The present application claims priority to European Patent Application 18164181.2 filed by the European Patent Office on Mar. 27, 2018, the entire contents of which being incorporated herein by reference.
The present disclosure generally pertains to the technical field of acoustics, in particular to loudspeakers.
Loudspeakers are technical devices which convert an electrical audio signal into a corresponding sound. The most widely used type of loudspeaker is the dynamic loudspeaker, in which sound is generated by a swinging diaphragm driven by an electromagnet, which oscillates in the external field of at least one permanent magnet. It uses a lightweight diaphragm, or cone, connected to a rigid basket, or frame, via a flexible suspension, commonly called a spider, that constrains a voice coil to move axially through a cylindrical magnetic gap. When an electrical signal is applied to the voice coil, a magnetic field is created by the electric current in the voice coil, making it a variable electromagnet. The coil and the driver's magnetic system interact, generating a mechanical force that causes the coil (and thus, the attached cone) to move back and forth, accelerating and reproducing sound under the control of the applied electrical signal coming from the amplifier.
There are also other technical concepts for realizing a loudspeaker. The most common alternative implementation of a loudspeaker is the electrostatic loudspeaker, in which not a magnet is used to drive the diaphragm, but the electrostatic Coulomb force is used. Those loudspeakers use a thin flat diaphragm usually consisting of a plastic sheet coated with a conductive material such as graphite near an electrically conductive grid, with a small air gap between the diaphragm and grid. The driving force is in contrast to a dynamic loudspeaker not the Lorentz Force but the electrostatic Coulomb-Force.
According to an aspect of the disclosure, a loudspeaker system is provided comprising a diaphragm and an electrostatic foil mounted on top of the diaphragm. Further aspects are set forth in the dependent claims, the following description and the drawings.
Embodiments are explained by way of example with respect to the accompanying drawings, in which:
Before a detailed description of the embodiments under reference of
The embodiments describe a loudspeaker system comprising a diaphragm and an electrostatic foil mounted on top of the diaphragm.
The electrostatic foil may be configured to emphasize predefined frequencies or frequency ranges where modal resonances of the diaphragm occur. The electrostatic foil may for example be configured to compensate the power loss due to partial oscillations occurring on a dynamic loudspeaker's diaphragm.
The diaphragm may be magnetically driven according to the principle of a dynamic loudspeaker. That is, the diaphragm may be a diaphragm of a dynamic loudspeaker, and the dynamic loudspeaker may comprise at least one of the following: a loudspeaker basket, a dust cap, a spider, a permanent magnet, a bottom plate, a voice coil, and a surround.
According to the embodiments, the electrostatic foil acts as an electrostatic loudspeaker. The loudspeaker system thus may combine the functionality of an electrostatic and a dynamic loudspeaker to enhance a dynamic loudspeaker, e.g. in the high-frequency region. Dynamic loudspeakers may show a good performance in the low-frequency region until a natural frequency of the diaphragm. For frequencies larger than the natural frequency, partial oscillations may result on the diaphragm which leads to an output loss in radiation power of the dynamic loudspeaker leading to decreased volume for those frequencies. Also, electrostatic loudspeakers may have a good high-frequency performance, but a very bad performance for low-frequency and standing on its own the sound quality is very bad, as a not-preventable clangor sound occurs.
According to an embodiment, the electrostatic foil comprises a stator that is mounted on the diaphragm of the dynamic loudspeaker and an electrostatic diaphragm that is mounted above the stator with a gap, e.g. an air gap, between the stator and the electrostatic diaphragm. An electrostatic loudspeaker mounted on a dynamic loudspeaker's diaphragm may for example be constructed based on the single-ended electrostatic speaker design.
According to another embodiment, the electrostatic foil comprises an electrostatic diaphragm mounted above the diaphragm of the dynamic loudspeaker with a gap between the diaphragm and the electrostatic diaphragm, and the diaphragm of the dynamic loudspeaker is a conductive diaphragm that is used as a stator of an electrostatic loudspeaker.
According to some embodiments, the electrostatic foil mounted on the diaphragm of the dynamic loudspeaker is separated into a plurality of individual segments. Each such segment of the electrostatic foil may be configured as an electrostatic loudspeaker that is driven individually.
The loudspeaker system may further comprise a controlling device configured to drive the electrostatic foil, the controlling device comprising a frequency-shaping filter. The frequency-shaping filter may for example be a frequency-separating filter for driving the electrostatic loudspeaker.
The frequency-shaping filter may for example comprise a high-pass filter, the high-pass filter having a cutoff frequency related to a mode of the natural frequency of the diaphragm of the dynamic loudspeaker.
Alternatively or in addition, the frequency-shaping filter may comprise one or more band-pass filters, each band-pass filter having a central frequency around a respective mode of the natural frequency of the diaphragm of the dynamic loudspeaker.
The loudspeaker system may be used as a two-way loudspeaker. For example, the dynamic loudspeaker by means of the magnetically driven diaphragm may provide the low and mid frequencies, whereas the electrostatic loudspeaker system by means of the electrostatic diaphragm may provide the high frequencies. Thus, the layered loudspeaker systems may add up to one multi frequency system with uniaxial characteristics.
A measurement and analysis of the capacity of the electrostatic foil may be performed. By measurement of the capacity of the electrostatic foil, the deformation of the dynamic membrane can be analysed. Thus, parameters for the correction function may be derived.
The loudspeaker system may further comprise a first voice coil that drives the diaphragm and a second voice coil to which a DSP corrected signal is applied.
The loudspeaker system may further comprise means for measuring the capacity of the electrostatic foil. By measuring the capacity of the electrostatic foil the deformation of the dynamic membrane can be analysed and a recalibration of the device due to aging effects that change the properties of the dynamic membrane can be achieved based on in-situ measurements. This dynamic recalibration that allows to compensate for aging effects of the membrane
Dynamic and Electrostatic Loudspeaker
The working principle of a dynamic loudspeaker is based on the Lorentz force FL
{right arrow over (F)}L=q·{right arrow over (v)}×{right arrow over (B)}
Driving an electrical signal (equals a current) through the voice coil 106 leads to the Lorentz force FL moving the voice coil back and forth as the signal current flows within the voice coil 106, which is placed in the extern magnetic field of the permanent magnets 104. Therefore the voice coil 106 moves synchronously to the signal current within. Synchronously to the voice coil 106 the diaphragm 101 moves producing sound as the air before (and behind) the diaphragm 101 is compressed/depressed.
Dynamic Loudspeaker with Modal Correction of Loudspeaker Membranes
An electrostatic foil 108 is mounted on the diaphragm 101 of the dynamic loudspeaker. The electrostatic foil 108 has electrical contacts (see
It should be mentioned that the electrostatic loudspeaker could also be comprised by two, three or another number of segments not explicitly shown in
The segmentation of the electrostatic loudspeaker or the structure of many electrostatic loudspeakers working as one large electrostatic loudspeaker allows a better fitting and more cost-efficient coverage of the dynamic diaphragm with the electrostatic loudspeaker.
Driving the Loudspeaker to Perform Modal Correction of Loudspeaker Membranes
As already mentioned above, the electrostatic loudspeaker has a good performance for high frequencies, while it may suffer a degraded performance and an unavoidable clangor sound for deeper frequencies. Therefore it is beneficial to drive at least the electrostatic frequencies with a crossover network, such that only those frequencies reach the electrostatic loudspeaker that improve the dynamic loudspeaker's performance.
It should be mentioned, that other frequency-separating filters are possible. For example, additional filters such as band-pass filters can be added by the skilled person, so that the embodiments are not limited to the specific frequency-separating filters described in
Additionally, the embodiments for structure of the diaphragms as shown in
Two-Way System (HF Distribution)
The loudspeaker system described above may be used to create a two-way loudspeaker by usage of the electrostatic foil (108 in
Measurement and Analysis of the Capacity of the Electrostatic Layer
By measurement of the capacity of the electrostatic foil (e.g. electrostatic diaphragm 403 in
Aspects of the above described technology are also the following:
[1] A loudspeaker system comprising a diaphragm (101) and an electrostatic foil (108) mounted on top of the diaphragm (101).
[2] The loudspeaker system of [1], wherein the electrostatic foil (108) is configured to emphasize predefined frequencies or frequency ranges where modal resonances of the diaphragm (101) occur.
[3] The loudspeaker system of [1] or [2], wherein the electrostatic foil (108) acts as an electrostatic loudspeaker.
[4] The loudspeaker system of anyone of [1] to [3], wherein the electrostatic foil (108) comprises a stator (401) that is mounted on the diaphragm (101) and an electrostatic diaphragm (403) that is mounted above the stator (401) with a gap between the stator (401) and the electrostatic diaphragm (403).
[5] The loudspeaker of anyone of [1] to [3], wherein the electrostatic foil (108) comprises an electrostatic diaphragm (403) mounted above the diaphragm (101) with a gap between the diaphragm (101) and the electrostatic diaphragm (403), and wherein the diaphragm (101) is a conductive diaphragm that is used as a stator of an electrostatic loudspeaker.
[6] The loudspeaker system of anyone of [1] to [5], wherein the electrostatic foil (108) mounted on the diaphragm (101) is separated into a plurality of individual segments.
[7] The loudspeaker system of [6], wherein each segment of the electrostatic foil (108) is configured as an electrostatic loudspeaker that is driven individually.
[8] The loudspeaker system of anyone of [1] to [7], further comprising a controlling device (402) configured to drive the electrostatic foil, the controlling device (402) comprising a frequency-shaping filter.
[9] The loudspeaker system of [8], wherein the frequency-shaping filter comprises a high-pass filter, the high-pass filter having a cutoff frequency related to a mode of the natural frequency of the diaphragm (101).
[10] The loudspeaker system of [8] or [9], wherein the frequency-shaping filter comprises one or more band-pass filters having a central frequency around a respective mode of the natural frequency of the diaphragm (101).
[11] The loudspeaker system of anyone of [1] to [10], wherein the loudspeaker system is used as a two-way loudspeaker.
[12] The loudspeaker system of anyone of [1] to [11], wherein a measurement and analysis of the capacity of the electrostatic foil (108) is performed.
[13] The loudspeaker system of anyone of [1] to [12], wherein the diaphragm (101) is magnetically driven according to the principle of a dynamic loudspeaker.
[14] The loudspeaker system of anyone of [1] to [13], wherein the diaphragm (101) is a diaphragm (101) of a dynamic loudspeaker, and in which the dynamic loudspeaker comprises at least one of the following: a loudspeaker basket (100), a dust cap (102), a spider (103), a permanent magnet (104), a bottom plate (105), a voice coil (107) and a surround (108).
[15] The loudspeaker system of anyone of [1] to [14], further comprising means for measuring the capacity of the electrostatic foil.
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