Universal ribbon element-module for two or more membrane-widths with optimized flow and drive

SWEDEN (12) PATENT (13) C2 tu) 522 334 (19) SE (51)

International class ⁷

H04R 9/06

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PATENT AND REGISTRATION (45) (41) (22) (24) (62) (86) (86) (83)

Patent filed Application widely available The patent application was submitted on expiration date

Application number International filing date

Filing date for European patent application Deposit of microorganism

2004-02-03

2002-03-27

2000-09-26

2000-09-26 (21) Patent Application Number Q003491-8

Application received as:

Swedish patent application completed international patent application with number □ converted European patent application with number (30) Priority information (73) (72) (74) (54) (56) (57)

Assignee

INVENTOR

AGENT

NAME

Bo Bengtsson c / o P Glaser, Bäverns Gränd 18 B ltr 753 19 Uppsala SE Bo Bengtsson, Uppsala SE

Universal belt element module for two or more diaphragm widths with optimized flow and drive CIVIL PUBLICATIONS:

US 4,319,096 (H04R 9/06)

SUMMARY:

The present invention relates to a new type of speaker module in the form of a band element so designed that the module can be optionally equipped with a membrane of width 50 mm or narrower, and a length freely selectable in the range 50 millimeters to 2500 millimeters. In cases where the module is to be used with a narrower band, the field-concentrating pole shoes are mounted between the magnets and the band. This results in a higher efficiency and reduces the risk of edge reflection. It is also advantageous if, in contrast to conventional practice, the soft-core coil shoes of the module are mounted alongside the magnets in such a way that the membrane is allowed to radiate freely both forward and backward.

It is further preferred that the magnetic system is provided with so-called booster magnets to reduce flow losses in the soft-iron coil foams and smooth out the flow at the ends of the magnetic system. Furthermore, it is preferred that the signal supply is designed as passive current supply, thereby eliminating the negative effect of the inductance on the frequency up to 1 / f point. Above the 1 / f point, the band is fed with a special circuit consisting of R and C whose sizes are selected so that the resulting frequency curve becomes straight for the entire operating range.

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The numbers in brackets indicate international identification code, INID code. Letters within clips indicate international document code.

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SUMMARY

The present invention relates to a new type of speaker module in the form of a band element, so designed that the module can optionally be equipped with a membrane of 50 millimeters or narrower width, and a length freely selectable in the range 50 millimeters to 2500 millimeters. In cases where the module is to be used with a narrower band, the firmly concentrated pole shoes are mounted between the magnets and the band. This results in a higher efficiency and reduces the risk of edge reflection. It is also advantageous if, in contrast to conventional practice, the soft-core coil shoes of the module are mounted alongside the magnets in such a way that the membrane is allowed to radiate freely both forward and backward.

It is further preferred that the magnetic system is provided with so-called booster magnets to reduce flow losses in the soft-iron coil foams and even out the flow at the ends of the magnetic system. Furthermore, it is preferred that the signal supply is designed as passive current supply, thereby eliminating the negative effect of the inductance on the frequency up to the 1 / f20 point. Above the 1 / f point, the band is fed with a special circuit consisting of R and C whose sizes are selected so that the resulting frequency curve becomes straight for the entire operating range.

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Background of the invention

1st FIELD OF THE INVENTION The invention relates to favorable designs of loudspeakers of the tape type.

2nd Prior art

The principle of the electromagnetic tape speaker is well known. In a magnetic field sits a band of electrically conductive material clamped, on both sides surrounded by strong longitudinal permanent magnets. When a tonal alternating current is applied to the band, the diaphragm will oscillate with the input signal.

Band speaker technology is wrestled with two major problems: first, the linearity of the magnetic flux is not homogeneous; (typical solutions are glued ferrite magnets) - firstly, the frequency response is not straight but falls with increasing frequency. The latter depends on the mass / inertia of the tape and the inductance of the tape and the supply cable. Last but not least, the band's width has a decisive effect on the amplitude. Wider bands result in higher radiation resistance, ie better connection to the ambient air, which means lower membrane amplitude and is essential if low frequencies are to be reproduced with sufficient sound pressure.

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Electrical limitations:

The low electrical resistance of the band speaker as well as its physical extension in space, results in an inductance that adversely affects the frequency response and, in particular, gives rise to serious phase distortions. The present invention solves this problem by passive power supply for the entire operating range below 1 / f and by separate passive compensation supply for the area above 1 / f. The band's physical mass in combination with the magnetic field's strength determines where the critical 1 / f point occurs. This is defined as the point at which the band switches from speed controlled to mass controlled state. Above this point, the band's output level is not linear, but falls with increasing frequency.

Mechanical limitations:

The band's physical mass in combination with the magnetic field's strength determines, as previously mentioned, where the critical 1 / f point occurs. This is defined as the point at which the band switches from speed controlled to mass controlled state. Above this point, the band's output level is not linear, but falls with increasing frequency.

Object of the invention and summary of the invention

A basic object of the invention is, on the basis of the above-mentioned technical limitations, known per se, to achieve an optimization, enabling high sound pressure with low distortion in the entire working area.

The present invention also intends to solve the above related problems by means of a long time modularisation of realizing a product with high performance which is also attractive in terms of production and cost.

The present invention relates to a full-frequency tape type speaker system, where a modulation of the technique enables the use of one and the same type of chassis for at least two or more membrane widths, preferably 25 and 50 millimeters, respectively, with opti

522 334 merging of the magnetic flux for respective working conditions and where the bands are driven with passive current supply to overcome inductance related problems and where any number of modules can be combined to enable high sound pressure with low distortion in the entire working area.

The invention also relates to a specially designed, preferred module which is suitable for use especially in a modulated embodiment of a speaker system.

The present invention thus relates to a new type of speaker module in the form of a band element, so designed that the module can optionally be equipped with a membrane of width 50 mm or narrower, and a length, freely selectable in the range 50 millimeters to 2500 millimeters. In cases where the module is to be used with a narrower band, the field-concentrating pole shoes are mounted between the magnets and the band. This results in a higher efficiency and reduces the risk of edge reflection. It is also advantageous if, in contrast to conventional practice, the module's soft iron coil shoes [(A1) / (A2) in Fig. 3 and Fig. 7 are mounted alongside the magnets in such a way that the membrane is allowed to radiate freely both forward and backward.

It is further preferred that the magnetic system is provided with so-called booster magnets to reduce flow losses in the soft-iron coil foams and even out the flow at the ends of the magnetic system. Furthermore, it is preferred that the signal supply is designed as passive current supply, thereby eliminating the negative effect of the inductance on the frequency up to 1 / f point. Above the 1 / f point, the band is fed with a special circuit consisting of R and C whose sizes are selected so that the resulting frequency curve becomes straight for the entire operating range.

Short figure description

Fig. 1 AE shows the frequency response of the band element type speakers for various examples given in the further description. Fig. 2A shows a wiring diagram for power supply of a speaker band. Fig. 2B shows an improved embodiment of a coupling 4

522 334 diagram for such power supply. Fig. 3 shows a front view of a tape module with magnets, pole pieces and a tape. Fig. 4 shows a cross-sectional view of a band inserted between magnets and pole pieces. Fig. 5 shows another cross-sectional view of the same tape module, with booster magnets. Fig. 6 shows an embodiment of a belt provided with a slit in the middle. Figures 7,8 and 9 show figures of another embodiment, corresponding to Figs.

3,4 and 5. Fig. 10 shows a combination of band modules enabling covering oceans throughout the tonal range between 20 Hz and 40 000 Hz. Fig. 11 shows an example of prior art in which the magnetic field feedback is located on the back of the sound-radiating band.

Detailed description of preferred embodiments of the invention

Fig. 1A shows typical frequency response for an uncompensated band element from 100Hz up to the 1 / f point. Fig. 1B shows the frequency response under the same conditions above the 1 / f point. Fig. 1C shows the resulting frequency response for the entire working area.

By coupling a power resistor with extremely low intrinsic inductance according to Fig. 2 (B) in series with the band, (depending on the resistance value of the resistor in relation to the band resistance) is obtained, a controlled voltage drop which results in the band being energized. This type of feed causes the problem of inductance in the band to be eliminated. The resulting frequency response for the frequency range up to the 1 / f point is shown in Fig. 1D.

Fig. 2A shows, inter alia, capacitor (A) constituting a first order partition filter with the slope of 6dB / octave.

In Fig. 2A, further (C) is the shunt capacitor with a value that compensates for the falling output level above the 1 / f point. Fig. 2A (D) is a low inductive resistor having a value in the order of 1/10 to 1/100 of the value of (B) in Fig. 2A. The resulting frequency response is shown in Fig. 1E.

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The component values ​​for R and C in Fig. 2A depend on the resistance value of the band (E) and the desired partitioning frequency, the latter being determined by the capacitor (A) and the resistance (B) in relation to the resistance value of the membrane (E).

In Fig. 2A (F) and (G) are the connection points to the circuit. (F) and (G) may be connected directly to a commercial power amplifier, capable of operating low impedance loads, as appropriate, or points (F) and (G) may be connected to the secondary side of a full transformer to meet CE electrical safety standards.

Fig. 2B shows the same scheme and functionality as Fig. 2A with the exception of the coil (H) which provides a 6 dB cut-up in frequency. This solution is used in cases where it is desired to use the wide band (preferably 50mm) in the module chassis, to reproduce frequencies below 1kHz. The coil (H) thus constitutes a first order low pass filter.

By increasing the magnetic flux in the gap and reducing the moving mass of the membrane, 1 / f can be moved upwards in frequency (but not completely eliminated). This method also increases the sensitivity of the system so that a lower electrical power is required for a given sound pressure.

For practical purposes, there is a limit to how thin the membrane can be made, with reasonable demands on mechanical strength and the ability to handle the input power. This has previously been usually solved by applying U-shaped pole shoes behind the magnetic system in order to achieve a closed flow. This process results in heavy and mechanically complicated systems which, in addition, grow in depth physically, and thus become more space intensive. Moreover, placing the pole shoes behind the magnets adversely affects the sound radiation, as it makes the band element design more difficult as a pure dipole, ie as an element that radiates as much forward and backward. With pole shoes placed behind the band element, part of the radiated energy will be reflected back, thus providing a coloration of the sound. Fig. 11 illustrates this. It emanates from a US patent application, (MAGNEPAN Inc.). and

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clearly shows that the space between the slots in the pole piece will reflect back the input signal and thereby induce resonances.

The present invention aims to remedy this problem by a method where the pole pieces are applied to the sides of the magnets instead of behind them, in such a way that the membrane is allowed to radiate freely both backwards and forwards.

Fig. 3, Fig. 4 and Fig. 5 illustrate how this is solved in the preferred invention. Fig. 3 (Al) and (A2) and Fig. 5 (Al) and (A2) show the physical io orientation of the soft-iron coil pieces in the plane in relation to the main magnets, the latter illustrated in Fig. 3 (Cl) and (C2), and Figs. .4 (Cl) and (C2). Fig. 3 shows the pole pieces from the front and Fig. 5 (A1) and (A2) shows the pole pieces with the module lying.

Fig. 4 (E) shows the orientation of the membrane with respect to the magnetic system (C1) / (C2) and relative to the flow-concentrating soft-iron coil pieces D1 / D2, the latter used when the narrow band module is to be used for reproducing frequencies above lkHz. these pole pieces are made to avoid edge reflection.

Fig. 3 (H) shows the direction of the magnetic field. Fig. 5 (H) shows the outer protective plates with their beveled, slit-shaped sound opening.

Fig. 3 (G) and (F) show the insulators on which the membrane rests. The insulators are provided with 4 through holes for use with any band.

To compensate for loss of flow in the pole pieces, so-called booster magnets have been introduced. These appearance and placement are shown in Fig. 3 (B1) and (B2) and Fig. 5 which shows the booster magnet (B1) from the underside. The resultant flow is shown, as previously mentioned, in Fig. 3 (H).

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By designing the magnetic system in this way, a system with extremely low physical depth is obtained, while the sound energy from the band is freely allowed to radiate both forward and backward. The interaction between the booster magnets, the main magnets and the soft-iron coil foam makes it possible to obtain a very high linearity in the gap, which allows the construction of long linear stroke strip elements, practically equal to the physical depth of the magnetic system according to Fig. 8, which shows diaphragm / magnetic orientation. in the case where the low frequency broad band is used. If the air gap (magnetic gap) in Fig. 3 preferably has a width of 50 millimeters and the pole pieces (D1) / (D2), illustrated in Fig. 3 and Fig.4 each have a width of 12 millimeters, the module is optimized for a 25 millimeter wide band. , resulting in a horizontal sound distribution of 170 degrees. The module length (L) can be freely selected within the range of 50 millimeters to 2500 millimeters. Thus, Figs. 4 and 5 show a configuration of the module as it is intended for high frequency reproduction in the range of 1kHz to 40kHz, provided with a membrane of pure metal, preferably aluminum, without any plastic film as a base.

The 25-millimeter diaphragm is further designed with a slit in the middle, (Fig. 6) to further reduce non-linear magnetic forces, which could otherwise result in a rupture of the diaphragm along the center line. This procedure is important when short modules come into use. Fig. 5 (H) shows the module lying, showing rear and front faceplates of non-magnetic material whose task is to mechanically join the structure. The bevelling of the edges of the gap opening prevents the appearance of cavity-related sound distortion.

If the pole pieces (D1) / (D2) in Fig. 3 are removed, a double-width singular band intended for low frequency reproduction can instead be mounted, see Fig. 7, Fig. 8 and Fig. 9.

Removing the tapered pole pieces (D1) / (D2) will double the linear stroke. What is thereby lost in magnetic flux is largely offset by the doubled surface of the tape. The efficiency is in practice the same. Figures 4 and 8 show the difference in the design of the magnetic gap in each case. By intention

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limiting the broad band upward in frequency, the same wide spread is obtained as for the high frequency version.

The band speaker has, due to its previous limitations, only been able to be used for the audio tones in audio which we call intermediate registers and treble, ie the range from 1 kHz to 20 kHz. New magnetic materials and an application of the tape technology in the form of a linear sound source, enable constructions that cover the entire tonal range from 20Hz to 40kHz; - see Fig. 10 as a pointer to an example of how a 2 meter high full-register system of tape type according to the line-sound source concept can be designed using the present invention. The extension down in frequency and related sound pressure is determined by the number of modules for low frequency. The more modules, the higher the radiation resistance, the higher the sound pressure.

Addendum

It has been found that the plate on which magnets C1, C2, pole pieces D1, D2 etc. are most preferably made of a non-conductive material. Attempts to manufacture it from aluminum turned out to cause worse sound, obviously due to eddy currents generated by the current through the tape.

Regarding the couplings with RC filters in Figs. 2A and 2B, designed for high frequencies and high frequencies respectively. low frequencies, it must be clarified that in Fig. 2A the resistor B must have sufficient resistance in relation to the impedance of the band E, so that something which from the point of view of the band E is obtained as a current source - that is, the current is approximately independent of variations in the band E impedance. The resistor B in Fig. 2B must meet the same requirements in that regard. In contrast, the capacitance of capacitor A in FIG. 2A dimensioned to limit low frequencies at a dividing frequency, e.g. 5 kHz, whereas capacitor A in Fig. 2B is sized to provide a downward limitation at e.g. 250 Hz. The inductance H of Fig. 2B aims to limit the supply of the band E to frequencies below the division frequency, e.g. 5 kHz.

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The parallel-coupled RC filters D + C in Fig. 2A and Fig. 2B are intended to provide increased feed at higher frequency and to provide some compensation for the mechanical properties of the band such as thickness etc.

In the first instance, it is envisaged that the low frequency is taken care of by wider bands than the high frequency, taking into account the different efficiency, but in many cases it is also advisable to work with the same width of the band in both the bass part and the treble part, as is also the case. it is possible to divide the audio frequency band into more than two parts by additional splitting filters.

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With the specified couplings and magnetic gap designs, it has been found that the band speakers are useful even with very long bands, and excellent function has been shown with bands 50 mm wide and having a free length of 500 mm. Fig. 10 actually shows a speaker where the wide elements have such dimensions. Some booster magnets according to Figs. 3 or 7 are then not in question.

The invention can be varied in many ways, and it is intended that it should not be regarded as limited other than by the following claims.

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