air molecules eat energy by producing warmth. Air can then be stated to be like a resistance. This acoustic impedance is generally very low, though at excessive audio frequencies it’s significantly higher than at low audio frequencies. In an effort to insure that the switch of diaphragm or cone movement to air movement happens with the best effectivity, it’s essential that the entire mechanical impedance of the system be as near the acoustic impedance of the physique of air it’s thrilling over as a lot of the audio vary as attainable.

To narrate the previous dialogue to the subject of the electrostatic transducer, it is going to be vital to stipulate the operational options of the push-pull electrostatic gadget. The earlier factors will probably be associated on the similar time to the operational options of the dynamic transducer. As illustrated in Fig. 1, the electrostatic transducer consists of a skinny membrane (diaphragm) product of Mylar that’s stretched and contained between two acoustically open plates. The 2 plates are related to both finish of a coupling transformer which offers the excessive voltage audio sign. The diaphragm is related to a excessive voltage, low present bias provide, which supplies an electrostatic cost that turns into trapped within the diaphragm.

In recent times a way referred to as “electretification” has been developed whereby the bias cost is completely embedded within the diaphragm materials, in order that the diaphragm is self-energized with out an exterior supply of bias voltage. The web outcome is identical in each instances. The 2 plates present an electrical subject that’s the voltage equal of the audio sign. Within the presence of an audio sign, the electrical subject exerts forces on the electrostatic cost that’s trapped within the diaphragm. These forces are transferred to the diaphragm, inflicting the diaphragm to maneuver in synchronization with these forces.

Against this, Fig. 2 will illustrate the make-up of a dynamic driver, which consists of a body housing, a magnet, and a voice coil hooked up to the apex of a cone which is suspended at its edge by a versatile material or different materials. The voice coil is about into movement in synchronization with an audio sign that causes present movement via the coil. Because the coil is about into movement by this sign, it in flip units the cone into movement.

Though each models obtain air excitation via diaphragm or cone movement, the way through which that is carried out includes radically totally different methods and outcomes. The electrostatic system employs using a shifting member for all its working frequencies that’s often solely zero.0004 inches thick (Word: the fabric utilized in Sound Lab audio system is just zero.00012 inches thick) and weighs solely as a lot as a physique of air 7mm thick (2mm thick in Sound Lab audio system) whose boundaries are equal to these of the shifting diaphragm.

The electrical area, which acts to make the diaphragm transfer, exerts its actuating pressure uniformly over primarily your complete space of the diaphragm. A diaphragm of such excessive lightness, together with an actuating pressure that’s uniformly distributed over the complete floor of the diaphragm, leads to a transducer whose transient response intently duplicates the electrical enter. The web result’s a diaphragm movement that may be a excellent duplicate of the electrical forces appearing upon it, with all sections of the diaphragm floor shifting with extremely correct part and amplitude linearity all through its whole vary of journey, in any respect frequencies inside its space of operation.

The forces appearing to maneuver the dynamic transducer’s cone, nevertheless, produce totally different outcomes. The appliance of the driving drive solely to the apex of the cone necessitates a sufficiently stiff cone to stop buckling and deformation of the cone construction. Such a stiff cone usually has appreciable mass, which degrades its effectivity, its transient response capabilities, and its excessive frequency efficiency. As well as, the forces utilized on the apex don’t act uniformly over the floor of the cone, inflicting the cone to “break-up” into an infinite number of vibrational modes, solely considered one of which is actually consultant of the unique sign. This mode of operation produces amplitude and part nonlinearity typically of appreciable magnitude, and these have a tendency to extend because the cone is pushed to higher excursions. Clearly, the dialogue of dynamic driver operation relates fairly strongly to the earlier dialogue in regards to the uncommon sensitivity of the human ear to the issues of transient response, amplitude linearity, and part linearity. The essential conclusion is that an electrostatic unit behaves with higher composure in all the above areas.

The second main distinction involving electrostatic transducers offers with the appreciable drawback of coupling to the air with affordable effectivity over the complete audio band. The electrostatic unit, due to its extraordinarily low mass diaphragm and the uniform distribution of’ the driving forces over the complete diaphragm floor, is inherently a unit with low mechanical impedance in any respect frequencies. As such, the coupling drawback at low frequencies (the place the issue is biggest) for electrostatic models is significantly lower than for dynamic models, that are encumbered by a excessive mechanical impedance. The results of these circumstances is that the electrostatic unit performs fairly properly right down to its frequency limits and inside its most excursibility with equal constancy in any respect drive ranges.

The dynamic cone unit, due to its poorer coupling, have to be pushed more durable to supply passable excitation of the air at low frequencies, and often encounters quite a few issues involving cone break-up, non-linear movement of the voice coil on account of lack of magnetic coupling within the hole, suspension non-linearities, and so on. In all equity, it have to be stated that the efficiency degree of at this time’s widespread dynamic acoustic transducer is extremely good given the financial and operational constraints of that sort of unit. However, the prevalence of the electrostatic precept has been demonstrated by the good acceptance of the growing variety of electrostatic headphones which have already emerged out there. As well as, in fact, a number of electrostatic speaker merchandise are extremely regarded by the audiophile group.”

We significantly respect Jacob Turner’s means to elucidate some great benefits of electrostatic know-how over typical dynamic (magnetic) know-how. We might add that the feedback relating to cone audio system apply to ribbon and different forms of audio system additionally. Within the case of ribbon audio system, they’re planar in nature however the proportion of the world of the diaphragm that’s instantly pushed is on the order of 30% to 50% as an alternative of 100% as within the case of electrostatic audio system because the driving pressure comes from a skinny piece of wire or foil that represents solely a fraction of the entire shifting space. Thus, as within the case of the cone speaker, a good portion of the diaphragm is just not immediately pushed and may inherit a number of the drawbacks of cones. Moreover, the wire or ribbon is often sandwiched between two plastic movies which provides to the shifting mass. Normally, the ribbon speaker is best than its cone counterpart when it comes to motional accuracy, nevertheless it has upwards of ten occasions the shifting mass of a correctly designed electrostatic speaker.

2. What Is The Relationship Between Audio system And Microphones And How Is It Optimized?

The aim of high-end audio is to recreate a sonic efficiency with as a lot accuracy and realism as potential. This calls for near-perfect efficiency from each element within the copy system, together with the traits of the sound room. Nevertheless it additionally requires a compatibility with sure circumstances concerned within the recording course of which need to do with the accuracy of the recreated stage (stereo picture, each measurement and site), ie: the spatial facet of the re-creation. Maybe, the extra essential of those has to do with the traits of the microphone(s) used to report the efficiency and their placement.

Not a lot might be carried out to compensate for sign timing corruption on account of mix-down procedures and weird microphone methods. These are within the palms of the recording engineer. However, one thing could be carried out regarding an acoustical precept that we discuss with as microphone/speaker reciprocity. Within the early days of stereophonic recording it was usually accepted that the “normal” microphone association was to put two microphones dealing with the orchestra which have been separated by eight ft. Reciprocally, the loudspeakers reproducing the recording would even be separated by eight ft. There have been many alterations to this easy geometry since then, comparable to using greater than two microphones to acquire particular results and sonic highlighting. Nevertheless, amid the quite complicated science of recording, one generality persists. Most microphones utilized in recording make use of a cardioid (directional) sample. A microphone having this attribute readily accepts info from the entrance however attenuates sound waves approaching from the rear. Contemplating out there models, the bounds of the cardioid acceptance sample is such that pickup sensitivity is diminished by 6dB (half strain) varies from about 30 to 45 levels both aspect of the central axis of the microphone.

The precept of reciprocity merely states that to be able to recreate a sound stage with good spatial accuracy, the dispersion angle of the loudspeaker and the acceptance angle of the microphone must be comparable. For instance, have been you to stroll round your sound room and examine the recreated sound area to strolling across the auditorium in the course of the precise efficiency, similarity of the stage picture can solely be achieved if the precept of reciprocity is carried out. Because of this all Sound Lab audio system are rigorously designed to satisfy this essential precept. Extra concerning the necessities for correct staging might be mentioned in a later part.

One other benefit that’s accrued from a wider dispersion angle is that harsh direct reflections from partitions are drastically lowered, making speaker setup a lot simpler since undesirable room modes are typically much less pronounced. Via expertise we’ve got discovered that horizontal dispersion angles from 45° to 90° work nicely within the house surroundings. The extra slender angle offers higher speaker sensitivity and dynamic vary whereas the broader angle offers a wider stage. Each angles can be found in our merchandise.

three. Sound Lab Audio system Don’t Appear To Sound Any Louder Up Shut Than They Do Far Away! How Is This Carried out?

The key behind this seemingly magical trait has to do with the traits of the acoustical line supply. All Sound Lab merchandise are categorically vertical acoustical line sources. My opinion is that the vertical line supply is the optimum acoustical geometry for correct staging and acoustical power management within the residence listening surroundings, which I’ll now try and justify.

Theoretically talking, a vertical acoustic line supply is a two-dimensional vertical line, having infinite size and 0 diameter, from which full-spectrum sound power emanates. It may be useful to ascertain an extended violin string, sufficiently lengthy with a purpose to produce decrease frequencies. In the actual world, the place an infinitely lengthy line is an abstraction, the size of this line must be giant in comparison with the all wave lengths that it radiates (there is a vital exception when utilized in an enclosed room, as might be mentioned later). If this criterion is met, the main attribute of the vertical line supply is that it disperses power solely within the horizontal path and none within the vertical course. In different phrases, all sound rays emanate perpendicularly from a vertical line. Subsequently, the radiation subject may be in comparison with the form of a slice of pie by which the highest and backside surfaces are flat (no vertical radiation) and aspect radiation is confined to a prescribed angle (horizontal dispersion). In distinction, most audio system out there available on the market are extra associated to the “level supply”, the attribute of which is a uniform radiation sample in all instructions: up, down and sideways.

My justification of why I consider the road supply to be superior to the purpose supply within the residence setting will now be thought-about. For many who don’t want to get entangled in arithmetic I’ll first give an evidence that appeals to the instinct. This shall be adopted by a extra rigorous strategy.

In your thoughts’s eye, envision an infinitely lengthy vertical line from which perpendicular power rays are being radiated. A bottle brush held vertically can be a superb analogy whereby the backbone is vertical and the bristles radiate horizontally. It ought to be intuitively clear that If a skinny flat floor, that’s parallel to the power rays, is positioned on the road, it might not disturb the rays since there can be no reflections. Now, place a second flat floor, parallel to and above the primary floor. Neither of the surfaces will intrude with the power rays. In different phrases, the sample of the rays between the plates wouldn’t be affected by the presence of the plates. Think about that the decrease and higher plates characterize the ground and ceiling of a listening room. The purpose being made is that if a line-source speaker is positioned in a room, the sound it emits will protect the traits of an infinitely lengthy line supply. One may ask what the advantages of this is perhaps. First off, it eliminates flooring and ceiling reflections, since all sound rays are parallel with the ground and ceiling. The consequence of that is that the complexity of interference waves inside the room is minimized, offering a extra pure sound subject. The horizontal dispersion of the audio system is designed to attenuate wall reflections. Secondly, because the line supply has no vertical dispersion, all power is concentrated within the horizontal course. The theoretical impact of this, ignoring the reflective area ensuing from wall reflections, is that sound drops off at solely 3dB per doubling of distance from the speaker somewhat than 6dB per doubling of distance as within the case of the purpose supply. Subsequently, because the listener walks towards or away from a line supply, modifications in loudness are a lot much less obvious. That’s the reason the sound degree of our audio system doesn’t appear to drop as one walks away from them, nor does it seem to turn out to be louder as one approaches them. Thus, the sound degree doesn’t range noticeably as one strikes towards or away the audio system, which makes all the room the proverbial “candy spot”.

One may marvel how a big speaker might probably perform as a skinny vertical line supply. As pragmatic proof, merely stroll round to the rear of certainly one of our audio system whereas it’s reproducing sound. Utilizing an ear as a detector, a dramatic improve in sound degree will probably be obvious on the middle of curvature of the speaker. The sound rays emanating from the horizontally curved radiating floor will converge at some extent about three ft behind the speaker, and past this level the rays will diverge. This focus is the digital line supply. Thus, as unimaginable as it might appear, the sound from our large audio system seems as whether it is being radiated from a minuscule vibrating vertical line. The extra close to the highest of the speaker is to the ceiling, the extra precisely it performs as an infinite line supply.

The one requirement for a truncated vertical line supply (being trapped between a flooring and a ceiling) to carry out as if it’s an infinite line supply, is for the ground and ceiling be acoustically reflective. It may be proven mathematically that the interplay between the ground and ceiling reflections create infinite phantom extensions of the road supply above and under the room. It really works on this method, the vertical element of any ceiling reflection can be cancelled by a complementary reflection from the ground (and vice versa) leaving solely the horizontal element. In the actual world the ground and ceiling will take up some sound power, however the impact shouldn’t be enough to change the road traits sufficient to be audible. The web result’s that the listener can sit down, get up, do deep-knee bends, stroll forwards and backwards and the sound picture doesn’t seem to vary. Some extent supply can’t give any such efficiency.

To make this extra significant, I shall be considerably rigorous mathematically. The acoustic depth (I) of a sound wave is outlined as the typical energy transmitted per unit space within the path of wave propagation:

The place:

I = common energy transmitted per unit space within the course of wave propagation

Prms = efficient strain in nt/m2 (newtons/sq. meter)

c = velocity of sound in m/sec (meters per second)

ρ = density of air in okay/m2 (kilograms per sq. meter)

With the purpose supply, the world that power is distributed over is quadrupled every time the space from the supply is doubled. Thus, in decibels, the depth of a sound drops roughly 6.02dB for every doubling of distance:

Since doubling distance reduces (I) by an element of 4:

As compared, with the road supply space, the sound degree modifications solely by an element of two for doubling the space towards the road supply, since doubling the space distributes the sound power over solely twice the world. Thus, doubling the space from a line supply reduces the sound degree by solely three.01 dB. In different phrases, sound depth drops off with growing distance considerably slower with the road supply than with the purpose supply.

For the mathematically inclined, a extra rigorous remedy of the road supply will now be given. To start with, when evaluating normal sensitivity measurements of level sources versus line sources, it’s common to misread the outcomes because it applies to sound strain ranges at commonplace measurement distances. The rationale for this controversy is because of the proximity impact of the road supply in comparison with that of the purpose supply. Sound degree varies because the inverse of distance for the road supply, whereas it varies because the inverse of the sq. of the space for the purpose supply.

Because of the distinction in proximity traits, evaluating the usual sensitivity measurement values of the road supply and level supply (usually measured at one meter with one watt of enter energy into eight ohms) to the sound strain degree measured at regular listening distances, the end result may be startling. Usually, the purpose supply speaker has a better power density at the usual one-meter distance than that of the road supply because of the power of the purpose supply being concentrated right into a smaller space in comparison with the road supply, and thus sometimes has a better normal sensitivity score than that of the road supply. Nevertheless, when the sound degree is measured at a typical listening distance from the speaker, say 25 ft, this distance in comparison with the usual 1 meter distance is about eight occasions larger, giving the road supply almost a 9 dB benefit over the purpose supply. Since this benefit will increase with distance, there comes some extent, we time period because the “important distance” the place the sound strain degree (SPL) of the road supply equals that of the purpose supply. Past this level, the road supply continues to extend in loudness at a +3dB/(doubling of distance) price in comparison with the purpose supply, as distance is additional elevated.

Thus, when normal one meter sensitivity measurements of a line supply and some extent supply are in contrast the outcomes might be deceiving. It solely is sensible to measure sensitivity on the listening distance somewhat than at one meter when evaluating point-source and line-source speaker sensitivities.

Maybe, the easiest way to narrate commonplace one-meter sensitivity values with the efficiency at typical listening distances is to calculate the space from the speaker at which the sound degree is identical as a perform of the distinction of the one-meter sensitivity scores of the 2 audio system. Maintaining in thoughts that the road supply SPL drops off at a slower fee than that of the purpose supply and additional, that the one-meter sensitivity score of the purpose supply is usually higher than that of the road supply, there’s inevitably a distance from the supply the place the sound degree would be the similar, past which the road supply will all the time be louder than the purpose supply. The truth is, the diploma that the road supply is louder than the purpose supply is proportional to this distance.

The formulation for this crucial distance (D), the place the road supply and level supply have the identical SPL, is given by:

The place:

D = the space in ft the place the point-source and the road supply have equal SPL

RP = Price of change of some extent supply SPL as a perform of doubling distance: -6dB/octave

RL = Price of change of a line supply SPL as a perform of doubling distance: -3dB/octave

SP = One-meter sensitivity of a point-source speaker: SPL in dB @ 1 meter

SL = One-meter sensitivity of a line-source speaker: SPL in dB @ 1 meter

SP and SL are obtained utilizing the usual technique of measuring speaker sensitivity. This equation assumes that the point-source speaker sensitivity (SP) is bigger than that of the line-source speaker close to the audio system, which is a protected assumption typically.

This equation is derived from the truth that the theoretical infinite line-source obtains a three.01 dB benefit over the theoretical level supply with every doubling of distance from the supply in an anechoic surroundings. In follow, precise audio system will differ from the theoretical mannequin by various levels relying on how intently they emulate both some extent or a line supply, therefore one may anticipate that the outcomes might differ considerably from the perfect case. However a departure from the perfect, the precept holds true and might be fairly vital.

A remarkably correct easy rule-of-thumb is:

“The essential distance D (in ft) is roughly equal (inside 10%) of the distinction between the one-meter sensitivity scores (in decibels) of the point-source and the line-source.”

That’s: D ≅ SP – SL (inside 10% accuracy)

For instance, our Mannequin Majestic 745 speaker has a one-meter sensitivity score of 89 dB. Let’s examine that to a hypothetical “Model X” point-source speaker having a better sensitivity score of 96 dB. The important distance calculates to be 7.63 ft (the rule-of-thumb provides 7 ft). Past this distance, the Majestic 745 might be louder for a similar enter voltage (this calculation assumes an anechoic surroundings). Acoustical environments which might be solely partially absorptive, corresponding to the typical residence listening room, will trigger some variation in precise measurements, however the basic precept nonetheless applies. The ethical to the story is:

“To correctly examine the sensitivities of line-source versus point-source audio system, measurements ought to be taken at regular listening distances slightly than at the usual 1 meter.”

Now, from a practical viewpoint, let’s interpret the above conclusions when it comes to benefits within the listening room. First, contemplate the consequences on the perceived sound area brought on by strolling to-and-fro in entrance of a reside orchestra in a symphony corridor. As one stands close to a aspect wall, the extra close to musical devices seem louder than those additional away, however they won’t masks (override) them. As one walks to the opposite aspect of the corridor, an identical impact is obtained. In different phrases, the acoustical sound stage is skewed as one stands to the aspect, however a three-dimensional picture of your complete orchestra stays. That is precisely the impact of listening to music reproduced by way of stereophonic vertical line sources. Extra particularly, as a listener walks to at least one aspect of the listening room, the speaker nearest him doesn’t turn into considerably louder and, therefore, doesn’t masks the sound of the opposite speaker. The truth is, because the listener strikes across the listening room the spatial picture of the reproduced orchestra responds very equally to that of an precise orchestra enjoying in a music corridor. In distinction, the point-source speaker turns into considerably louder as one approaches it, and is thus able to masking the sound of the extra distant speaker. Subsequently, one should stay equidistant from the 2 audio system to acquire correct staging.

The road supply has additional benefits. As talked about beforehand, sound rays emanating from a line supply radiate perpendicularly from the road. Thus, the sound that reaches the ear comes from sound rays which are on the similar degree because the ear. Subsequently, because the listener stands or sits the sound is identical. Thus, one by no means listens “as much as” or “right down to” the sound supply. The purpose-source, on the contrary, has a really distinct vertical place that may be simply localized, which can give music a man-made vertical localization impact. Opposite to some widespread beliefs, stereophonic music doesn’t include any vertical localization cues and, subsequently, a real vertical picture doesn’t exist. To create a real vertical picture it will require an higher and a decrease set of audio system (with the corresponding four-channel microphone/recording setup with which to make such a recording) to concurrently reproduce the vertical and horizontal photographs. Thus, the line-source speaker doesn’t create synthetic vertical localization akin to a number of driver point-source audio system can do.

four. How Does Sound Lab Obtain Profound Bass Response With Dipole Panel Audio system?

If a compliant materials, similar to a drumhead, is stretched over a body and the drumhead is tapped with a mallet it’s going to produce a sound having a definite frequency, which is known as the drumhead resonance. It requires much less power to trigger the membrane to vibrate at this frequency than some other frequency. Thus, if a vibrator is coupled to the drumhead and the frequency of vibration is various, when the drumhead frequency is approached the vibration of the membrane will turn out to be a lot larger than at different frequencies. That is the case with the electrostatic speaker as properly, since a membrane is equally stretched over a body. As with the drumhead, the membrane of an electrostatic speaker will exhibit a robust resonant sound with comparatively low enter power. This can be a drawback since when the audio sign hits the resonant frequency the membrane will amplify that exact frequency extra so than all others. If not tamed, the resonant power will create a coloration to the sound. Moreover, because the membrane vibrates larger at resonance for a given enter sign degree, the membrane can simply be pushed into the stators, which limits the usable dynamic vary of the speaker. This resonant peak may be 20dB or larger and often happens on the lowest frequency of the membrane’s cross band.

Numerous strategies have been employed to get rid of this resonance. Some designers have used acoustical damping, resembling stretching a high quality mesh, just like that utilized in nylon stockings, throughout the speaker. This strategy certainly damps the resonance, nevertheless it additionally reduces membrane motion at different frequencies to a lesser diploma, reducing the vitality of the sound. Different approaches have been used to remove this nasty peak of power, however all have exhibited unfavorable uncomfortable side effects.

It might not be shocking if we have been requested how we remove the membrane’s drumhead resonance. An historic thinker as soon as said: “Asking the right query results in the reply”. Making use of this knowledge, we requested ourselves: “As an alternative of allowing your complete diaphragm to contribute to at least one resonant peak, why not arrange a state of affairs the place totally different sections of the diaphragm resonate at totally different frequencies in a graded trend, which might break up the drumhead resonance right into a collection of manageable resonances? The ensuing set of resonant frequencies could possibly be distributed over the cross band of decrease frequencies and would haven’t any impact on greater frequencies. And, by judiciously choosing the person frequencies the bass response of the speaker might be equalized”. We tried it. Two fantastic outcomes have been realized: the “drum-head” resonance was eradicated and the effectivity of decrease frequencies was dramatically elevated since all was performing on very responsive resonant power. The ensuing bass response was flat, quick, dynamic and unrestrained. Because it seems, the “nasty” membrane drumhead resonance is a free supply of power that may be distributed to equalize the bass response of the speaker.

The distributed resonance precept additionally solves a nasty drawback related to dipole radiators: dipole cancellation. An acoustic dipole radiator is principally a vibrating membrane by which the acoustic power emanating from each of its sides is permitted to radiate freely. Dipole radiation has vanishing acoustic “coloration” since it’s devoid of enclosure resonances. Nevertheless, because the two waves radiating from reverse sides of the diaphragm are mutually out of part, they start to cancel each other at decrease frequencies, which leads to a prematurely rolled-off bass response, often occurring simply above drumhead resonance. By judiciously choosing the “regulation” by which the resonant power sectors are distributed, the consequences of dipole cancellation might be nearly eradicated. Determine three exhibits the standard response of an unequalized dipole radiator taken axially to at least one aspect. Determine four exhibits one among a number of strategies of sectoring a membrane to distribute resonant power. fl, f2, and so on., characterize the resonant frequencies of every of the sectors. Determine 5 exhibits how the bass equalizing response contour is generated by dividing the membrane right into a distribution of resonant sectors.

It must be readily obvious from learning these figures that the bottom frequency sectors are positioned on the excessive ends (prime and backside) of the panel. This causes the obvious measurement of the radiator to seem equal to the peak of the speaker. The consequence of that is to scale back the vertical dispersion of decrease frequency power (ie: greater directivity), thus growing power density. In audio phrases, this represents a rise in bass dynamics. We seek advice from this as our “Bass-Focus” know-how. That is just like the work of Joseph D’Apolito, who employed this precept with dynamic audio system.


Within the “near-field” (that’s, when one could be very near the speaker) the bass response of the speaker has a rising impact as frequency is lowered. This happens as a result of up near the speaker the consequences of dipole cancellation will not be as obvious. Nevertheless, within the far-field (which means regular listening distances and past) the rising attribute seen on the “near-field” disappears and on account of resonant power distribution simply the correct quantity of power is provided at every frequency to provide the power misplaced resulting from dipole cancellation.

The ensuing frequency response is flat and prolonged. In different phrases, the “regulation” of the distribution of frequencies is such that it offers the complement of the membrane’s unaltered pure frequency response curve. Clearly, an digital equalizer might be used to acquire the identical impact, however it might scale back the efficient dynamic vary of a given amplifier by 15 dB or extra. Through the use of “distributed-resonance equalization” the dynamic vary of the amplifier shouldn’t be compromised. That is how the nasty drumhead resonance power is put to good use. That is about as shut as one can come to “having your cake whereas consuming it”.

5. The Electron: The Spine of the Electrostatic Speaker:

In a standard (dynamic) loudspeaker magnets are used to create a pressure area. Electrical cost is employed to do the identical within the case of the electrostatic speaker. The standard of the efficiency of the electrostatic speaker is instantly related to how dense and the way uniformly the cost area is distributed upon the membrane. Sound Lab employs a pure copper cost diffusion ring across the outer boundary of the membrane to feed cost into the middle of the membrane from all instructions. The low impedance of this ring insures that leakage paths, brought on by things like moisture condensing onto the membrane from humidity, has no impact on the efficiency of the speaker. The cost on the membrane is thus exceptionally uniform and dense. The membrane floor have to be electrically conductive to allow the cost emigrate, however the resistivity of the conduction should not be too excessive nor too low, and it should not burn off or deteriorate with time. Such is the conductive membrane floor of Sound Lab’s audio system.

Moreover, because the cost is fed from all factors across the periphery of the membrane, the speaker “costs up” shortly. Subsequently, the speaker might be disconnected from the mains if desired with out requiring time to recharge when it’s desired to take heed to them.

6. Geometrical and Development Issues:

The excessive efficiency functionality of our audio system has a lot to do with the interior geometry of the electrostatic panels. First, the spacing between the stators and the membrane is extraordinarily important with a view to acquire the right electrostatic area depth plus having enough room for the membrane to maneuver. Moreover, the spacing have to be precisely the identical for each the back and front stators with a purpose to have optimum push-pull motion and low distortion.

The framework of the panel can also be crucial. The entire objective of the framework is to take care of the right geometrical relationship between the stators and the membrane. It have to be very inflexible, precisely constructed and non-resonant. Moreover, the fabric used have to be moisture resistant and never degrade with time and environmental circumstances. We subsequently fabricate the interior members of the construction from a plastic that could be very robust, dense, non-resonant, non-hygroscopic and resistant to environmental elements. Thus, the integrity of the panel is preserved underneath all affordable circumstances.

The best common criticism of electrostatic audio system has been that they simply “arc over” and are thereby broken. Some early design makes an attempt have resulted in panels that break down simply which has created a nasty identify for electrostatics. Understandably, this might trigger individuals to draw back from them. Sound Lab engineers have nearly eradicated this concern by using state-of-the-art cross-linked insulating materials. This can be very uncommon for a Sound Lab speaker to expertise a voltage breakdown, even beneath excessive overload. This eliminates the best concern of those that choose electrostatic sound. To insure the integrity of the audio system we manufacture, every panel is examined on the most rated energy earlier than it’s shipped.

Another essential geometrical consideration ought to be talked about. Some designers have tried to offer horizontal dispersion of sound power through the use of a curved geometry, whereby the membrane is suspended such that it assumes a very curved floor. It’s intuitively apparent that such a form supplies a non-symmetrical transduction attribute, because the membrane pressure will increase because the membrane expands outwards and it loses pressure because it strikes inwards. This unsymmetrical attribute creates extreme mechanical limitations and thus prevents the speaker from performing as a very full-range speaker. In truth, for a given membrane width, because the radius of curvature is elevated the severity of the issue will increase proportionately for a given membrane displacement. Because of this the horizontal dispersion angle of a very curved membrane have to be restricted to a slightly small angle.

In distinction, Sound Lab employs a piecewise approximation of a curved floor utilizing flat surfaces (sides). The flat floor supplies a symmetrical attribute that allows giant linear displacements. Subsequently, the flat membrane strategy is the one approach a very full-range membrane speaker might be realized. By judiciously choosing the right angle between adjoining flat sides, the dispersion of the sound area may be as clean because the curved membrane however with out the extreme displacement restrictions of the curved membrane. One other profit is that there isn’t a restrict to the quantity of horizontal dispersion that can be utilized because the membrane dynamics aren’t affected by the angle of dispersion as is the case of a curved membrane. Audio system have been manufactured having as much as 360 levels of horizontal dispersion, however we use an angle in our audio system that we have now discovered to be the perfect angle for common itemizing rooms. We provide 90 diploma dispersion panels for broad rooms to ensure that the sound to embody the room, and 45 diploma dispersion for extra slender rooms to attenuate side-wall reflections. We’ll customized construct panels for different angles upon request, as much as 360 levels.

The membrane is one other important a part of the speaker panel that must be talked about. Low mass and resistance to environmental elements are essential necessities. Sound Lab makes use of a polyester materials that’s solely 120 millionths of an inch thick, which offers the excessive compliance mandatory for giant, linear membrane excursions. Additionally, the shifting mass is so low that it represents solely a fraction of the mass of the air quantity it strikes. Moreover, Sound Lab makes use of a singular mechanical/adhesive system to insure that the membrane by no means slips and loses its correct rigidity. Lastly, the membrane is coated with a particularly skinny proprietary substance to offer it precisely the right electrical conductivity. This coating is nearly indestructible and won’t vaporize when the speaker is performed loudly.

7. Ultimate Remarks

Sound Lab gives fifteen fashions, all of which make use of the applied sciences defined on this paper. Why so many fashions? We provide three types, the Final collection with its metal space-age body, the Audiophile collection with its beautiful wrap-around furniture-grade wooden body, and the Majestic collection having a extra easy trendy contact with furniture-grade wooden trim.

5 panel sizes can be found for every of the above talked about types. The sizes vary from our lately launched compact collection, standing solely fifty inches tall, to our largest panels standing at a monumental 9 ft peak. In different phrases, there’s a measurement to satisfy all installations. The panels used on all fashions of a given measurement are similar. Additional, the similar electronics are employed on all fashions. Consequently, there are not any choices to be provided aside from panel measurement and elegance. Our electrostatic sub-woofers and our hybrid fashions haven’t been thought-about on this paper so as to absolutely concentrate on our really full-range electrostatic audio system. We invite you to contact us if you need to know extra about these.

Congratulations! It understandably requires a little bit of effort to work by means of the small print of this paper. Rather more might be introduced to discover our know-how in additional element, however the actual check is within the sound. We’re pleased with our know-how, and we really feel that our audio system are based mostly on crucial acoustical rules that apply to sound copy within the residence. If this presentation has not answered all your questions, we invite you to contact us for the solutions. We additionally welcome any recommendations that you might have.

Sound Lab Electrostatic Loudspeakers
P.O. Field 409, Gunnison, Utah 84634 USA Ph. 435-528-7218
www.soundlab-speakers.com           soundlab@burgoyne.com

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