FR3064146A1 - MONOBLOC AND STEREOPHONIC DEVICE WITH AMPLIFIED ACOUSTIC ENCLOSURE - Google Patents

Abstract

The present invention relates to a monobloc device and stereophonic amplified acoustic speaker. The amplified loudspeaker according to the invention comprises in particular: * two central loudspeakers intended to reproduce the low frequencies, one located on the front and the other placed near and behind the latter, connected pneumatically between them in a sealed compartment, * at least one vent not communicating pneumatically with this sealed compartment and connecting the inner part of the enclosure to the outside thereof, Each of these two loudspeakers (1) and ( 2) for reproducing the low frequencies is fed by separate amplification channels (3) and (3 ') and each having their specific frequency band.

Description

(57) The present invention relates to a monoblock and stereophonic device for an amplified acoustic enclosure.

The amplified acoustic enclosure according to the invention notably comprises:

* two central speakers intended to reproduce the bass frequencies, one located on the front and the other placed near and behind it, pneumatically connected to each other in a sealed compartment, * at least one vent not communicating pneumatically with this sealed compartment and connecting the inner part of the enclosure to the outside thereof,

Each of these two loudspeakers (1) and (2) intended to reproduce the bass frequencies is supplied by separate amplification channels (3) and (3j and each having their specific frequency band.

The present invention relates to a monoblock and stereophonic device for an amplified acoustic enclosure.

As anyone can see with their phone, a small speaker is unable to reproduce bass frequencies. More generally speaking, compact audio products, the amplifier / speaker combination available does not generally allow this objective to be achieved due to a lack of means: amplifier power (or batteries) too low, distortion rate in the bass frequencies important at high level, the whole coupled to speakers there too too small.

Thus the audio market for decades has been divided globally in two with, on the one hand, bulky and expensive high-fidelity systems and, on the other, compact systems of mediocre quality, making it impossible, among other things, to coexist quality listening in the low frequencies with a high sound level.

There are technical solutions to compensate for the lack of volume in the loudspeakers. Powerful built-in servo systems allow you to control the elongation of the woofer's membranes. While increasing their movements and thereby their noise level in the low register, we control these same movements by limiting them when the voice coil deviates too much from its magnetic field, so that any distortion can be contained constantly, regardless of the power level. These systems, which require complex electronic circuits as well as amplification which is all the more powerful as the size of the speakers decreases, are unfortunately unfortunately reserved to date for high-end realizations.

Essentially, many compact speaker systems are developed using large elongation loudspeakers placed under closed load. This technique, which makes it possible to accept a certain theoretical power does not, however, make it possible to offer, particularly with small diameter speakers, sufficient acoustic efficiency given the significant drop in sound level observed in the low frequencies using this technique; the following diagram illustrates the above. It is also possible and very common to use speaker systems loaded by a vent. These systems, as can be seen comparatively on the same diagram below, allow better acoustic performance in the low frequencies. Taking into account the significant elongations of the subwoofer concerned - except when this one is of large diameter - which are no longer controlled by the compression of the volume of closed air placed at the rear of the diaphragm thereof as on a closed enclosure, there is a significant increase in the distortion measured at high power in the low register.

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It is the same with another type of technology which has spread widely in recent years, especially for the production of miniature speakers on batteries: it is the passive radiator, which doubles the radiation of the speaker at the bottom of the sound spectrum and thus significantly increases the sound level in this frequency range. But which also does not allow to support without distortion a significant sound level.

However, there is a solution which makes it possible to reconcile these different advantages without their main disadvantages, described above. Such a solution is described in French patent No. 76 0625 dated March 5, 1976.

This patent will be considered to be the closest state of the art to the present invention. The device described in this patent consists in placing two speakers one behind the other. A vent pneumatically sealingly connects the outside of the enclosure to its internal rear volume and passes through a baffle parallel to the front, perforated and supporting the second loudspeaker, makes it possible to recover the rear wave emitted by this one.

Thanks to the mechanical action generated by the volume of air between them, the two loudspeakers control their possible excessive elongations and thereby, at equivalent sound power level, significantly reduce the distortion observed in the low frequencies compared to that of a conventional loudspeaker of equivalent size.

We also obtain a better sound level in the low register than with a conventional closed load while retaining, as for a vented enclosure, a good level bandwidth at the bottom of the sound spectrum while remaining compatible with power without distortion.

This system, which by definition involved traditional enclosures equipped with passive filters, however has some drawbacks.

The speakers of such a device are intended to be connected to a versatile external amplifier. The rear speaker, connected to the audio output of the external amplifier, is connected to the front speaker according to a parallel wiring diagram. The front speaker, which is only relayed in frequencies towards the top of the sound spectrum by tweeters, is responsible for reproducing in this classic configuration scheme the bass register as well as the mid / high register. Said rear speaker, the cone of which is directed towards the rear of the membrane of the front speaker and which is therefore not filtered separately, logically increases in frequency like the front speaker, producing in the direction of the behind the membrane of the latter interference in the form of standing waves harmful to sound reproduction in the medium register of the entire system. On the other hand, the double partition leads to a compulsory complication of the traditional cabinetmaking scheme, to a larger and less watertight volume as well as to a complication of the assembly labor dedicated to this second internal speaker. .

The object of the present invention aims to use such a layout of the speakers but also to overcome these various drawbacks while seizing the opportunity offered by the recent technical possibilities in terms of amplification.

The characteristics of the device according to the invention will emerge more clearly on reading the description which follows, with reference to the following figures given for information and in no way limitative, among which:

Figure 1 is a cross-sectional view of the device according to a first embodiment of the invention, Figure 2 is a variant plan view of the device illustrated in Figure 1, and Figure 3 is a plan view of the device according to another embodiment of the invention.

This device according to the invention, reference being made to Figures 1,2 and 3, consists of a front loudspeaker (1) and a rear loudspeaker (2), mechanically coupled together by the intermediate a small volume of air itself preferably delimited by a connecting piece forming a watertight partition (4) and connecting these two speakers. This connecting piece can be of complex shape, adapted to the geometry of said speakers and manufactured by possibly using injection, thermoforming or 3D printing techniques. A vent (5) provides the pneumatic connection between the outside air and the internal part of the enclosure located outside this sealed volume; a second vent (5 ') can also be provided as shown in Figure 3. This or these vents allow to recover the acoustic energy produced by the rear speaker (2) and can lead either forward of the enclosure (Figures 2 and 3) or towards the rear of it (Figure 1). According to an embodiment of the invention, the rear speaker (2) has a lower resonant frequency than that of the front speaker (1). The device according to the invention also comprises an internal amplifier, preferably of class D, integrated into the enclosure. It consists of at least two channels (3) and (3 ’) connected separately to each speaker (1) and (2). Each of these two amplified central channels is calibrated to allow precise and differentiated modulation of their frequency ranges for each loudspeaker (1) and (2) and, where appropriate, their respective sound levels. This filtering makes it possible in particular to avoid any negative interference from the rear speaker (2) on the front speaker (1), almost inevitable with a configuration of conventional speakers equipped with passive filtering. On the other hand, the natural drop in sound efficiency observed for any low volume loudspeaker in the low frequencies can thus be actively corrected by a dedicated electronic adjustment which makes it possible to obtain a significant and real accentuation of the sound level of these frequencies. serious, without altering the distortion rate or the intelligibility of low mid frequencies. The distance from the distortion limit obtained advantageously allows, thanks to this high amplification level integrated in the enclosure, to achieve compensation of at least + 3db below 200 Hz (which corresponds to true serious) relative to the average linear level of amplification relative to the frequencies situated above this threshold of 200 Hz. In the same way, the device according to the invention allows an optimization of the feedback rate of the amplifier. An external amplifier must be versatile and its feedback rate is high (generally located at around 1 volt for a gain of 2000). By lowering the feedback rate of a standard amplifier, it would be possible to obtain with traditional acoustic speakers a widening of their bandwidth but the speakers of these speakers would not fail to quickly saturate, distort, then deteriorate . The device according to the invention makes it possible to circumvent this problem and to reduce the rate of feedback of the dedicated amplifier for gain values significantly less than 1000 for 1 volt while keeping a low distortion of the speakers and a sound more natural.

Two or four possible additional amplified channels will also make it possible to separately supply the loudspeakers specialized in the high frequencies (6) and (6 ′) relating to the treble and possibly the midrange, as provided in an alternative embodiment of the present invention. Advantageously, the tweeters (6) and (6 ’) and possibly the midrange, will be powered separately by differentiated amplifier channels.

As is apparent from the above, several alternative embodiments of the device according to the invention are possible, without departing from the scope of said invention.

The variant of FIG. 1 relates to a device in which the two loudspeakers (1) and (2) are represented diagrammatically inside a monobloc stereophonic speaker amplified of conventional architecture and provided with a single vent (5) facing the rear of the enclosure; in Figure 2, this vent (5) faces the front of said enclosure.

The variant illustrated in FIG. 3 relates to a device in which the two loudspeakers (1) and (2) are represented diagrammatically inside an amplified stereophonic monobloc enclosure, equipped with a treble diffusion system from the high -Speakers (6) and (6 '), as well as two vents (5) and (5') facing the front of said enclosure.

In an easy way to achieve, in this way, in a particularly compact speaker volume and where a single speaker would have more quickly reached its limits in terms of admissible power, an active configuration of speakers allowing obtain a particularly low distortion rate in the low frequencies as well as a high level of high-fidelity sound. This is achieved by integrating and calibrating an internal amplifier comprising at least two independent channels (3) (3 '), the sound level of each channel is filtered and modulated in order to avoid any negative interaction between the two loudspeakers (1) and (2) and so that it can be raised significantly (at least + 3 dB) for frequencies below 200 Hz (register of "real" bass frequencies). Recent advances in the digital domain (class D amplifiers) also make it possible to advantageously have a large and modular power in the low frequencies at relatively low cost, all in a small footprint and without fear of uncontrolled elevation of the internal temperature of the system. The set can also integrate speakers (6) and (6 ') responsible for reproducing the treble and possibly mid frequencies, which can thus be placed, either according to conventional speaker diagrams (Figure 1 - side view and Figure 2 plan view) or possibly according to more complex diagrams (Figures 3 - plan view). In Figure 3 the loudspeakers (6) and (6 ') responsible for restoring the high frequencies and thereby the stereophonic effect have been advantageously tilted upwards and positioned in an opposite direction from the loudspeakers (1) and (2) in order to make the whole benefit more of a spatial effect. A more traditional configuration is shown in Figures 1 and 2 for these tweeter and / or midrange speakers that are not tilted.

All of these different loudspeakers dedicated to high frequencies can be controlled in frequencies by conventional means (passive filters) or preferably by specific active systems (amplifiers).

Claims (9)

1) Amplified acoustic enclosure of the type comprising: * two central speakers intended to reproduce the bass frequencies, one located on the front and the other placed near and behind it, pneumatically connected to each other in a sealed compartment, * at least one vent not communicating pneumatically with this sealed compartment and connecting the interior part of the enclosure to the exterior thereof, characterized in that each of these two loudspeakers (1) and (2) intended to reproduce the bass frequencies is fed by separate amplification channels (3) and (3 ') and each having their specific frequency band. 2) Enclosure according to claim 1 characterized in that the channels (3) and (3 ') come from an internal amplifier whose power levels, within a frequency range between 20 Hz and 200 Hz, are read by at least + 3db compared to the average level of the passband of said amplifier corresponding to frequencies above 200 Hz. 3) Enclosure according to one of claims 1 or 2 characterized in that said differentiated channels (3) and (3 ’) make it possible to supply each speaker (1) and (2) separately in terms of power level. 4) Enclosure according to any one of claims 1 to 3 characterized in that the internal amplifier's feedback is calibrated for values corresponding to a gain of less than 1000 for 1 volt. 5) A speaker according to any one of claims 1 to 4 characterized in that the rear speaker (2) has a lower resonant frequency than that of the front speaker (1). 6) Enclosure according to any one of claims 1 to 5 characterized in that the speakers (1) and (2) are supplemented by two stereophonic tweeter speakers (6) and (6 ’). 7) Enclosure according to any one of claims 1 to 5 characterized in that the speakers (1) and (2) are supplemented by stereophonic tweeter speakers (6) and (6 ') and midrange . 8) A speaker according to claim 7 characterized in that said tweeter (6) and (6 ’) and possibly midrange, are powered separately by differentiated internal amplifier channels. δ 9) Enclosure according to any one of claims 6 to 8 characterized in that said tweeter (6) and (6 ') and optionally midrange, are oriented in the opposite direction of the speakers (1) and (2) and tilted upwards. Plate 1/2 X X hX'xV