WO2018208675A2

WO2018208675A2 - Common aperture extensible loudspeaker array

Info

Publication number: WO2018208675A2
Application number: PCT/US2018/031396
Authority: WO
Inventors: Anthony BISSET; Miles CALLAN; Daniel KINGSBOOK; Quang-Viet Nguyen
Original assignee: Bisset Anthony; Callan Miles; Kingsbook Daniel; Nguyen Quang Viet
Priority date: 2017-05-06
Filing date: 2018-05-07
Publication date: 2018-11-15
Also published as: WO2018208675A3

Abstract

A high-output bass and mid-bass loudspeaker system topology is prescribed according to a common specification for multiple (ideally identical) speaker enclosures that are connected via a common acoustic aperture at the adjoining walls of the said enclosures, wherein the apertures are in communication with a common acoustic duct that transects two or more walls of the enclosure such that sound from one enclosure can be transmitted to another, and ultimately to the outside environment. The connection of additional speaker enclosures along the direction of sound propagation permits the Common Aperture (CA) Extensible Loudspeaker Array (XLA) through use of a computed and prescribed temporal delay algorithms to achieve higher SPLs, lower frequency bass response, and lower harmonic distortion than prior state of the art loudspeaker systems.

Description

COMMON APERTURE EXTENSIBLE LOUDSPEAKER ARRAY

FIELD OF THE INVENTION

This invention relates to a class of devices and their respective methods for forming a so called extensible loudspeaker array (XLA), which is generally defined by a plurality of modular loudspeaker enclosures conforming to a prescribed enclosure specification, which includes, but is not limited to, each conforming loudspeaker enclosure having one or more exterior surface(s) that contain an aperture for sound output, and said aperture is connected to an internal acoustic duct that transects two or more walls of the said conforming speaker enclosure, and one or more of these planar or curved planar faces can be fitted to a neighboring loudspeaker of the same or similar physical and performance specifications, thereby creating a sealed acoustical coupling of the two shared conforming speaker enclosures which now have a common acoustical output aperture. By positioning two or more of the said conforming loudspeaker enclosures within the XLA described in the present invention, the combined XLA enhances both the lower bandwidth and overall maximum sound pressure level (SPL), while reducing harmonic distortion, thus fulfilling the acoustic requirements for a loudspeaker array capable of, but not limited to uses in: home theater (HT), public address (PA), professional sound reinforcement (SR), long range wildlife deterrence, defense applications, and research applications within the ultra-low-frequency (ULF), very-low frequency (VLF), infrasonic, bass and mid-bass regions of the human and mammal hearing ranges (from below 10Hz to over 200Hz) with sound pressures in excess of 130dB.

BACKGROUND OF THE INVENTION

The present state of the art of moderate to high SPL bass reproduction loudspeaker technology are so called 'subwoofers' which refer to a generic high output, high efficiency bass production loudspeaker that is box shaped and designed for professional sound reinforcement applications. Typical subwoofers suffer from a variety of inadequacies and compromises that create physical challenges for the end user due to their inherent large weight and size which makes transportation challenging for a single person without assistance from dollies, forklifts, etc. Another shortcoming of present day subwoofers is their limited ability at the single unit level, to generate high SPL levels with low distortion, depth of bass extension and high efficiencies. The tradeoffs between enclosure size, system sensitivity and low frequency reach is described by Josef Anton Hofmann's "Iron Law" of loudspeaker performance. Furthermore, many commercial vendors of subwoofers, under the pressure of increasing the max SPL per unit, are producing subwoofers that take up very large volumes of space within sound rental facilities, storage spaces and rental trucks. This egregious occupation of volume during transport reduces the space available for other equipment and supplies (such as stage hardware, chairs, lighting, and even balloons). Companies organizing professional events are thus forced to use more trucks, and this increases the cost of ownership of the typical subwoofers and contributes to a larger carbon footprint of sound-system rental and use.

Another problematic aspect of modern subwoofers, is the industry trend to sacrifice electrical efficiency for enclosure size in a bid to remain physically enticing to the consumer. It is not often discussed however the power laws defining the total potential SPL vs the total electrical input into a speaker are not linear; it is in fact exponential by doubling. So for example in order to have a speaker produce twice the acoustic output SPL (+3dB), the electrical power has to be doubled for each 3dB. So for a 100dB (1 watt at 1 meter) sensitive speaker to reach a 133dB output that is +33dB or 33/3=1 1 doublings or 2¹¹ = 2048 times more power, and this translates to 2048 watts required to produce this level of sound. However, if a speaker is 106dB sensitive, then the power requirement is only 512w to reach the same 133dB level - a significant savings in electrical power, especially when multiplied by the typical 50 to 100 subwoofers used at a typical large scale venue like a stadium concert.

[0003] In the past it was common to control acoustic dispersion through the utilization of large ¼-wave horns and waveguides, however, such large speakers require large transit vehicles and ample storage space which has resulted in their use falling to a fraction of the existing Sound Reinforcement market. Since the late 1980's the state of the art has moved to the use of acoustic arrays based on line source emission geometries with individual loudspeaker elements being digitally filtered and delayed, so as to accomplish frequency shading and beam steering which are common uses of acoustic cancellation and reinforcement from a linear or planar emission source. One of the earliest examples of altering phase as it relates to frequency to accomplish directivity comes from Isao Yamamuro's Loudspeaker system - US4472834 A, wherein drivers are individually processed with digital delay and filtering along a line to increase or reduce directivity. Line arrays have since become an industry standard in PA and SR applications.

[0004] More recently, planar arrays using individually processed array elements on an X-Y grid have been utilized to accomplish increased directivity and pattern control beyond the capability of line source arrays.

[0005] Planar and line source arrays are both effective in steering frequencies as long as the array's dimensions are acoustically long compared to the frequencies being produced. As bass wavelengths are physically long, e.g., 20 Hz being a 55-foot cycle, it is usually not practical to construct planar or line arrays with one or both dimensions being 55 feet in length. As such controlling and steering bass remains a primary problem in acoustics. The present state of the art in low frequency acoustics centers around the so-called 'end fire' subwoofer arrays which are constructed from multiple delayed elements running phase shifted versions of the program material so as to create a wideband cancellation null behind the speakers, reduced output to the sides, and create a positive wideband reinforcement in front of the speaker (towards the intended audience.) As the wavelengths that represent omnidirectional bass vary in cycle size from 9 feet to greater than 55 feet there is no delay setting that is non-destructive to the entire bass range. As such, cardioid bass arrays are crippled in their directivity as the technique can only apply to particular narrow subset of the total bass-frequency range without significant temporal smear of the impulse response. In addition to the impulse response artifacts of cardioid bass arrays are their side lobes of acoustic energy, which are of reduced intensity yet still strong enough to disturb performers on stage.

SUMMARY OF THE INVENTION

[0002] In accordance with the present invention a modular loudspeaker enclosure sound reproduction system is provided which is characterized by its scalable or extensible architecture allowing individual loudspeaker enclosures to join into an array by use of a common output aperture. The individual speaker enclosures need to conform to a prescribed physical specification which enables the said individual speaker enclosures to form a contiguous and extensible acoustic array along the path of sound transmission which then derives advantages of increased acoustic bandwidth and maximum SPL, along with additional advantages of increased directivity and global frequency response shaping via prescribed time delays between the individual speaker enclosures.

Several embodiments of the present invention can be used to accomplish primarily VLF and ULF frequencies, while other embodiments of the present invention can simultaneously produce VLF, Bass and Mid-bass frequencies i.e., from 18 Hz to 200 Hz. While a single loudspeaker enclosure embodiment conforming to the present invention's physical and acoustical specifications can achieve at least a bandwidth from 45 Hz to 140 Hz averaging 97dB(C) (decibels, C-weighted) at 1 meter and 2.83 volts rms (Vrms), from an enclosure of no more than 1 14 liters. Two of the present invention's conforming enclosures coupled can achieve at least a bandwidth from 32-140 Hz averaging 102dB(C) at 1 meter and 2.83 Vrms, while three enclosures coupled can achieve at least a bandwidth of 20-200Hz averaging 105dB(C) at 1 meter and 2.83 Vrms. The disclosed invention's array behavior of simultaneous increase in both SPL and low frequency acoustic bandwidth is surprising to one skilled in the art and is particularly suited for use in SR and PA type settings that require strong bass covering large physical spaces or outdoor areas. Such embodiments of the invention are particularly advantageous in situations where multiple persons rendezvous carrying lightweight XLA modules conforming to array specifications that enable an improvement in acoustic bandwidth or an improvement in SPL or an improvement in both. By meeting or exceeding these performance

requirements, it is the objective of this invention to encourage and facilitate users' ability to erect collaborative sound systems of scale that would not ordinarily be possible unless significant financial and planning hurdles were overcome to make a comparable loudspeaker PA rental and exert the effort to assemble a concert-level sound system (with all the requisite skills and talent current state-of- the-art systems require from their users.)

In concert sound applications where very high SPL is required, one embodiment of the disclosed invention provides a previously impossible point source coupling of an extraordinarily high number of bass drivers. Said embodiment can align more than quantity 64 10-inch speaker drivers within ¼-wave at 60 Hz (which was previously impossible due to loudspeaker enclosure topologies physical requirements not allowing such compactness.) The present invention's ability to geometrically position many large bass drivers into a combined point source, for example a 2x2x4 array, (being two loudspeakers tall and two loudspeakers wide and 4 loudspeakers deep), totaling 16 loudspeaker enclosures holding at least 4 drivers each allows for much higher acoustic power density than any previous array technique, and by extension much higher levels of efficiency.

For example, using one un-optimized embodiment of the present invention in one of the disclosed array configurations (FIG. 13) of a size numbering 16 speakers each with 97dB sensitivity at 1 watt can produce a sustained RMS output of 1 17dB, while 1600 watts input to the same array will produce a sustained output of 129dB, while 6208watts input will produce 135dB (dB levels cited have been de-rated by 1 dB given acoustic losses in the discussed embodiment's summation architecture.) Due to the aforementioned embodiment's small physical format, it is not unreasonable to expect arrays of up to 64 enclosures to be used at festivals and concerts to provide strong bass to large audiences with a minimal footprint. It is known to the inventors that various optimizations can be applied to the disclosed invention allowing higher performance SPL of both single enclosures and arrays, which radically changes the value equation of the state of the art monolithic loudspeakers vs. the improved loudspeaker array and enclosure format disclosed herein.

Because low frequencies require the most electrical power due to poor impedance matching between speaker driver cone and the air mass, the present invention's modular approach to loudspeaker deployment is between 10x and 100x more efficient than the current trend of 2kW to 8kW subwoofers providing LF reinforcement. Furthermore, the compactness of many of the disclosed invention's embodiments encourages use in array sizes greater than count of 16. And finally, in the disclosed invention's spirit of enabling of crowd-sourced speaker systems, large numbers of loudspeaker enclosures conforming to the present invention's specifications could be assembled towards the goal of highest SPL for lowest electrical input, allowing strong bass from low wattage renewable or non-petroleum-based power sources within environments that appreciate such ecological concern. It is possible that 2048 electrical watts input into a properly configured 512 unit XLA system will at the low corner bass frequency produce greater than 160dB summed output.

It is another advantage of the present invention that it brings an extensible array format to home theater users which can be tuned for the desired SPL and bandwidth by simply varying the number of arrayed enclosures or varying the array's coupling conditions, e.g., spacing the contiguous enclosures more than 1 mm apart to reduce the low frequency gain of the array. This can be appreciated by home theater users who value realistic bass reproduction.

Because of the present invention's low human impact (portability and cost), its natural extension of low frequency energy, and its preservation of acoustic efficiency, the disclosed invention enables the new phenomenon of crowd- sourced PA systems and new opportunities in SR applications.

BRIEF DESCRIPTION OF THE INVENTION

[0006] The present invention is a new acoustics array method and requisite conforming loudspeaker enclosure topology which enables the formation of a Common Aperture (CA) Extensible Loudspeaker Array (XLA) by use of multiple loudspeaker enclosures sharing a common acoustic channel that runs through multiple enclosure's apertures, wherein the said apertures are characterized by a blind-hole or thru-hole duct that transects two or more walls of the loudspeaker cabinet.

[0007] To accomplish the present invention not only does a conforming enclosure require a centralized or constrained aperture, but it also requires an internal loudspeaker topology that supports the present invention's operating modes, the simplest mode being more than one loudspeaker enclosure temporally configured to coherently energy along a common acoustic aperture, while the most complex mode, so far proven by the inventors, is that of multiple temporally configured loudspeaker's each containing a resonant chamber and waveguides such that the loudspeaker array breaks symmetry and shares acoustic volume and shares waveguide path-lengths to form an acoustic superstructure. To accomplish a successful shared volume and path-length combining, such an enclosure must provide acoustic energy access to not only a waveguide but also the loudspeaker's back chamber through a port, vent, transmission line, horn or other acoustical energy sharing mechanism.

One improved embodiment of the CA XLA enclosure format is a loudspeaker enclosure featuring a polar rotational latching face which varies the aperture size by enclosure's axial rotation relative neighboring enclosures, thus it is possible for the end user to rotate cabinets along the CA XLA creating a tapered multi- aperture duct of linear, hyperbolic, parabolic or exponential expansion.

It is one aim of the present invention to produce a unipolar sound field into the deepest musical registers.

It is another aim of the present invention to reduce the weight and extensive rigging presently needed to array subwoofers.

It is yet another aim of the present invention to allow extremely large arrays (of a scale not possible with traditional lines and planes) to be rapidly deployed by individuals who have not previously met. DETAILED DESCRIPTION OF THE INVENTION

FIG. 01

Figure 1 depicts a CA XLA conforming to the minimum architectural properties required for a effective arrays wherein enclosure physical volume and physical path-lengths can be incorporated into a combined array response not reflective of how individual enclosures behave on their own. In detail the enclosure 1 , holds one or more drivers 2, which are in communication with a back chamber 4, and a front waveguide, chamber or duct 5, which leads to the common acoustic duct 3, and the common apertures 6, which conform to a common specification for the aperture 6, and the adjacent wall face 7, shown by dashed line;

FIG. 02

Figure 2 illustrates 3 distinct CA XLA serial drive configurations, the first stacked array at left shows a blind-hole 1 1 , aperture sealing element forcing the shared aperture 12, and an output aperture 13. The addition of more extensible speaker enclosures to the CA XLA with 3 units 14, and 4 units 15, are shown as progressions to the right side of the Figure.

FIG. 03

Figure 3 shows another embodiment of the CA XLA wherein bifurcating conduits 21 , which equalize the pressure along an ever-growing lateral array count of loudspeakers 22, which reduces velocity lock and increases overall performance of the array (note that bifurcating ducts 21 , are depicted in an expanded for clarity - they are physically flat and short to reduce resonance effects);

FIG. 04

Figure 4 shows the preferred embodiment in a linear serial 3-unit array with the central most unit removed displaying a hypothetical waveform 33, transiting between the first speaker 32, aperture 31 , to the remaining loudspeakers 34, in the array;

FIG. 05

Figure 5 shows the block diagram for the steps taken by the XLA speaker enclosures to synchronize and receive their programming of their specific time delay(s) from the master node, generally the centrally located speaker cabinet. The steps show the digital communication process that occurs between the cabinets via the optical transceivers in proximity between the cabinets. Basically, the process starts with the master enclosure (node=0) polling the other speaker enclosures via the, for example, built-in digital optical transceiver (typically an IR LED/photodiode pair in proximity contact), the master micro-controller on node 0 then continues to poll all attached speaker enclosures from node=1 , node=2, node=n, where n is the total number of enclosures. Each enclosure will provide the master node its metadata which may include its impedance, sensitivity, driver arrangement, volume, physical dimensions, and spatial location in X-Y-Z position (via for example, an infrared (IR) optical transceiver is activated on the faces in contact with another enclosure). The master node will then calculate the optimal time delays for each enclosure following a prescribed algorithm which aims to maximize the SPL efficiency (this is done using basic time-of-flight sound propagation principles combined with knowledge of the X-Y-Z location of the enclosure). The slave nodes then all receive the calculated delays and store the value onboard their non-volatile memory such as that used by a microcontroller, for example, like an Arduino. The microcontrollers for each enclosure also are connected to the digital to analog converter (ADC) and the audio signal that is distributed by the master node is then played with the appropriate delay(s) on the slave speakers.

FIG. 06

Figure 6 shows the predicted frequency response of a simple sealed alignment XLA comprised of up to 3 speaker enclosures that are connected end-to-end via their apertures. Each individual enclosure contains quantity 4 x 10-inch diameter woofer drivers connected in parallel and with an adjustable time delay. The enclosures measures 24 inch wide x 24 inch tall x 12 inch deep, each with a 10 inch x 10 inch square aperture that is centrally located on the front and back faces and connected to a square duct that transects the two faces. The volume behind the driver faces are 93L for every 4 drivers. Fig. 6 shows the additional bass extension achieved for each additional enclosure added, along with the increase in maximum SPL. We can see that the bass extension, defined as the - 6dB point for the single enclosure case is about 49Hz, and this increases to about 47Hz, and for the triple enclosure case, the -6dB point is about 42Hz. The increase in maximum SPL went from about 120dB to 128dB. This increase in the bass extension is demonstrated computationally for a simple sealed alignment. Note that other alignments such as but not limited to: bass reflex, 6th order bandpass, tapped horn, or transmission lines can also work and provide even more bass extension and higher sensitivities. The XLA topology construct can work with almost any speaker alignment by providing a convenient means of extending the bass frequencies and increasing maximum SPL.

FIG. 07

Figure 7 shows some examples of how time delays can be used to shape the response of the XLA almost like a parametric equalizer. Four curves are shown for various delay settings shown by the notation delayl / delay2 / delay3, where delayl is the delay in milliseconds for enclosure 1 , which is in the middle of the triple enclosure stack; delay 2 is for the enclosure in the front (facing audience); and delay3 is for the back enclosure. As can be see, widely varying outputs in frequency response can be obtained, and a very flat response with usable output up to 200Hz can also be obtained, while one of the responses permits a very steep fall-off to the right, which is useful to aid a lower order electrical crossover with an overall electro-acoustic slope that is very steep to reduce woofer bleed- thru into the mid-bass and lower-midrange region.

Claims

CLAIMS What is claimed is:

1.) A plurality of individual loudspeaker enclosures forming a loudspeaker array, comprising: the individual loudspeaker enclosures, each having a plurality of acoustic transducers in communication with a centrally located acoustic aperture, such that the acoustic aperture connects through all adjoined loudspeaker enclosures forming a contiguous acoustic summation duct or channel which penetrates through the adjoined loudspeaker enclosures assembled as the loudspeaker array.

2. ) The loudspeaker enclosure of claim 1 , wherein:

at least two of the loudspeaker enclosure's exterior walls contain a bi-directional optical transceiver module embedded or installed behind a transparent or perforated surface.

3. ) The bi-directional optical transceiver module of claim 2, comprising: a microcontroller, an optical format data transmission circuit, an optical format data reception circuit and a means for said microcontroller to poll said

transmission circuit and said reception circuit for the purpose of determining a loudspeaker array topology such that each loudspeaker enclosure's position within said loudspeaker array topology is registered within the microcontroller.

4.) A plurality of loudspeaker enclosures forming a loudspeaker array, comprising: the individual loudspeaker enclosures, each having one or more acoustic transducers, in communication with one or more waveguides or one or more resonant chambers in communication with a centrally located acoustic aperture, such that the acoustic aperture connects all adjoined loudspeaker enclosures forming a contiguous acoustic duct or channel which penetrates through the loudspeaker enclosures assembled as the loudspeaker array.

5. ) The loudspeaker enclosure of claim 4, wherein:

more than one of the loudspeaker enclosure's exterior walls contains a bi-directional optical transceiver module embedded or installed behind a transparent or perforated surface.

6. ) The bi-directional optical transceiver module of claim 5, comprising: a microcontroller capable of digital signal processing, an optical format data transmission circuit, an optical format data reception circuit and a means for said microcontroller to poll said

7. ) The loudspeaker enclosure of claim 4, wherein:

the loudspeaker enclosure is shaped substantially similar to a torus, cylinder, rectangular prism, pentagonal prism or any other regular or irregular polygonal prism.

8. ) The loudspeaker array of claim 4, wherein:

the loudspeaker enclosures are oriented and assembled so as to perform a serial, parallel, or bifurcating loudspeaker array.

9. ) The loudspeaker enclosure of claim 4, wherein:

the loudspeaker enclosure's centrally located acoustic aperture is formed such that contiguously arrayed loudspeaker enclosures assemble a duct or channel of increasing cross sectional area along an axis of adjoined apertures.

10. ) The loudspeaker enclosure of claim 4, wherein:

the centrally located acoustic aperture is formed by a series of ports or perforations in at least one of the loudspeaker enclosure's exterior walls.

1 1. ) The bi-directional optical transceiver module of claim 6, wherein:

an audio input signal is processed by the microcontroller running a digital signal processing algorithm which produces a plurality of audio output signals specific to each loudspeaker enclosure and the acoustic transducers therein.

12. ) A method of configuring the loudspeaker enclosure of claim 4, such that: the individual loudspeaker enclosure's centrally located acoustic aperture contains a removable or integrated blocking element which supports reconfiguration of the loudspeaker as a blind-hole or through-hole acoustic emission source.

13.) A plurality of loudspeaker enclosures forming a loudspeaker array, comprising: the individual loudspeaker enclosures, each having a plurality of acoustic transducers in communication with a plurality of acoustic apertures, such that all the acoustic apertures connect through all the adjoined loudspeaker enclosures forming multiple contiguous acoustic summation ducts or channels which individually penetrate through the adjoined loudspeaker enclosures assembled as a loudspeaker array. ^'

14. ) The loudspeaker array of claim 13, wherein:

the loudspeaker enclosures are oriented and assembled as a serial, parallel or bifurcating loudspeaker array.

15. ) The loudspeaker array of claim 13, wherein:

an audio input signal is processed by a digital signal processing algorithm which modifies the audio output signal specific to each loudspeaker enclosure and the acoustic transducers therein.