EP4013064A1

EP4013064A1 - Transportable apparatus for the high efficiency sound reinforcement of audio frequency signals

Info

Publication number: EP4013064A1
Application number: EP21020487.1A
Authority: EP
Inventors: Fabio LARIZZA
Original assignee: Individual
Current assignee: Individual
Priority date: 2020-09-25
Filing date: 2021-09-25
Publication date: 2022-06-15
Also published as: IT202000022627A1

Abstract

A transportable apparatus for the high-efficiency sound reinforcement of audio signals comprising an electrodynamic loudspeaker and a passive radiation diaphragm, with small size and weight, suitable to be lifted and transported easily from single person, powered by an energy group in order to reproduce the signal of musical instruments such as electric guitar and bass (also electronic keyboards and human voice), ensuring faithful and high-quality reproduction over a very extended frequency spectrum especially at lower frequencies which require more amount of energy, being able to produce a considerable volume power for a certain period of time without having to use the electricity mains, being therefore usable and portable in any place and situation, and able to feed a large number of external and internal signal processing devices such as effect pedals, and including means of lifting and fixing on various surfaces.

Description

The present invention is placed among the transportable apparatuses for the reinforcement of sound signals, more commonly known as loudspeakers for amplification, and more specifically refers to that field of acoustic diffusion apparatuses designed for high efficiency, i.e. possibility of reproducing an unprogrammed excursion signal (high dynamic range) over a very wide frequency spectrum, especially at the lower frequencies which, as is known, require more energy, being able to produce a considerable volume power for a certain period of time without having to use the electricity grid and, at the same time, being able to power a large number of external and internal devices suitable for processing the signal in question, with certain autonomy from the electricity grid and being, moreover, easy to transport.
The technical field of use of the present invention differs from those devices designed for the reproduction of "sound programs", as that of reproduction, with a degree of compromise in qualitative fidelity between spectral extension and reproducible volume, of radio-broadcast signals, physical or digital media known as "liquid contents" containing recordings of musical works, songs and, in a general sense, recorded signals ("program" signals), since the recording medium itself imposes dynamic range limits that are always controlled and it is therefore possible to reproduce those signals - at a relatively low volume - on a more selective frequency spectrum where a qualitatively undemanding listening is necessary: this can be achieved by means of very small (practically pocket-sized) loudspeakers, goal that already finds satisfaction in pre-existing findings already disclosed and discussed in other patents, which allow listening to this sound material also by means of direct connection via cable or over-the-air transmission (in Frequency Modulation or Bluetooth protocol).
Reproduction on these peripherals can also take place in places not served by the electricity grid and this is possible by means of an incorporated accumulator (hereinafter referred to as "energy group") which, after complete recharging, allows its use for the duration of a specific time lapse.
The invention discussed in the present invention, on the other hand, finds greater - but not exclusive - use in live entertainment and in the amplification of electric musical instruments, ensuring correct reproduction of signals coming from electric cordophones such as guitars, basses, mandolins but also electronic instruments ( keyboards, synthesizers, samplers, sequencers, drum machines) which reproduce signals recorded for concertation use or produced through electronic synthesis, as well as the human voice.
The amplifiers for electric musical instruments are considered, from their original invention, to be an essential complement to the instruments that would otherwise be silent due to their physical characteristics such as solid-body cordophones (electric guitars and basses) or electronically sounded keyboards.
In the case of instruments of a mechanical nature, the vibration of metal strings or other types of means interferes with the magnetic field generated by a transducer capable of transmitting the sound signal in electrical form, so the amplifier must guarantee a satisfactory amplification of a signal with strong dynamic excursions, being able to reproduce it at a sustained volume in such way that it can be appreciated in public and crowded places, with an adequate frequency response on the entire spectrum of the signal as directly transduced by the instrument (fidelity over the entire useful bandwidth).
Instruments that generate high frequencies require loudspeakers and amplification stages capable of reproducing these frequencies correctly and with a fairly wide beam angle, due to the rigid directivity with which these frequency bands are mechanically reproduced, while those instruments dedicated to production of low frequencies, as well as those instruments that produce signals extended over the entire audible range require, in addition to very powerful and robust power amplification stages, also very large speakers capable of moving large masses of air and consequently the loudspeakers enclosures (cabinets) will become sufficiently large to be able to accommodate both said loudspeakers and an amount of air adequate for the correct working of these transduction components.
Therefore, amplifiers for musical instruments have always been characterized not only by the need for an external power supply, but also by a considerable size, that of the entire cabinet containing the loudspeakers dedicated to reproduction and sometimes even the signal amplification stages, useful for their driving; but also by a significant weight, since the vibrations at the lowest frequencies to which the acoustic apparatus is subjected are able to move both the surrounding air (for the purpose of sound production) and unintentionally the apparatus itself. Consequently, these request appropriate counterbalancing or even suitable fastening means to the supporting surface.
The most effective solutions for controlling such "parasitic" vibrations are known: a correct sizing of the cabinet, the choice of construction materials and their thickness, the use of bracings inside the enclosure and other absorbing materials in order to better distribute the kinetic forces on the cabinet walls by reducing the amount of sympathetic vibrations (if present, they would actually affect the quality of the sound performance and it's therefore necessary to reduce them at the minimum), and possibly the use of mechanical suspensions, counterweights and other resolving techniques.
With the passing of time and looking at the progress of available technologies, the demand for amplification systems of ever smaller size and weight had to lead significant advantages for all those musicians who need to move more easily, on foot or by public and private transport) and therefore often with little space available, then to be able to perform anywhere without the need for a connection to the electricity grid, albeit at the expense of a reproduction of the acoustic spectrum extended according to the instrument to be amplified (in this case for the critic very low frequencies); a sufficient loudness to perform in the presence of other instruments with equivalent (and potentially higher) sound volume; the convenient portability which unfortunately finds disadvantage in the correct volumetric and weight sizing of the diffuser, as well as, always in the absence of an auxiliary power supply, to achieve the possibility of processing the signal produced by their instrument through other electronic devices, called "effect pedals", necessary to distort and manipulate the sound signal generated by their instrument before it gets reproduced by the amplification system. Any effect pedal requires an adequate electric power supply for their operation, supplied through alkaline batteries placed inside each single pedal (and well known to provide a very short autonomy and in this sense considerably not eco-sustainable) or, as well as for the amplifier, can be powered on by the mains supply.
The lack is often compensated, on those products formulated for the portatile amplification, by providing some common effects and digital sound modelers, whose effectiveness is almost always subordinated to the overall quality of the portable device, hardly meeting the real needs of the professional musician.
The main purpose of this invention is therefore to provide an apparatus capable of allowing to each musician the possibility of performing in any place and on any occasion, being able to produce a listening volume useful for concerting in enseble with instruments yet characterized by high volumes of sound, such as drums, offering a satisfactory technical complement from the point of view of the quality of the sound performance, as for portability, as for a large number of effect pedals arranged by the musician to his personal choice.
Another purpose of this invention is to ensure autonomy from the electrical grid for a reasonable number of hours, extending the autonomy of the apparatus also to a wide range of external devices such as effect pedals and pedalboards.
A further purpose of this invention is to ensure maximum portability of the apparatus in question, reducing its weight and volumetric dimensions without affecting the aforementioned quality of acoustic performance: as well as adopting the particular configuration of the passive radiator for the type of casing completely sealed, the apparatus is equipped with lifting and transport means which, at the same time, can be used for fixing on various surfaces (from flooring of all types to mechanical supports for incorporating the apparatus, or more apparatuses, with other auxiliary equipment).
A final purpose of the present invention is to expand the technical possibilities of the proposed apparatus to the most varied signal processing paths and to more avant-garde functions while maintaining the dimensions, weight and portability of the apparatus in its primordial version: through plug-in interfacing cards it is possible to implement additional functions such as processors, effects, and various kinds of computerized controls and sensors.
These - as well as other - purposes can be achieved with the transportable apparatus for the high efficiency sound reinforcement of audio frequency signals described below, illustrated in the attached figures, without precluding further improvements within the scope of the present invention:

FIG. 1 - lateral exploded view of the apparatus in its essential parts
FIG. 2 - transparent view of the acoustic box (10) and of the internal reinforcement structure made through strips (21) of wood or polymeric material
FIG. 3 - transparent view of the acoustic box (10), complete with amplification circuits, heatsink pin (42), voltage boosting device (33), various controls and connectors exposed on the walls
FIG. 4 - transparent view of the same acoustic box (10) on the complementary side
FIG. 5 - isometric detail of the power amplifier stage (32) and heatsink body (41) assembly
FIG. 6 - view of the apparatus equipped with effect pedal (62) and charging device (61)
FIG. 7 - side view from below, showing the passive radiator (12), the heatsink pin (42), the fast coupling fashion handle (73), the Speakon power signal connector (161) and the relative switch (71) changing over between the power amplification stages (32) inside the apparatus and other power amplification stages eventually provided externally FIG. 8 - block diagram of the entire electronic
FIG. 9 - detail of the complementary fastening system (fast coupling fashion handles (73))
FIG. 10 - exemplary view of the fixing system of the apparatus on an adjustable support
FIG. 11 - rear isometric view of the apparatus equipped with means of backpack (1102) and removable lifting means (1108) suitable for any surface
FIG. 12 - isometric view of the apparatus illustrated so far, complete with speaker protection grilles and pockets for inserting plug-in expansion cards

The measurements carried out on a first prototype of a complete apparatus made according to said drawings, having an overall volume of less than 27 cubic decimeters and a weight not exceeding 11 kg verify a sound volume higher than 90dB SPL (constant) at the frequency of 24Hz with a harmonic distortion of 10% for at least three hours.
The production, the development and the maintenance of this apparatus are very simple and possible at very low costs because the particular configuration of the passive radiator transcends the volumetric sizing of the diffuser a priori, offering a more practical possibility of tuning the frequency of resonance of the entire system when construction has already been completed; the bulky and efficient nature of the battery that gives power to the whole internal and external electronic system is instead exploited as a counterweight useful for stabilizing the apparatus if assisted by suitable anchoring (and lifting) means to any type of surface; and most importantly, the simplicity with which it can be put into operation in the absence of connection to the grid is even more evident: needing the little necessary and connecting a very limited number of cables (for the direct connection of the instrument enoughs just one signal cable, while to connect an effects pedal, requires two signal cables and one for power supply between the output of the device and the input of the effect pedal or pedalboard) and, by switching on, the set-up is ready for several hours of high perfomance over a wide frequency spectrum.
The first problem faced by the inventor to choose a design model of an acoustic box that had a very low sizing and weight while maintaining, in fact, a satisfactory reproduction at the lower frequencies. These, as is known, require a very large mass of air to be moved both outside the case, where the sound is reproduced, and inside, to counteract the physical forces to which the loudspeaker is subjected. Both the infinite baffle model (or simply closed box) and the ventilated or reflex model require an internal air volume proportionate to the lowest frequency to be reproduced and to the size of the speaker, thus resulting in an overdimensioning not suited to our needs.
Furthermore, in the case of the infinite baffle, the response at very low frequencies would be too much dampened, resulting not so efficient and therefore not very adequate to expectations; a ventilated speaker (reflex) would be instead more responsive in the aforementioned range, requesting less power supply from the amplifier, but the dimensions of the port would have entailed an excess not only on the overall dimensions of the enclosure, but as is also known on the design tolerances, due to the tuning of the port to the overall resonant frequency. It was therefore decided for the acoustic box (10) sealed with passive radiator - illustrated in figure 1 without the side walls to easily observe the inside - where at least one loudspeaker diaphragm of the electrodynamic speaker diaphragm (11), being driven by a power amplifier stage, acts on an air mass inside the acoustic box (10) served by at least a second diaphragm, the so-called passive radiator (12), more larger in diameter. It is also possible to opt for the addition of several smaller passive radiators.
Said passive radiator (12) seen from the outside is apparently identical to an electrodynamic loudspeaker except for the total absence of the magnetic group, which on the eletrodynamic speaker diaphragm (11) features a magnet and a coil: since it cannot be driven in any electrical way, the passive radiator is an inert surface, but in the special configuration of the sealed case, this shares the same internal air load as the electrodynamic speaker diaphragm (11) and these two diaphragms working together in harmony, produce an extension of the spectrum below the resonant frequency possible with only the active part (said frequency is the minimum reproducible by the electrodynamic speaker diaphragm (11) and should be electronically filtered in order not to be reproduced by this transducer - a penalty would be the malfunction of the whole vibrating apparatus and a poor acoustic and mechanical response).
In the case of the passive radiator configuration, as is known, the resonance frequency of the entire system transcends the volumetric sizing of the acoustic box (10), being delegated to the mass of the resonator diaphragm (the passive radiator (12)): thus a relatively very small acoustic box (10) can be obtained, with a smaller air volume than necessary and thus it becomes possible to tune the response to low frequencies simply by varying one or more small iron weight samples, firmly bolted on the dome located in the center of the vibrating membrane (121) of the resonator diaphragm.
The same acoustic box (10) now observable in figure 2, inside, is reinforced with wooden or polymeric material buttresses (21) that run on the walls and get structured with precise distribution criteria, in order to discharge the kinetic forces and stabilize the apparatus when the vibrations reach the resonant frequency.
They also deal to keep in a steady position some critical parts, including the energy group (14) already illustrated in figure 1, which will be detailed below.
The acoustic box (10) can be designed in the shape of a parallelepiped, cube, spheroid or wedge, provided that, once all the components have been installed, it results completely sealed. Among these forms, the wedge offers the possibility of resting on the surface of the floor in the immediate vicinity of the standing or seated musician, in such way the electrodynamic speaker diaphragm (11), positioned on the frontally inclined wall (13), lies always oriented towards the ears of the performer. On this wall (13) it is also possible to feature the presence of one or more tweeters, active speakers for high frequencies (not shown) of the orbitally orientable type, with the appropriate electronic low frequency filtering, if connected to the same power output as the main active transducer; alternatively, deriving a cross-over output from the pre-amplification circuits in order to drive a power amplifier dedicated to high frequencies.
The active loudspeakers for high frequencies can be controlled by rheostat and deactivated by means of a SPST type switch positioned on the subfrontal wall (18). Often, a combined situation is adopted between these two, which allows the tweeter output to be attenuated to the minimum: here a switch mechanism will completely open the output circuit, deactivating the high frequency transducer. This particular rheostat-disconnector is often bulky and must therefore be easily located on one of the side walls of the apparatus.
The positioning of a single or more passive radiators (12) can be arranged on any wall.
If there are an even number of them, it is always advisable that they are located on opposite walls so as to neutralize the kinetic forces produced by the lowest vibrations, as these could cause trembling and unwanted movements of the apparatus.
In the simplest embodiment, again illustrated in Figure 1, only one passive radiator (12) is positioned on the wall below the acoustic box (10), pointing towards the floor.
The passive radiator (12), as usual, consists of the same vibrating membrane of woofers but can also be a flat panel suitably suspended by means of an elastic material; said passive radiator (12) is constrained to a frame or basket (in the case of the traditional speaker form), featuring a rubber, foam or cardboard suspension on the largest external diameter, closest to the mouth of the loudspeaker (10) and a web centering device (called spider) on the smaller internal diameter, in the rear position.
These parts are substantially identical to those commonly found on any electrodynamic active diffuser (11). The center of the passive radiator (12), known as dome, is originally intended to proctect the coil and center it in its magnetic group: in the passive version it is replaced by a cap in polymeric or wooden material on which it is possible to bolt a weight sample of the weight necessary to tune the resonant frequency of the loudspeaker (10), once construction and sealing have been completed. Since the internal volume of the acoustic box (10) and therefore the overall dimensions of the apparatus no longer represent a problem, appears appropriate to incorporate the energy group (14) - made up of the by one or more buffer batteries (141) - connected in series, with the aim of reaching the total voltage of 12 Volts. An energy group (14) suitable to be confined in an enclosed space even if the apparatus is stored or transported in different positions becomes necessary: AGM type batteries (or alternatively Lead-GEL) whose technology refers to the category of completely sealed batteries can be mounted in any position and, in addition to ordinary recharging cycles, do not require any other type of maintenance. A better choice, but more expensive, is represented by Lithium-Iron-Phosphate batteries, noticeably lighter and more efficient: weight a fifth of a Lead or AGM battery, the Lithium battery can deliver double the Ampere-hours and represents a more eco-sustainable choice, considerably reducing the space occupied inside the apparatus.
The weight of said batteries (141) certainly contributes to the counterweight of the acoustic box (10), making it less susceptible to the movements induced by vibrations at certain frequencies. It's convenient to opt for a simple series of two nominal 6V batteries (141) in order to obtain an adequate power supply for the whole circuitry that will be discuss shortly, especially those that require a "dual type" power supply (having with the same voltage value for both positive and negative signs, with reference to the common ground potential). Alternatively, a single 12V battery supplying 18 or 22AH may be sufficient for a longer duration of operation in single power supply. In the case of the Lithium-ION battery type, it is advisable to adopt a 35Ah bulk.
The energy group (14) is permanently installed inside the acoustic box (10); it can be easily removed for immediate replacement by providing a suitably sized and watertight space inside the acoustic box (10) (in the form of a second cavity), accessible from the cover on the rear wall (not shown).
As shown in figure 3, an on/off switch (31) for the entire main system supply, located on the subfrontal wall (18) of the loudspeaker box (10), has been connected to one of the poles of the energy group (14) and, by convenience, to the negative.
The electrodynamic speaker diaphragm driving is obtained by a power amplifier stage (32) in AB-class (which involves the best reproduction quality but a greater energy consumption due to a greater activity of the power transistors) or in D-class (obtaining maximum efficiency in terms of power, minimum energy consumption and minimum heat production at the expense of a satisfactory reproduction quality only at low frequencies), or even in class G or H, which allow rapid switching of the general power supply line according to the power needed to reproduce the signal, even if these commonly require more complex design solutions.
For the testing of the power amplifier (32) in AB-class, the integrated circuit component TDA7379 from ST Microelectronics was chosen, as it is designed to produce a convenient power starting from only the 12V supplied by the energy group (14). The integrated circuit component involved can deliver four outputs, but can in fact produce up to 38W at a frequency of 1kHz on each of the two pairs of outputs in the Dual Bridge configuration with only 18V of DC power supply (repetitive peak of 5A). In order to exploit the maximum power available on the integrated circuit component, an electrodynamic speaker diaphragm (11) would need two separate coils, being suitable for producing a frequency response between 50 and 5000Hz. An electrodynamic speaker diaphragm (11) of the dual-coil subwoofer type with a diameter of 165 mm with a total merit factor (QTS) suitable for the type of project was therefore chosen. A pair of outputs of the TDA7379 integrated in Dual Bridge configuration was therefore connected to each of its coils.
In order reach obtain the total 78W on both coils (112) of the small electrodynamic speaker diaphragm (11) it was necessary to raise the primary voltage of 12V to 18V, therefore it was convenient to introduce an additional circuit called voltage boosting device (33) or DC-DC converter, between the switch (31) connected to the battery (141) and the power amplification stage (32) by means of the positive terminal.
Said voltage boosting device (33), delivering a sufficient current to support the absorption peaks of the power amplifier in question, proved to be useful in raising the battery voltage (141) from the initial 12 Volts to 18 Volts, ensuring operation to all the electronics subordinate to it, including the power amplifier (32) for an autonomy of at least three hours. In other cases, to feed more powerful power amplifiers, such as those in class D, G or H, the voltage raising device (33) should be able to raise the primary voltage from 12V up to 36V In this case, however, it is advisable to resize the whole project assuming: dimensions of the speakers, number of batteries and maximum tolerance of current that can be supplied by the voltage boosting device (if present).
Furthermore, the voltage boosting device (33) is equipped with a segmented numerical display (34), which can be shown through one of the walls of the sound box (10) in order to have a constant measurement of the charge level when the apparatus is running. We can find it in figure displayed on the upper wall (15), and must be not positioned too close to the energy group (14) for safety reasons: if the latter is too bulky, it is advisable to place the voltage boosting device (33) on the frontally sloping wall (13). The display (34) placed inside the acoustic box (10), when turned on to indicate the charge level, is now visible on the outside of the acoustic box (10) sealed by means of a transparent or translucent glass frame. One or more LEDs can be provided and exposed outside the acoustic box (10): at a certain minimum voltage threshold supplied by the energy group (14), a microcontroller on the voltage boosting device (33) will switch on the LED by communicating to the user to promptly recharge the device before it runs out of battery, also avoiding damage to the energy group (14) (as the buffer batteries advisably cannot remain totally discharged for a long time).
The rear side of the TDA7379 integrated circuit is soaked with thermoconductive paste and fixed on a piece of aluminum bar (41) now visible in figure 4, called heatsink (41), in the form of a parallelepiped or on a finned aluminum profile. This heatsink (41) has one or more female-threaded holes (411).
One or more holes (412) of the same nominal diameter are made on the wall (16) of the acoustic box (10). A plurality of male heatsink pins (42) are made from a solid aluminum round with the same thread; in turn it's soaked with thermally conductive paste and screwed onto the threaded seat of the heatsink (41), as illustrated in detail in figure 5, so that the head of the pin (421) is outside the side wall (16) of the loudspeaker (10) and that the heatsink (41) is inside: in this way it is possible to fix the dissipator of the integrated on the wall (16) of the loudspeaker (10) and obtain the conduction of the heat produced during operation towards the outside of the apparatus without compromising the seal of the acoustic box (10).
The heatsink (41) must be mounted as far as possible from the rechargeable batteries (141), in order to avoid overheating of these beyond the allowed limit and consequent damage: generally, however, the air motion inside the acoustic box (10) induced by the diaprhagms (11) and (12) help to drastically reduce the temperature of this space. Looking at the detail of figure 5, the head of the heatsink pin (421) which is located on the outside may have a broach in the shape of a cut, a Phillips cross, a hexagonal head socket (Allen key); it can be milled in the form of a hexagon to be screwed with a wrench, or, made in a round shape as in figure, featuring a threaded hole much smaller than the pin (42) thread (conventionally M6 ISO) threaded in the center.
Using a further M6 male pin (423), a nut (424) and a counterlock nut (425) it should be possible to obtain a single block integral with the pin (42), useful to screw it firmly on the heatsink (41); after that, will be possible to remove the second pin and the two nuts as shown in the figure. Similarly it will happen for disassembly.
The SPDT type (single way, two positions) switch (31) connected to the energy group (14) as we said can have the central pin connected to the negative pole; the power amplifier (32) and the other electronic circuits connected to one of the two position pins (by convenience, the other electronic circuits get conduction with the energy group (14) if the switch (31) is activated towards top) while, on the opposite position pin, the switch (31) may have connected an external connector (35), exposed on the other side wall (17) of the acoustic box (10). Thus by setting the switch (31) to the off position (for convenience downwards) it will be possible to have a direct connection on the external connector (35) with the poles of the energy group (14). On this connector (35), the presence of a diode will prevent accidental inversion of the voltage connected to the poles of the connector (35) from damaging the battery. The purpose of the connector (35) consists of the recharging of the batteries (14) by means of a charging device (61) visible in figure 6, optimized to manage different charging phases and bring the energy group (14) back to maximum its state of charge in safety, without damaging it and without having to remove it from its position inside the acoustic box (10). Said self-ventilated charging device (61) can be equipped with recharging voltage monitoring circuits.
The charging device (61) can also be implemented internally on larger devices, if adequate ventilation is provided: in this case a small containment chamber (not shown) must be prepared as a separate cavity inside the acoustic box (10), in such way to arrange a simple mini-VDE connector on the external wall (17) of the apparatus in order to connect the charging device (61) to the mains.
Inside this separate cavity, the presence of a second switching type mains PSU will make the apparatus versatile also in those situations in which a mains supply is available.
On smaller apparatuses it is convenient to arrange the charging device (61) outside of the acoustic box (10). The charging device (61) is connected to the apparatus by means of a threeway connector, to distribute two separate conduction lines (considering a common ground pole): in this way it will supply the charging device (61) for the batteries on the first conductor way (141) and at the same time, on the second conductor way, a 12V switching power supply will be delivered separately.
Thus, it will be possible to enjoy the full functionality of the apparatus, excluding the batteries (141) as a power source during the recharging cycle. In this embodiment, the switch (31), in the recharging position, will activate the apparatus by means of the mains power supply, in the meantime that the charging device (61) recharges the energy group (14) with no load connected to. Preferably it will be necessary to integrate a second stand-by switch that deactivates all the acoustic diffusion functions, if the device is not used during the charging phase, or to use a single switch with several positions and poles: 1) off, 2) charging only , 3) switched on and, if connected to the mains, charging (with operation and charging arranged for separate lines). In any case, the charging device (61) must first be connected to the mains and only subsequently to the energy group (14), therefore, during the connection to the mains, the switch (31) must be in the off position otherwise the energy group (14) could be damaged.
For this purpose, with the charging device (61) inside the acoustic box (10), a microcontrolled circuit or a special switch must also be prepared, allowing the batteries to be recharged only when the charging device (61) is already connected to the mains.
The energy group (14) supplies all the circuits, internally or externally provided and useful for the operation of the apparatus: in addition to one or more power amplification stages (32) and to the voltage boosting device (33), which are able to work with a single voltage of 12V, we will find pre-amplification (and processing) circuits of the signal supplied from the outside instruments.
In figure these have been conventionally illustrated incorporated in the same power amplifier (32) board while not excluding the possibility of adopt different printed circuit assemblies.
These pre-amplification (and processing) circuits may require two equal and opposite voltages, one positive and one negative, referred to a central value (common ground), in a configuration conventionally defined as "dual" or a single voltage referred to the ground potential (as usual for effect pedals and pedalboards).
A preamplifier circuit must be capable to ensure a signal level able, at least virtually, to bring the entire power stage to the saturation threshold within the limit allowed by the swing of the power supply voltage applied to it.
The connector (44) for the signal input to be amplified is located on the subfrontal wall (18), it belongs to the standard TRS JACK 6.3mm (unbalanced or balanced) or XLR (balanced). The sleeve (same for the casing) of this connector refers to the ground of the apparatus and the conducting tip (tip) conducts the signal line.
Among the signal processing circuits that can be positioned inside the apparatus, it is possible to mention: low or high frequency filtering circuits to allow a better reproduction of the signal from the apparatus, avoiding frequencies lower than the resonant one of the system or higher than the spectrum reproducible as they would lead to an excessively intermodulated and distorted sound reproduction, reducing the sound efficiency obtainable from the apparatus, to the point of damaging the electrodynamic speaker diaphragm (11) and the power amplifier (32) in a short time; impedance matching circuit for direct connection of the instrument, with unity gain or negative feedback; signal equalization circuits, of the graphic, parametric or fixed cut (changeover) type; mixing circuits useful for combining the signal of the instrument to be amplified with other auxiliary signals (eg input for backing tracks); optional buffer circuits to take out the pre-amplified and processed signal before entering the final stage (i.e. headphone output).
A remarkable circuit, which can be made with a few simple diodes, is the soft-clipping limiter. This circuit is connected between the last processing circuit and the input of the power amplifier (32) and transmits a signal which, thanks to the diodes, can never exceed a certain potential, avoiding that excessive harmonic distortion that often cause damage to the final stage (32) and to the electrodynamic speaker diaphragm (11) coils.
All the typical regulation controls of the preamp (and processing) circuits can be positioned on the frontal (13), subfrontal (18) or upper (15) wall of the apparatus, for an easy accessibility. To reduce their size and aesthetic impact, they can be flush-mounted by means of counter bores on the panel, equipped with pull-out or push-button knobs (37).
In the same way it is possible to provide more sophisticated processing circuits including signal compressors and on-board sound effects (such as the classic reverbs, echo, delay, chorus, flanger, tremolo, vibrato and DSP digital processors).
As yet said, such effects are often impractical if provided directly on the amplifier, since professional musicians prefer to opt with their choice, mostly obtainable through external devices. Before being supplied to the amplifier (32), the instrument signal is processed through an external peripheral called "effect pedal" (62) illustrated in figure 6, getting possible to parameterize the type of effect which you prefer.
These effect pedals (62) are produced in a very wide variety by big and small producers around the world, but they all share the fact that they require a negative power supply: the -9V standard is the most widespread, although occasionally also pedals operating at -12V are found.
The apparatus is able to supply, in parallel with the internal devices, an adequate power supply useful for supplying various effect pedals (62). Through a voltage regulator it is possible to derive two lines of negative voltages directly from the battery, supplying them on two distinct connectors positioned in the vicinity of the power connector (35): the first for the voltage of -9V (351), while the second can be connected (in reverse) directly to the energy group (14) without stabilizer, so that it can supply a voltage of -12V (352).
Becomes obvious that the greater number of effect pedals (62) will be connected in parallel to these external connectors (351) and (352) and the shorter the charging time of the energy group.
A 5V output arranged on a USB-A female connector (63) provided on one of the walls of the acoustic box (10), like the subfrontal one (18) and in turn connected internally with the energetic group (14) or the internal electronic devices provides a useful charging source for smartphones and other peripherals that can be powered at this voltage, again by means of a suitable voltage regulator.
A further input for power signals coming from any externally provided power amplifiers can be installed in the form of a Speakon type connector (161) on a side wall (16) as in figure 7. A switch (71) positioned on the same wall (16) will then switch the terminals of the active speaker to this input or alternatively to the amplifier already in operation inside the device, so that it is possible to use the device with external power amplifier (not shown), possibly by turning off the internal power amplifier (32), while all the other devices connected to the energy group (14) will continue to operate normally.
A more detailed block diagram of the entire electronic system is summarized in figure 8.
The sealed acoustic box (10) arranged in figure 7 can be completely covered with shockproof material, such as linoleum, carpet or rubber; possibly completed with shockproof angles (72) in iron, ABS or rubber, taking care to leave free the power supply connectors, the counter bores of the recessed controls, the acoustic diaphragms (11) and (12), and if present, the tweeter.
On the side walls (16) and (17) and on the upper one (15) can be provided some comfortable handles (not shown) covered in leather or rubber, for an easy grip. Alternatively, the handles can be made in the form of metal plates (73) with rounded edges, which can be raised upwards like wings and equipped of with a return spring for quick repositioning.
This convenient mechanical configuration allows them to be quickly coupled with other devices (90) of the same shape and size, not discussed in this patent, that could be mixing consoles, recorders or other musical instruments. On the sides of these devices (90) there are the quick coupling pockets (731) illustrated in detail in figure 9, and each device (90) can thus mount up to two transportable apparatuses for sound reinforcement, one for each side in stereo configuration. As shown in the figure, the metal plate (73) is inserted into the quick coupling pocket (731) and the tightening between the parts takes place by means of two bolts (732).
The quick coupling pocket (731), equipped with through holes for convenient surface fixing by means of further bolts or through screws (733), can have a rotating counterplate (74) visible in figure 10, so that the transportable apparatus for sound reinforcement, once joined to the device (90), can be rotated and oriented towards other directions.
A useful accessory for supporting the apparatus is provided in the form of a support bar (751), as shown in figure 10.
At the two ends of the support bar there are two brackets (75) suitably spaced and shaped for quick coupling with the metal plates (73), while below the bar there is a conventional cylindrical socket (76) sized for housing on rod type standard supports and equipped with a throttle pin (not shown) for tightening on them. In this way, the rotating counterplate (74) allows the plates (73) to allow the apparatus a comfortable orientation towards the desired direction.
The rear wall of the apparatus, as shown in figure 11, remains free from connections and controls, in order to be covered with a cushion in soft sponge (1101) or other silicone materials, to be comfortably carried on the shoulder. Said wall can be glued on the battery compartment cover previously discussed (not shown) preventing access to the battery compartment.
A pair of soft removable backpack shoulder straps (1102), fixed by means of hooks or buckles, allow the transportability of the device on the shoulder with minimum bulk, and occasionally the use of the device in mobility.
The electrodynamic speaker diaphragm (11) and the passive radiator (12) can be protected by means of special grids (1103) or fabric masks (the latter particularly useful for improving the directivity of emission of high frequencies), as long as these are in the position of relief (1104) and allow the two diaphragms to move freely throughout their excursion.
Finally, it is necessary to ensure that the apparatus, so contained in its dimensions and weight, remains firmly anchored to the floor and does not move due to the strong dynamic excursions at very low frequencies, and this can be achieved by means of fixing to the ground surface.
The provision of rubber feet (1105), which act not only as a support surface but also as vibration dampers, may not be sufficient and its usefulness would be limited only to certain types of surfaces. For affixing to sand, ground, stone and fabrics, it is suitable to opt for spikes (1106), although for carpets and rugs the best solution could be velcro tape (1107): this is also useful on smooth surfaces , applying on them the complementary adhesive velcro counterpart. In any case it is necessary that the apparatus is always sufficiently raised from the ground to allow maximum air flow on the underlying wall, where the passive radiator is located.
Special removable lifting means (1108) based on a rotating orbital surface (1109) have therefore been formulated, on which both the rubber feet (1105) and the spikes (1106) and the feet equipped with velcro tape (1107) sets are accomodated. It is also possible to completely unscrew the bases of the removable lifting means (1108) and replace them with simpler or other feet (not shown), i.e. these can be interchangeable. On the corners of the lower wall there are the four removable lifting means (1108), accurately leveled. By rotating these inclined platforms until they click mechanically, it is possible to set one of the three desired fixing modes and place the apparatus in the correct position for use, according to the floor conditions.
A more advanced embodiment of the present invention, not illustrated, has every parametric control (those exposed in recessed fashion on the frontal wall of the sound box (10)) replaced with a digital data connector, mounted on a panel on a wall of the apparatus - i.e. frontal (13) or subfrontal (18), which can be, for example, USB, micro-USB or even replaced by a Bluetooth transceiver, internally connected to an advanced control system of the same parameters through the use of so-called "digipots", an integrated substitute of the mechanical potentiometer, this time by means of numerical control. This advanced numerical control system can be put in communication (through the connection via serial USB cable or the wireless Bluetooth protocol) with a computer, a tablet, a smartphone or other peripherals intended for remote control of the device; therefore a dedicated software, available for the various operating systems provided according to the chosen peripheral, allows the user to adjust the individual parameters, instantly transmit the information to the control system inside the device and modify the settings without the need to use the physical knobs.
In turn, these peripherals can, if necessary, be recharged from the 5V USB output provided on the wall of the loudspeaker (10).
A further embodiment of this transportable apparatus for sound reinforcement would have socket-type connectors (1201) on the frontal wall, illustrated in figure 12. Said connectors have points of connection of the power supply coming from the batteries and points of input and output of the audio signal coming from the musical instrument. By inserting external "plug-in" circuit boards (not shown), supplied bare or in cartridge form, it is possible to enable further preamplification, processing and effect stages on the previously diverted audio signal.
The circuits include a microcontroller engineered in such way to control those parameters and knobs necessary for the regulation of the circuit; said microcontroller communicates by serial data with the main control unit inside the apparatus already in communication with the control system previously discussed. The parameters of the external "plug-in" circuits are thus displayed and controlled on the system.
When not in use, the sockets (1201) can be protected from contamination with dust and sand by rubber covers (1202), snugly molded for an interlocking tight.
A simpler embodiment considers a panel which, when hooked to the subfrontal wall (18), provides for the direct insertion of the pin into the inlet (44); the panel is powered by the lateral connection (352) at -12V and has all the typical controls of an amplifier panel: gain, equalizers, effects and anything else necessary to prepare the signal for driving in the amplifier stage (32) .
Musicians, disc jockeys, music lovers, street artists will thus be able to face their performances by carrying the device on the shoulders, finally free from the need to connect to an electrical outlet, in any place or situation, being able to have a high volume of sound reproduction, extended frequency response and exceptional acoustic performance.

Claims

A transportable apparatus for the high efficiency sound reinforcement of audio frequency signals characterized by:
an acoustic box (10) of the single cavity type, completely sealed, made of wood or polymeric material, in the form of a parallelepiped, wedge or spheroid;

the presence of at least one electrodynamic speaker diaphragm (11), with one or more coils, being integral to one of the walls and exposed towards the outside of the acoustic box (10);

the presence of at least one diaphragm of the passive radiator type (12) being integral to one of the walls and exposed towards the outside of the sealed acoustic box (10), making the sizing of the case negligible by virtue of the possibility of tuning the apparatus to the desired resonance frequency through appropriate modification of the resulting mass of the passive radiator (12);

one or more energy accumulators (141) or batteries of the AGM or Lead-GEL or Lithium-Iron-Phosphate type, incorporated in the apparatus, connected in series or in parallel to each other to constitute a rechargeable energy group (14), by means of dedicated charging devices, in order to operate at a continuous voltage between 5V and 18V (possibly negative) up to a maximum of 36V (positive referenced) having enough autonomy for the operation of the entire apparatus and other external or internal devices, in absence of external electrical supply for at least five hours; said accumulators (141) being positioned permanently or in removable way in a separate cavity inside the acoustic box (10) if equipped with lid, without obstructing, in any way, flow of air shared between the two diaphragms;

pre-amplification circuits and one or more power amplification stages (32) placed internally or externally to the apparatus which deliver a total power exceeding 60W even if divided over a plurality of different outputs which can be coupled together in a Power Bridge configuration in such way that an electrodynamic diaphragm with multiple coils can be driven from separated pair of Power Bridge output, said power amplification stages (32) being able to reproduce an audio frequency signal supplied through external instruments with non-programmable dynamic range (i.e. not subject to amplitude limitations imposed, for example, by means of signal recording) and producing a sound volume higher than 90 dB SPL for frequencies below 50Hz as well as for the entire passband of the given signal (portion of spectrum useful for expressing the sound content);

being able to dissipate the heat produced by the internal components towards the outside of the acoustic box (10) through aluminum thermal dissipation means (i.e. heatsink pin (42)) placed through one or more walls of the acoustic box (10) so that the ari content remains airtight sealed inside of it;

being realized in its final form with dimensions, weight and means such as to be easily lifted and carried by hand or shoulder by a single person and by means of removable lifting means (1108) to lift the apparatus from the support surface, suitable to provide adequate space for the motion of the air content when the passive radiator would be provided on the underlying wall as well to contain the excess of vibrations and preventing involuntary movement of the apparatus; said removable lifting means (1108) being implemented by a rotating platform on which various anchoring means suitable for various types of surfaces are mounted (i.e. rubber feet for smooth surfaces (1105), tips for soil or sand (1106), velcro tape for carpets and fabrics (1107)) interchangeable with each other; said apparatus comprising waterproof means for protection from water, dust and bad weather, suitable to rapid covering of the entire apparatus.
A transportable apparatus for the high efficiency sound reinforcement of audio frequency signals according to claim 1 comprising at least one directional tweeter (high frequency transducer) o an orientable (orbital) tweeter being integral to one of the walls and exposed towards the outside of the sealed acoustic box (10), said tweeter being internally connected to one of the amplifier stages (32) dedicated to its driving by means of connections, said tweeter being serially coupled with an high-pass filter stage and a switch or power rehostat (or both in combination) in order to attenuate or exclude the tweeter functionality during the operation of the apparatus.
A transportable apparatus for the high efficiency sound reinforcement of audio frequency signals according to claim 1 comprising, exposed from one of the acoustic box (10) walls, a signal input connector (44) for plugging an externally provided microphone or line sound signal directly from an audio frequency source or from the output of the external signal processing devices (i.e. effects pedals (62)); said connector being connected inside, by means of conduction cables, to a chain of internal signal processing devices (i.e. pre-amplification circuits) if these are provided inside the acoustic box (10); the output of the chain being connected directly to one or more of the power amplifier stages (32), if these are provided inside the acoustic box (10); otherwise in the absence of said chain of internal signal processing devices, said signal input connector (44) being internally connected, by means of conduction cables, directly to one or more of the power amplification stages (32), if provided internally; said apparatus comprising a power signal connector of the Speakon type (161) located on a wall of the apparatus as a power signal input (already amplified in power), connected to the electrodynamic speaker diaphragm (11) by means of a changeover switch (71 ) to divert the signal between the Speakon power signal connector (161) input - for the operation of the apparatus with external power amplification stages, with the simultaneous deactivation of one or more internal amplification stages (32) - and the output of one or more of the amplification stages (32) inside the apparatus.
A transportable apparatus for the high efficiency sound reinforcement of audio frequency signals according to claim 1 characterized by the presence of a plurality of electronic devices, arranged inside or outside the acoustic box (10) in the form of additional modules suitable to the lifting and regulation of the voltages produced by the energy group (14), and other pre-amplification circuits for the sound signals provided externally, said additional modules suitable to the lifting and regulation of the voltages being able, in combination with the power amplification stage or stages (32) if more than one, to raise the adequate electrical power to amplify the said sound signal up to produce, through the electrodynamic speaker diaphragm (11), a consistent acoustic performance higher than 90dB SPL for frequencies below 50Hz as well as for the whole passband useful to the signal to be amplified; said other pre-amplification circuits being powered by the energy group (14) located inside the acoustic box (10) and equipped with controls (37), buttons and knobs, signal input connector (44) and output connectors for microphone, line or power signals from the Speakon connector (161) necessary for adjusting the amplification and processing parameters, said controls, button, knobs and connectors being exposed on the walls of the acoustic box (10) in recessed fashion.
A transportable apparatus for the high efficiency sound reinforcement of audio frequency signals according to claim 1 comprising, exposed from one of the walls of the acoustic box (10), a power on and off switch (31) connected between the energy group (14) and the electronic devices for the lifting and regulation of the voltages in turn connected to the pre-amplification circuits and one or more of the power amplification stages (32) and an electric multipole connector (35) for recharging the energy group (14) from the mains supply, said connector (35) being internally connected, by means of conduction cables, directly to the energy group (14) or through charging device (61) located inside or outside the acoustic box (10); said charging circuit can be equipped of a parallel power supply line of type switching, for the operation of the apparatus exclusively through the electrical network, allowing the simultaneous recharge of the battery.
A transportable apparatus for the high efficiency sound reinforcement of audio frequency signals according to claim 1 comprising, exposed from one of the walls of the acoustic box (10), a voltage boosting device (33) placed internally or externally to the acoustic box (10) equipped of LCD display being visible from the outside by means of a glass frame of trasparent material, said voltage boosting device (33) being connected to the energy group (14) by means of electrical connectors provided inside the acoustic box (10), said voltage boosting device (33) being dedicated to raising the voltage supplied from the energy group (14) to higher voltages (from 12 to 36V) and monitoring of the state of charge of the energy group (14), said device further equipped with a LED diode indicator exposed from the outside of the acoustic box (10) which, for a certain minimum charge threshold, lights up indicating the need to recharge the energy group (14) incorporated in the apparatus to prevent its damage.
A transportable apparatus for the high efficiency sound reinforcement of audio frequency signals according to claim 1 comprising electronic devices for lifting and regulating the voltage supplied by the energy group (14) or by a voltage boosting device (33), said regulating devices outputting to electrical connectors (351) and (352) exposed outside the acoustic box (10), suitable for powering other electronic devices (i.e. effect pedals (62)) placed externally by the user with a continuous voltage between 5V and 18V, possibly as negative voltage up to 36V (positive referenced), and a USB type connector (63) ouputting a regulated 5V continuous voltage for charging smartphones and other peripherals that can be powered at this voltage.
A transportable apparatus for high efficiency sound reinforcement of audio frequency signals according to claim 1 comprising means for lifting and transporting by hand, in the form of handles, which can be made in simple form or in fast coupling fashion (73) for immediate mounting on other devices and equipment equipped with a complementary coupling system (731) and being able to rotate on its axis by means of a counterplate (74).
A transportable apparatus for the high efficiency sound reinforcement of audio frequency signals according to claim 1 comprising a connector for digital data or a bluetooth device, internally connected to an advanced automated control system for the regulation for the parameters of the pre-amplification circuits provided internally to the acoustic box (10), said connector or bluetooth device being connectable to external computerized peripherals such as computers, tablets, smartphones, said peripherals provided with software dedicated to remote control of the parameters of the apparatus.
A transportable apparatus for the high efficiency sound reinforcement of audio frequency signals according to claim 1 comprising at least one socket type connector (1201), protected by a special cap in polymeric material (1202) when not in use, said socket type connector (1201) exposed from the front wall at which external "plugin" circuit boards can be connected, said circuit boards being bare boards or in the form of a cartridge (electronic card module), said connector provided with connection inside the acoustic box (10) needed for powering said circuit boards, deviating at the same time the signal path from the signal input connector (44) to the power stage or stages (32) if more than one, as shown in block diagram (fig. 8) for the "Expansion FX Cards" block), so that the diverted signal can be processed by said external circuit boards.