DE3248650A1 - HOOD DRIVER WITH MOVABLE COIL FOR A SPEAKER AND MEMBRANE FOR SUCH A DRIVER STAGE - Google Patents

Description

Hood driver stage with moving coil for a loudspeaker and mem brane for such a driver stage

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description

The invention relates to a loudspeaker with a movable coil and with a permanent magnet driver

2Q level? such loudspeakers are also referred to as "electrodynamic loudspeakers". In particular, the present invention relates to hood driver stages and to the design of the diaphragms for such driver stages. As used herein, the term "driver stage ¹¹ " is intended to denote a single loudspeaker, while the term "loudspeaker" covers a combination of driver stages which are organized as an integrated system.

It is desirable to develop loudspeaker systems that Effectively radiate sound waves over the entire range of sensitivity of the human ear; usually it is assumed that the upper and lower limits of this range are 20 Hz and 20 KHZ, respectively. To this end Usually two or more driver stages are provided in a loudspeaker system, with each driver stage im essentially only radiates the sound waves in a part of this total area. Electronic crossovers are used to distribute the electrical audio output power to the driver stages in such a way that, measured in deci-

OQ in acoustic output power per unit electrical Energy, a composite output signal and thus a response behavior that is almost uniform over the entire sensitivity range as is possible. When developing such systems, the

gc dispersion or distribution of sound energy special Attention should be paid, taking over the entire area

in general, "broader spreading is sought after will. In addition, special attention must be paid to

the physical resistance and thus the 5th

Lifespan of speakers to be addressed; this is especially true for the membranes, which are generally a have extensive surface area and are made only of thin, sheet-like material. Also still have to

the harmonic distortions are taken into account. .

When developing such systems with multiple driver stages represents the selection of the primary sound source for low frequencies, i.e. the bass or. Bass speaker. " the most serious decision.

A cone driver stage is usually selected for this. The response at low frequencies however, this driver stage generally depends on the diameter of the cone, while the response at high

Frequencies is inversely related to this diameter. For cone loudspeakers, as here, too, generally that the distribution of the radiated sound waves by the expression

(1) 'λ = 77d

is limited, where d is the diameter of the cone and / Cdie Are the wavelength under which the distribution or scattering is directed. The choice of the diameter therefore determines

both the characteristic curve at low frequencies and the degree of dispersion '. In any event, it is often desirable to improve the response of the system at frequencies above the radiating capacity of the woofer by using a tweeter, with or without an intermediate or midrange speaker.

Hood driver stages are known. Examples are U.S. Patent 3,328,537 issued June 27, 1967 (Hecht) and U.S. Patent 4,190,746 on February 26, 1980 (Harwood et al.). because '"vs-

the diaphragms of these driver stages in the direction in which the sound waves are radiated, are convexly curved, they have an excellent scattering at high frequencies. Thus, the combination of cone-woofer speakers with hood driver stages with appropriate dimensions is used for the response at higher frequencies to maintain sound dispersion, the more the of woofers, compared to combinations of cone woofers with cone tweeters. However, if you put hood driver stages, such as those in the above patents can be inferred so that they have an adequate response at the highest frequencies to which the system is tuned, they do not provide sufficient response behavior at medium frequencies above the frequencies at which the woofer is effective. This deficiency can in some cases make use of it require a third driver stage for the medium frequency range. If, conversely, a hood driver stage is designed for a response that is adequate

for the compensation of the cutoff frequency of the bass loudspeaker at frequencies in the middle range is often the response behavior at high frequencies is severely restricted, so that a third driver stage, i.e. a tweeter, must be used in order to

behave at high frequencies to expand.

With the foregoing in mind, it is therefore an essential object of the invention to provide a driver stage

to create that both in the medium frequency range and 35

a sufficient response behavior at high frequencies

Has; In addition, this driver stage should have a much broader characteristic curve than cone driver stages.

Furthermore, a driver stage of the type specified above with a very stable structure is to be created that also Can absorb relatively large acoustic performances with minimal fatigue and disturbances, especially fractures.

It is a further object of the present invention to provide a low distortion driver stage of the type set forth above to create in the range of medium frequencies.

And finally, a driver stage should be proposed

which is made up of materials that have very uniform properties and by moisture, changes or Extreme values of the temperature as well as by signs of fatigue are practically not influenced.

For this purpose, the invention proposes a hood driver stage with a membrane made of a hood area and a pleated, annular surrounding area, which is constructed in such a way that it contributes the essential acoustic energy Emits frequencies below the range in which the hood section would effectively radiate if it passed through a conventional shape environment would be maintained.

The surrounding area of this invention has an annular mounting arrangement which, in relation to the

Permanent magnet structure is fixedly arranged; the spatial arrangement of this attachment is at a relatively large distance from the voice coil, where the Haubenbe rich and the surrounding area are connected.

That is, the diameter of the membrane, measured on the annular Fastening with the fixed magnetic structure, essential

ι. · Η

borrowed larger than the diameter of the hood area and the voice coil is. According to a preferred embodiment the ratio of the first-mentioned diameter to the last-mentioned diameter is greater than 2.25.

The hood section itself can have the shape of a partial sphere or parabolic shape; the last-mentioned embodiment provides in comparison with the first-mentioned embodiment- ' form a broadened response behavior at high frequencies.

By suitable selection of materials for the membrane structure, especially materials with adequate internal Attenuation, it is possible to have a mid-range speaker with a smooth frequency response characteristic, with great dynamic range as well as with a broadened frequency characteristic.

The invention is illustrated below with the aid of exemplary embodiments explained in more detail with reference to the accompanying schematic drawings. Show it

1 shows a diametrical section through a first, preferred embodiment of the invention,

FIG. 2 is a plan view of the embodiment according to FIG. 1,

3 shows a diametrical section through a second embodiment of the membrane with a parabolic one Hood, and

4 shows the frequency response characteristic for comparison purposes for the driver stage.

Figure 1 shows a preferred embodiment of an all-, common by the reference numeral 12 indicated forcing stage of the hood type. This driver stage has a Permanent magnet structure of conventional shape including a pole piece 14 with an integral bottom plate 16, at least one permanent magnet 18 and a cover plate 20? these parts are suitably interrelated

• jQ connected? an adhesive process is preferably used for this purpose. The magnet or magnets form a permanent magnet - flux in an annular gap 22. A mounting plate 24 is attached in a suitable manner to the cover plate 22? a clamp plate 26 is suitable

each attached to the plate 24 so that a membrane 28 on the Plate is clamped «The diaphragm is attached to a voice coil 30, which is activated by the flow of current in the coil in Vibrations can be set so that sound energy waves are radiated «The sound energy is also created

2Q if due to the current flow in the coil.

The membrane 28 has two sections, namely a hood-shaped section 32 and a surrounding section In the illustrated and presently preferred embodiment, these sections are formed by a vacuum forming process or in some other way - formed from a sheet-shaped material, so that they consist of a single part. Alternatively, the two sections can be made up of separate sheet-like materials are formed, wherein

₃ Q the outer circumference of the hood section and the inner circumference of the surrounding section are connected to one another in a suitable manner, for example by means of an adhesive. If in the following it is said that the hood section and the surrounding section are "connected to one another"

gg, this term is intended to include both the above-mentioned, preferred, one-piece design as well as the alternative

Embodiment are included; if it is further said that the surrounding section is "folded",

so it is meant that it has a curved 5

Has shape, as can be seen in FIG. The curvature of this shape is in a preferred embodiment essentially circular.

At the connection line between the hood and the surrounding area, a cylindrical coil form 36 is attached, the holds the voice coil 30 in the gap 22. The membrane 28 also has a flange 37 between the plates 24 and 26 is attached. According to a preferred embodiment, the hood section and the surrounding section contain no perforations and have in all sections on planes that run through the axis of the driver stage, as in Fig. 2 is indicated, the shapes shown. In the plate 36 holes 38 are for the attachment of this plate 26-means

Screws are provided on the plate 24. 20th

On the plate 26 connections 40 are attached, which via lines 42 and 44 with the opposite ends of the Voice coil 30 are connected.

A capsule or shell or shell 46 has a body made of fiberglass, a plastic foam or a fiber mass and is attached to a surface of the pole piece 14 under the hood 32 by means of an adhesive; these

Sheath 46 serves to remove from the bottom surface of the hood 30

32 to absorb radiated sound energy, whereby the reflections from the pole piece 14 are kept extremely low; the reflections from the pole piece 14 would otherwise lead to interference or disturbances of the sound energy

is emitted directly from the hood surface. 35

/ 11

The mentioned gap 22 includes both the space between the mold 36 and the pole piece 14 as well as the space between the voice coil 30 and the cover plate 20. This Gap is essentially filled with a "ferrofluid", i.e. a liquid in which magnetic particles are suspended are? Such a liquid is usually used in loudspeakers to ensure heat conduction from the Voice coil to form the plate 20. '

In the structure according to Figures 1 and 2, the relative Dimensions of the hood and the surrounding section selected so that the surrounding surface as a radiator or transmitter for relatively high sound power is used. Around

To illustrate the importance of the optimal dimensions, the letters "a" and "d" are entered in Figure 1, which represent the edges of the outer periphery of the surrounding area 34? the letters "b" and "c" represent the connection points between the hood and the surrounding area

dar? the letters "e" and "f" indicate the points on the surrounding area which are from the plane of the annular Attachment of the surrounding area between panels 26 and 24 are furthest away? the letter "g" finally shows the point on the hood that is furthest from this plane.

The letters "h", "i" and "j" represent points in the same plane on the perpendicular thereto, each going through the points "g", "e" and "f" run respectively. At the moment

In the preferred embodiment, the following dimensions are used:

route 1 cm (4th , 6 inches) ad 5 1.684 (2 Customs) be 1 , 080 (0 , 47 inches) ei = f j 1 , 1938 (0 , 63 inches) gh , 6002

It should be noted that the ratio of "ad" to "bc" is 2.3. In practice, the above can be used

Dimensions can be varied in size and in relation to one another, depending on the frequency range the usable response, what is to be achieved and the power consumption of the used Materials. To get a sufficiently low output signal

To obtain medium frequencies with a structure that is sufficiently stable for adequate power consumption at The available methods and materials of membrane construction must be the diameter of the hood at its circumference and the inner edge of the surrounding area

riches should be approximately at least 3.81 cm (1.5 inches). In addition, the ratio ad / bc should be at least 2.3 be. Finally, according to a preferred embodiment, the ratio ei / ab should also be at least 0.33.

The materials from which the membrane is constructed are of great importance in order to achieve the desired power absorption without breaks, the ability to withstand different operating conditions, such as humidity, heat and cold to endure, as well as resistance to failure

due to material fatigue. The currently preferred membrane material for both the hood and for the environment is a leaf-shaped, filled with sebum Poly.propylene material. Other membrane materials that could be used are a vinyl film on the one Aluminum layer, deposited under negative pressure, especially on

ns

as well as a polycarbonate film.

Figure 3 shows a second embodiment of the membrane according to the present invention. This embodiment corresponds essentially to the embodiment according to the figures 1 and 2 with the exception of the cross-sectional shape of the hood. A hood 48 with a parabolic cross-section is integral with an annular, fallen environment 50 is formed, which has essentially the same shape as the surrounding area 34? as Alternatively, can the hood 48 be attached to an annular environment of the same shape? the Diaphragm has a flange 52 for annular attachment in fixed relationship with the permanent magnet components on. A coil form 54 is attached to the connection points of the hood and the surroundings and holds a helical one Voice coil 56. The parabolic shape of the hood extends the high frequency end of the response curve, as follows will be described in detail with reference to FIG.

FIG. 4 shows typical frequency response curves for three driver stages which are used for comparison purposes will. The solid line 58 shows the response of the embodiment according to Figures 1 and 2 with a hood, -die has the shape of a partial sphere. The dashed line 60 represents part of the response curve of a conventional one Hood driver stage with the same hood dimensions as Fig. 1, however, shows a conventional environment

conventional driver stage, the surroundings are only used to hang or hold the hood. Such environments can be made of the same material as the hood or of a different material; in the radial direction with respect to the axis of the loudspeaker -

the surroundings have relatively small dimensions. The curve

60 finally shows an embodiment in which the "Ab" clearance is 1/4 inch or less (6.35 mm) or less. The sound radiation capacity of this embodiment is only slight. Curves 58 and 60 merge at. a frequency slightly above 1000 Hz; at higher Frequencies, the curves practically coincide due to the common characteristics of the hoods.

Figure 4 also shows a dashed line 62 showing the response of a driver stage according to the embodiment according to FIG. 1, but with the membrane according to FIG. 3. This curve shows an extended response behavior at high frequencies, merging with the solid line 58 at approximately 10,000 Hz. At lower frequencies, the embodiment with the parabolic hood has the same characteristic as the hood embodiment according to FIGS. 1 and 2.

An examination of the curve according to FIG. 4 shows that the embodiments according to FIGS. 1 and 3 are essential Improvement compared to the conventional hood shapes due to the extended response at low frequencies. Assuming that the Area with a substantially "flat" response curve representing zero decibels, for example, can be assumed Be sure that the effective frequency range of this driver stage contains the frequency that is less than 6 decibels below the zero value. On this basis, the conventional hood driver stage has a usable range of approximately 650 to 10,000 Hz, while the driver stage with the partial sphere hood according to the present invention a range of about 300 to 10,000 Hz and the loudspeaker with the parabolic hood according to the invention has a range of approximately 300 to 15,000 Hz.

In certain embodiments of the parabolic loudspeaker, the response at high frequencies

can be further improved, with the upper limit of the usable response behavior close to the limit value of 20,000 Hz? this allows for the installation of a separate Tweeter can be dispensed with in the system.

In implementing the basic principle of the present invention, the points on the surrounding area that are furthest from the plane of its annular attachment, such as points "e" and "f" in Fig. 1, closer than the point on the hood, which is furthest from such a plane, such as point "g". This criterion is guaranteed better dispersion or radiation of the sound energy over a wider frequency range, and in comparison with cone speakers with the same dimensions.

As mentioned above, one of the advantages of the present invention is the life of a typical one Hood driver stage designed to an adequate range of frequency response for the mid-range driver stage in a speaker system with several driver stages. When the forms of the Hood and the environment for the desired frequency response selected and the above-mentioned preferred Materials are used, the risk of rupture of the membrane is negligible. In addition, the Use of the mentioned preferred materials that this driver stage also under different conditions in relation on humidity and temperature determined by the specification specified requirements are met.

Although for the shape of the hoods in the illustrated embodiments a partial sphere or a parabolic shape have been specified, in practice changes to the

sen forms are made due to the manufacturing conditions. Empirical methods can also be used to determine the exact impact of these changes on the overall performance of the driver stage. Even however, such changes are within the scope of the invention.

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Claims (13)

Claims Driver stage · with moving coil for a loudspeaker / characterized by a permanent magnet arrangement with pole pieces which defining an annular gap through a membrane (28, 48) having a dome-shaped section (32, 48) ,. which is at least 3.81 cm (1.5 inches) in diameter around its circumference, and with a folded one , annular surrounding area (34, 50), wherein the hood area (32, 48) on its periphery is connected to the inner edge of the surrounding area and the outer edge of the surrounding area has an annular fastening device which is in a fixed relationship to the permanent magnet arrangement κ «« «•••» τι ί> · is attached / and by a on the membrane (28/48) Coil attached to the connection between the hood area and the surrounding area, which extends into the gap, wherein the diameter of the surrounding area on the mounting arrangement is greater than 2.3 times the diameter of the coil. 2. Driver stage according to claim 1, characterized in that the hood region (32) is substantially in the shape of a Has partial sphere. 3. Driver stage according to claim 1, characterized in that the hood region (48) has a substantially parabolic shape. 4. Driver stage according to one of claims 1 to 3, characterized in that the surrounding area in each diametrical Cross-section of the membrane has essentially a circular curvature. 5. Driver stage according to one of claims 1 to 4, characterized in that the maximum "distance of the surface of the hood area from the plane of the annular mounting arrangement is greater than the maximum distance of the surface of the surrounding section from this plane. 6. Driver stage according to one of claims 1 to 5, characterized characterized in that the maximum distance of the surface of the surrounding portion from the plane of the annular Fastening arrangement at least one third of the distance from the coil to the annular fastening arrangement amounts to.. 7. Diaphragm for a driver stage with moving coil, 35 characterized by a hood portion (32, 48) having a diameter of at least 3.81 cm on its circumference (1.5 inches), and by a pleated inner surrounding area that runs along its inner edge is connected to the circumference of the hood area (32, 48) and has an outer edge for an annular , _ Fastening is suitable, the diameter of the outer edge is larger than 2.3 times the diameter of the inner edge. 8. Membrane according to claim 7, characterized in that the hood area (32, 48) and the surrounding area (34, 50) can be formed by a single, integral body. 9. Membrane according to one of claims 7 or 8, characterized in that that the hood area (32) is essentially has the shape of a partial sphere. 10. Membrane according to one of claims 7 or 8, characterized in that that the hood area (48) is essentially Has parabola shape.
20th 11. Membrane according to one of claims 7 to 10, characterized in that that the surrounding area (34, 50) in each diametrical cross-section of the membrane substantially one has circular curvature. 12. Membrane according to one of claims 7 to 11, characterized in that that the maximum distance of the surface of the hood area (32, 48) from the plane of the outer circumference greater than the maximum distance from the surface of the vice-30 practice area. (34, 50) is from this level. 13. Membrane according to one of claims 7 to 12, characterized in that that the maximum distance of the surface of the Surrounding area from the plane of the outer perimeter little-35 at least one third of the distance from the connection between the surrounding area and the hood section to the outer one Scope is.