FR2947689A1 - High-technology loudspeaker for acoustic enclosure, has damping suspension provided with two rubber masses at its respective ends for damping vibrations in membrane, where controlled linearity rupture spider is connected to suspension - Google Patents

Abstract

The loudspeaker has a controlled linearity rupture spider (SPD) connected to a peripheral damping suspension (SP) whose section has less thickness at its central part. The peripheral damping suspension has two rubber masses at its respective ends for damping vibrations in a flexible membrane (M). The spider has a skewed outer corrugation (CR) provided with a single fold and a skewed inner corrugation provided with two central folds.

Description

Combination of spider with controlled linearity breaking and damping suspension in a speaker for a loudspeaker area Technical area of the invention:

The present invention relates to the technical field of loudspeakers and loudspeakers of high technology. Technical reminders:

The moving membrane of a cone loudspeaker is guided by a peripheral suspension SP, which links the membrane at the top of its cone to the end of the salad bowl, to ensure its proper oscillation movement.

This is shown for a good understanding in the appended FIG. 4, in which SP is the peripheral suspension (or first guide) of the membrane M, the arrows represent the oscillation movement of the membrane M, under the action of the moving coil B to which it is connected by a cone C itself mechanically connected to the coil support SB, this cone being preferably a W cone developed by the Applicant and described in another patent application. At the level of the spool and more precisely of the spool support, mechanically attached to the cone, is disposed a second SPD guide called a spider (name spider, name given at the beginning of the 20th century to these guides because of their bakelite construction and a spider-like shape). We will preserve, having explained it, this term which is that universally used by the craftsman.

This spider has a dual role: to guide the moving equipment (that is to say the membrane assembly and moving coil) in its movement back and forth, 35 and define thanks to its flexibility, the resonance frequency of the 'together. Flexibility more generally defined as compliance (also universally used term) is obtained by the thickness of the spider material (usually cotton or a braided polyamide), and the height of the corrugations. To avoid a mechanical overload of the mobile equipment (too much elongation at high levels of listening), the spider has a greater or lesser hardness to limit these excursions. Nevertheless, too much hardness also increases the resonant frequency of the moving equipment.

This is counterproductive for a deep bass response. 10 Technical problems:

This forms a first technical problem to solve.

We have seen that the development of a loudspeaker requires a compromise between two factors: first, the implementation of a soft spider to obtain a high level of dynamics but with risks; deterioration during large amplitude movements of the low-frequency membrane, and secondly, the implementation of a hard spider whose rigidity and resistance can cope with these mechanical stress at low frequency but affect strongly the dynamics of the transducer and negatively impact the resonant frequency of the membrane. Overall, the compromise chosen is often unsatisfactory.

To overcome the problem mentioned above, progressive hardening spiders SPD have been developed but have a major drawback: the hardening of the spider is as its name suggests, gradually, in a linear manner. At high elongation, the resonant frequency increases, and despite the increase in the displacement of the membrane (for precisely having a more serious sensation), the bass does not increase.

OBJECT OF THE INVENTION The object of the present invention in this field is to overcome this problem that has not been solved until now, by designing a new generation of spider that combines power handling and correct response, through the creation of a spider which will be defined here as a progressive 40 spider with controlled linearity breaking.

The Applicant has therefore sought to create a new generation (deliberately ambitious searches and not simple improvement) of progressive spider (SPD) 45 which does not harden linearly, but remains flexible up to about 85% before hardening more quickly. Its hardening curve is somewhat like a logarithmic curve, and keeps the membrane at a high level. This new concept would definitively overcome the problems of resonance frequencies encountered during the implementation of existing progressive spiders. The evaluation of this percentage is represented with the aid of the appended FIG. 7, accompanied by the following technical comments: the total movement of the membrane M in one direction and the other is mechanically defined by the coil B (winding height) , housed in its gap (PC field plate). By way of nonlimiting example, a 16 mm high coil, in a gap of 6 mm, is translated by a total excursion of 10 mm (16 mm - 6 mm = 10 mm), in one direction and the diaphragm will therefore move from 5 mm, and also 5 mm in the other direction. This total excursion is the 100% of the movement, the 85% cited therefore represent 7.6 mm (85% of 10 mm). When moving the membrane forward (ie 5 mm in total), the flexibility is maintained up to 3.8 mm (7.6 / 2), beyond (the remaining 1.2 mm) the spider hardens. It's not as brutal and precise as the transition is more fluid in reality.

Furthermore, another objective of the present invention is the control or even the suppression of the memory effect of the spider: in fact, the existing spiders experience internal resonance phenomena with the presence of internal stationary waves: a standing wave in a spider means an energy present in the spider's material which, once reflected by the end, returns with a significant energy and then disturbs the membrane - a movement that has already been exerted by the membrane and should have gone out - but that the membrane must therefore again reproduce; it is then considered as a distortion since this parasitic energy should not be there and should not therefore generate parasitic movement of the membrane which, of course, alters for a listener the quality of the reproduction, the coloring of a instrument, etc ... This is due to the linear and repetitive shape of the spider, ideal condition for the propagation of these standing waves.

Note the strategic nature of the invention and its objectives, the result of which is likely to have a significant impact on the level of performance of all medium-to-serious and serious transducer ranges produced by the manufacturers and therefore the greater part of their productions of very high technology acoustic reproduction systems.

Previous Art

The phenomenon above is very generally found, for a long time, and concerns the entire speaker industry, without a valid solution to date. Some research has already been done, which partially solved the problem. We can quote a booklet in English called Spider testing and design by Myra L. Stewart, who was responsible for the spiders for 30 years at the American manufacturer Nu Way. This booklet describes the problems encountered during the development of spiders, and their manufacture, but does not mention any particular solutions. It can be useful for information purposes regarding this problem.

The archives of the A.E.S. (Audio Engineering Society) offer hundreds of articles around the speaker.

The solution currently used by the global manufacturers of loudspeakers is that of the progressive spider which has the disadvantage of the appearance of low frequency resonance phenomena. Moreover, there is no effective solution for dealing with the spider's memory effect.

Summary of the invention

The objective of the research work undertaken is to create a new generation of spiders around the concept of spider with controlled linearity breaking, allowing:

the obtaining of transducers having a high level of dynamics, the suppression of resonance phenomena encountered on existing progressive spider systems, the control or even the suppression of spider memory phenomena.

Detailed description of the invention

The approach of the original drawing results, despite the many references consulted, cf. above, purely of an intuition that could not guide or suggest any prior art. The intuitive concept is based on an SPD spider with asymmetrical cross section. On its own, this concept has the value of a general means ensuring the main objectives.

According to a preferred embodiment, the last corrugation CR (or outermost corrugation) has a single fold. Inner corrugation can have two folds.

According to another preferred mode, the inner corrugation has two folds. The invention further relates firstly to the combination or coupling of the suspension with such a spider.

The use of a reduced compliance suspension makes it possible to obtain a lower apparent mass 45 of the moving equipment and thus to obtain a better so-called acceleration factor. The invention also allows better control of the cone-suspension connection which creates a damping effect through a profile ensuring a more intimate connection associated with a better distribution of masses.

The whole is controlled, hence the term combination suspension-spider by the synergy generated by the spider breaking linearity controlled which offers: - on weak signals, less retained and therefore a better definition, - on strong amplitudes decreased compliance (since steeper) which increases control.

According to another preferred variant, the spider according to the invention comprises three corrugations.

However, one skilled in the art knows that various corrugations can be employed. Cross-sections of preferred examples according to the invention of such corrugations are shown in Figure 6 attached which consists of Figures 6a to 6d by way of non-limiting examples. Each peak represents a corrugation. These variants are therefore preferred, but not limiting, variants of the cross section of the spider.

There was, of course, a very important technical prejudice against such an asymmetrical structure: extensive studies allowed the Applicant to control them. It was known that, in acoustics, asymmetry is often applied (eg asymmetrical HP cone shape to attenuate or eliminate internal resonances in the membrane).

On the other hand, the interest of an asymmetry, or even the simple fact of considering a circular asymmetry in a spider (slightly oval shape), was considered unrealistic. The present invention results in the following combination of characteristics, very original, and which has lifted the prejudice: in the spider according to the invention, it is the shape of cut which is asymmetrical; in the circular direction, the element is perfectly round and symmetrical.

The difficulty was first to establish the geometry of the corrugations, to obtain our limitation with strong elongation. The specific simulation software of the Applicant, Loudsoft FineConeTM did not show the expected results, this is because it is only a dynamic simulation static, and not dynamic impulse. It was then necessary to resort to the old method trial & error (tests and failures). The first series of prototypes simply did not work, and after analysis, it was necessary to move a corrugation towards the outer end to obtain the rupture.

Then, it is the composition of the fibers, and the deflection (which defines the compliance) which were studied and required the realization of many tests, this in real situations that is to say by mounting many prototypes of bass speakers, and measuring them.

The realization of this research required a large number of experimental tests very iterative, given the large number of parameters involved and interactive between them. The first generation of prototypes was made with different compliances, since the Applicant had no experience with the new spider of the present invention.

Since the role of the spider is to let the cone move back and forth (and then return the cone to its initial position), it does so with a defined flexibility (which also defines the resonant frequency). This flexibility is defined in mm by 50 gr applied. To do this, the spider is mounted on a horizontal support, and necessarily straight. In the center, there is then placed a piece NYL nylon (a small disk with the diameter of the inner hole of the spider), which weighs 50 grams. The spider sinks x mm; the more flexible it is, the more it is sinking, and this movement is called deflection. It is for all intents and purposes reminiscent of deflection being defined by one skilled in the art as the deviation of the center of the spider from its initial position. . This will be better understood using the attached figure 8.

The center of the spider is substantially the diameter of the spool support.

In Figure 4, the spider is set slightly below the top of the spool support but this is not important; the spider could be fixed higher on the reel stand or lower. The point of attachment is determined by the fact that the winding must be centered in the gap.

The deflection of the spider is expressed in mm per 50 g applied, as explained above for a spider of the prior art, normal; but in the new spider this might not be able to be measured in the same way since it displays according to the invention a different behavior which makes it possible to solve an important technical problem, and to overcome the prejudiced prejudice. This new, unpredictable behavior in turn posed a new technical problem.

After the completion of the first generation of prototypes, it has been found that the method applied could be applied identically to conventional spiders as well as to the new spiders according to the invention, with controlled linearity breaking. . On the other hand, because of the radical curing with great elongation of the spider, the membrane was better controlled, and with this characteristic the inventors were able to opt for greater compliance (hence: greater deflection), which ensured a higher resonance frequency. low, and thus a better response in the low level low.5 The spider apparently worked, but when in the tests the Applicant has forced the amplitude level, noise has appeared, which is obviously strictly unacceptable in high fidelity. The first corrugation near the center (that of the center) bent itself by reversing itself.

The drawing was then changed and this first corrugation received a second fold; moreover, the second fold has been removed from the last corrugation at the periphery of the spider (outer), where the elongation is the weakest and a second fold has proved unnecessary.

A second generation of prototypes was launched, and the results of the samples received were finally at the height of the new generation objectives: important control of the movements of the high elongation membrane (high power), clear and tense response in the bass.

To verify the theory of elimination of the effect of memory in the spider, intensive measurements have been made to verify this phenomenon, which is difficult to quantify, and only comparative listening by auditors trained on a very sensitive material capable of to reveal these differences could confirm the Applicant's theories.

A measurement is almost capable of verifying the correctness of the elimination of this memory effect: a cumulative extinction measure of the spectrum. This measure, which is commonly called waterfall (waterfall in English, because of its graphic resembling a waterfall precisely). In this case, the loudspeaker is animated by a wide-band signal, thus exciting it over its entire frequency band. After the signal stops, sounds from the speaker should be interrupted immediately or instantly. The microphone capturing these sounds that can measure very weak signals would be able to detect if, after the signal is turned off, the loudspeaker still emits sounds, due to sounds left in a device of the membrane, or the membrane itself, and obviously not desired because here again they create a distortion of the faithful reproduction of the sound, the color of an instrument etc ...; this memory effect is obviously unacceptable in very high fidelity, and must be reduced to its absolute minimum.

FIG. 9 represents in cross-section a spider with controlled linearity breaking according to the invention; we notice the central double inner folds (INT) and the simple fold of external corrugation (EXT).

Figure 10 shows a spider of the prior art. The linearity control will be better understood with reference to the accompanying figures and the explanatory curves (FIGS. 11, 12 and 13). Criteria that play a key role are: high compliance at low level (up to 85%) and a lack of brutal saturation at the additional 15%. Corrugations too high in the shape of the cut must also be avoided; are obligatory the presence of double folds with a simple fold on the external corrugation.

It is noted that the last single-fold corrugation controls the remaining 15% (it retains when the amplitude is the highest), the rest of the double corrugations are responsible for 85%; it is the optimization of a nonlinear mechanical system to approach a type C response (curved drawing). The spider can have other types of shapes, number of corrugations etc ... (See Figure 6).

Explanation of the functionality of a linear, progressive compliance and progressive linearity break.

Fig. 11 shows an example of a conventional spider: it has a large linear range of compliance, but stiffens in stiffness. According to the compliance (value defined by the designer at the beginning), it is either: a) steep on all the range, or: b) flexible on the whole beach. Both cases have advantages and disadvantages.

Figure 12 shows an example of a progressive spider: it has a nonlinear compliance range, it enters hardness slowly at the beginning, to harden abruptly. This type of spider is interesting for speakers requiring as a major factor a significant power handling, without concern for details.

Figure 13 shows an example of a spider with controlled linearity failure: the spider enters quickly in compliance - and because it follows the movements of micro information easily, remains linear in its compliance up to 85% of its excursion, to then stiffen in a soft and linear way, for a good behavior in power without distortion.

The invention also comprises as an essential feature the combination or coupling of the inventive spider described above, linearly controlled with a suspension itself adapted for said combination.

Functionality of the suspension. A membrane can exist in two forms: the flexible membrane (paper, polypropylene ...) which has a high internal damping, and which at the end of the band (ie towards the high frequencies, where it is supposed to attenuate its level naturally) do not show any accidents in the response curve, with a natural attenuation. This diaphragm, however, does not act as a piston, with a less accurate sound in the bass, and a matt medium due to the intrinsic over-damping of the membrane.

The hard membrane (this is the case of the Applicant's membrane W, for example, used in the speakers which will be equipped with asymmetrical spider and suspension) on the other hand, reacts like a piston (see Figure 3 movement of the membrane: distribution of sound with low frequencies <1500 Hz) and at high frequencies then breaks up (vibrating) (see Figure 2 membrane movement: sound distribution with high frequencies> about 1500 Hz), and behave like a bell, or a glass. This vibration is damped by the suspension (a bit like a hand that is placed on the glass in vibration). (see FIG. 5) It can be seen in the appended FIG. 5 that the sectional shape of the membrane suspension coupling allows the vibrations of a fragmented membrane to abut against a rubbery mass (or other equivalent material) which dampens the vibrations and that On the other end, a rubbery mass AM plays a damping role of the vibrations deported at this level.

FIG. 1a appends a conventional suspension and in FIG. 1b appended a suspension of variable thickness according to the invention. Overall, a normal suspension is formed by a half-roll which is seen here in section, of constant thickness, in particular 0.6 mm; according to the invention, the new suspension is called damping and it is essentially characterized by a variable thickness, as shown in a non-limiting manner in Figure 1b appended, with the addition of MC rubber masses at both ends and on the contrary very thinning the central portion (Z) of the half-roll, for example 0.2 mm (non-limiting values) .The forms are also non-limiting in that they can be optimized by those skilled in the art. This suspension, often butyl, dampens according to its thickness, and / or its density.

This results in a suspension that is often thick, or with a high degree of Shore (the Shore hardness is a well-known definition parameter and in our test depending on the density of the artificial rubber that is butyl), which translates into some rigidity. This rigidity slows the movement of the membrane, and is therefore counterproductive to the impulses. If spider searches go in the direction of a significant acceleration, it is very unfortunate that the gains obtained are wiped out by a slow suspension. To mount a thin and light suspension would have been a solution, but the vibrations would not be damped - although there is the solution to filter them electrically, which is less elegant, less effective and above all, this energy generated by the vibrations remains present in the membrane and disturbs the sound at many frequencies, not to mention the additional cost.

The suspension according to the invention damping, according to its name, is in fact a thin and light suspension, which allows to maintain the free movement of the membrane, while damping vibrations by adding rubbery mass to specific locations. Clearly, in the center of the half roll the thickness is low, to ensure fast movements, at the ends it is thicker for the damping effect (Fig 1, see explanation above and also in relation to Figure 5). We are here in front of a loudspeaker that combines speed, precise bass (rigid membrane), and clear medium (vibration damped). The spider according to the invention with controlled linearity breaking can work with a conventional suspension in certain cases (for example, less rigid membranes), but finds its ideal complement in the damping suspension since it is a complement of the initial idea the effect of the spider. The invention thus relates to the combination of a damping suspension and a spider with controlled linearity failure. This combination provides a better definition on small signals, avoids the peak at the end of the band (see previous page), due to the fragmentation of the cone which is not sufficiently damped by a conventional suspension. Combination A + B functions very preferably with W (rigid) membranes in high-end applications, and would be applicable but less effective on so-called flexible membranes.

Results and technical progress: 20 Originalities of the chosen solution in terms of performance

The realization of this work made it possible to concretize the concept of spider with controlled linearity breaking: the desired rupture of movement is present, this results in a much better impulse response than during the implementation of conventional spiders. Listening to the speaker in a system reveals a noticeable improvement such as faster bass.

The intuitive creation of an asymmetrical shape of the corrugations compared to those of a classical spider also makes it possible to avoid any form of internal resonance in the spider since the wave does not see perfectly symmetrical conditions for being able to get there. spread, but is broken before reaching the other end. As a result, the phenomenon of spider memory is completely under control.

The Applicant used simulation and measurement software for the development of: - Loudsoft FineCone TM '; 40 - DRALabs MLSSA TM '; - ADM DAASPro 192 T'A

Claims (9)

REVENDICATIONS1. Acoustic loudspeaker speaker characterized in that it comprises a SPD cross-section spider with asymmetric corrugations combined with a damping SP suspension whose section is of variable thickness, lower in its center Z, and comprising at each of its ends two masses of rubber MC whose function is to dampen vibrations. 2. Loudspeaker according to claim 1, characterized in that the last corrugation CR, or corrugation being the outermost, comprises a single fold. 3. Loudspeaker according to claim 2, characterized in that the inner corrugation comprises two folds. 4. Loudspeaker according to claims 1 to 3, characterized in that the spider according to the invention comprises three corrugations. 5. Loudspeaker according to claims 1 to 4, characterized in that the cut shape which is asymmetrical while in the circular direction, the element is perfectly round and symmetrical. 25 6. Loudspeaker according to claims 1 to 5, characterized in that the linearity control is obtained by high compliance at low level, up to 85%, and a complete absence of saturation at 15%. 30 7. Loudspeaker according to claims 1 to 6, characterized by the presence of double folds with a simple fold on the outer corrugation. 8. A loudspeaker according to claims 2 to 7, characterized in that the last single-fold corrugation controls the remaining 15% (it retains 35 when the amplitude is the highest), the remaining double corrugations are responsible for the 85%. % it is the optimization of a non-linear mechanical system to approach a type C response. 9. Loudspeaker according to claims 1 to 7, characterized in that 40 the new suspension is said damping and is characterized essentially by a variable thickness, with addition of masses of rubber MC at both ends and on the contrary very thinning of the central part Z of the half-roll, for example to 0.2 mm. 45