WO2023052632A1

WO2023052632A1 - Method of controlling a sound reproducing system and a sound reproducing system

Info

Publication number: WO2023052632A1
Application number: PCT/EP2022/077393
Authority: WO
Inventors: Dennis Laust SØRENSEN; Bálint NAGY
Original assignee: Kombo Audio Aps
Priority date: 2021-10-01
Filing date: 2022-09-30
Publication date: 2023-04-06

Abstract

The invention relates to a method of controlling a sound reproducing systemcomprising a plurality of audio devices. The plurality of audio devices comprises two or more signal reproducing devices, each comprising a logic circuit and a loudspeaker arranged in a housing. Each signal reproducing devices further comprises a first and a second optical data connector that are in data communication with the logic circuit and are arranged on different sides of the housing, and optionally, an additional optical data connector. The signal reproducing devices are configured to be mutually arrangeable such that the first optical data connector on one signal reproducing device is connectable directly with the second optical data connector on a proximal signal reproducing device in an arrangement to establish a bidirectional data communication link between the logic circuits of the signal reproducing devices. The method comprises arranging the two or more signal reproducing devices in sequence in an arrangement to establish the bidirectional data communication link. For each of the signal reproducing devices in the sequence, if one or more digital input audio streams are received via the first, second, and/or additional optical data connector(s), mix the digital input audio streams into a combined digital audio stream. If there are additional signal reproducing devices in the sequence, transmit the combined digital audio stream as a digital input audio stream to a next signal reproducing device in the sequence, else transmit the combined audio stream as a master audio stream to all of the signal reproducing devices in the arrangement for reproduction. The method additionally comprises determining a stack position of the signal reproducing devices in the arrangement, and establishing a device-specific audio signal correction for each of the signal reproducing devices, wherein the device-specific audio signal correction is based on the stack position of the specific signal reproducing device. Finally, the method comprises preparing a device-specific output audio stream from the master audio stream by applying the device-specific audio signal correction for each of the signal reproducing devices, and reproducing the device-specific output audio stream via the loudspeaker of each of the signal reproducing devices. The invention also relates to a sound reproducing system.

Description

METHOD OF CONTROLLING A SOUND REPRODUCING SYSTEM AND A SOUND REPRODUCING SYSTEM

FIELD OF THE INVENTION

The present invention relates to a sound reproducing system and a method of controlling the sound reproducing system.

BACKGROUND OF THE INVENTION

Recent developments in the audio communication industry have been focused on achieving a reliable, low latency, high data rate wireless data transmission between multiple audio devices.

These developments have included developments such as bluetooth 5.0, or wifi based audio transmissions, which enables the communication between several audio devices through radio frequencies. The application of these technologies are however limited by their ability to reliably transmit data in environments with high radio noise levels, and therefore generally have to sacrifice data rates, and/or implement data buffers (increasing data latency) to ensure a stable performance regardless of radio noise. The technologies are therefore often not applicable in critical applications that require low latency, high reliability and high data rates. An example of such applications is the live audio industry, where industry actors prefer wired solutions over radio based solutions, as wired solutions offer higher data rates, lower latency and much higher reliability compared to radio based communication. This is also true for professional speaker technology, where operators spend hours rigging up the correct signal chain and inputs, wires for each speaker, and the speakers themselves before a concert, or live audio applications.

Although optic communication through optic fibers have previously been used in audio applications, it has slowly been phased out, as they suffer from a low tolerance to bending of the fiber, resulting in low system reliability which is a key performance factor for the actors in the live audio reproduction scene.

In another example, live audio solutions require a large amount of setup and tuning of devices, as each device has to be compatible with, and therefore adjustable for, other devices. This means that even simple live audio systems can become difficult to operate for non-technical users (e.g. musicians). Hence, an improved audio system would be advantageous, and in particular a more user-friendly, easy to setup and/or improved communication between audio devices in an audio system would be advantageous.

OBJECT OF THE INVENTION

It is an objective of the present innovation to overcome the presented limitations in the prior art. In particular, it is an objective to provide a method of controlling a sound reproducing system that enables fast and user-friendly setup, and a sound reproducing system for the same.

It is a further object of the present invention to provide an alternative to the prior art.

SUMMARY OF THE INVENTION

Thus, the above-described object and several other objects are intended to be obtained in a first aspect of the invention by providing a method of controlling a sound reproducing system, wherein the system comprises a plurality of audio devices. The plurality of audio devices comprises two or more signal reproducing devices, and each signal reproducing devices comprises a logic circuit and a loudspeaker arranged in a housing. The loudspeaker is arranged to receive an audio signal for playing from the logic circuit via digital to analog converter, DAC, and an amplifier. Each signal reproducing devices further comprises a first and a second optical data connector that are in data communication with the logic circuit and are arranged on different sides of the housing, and optionally, an additional optical data connector in data communication with the logic circuit, The two or more signal reproducing devices are configured to be mutually arrangeable such that the first optical data connector on one signal reproducing device is connectable directly with the second optical data connector on a proximal signal reproducing device in an arrangement to establish a bidirectional data communication link between the logic circuits of the signal reproducing devices. The method comprises arranging the two or more signal reproducing devices in sequence in an arrangement to establish the bidirectional data communication link. For each of the two or more signal reproducing devices in the sequence, if one or more digital input audio streams are received via the first, second, and/or additional optical data connector(s), mix the one or more digital input audio streams into a combined digital audio stream. If there are additional signal reproducing devices in the sequence, transmit the combined digital audio stream as a digital input audio stream to a next signal reproducing device in the sequence, else transmit the combined audio stream as a master audio stream to all of the two or more signal reproducing devices in the arrangement for reproduction. The method additionally comprises determining a stack position of the two or more signal reproducing devices arranged in the arrangement, and establishing a device-specific audio signal correction for each of the two or more signal reproducing devices in the arrangement, wherein the device-specific audio signal correction is based on the stack position of the specific signal reproducing device in the arrangement. Finally, the method comprises preparing a devicespecific output audio stream from the master audio stream by applying the devicespecific audio signal correction for each of the two or more signal reproducing devices, and reproducing the device-specific output audio stream via the DAC, amplifier, and loudspeaker of each of the two or more signal reproducing devices. In this way, a master-less audio reproducing system may be achieved, in which a large degree of freedom in connecting audio sources to the system for providing input audio streams is obtained. This means that an input signal may be provided to any signal reproducing device in the arrangement, after which any input streams are sequentially mixed into a combined digital audio stream and transmitted to the next signal reproducing device in the arrangement. The last signal reproducing device in the sequence then retransmits the combined digital audio stream as mixed by that device as the master audio stream to all signal reproducing devices in the arrangement. As there is no master device in the arrangement, any device may add modifications to the combined digital audio stream, and thereby to the master audio stream. For instance, a volume change on any of the devices may be distributed as a corresponding change on all devices of the system. It is noted that the signal reproducing devices according to this invention are configured to fulfill at least two distinct roles in the system: mixing any digital input audio streams received by the device into a combined digital audio stream for further distribution in the system, and reproducing a master audio stream using the loudspeaker of the device. In this context, the signal reproducing devices being mutually arrangeable is taken to mean that they may be stacked vertically one on top of another, or stacked horizontally in physical contact or in close proximity with each other. The optical data connectors are arranged in the housing of the audio devices such that they will align to enable the data communication link simply by arranging the devices in this way. Thus, a user friendly modular system is obtained. However, connecting even nominally identical signal reproducing devices, i.e. loudspeakers, and having them operate with identical sound settings will generally not result in an optimal sound experience as observed by a listener. Rather, the listener may experience cancelations, levels may be off, different frequencies may be dampened etc, unless the system is appropriately adjusted. Therefore, the individual sound reproducing devices in an arrangement should be individually calibrated in order to improve the sound experience. This method allows the sound system to automatically calibrate the devices to improve sound quality.

The method exploits that since the modular sound reproducing system uses a direct connection between the individual device, the system is able to determine a spatial configuration of the system, i.e. how many devices, in which sequence, and arranged in which geometry, and is therefore capable to automatically calibrate the devices accordingly.

In an embodiment of the method according to the invention, wherein the method comprises the step that if the first signal reproducing device receives no digital input audio stream, it transmits an empty stream to the next signal reproducing device in the sequence.

In an embodiment of the method according to the invention, the device-specific audio signal correction comprises a phase correction for compensating a sound path length difference to a listener. In this way, a phase error that would otherwise occur if all devices reproduced the same audio stream may be reduced or alleviated. For instance, if the sound reproducing system is located on a floor, and the listeners are located at a higher elevation, audio from a bottom-most sound reproducing device will have a longer path to the listener than audio from a top-most device, resulting in audio from the bottom-most device being delayed with respect to audio from the topmost device. Therefore, by introducing a slight phase delay to the audio from the top-most device, this path length delay may be cancelled.

In an embodiment of the method according to the invention, the device-specific audio signal correction comprises a correction for a communication delay between the audio devices in the sound reproducing system. In this way, the system may be controlled so as to precompensate for communication latency between the devices of the system.

In an embodiment of the method according to the invention, the device-specific audio signal correction comprises a volume attenuation of at least a part of the frequency spectrum for compensating for proximity effects from a wall or floor. Sound reproduced from a sound reproducing device located directly on the floor tends to exaggerate a bass component of the sound, due to reflections from the floor. A similar effect may be observed from a sound reproducing device located against a wall. Thus, by attenuating the audio signal from such a device, a more uniform sound may be reproduced by the system as such.

In an embodiment of the method according to the invention, the device-specific audio signal correction comprises an equalizer compensation. In this way, detrimental differences in a spectral response of the sound reproducing devices may be compensated.

In an embodiment of the method according to the invention, one audio device of the sound reproducing system determines the device-specific audio signal correction for the two or more signal reproducing devices. In a particular embodiment, the devicespecific output audio stream for each of the signal reproducing devices is prepared by one audio device in the system and subsequently transmitted to the corresponding signal reproducing device via the data communication link.

In an embodiment of the method according to the invention, the device-specific audio signal correction is determined individually by each signal reproducing device, based on the stack position of said signal reproducing device.

In an embodiment of the method according to the invention, the device-specific output audio stream for a particular signal reproducing device is prepared by said signal reproducing device from the master audio stream and the device-specific audio signal correction.

In an embodiment, the device-specific audio signal correction for a specific signal reproducing device is further established based on device capabilities of said signal reproducing device. Such device capabilities may for instance be a frequency band of operation of the device, e.g. the device being a subwoofer or a tweeter.

In other embodiments, the device-specific audio signal correction of a specific signal reproducing device is further established in response to a device metrics. For instance, the device metrics may be a measure of how much power is left on a battery powering the device. If the device is running low on battery power, it can reduce its volume to keep the audio transmission flowing, which reduction has to be compensated for.

Alternatively, the device metrics may be a temperature measurement: If a speaker amplifier or speaker is running hot, the individual device may reduce its volume for a short while, which will also require compensation in the systems signal processing.

In an embodiment of the method according to the invention, at least one of the two or more signal reproducing devices further comprise an accelerometer for determining a device orientation, and wherein the method comprises further establishing the device-specific audio signal correction based on the device orientation. The accelerometer provides additional information about the configuration of the sound reproduction system, which is useful for further optimizing performance of the system by compensating more specifically to the physical configuration of the system. For instance, if the arrangement is made with the two or more signal reproducing devices side-by-side on a floor or ground, no device should be compensated as being relatively closer to the ground, unlike if the devices are stacked vertically.

According to a second aspect of the invention, the invention provides a sound reproducing system comprising a plurality of audio devices. The plurality of audio devices comprises two or more signal reproducing devices, wherein each signal reproducing device comprises a logic circuit and a loudspeaker arranged in a housing, wherein the loudspeaker is arranged to receive an audio signal for playing from the logic circuit via a digital to analog converter, DAC, and an amplifier. In some embodiments, the DAC and amplifier may be integrated in a combined unit. Each audio device further comprises a first and a second optical data connector, the first and second optical data connectors being in data communication with the logic circuit and being arranged on opposite sides of the housing. The two or more signal reproducing devices are configured to be mutually arrangeable such that the first optical data connector on one signal reproducing device is connectable directly with the second optical data connector on a proximal signal reproducing device in an arrangement to establish data communication link between the logic circuits of the signal reproducing devices. The logic circuit of each of the two or more signal reproducing devices are configured to perform the method according to the abovementioned first aspect of the invention.

In an embodiment, at least one of the two or more signal reproducing devices comprise an additional optical data connector, the additional optical data connector being in data communication with the logic circuit. In this way, digital input streams e.g. from a connected musical instrument may be conveniently coupled to the sound reproduction system.

In an embodiment, the signal reproducing devices further comprise an accelerometer for determining a device orientation of the device, e.g. horizontally, vertically, etc.. In this way, the device orientation may be used as a factor when determining the device-specific audio signal compensation for the signal reproducing device, as mentioned above.

The first and second aspects of the present invention may be combined. These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter. BRIEF DESCRIPTION OF THE FIGURES

The sound producing system and method of controlling said system according to the invention will now be described in more detail with regard to the accompanying figures. The figures show one way of implementing the present invention and is not to be construed as being limiting to other possible embodiments falling within the scope of the attached claim set.

Figure 1 illustrates embodiments of sound reproducing systems according to the invention,

Figure 2 illustrates data communication between two audio devices according to an embodiment of the system of the invention,

Figure 3 is a flow chart of the method according to the invention,

Figure 4 illustrates different types of device-specific audio stream corrections, Figure 5 illustrates a signal flow useful in connection with the method and system according to the invention,

Figure 6 shows details of an embodiment of the sound reproducing system according to the invention, and

Figure 7 illustrates mixing of audio streams into the master audio stream according to the invention.

DETAILED DESCRIPTION OF AN EMBODIMENT

Figure 1a illustrates a sound reproducing system 100 according to an embodiment of the invention in a non-connected state. The modular system 100 comprises a first audio device 110 and a second audio device 120. The audio devices 110, 120 both comprise a loudspeaker 130 mounted in a first and second housing 140, 150, respectively. The audio devices 110, 120 are therefore also called signal reproducing devices 160. Further, in each of the first housing 140 and the second housing 150 are mounted a first optical connector 142 and a second optical connector 152 on opposite sides of the respective housings 140,150. The optical connectors 142, 152 are arranged for enabling bidirectional, close-distance, free- space communication (e.g. millimeter or centimeter scale distances) with other audio devices, such as between the first and the second audio device 110, 120. Thus, simply by placing the second audio device 120 on top of, or beside, the first audio device 110 such that the first and second free-space optical connectors 142, 152 align, communication is enabled between the two audio devices 110, 120. The audio devices 110, 120 may advantageously be provided with alignment aids to enable the user easily and robustly achieve such alignment. Figure 1b illustrates the sound reproducing system 100 of figure 1a having been expanded with additional audio devices, specifically two more signal reproducing devices 160 for a total of four, and an additional audio device. In this example, the additional audio device is shown as a signal generating device 170, i.e. as a device adapted for generating a signal for the signal reproducing devices 160 to reproduce. For instance, a signal generating device 170 may be adapted for receiving an audio signal from, e.g., a microphone or an instrument, and for generating a digital audio stream for further use in the signal reproducing system that corresponds to the received audio signal. Alternatively, the sound reproducing system could be expanded with a signal modifying device adapted for modifying a signal received from the other audio devices 110,120 before transmitting the modified signal back to the sound reproducing devices 160 for reproduction, or a signal recording device adapted for recording a signal as also played by the signal reproducing devices 160. In this figure, all four signal reproducing devices 160 are shown to be substantially identical. However, in other configurations, different types of signal reproducing devices 160 could be combined in a system, such as a high frequency reproducing device and a low frequency reproducing device, e.g. a separate subwoofer and/or a tweeter. We also note that this configuration is merely an example and that many other configurations or combinations are envisioned, e.g. having three, four, or six devices (rather than the two of figure 1 a or 5 of figure 1b), or that signal modifying devices or signal recording devices could also be included. The system is modular such that the first audio device 110 may be used by itself as a loudspeaker, or such that additional audio devices may be added e.g. to increase a maximum sound volume obtainable by the system 100, or to provide additional capabilities to the system 100.

Figure 2 illustrates details of the sound reproducing system 100 according to the invention. The first audio device 110 is here illustrated to be placed as a bottom device of a stack, and the second audio device 120 is being placed thereon as a top device. For illustration, the distance between the two devices 110, 120 has been exaggerated. The first optical connector 142 on the first audio device 110 is seen to be arranged on a top side of the device 110 so as to allow data communication after stacking the devices. The first optical connector 142 comprises a first optical transmitter 144, such as a light emitting diode (LED), and a first optical receiver 146, such as a photo diode. The second optical connector 152 corresponds to the first optical connector 142, and also includes an optical transmitter 154 and receiver 156. As the audio devices 110, 120 are designed to be in close contact before establishing the data connection via the optical connectors 142, 152, LEDs having a relatively broad emission cone may be tolerated, as the optical receiver 146, 156 is close and therefore covers a broad part of the emission cone. Figure 3 is a flow chart of the method 300 of controlling a sound reproducing system 100 according to the invention. First step is arranging 302 the two or more signal reproducing devices in an arrangement to establish a data communication link. This may for instance mean stacking the devices on top of each other, or in a side-by- side configuration. One or more digital input audio streams 303 are then received 304 by the signal reproducing devices 304, either by receiving a direct analog audio input via an analog to digital converter, ADC, or from a signal generating device coupled to either of the signal reproducing devices. Thus, the system provides a great degree of freedom in setting up signal inputs. Each of the two or more signal reproducing devices, in turn 305, receives and mixes 304 any digital input audio streams 303 received into a combined digital audio stream, which is then transmitted to a next signal reproducing device in the arrangement. The last signal reproducing device in the arrangement then mixes the combined digital audio stream as received from a preceding signal reproducing device and any digital input audio streams received directly by the last signal reproducing device into a master audio stream 306 for reproducing by the signal reproducing devices. The master audio stream is then distributed 308 to all of the two or more signal reproducing devices in the arrangement. Mixing of the combined digital audio stream and distribution as the master audio stream is further illustrated in FIG. 7 and the description thereof below. A stack position of each of the two or more signal reproducing devices is then determined 310, either by one of the signal reproducing device for all the signal reproducing devices or individually by each of the signal reproducing devices, which stack position is then used as a basis to establish 312 a device-specific audio signal correction for each of the two or more signal reproducing devices in the arrangement. Finally, a device-specific output audio stream is then prepared 314 by applying the device-specific audio signal correction to the master audio stream for each of the signal reproducing devices, before reproducing 316 the individual device-specific output audio streams by the respective signal reproducing devices. We note that one or more of the steps may be performed in another order than listed here. For instance, step 310 may in some embodiments be performed before step 308.

Figure 4 illustrates different types of device-specific audio stream corrections, which may be desirable for certain user environments.

In figure 4a, a sound reproducing system 100 with three signal reproducing devices 160 is located on a floor or on the ground 400. This placement will particularly influence the sound 402 from the bottom-most device, Device C, as at least some frequency bands will tend to be reflected more than others by the floor 400. This proximity effect on the sound will decrease with distance from the floor, such that Device A will be the least affected and Device B will be in between. By providing a device-specific audio signal correction to account for this effect to the output of Device C, and optionally to a less degree to the output of Device B, this problem may be alleviated. In some cases, a simple volume attenuation may be sufficient, while in other cases an equalizer compensation is needed.

Figure 4b illustrates that if a listeners position 404 is not centered with respect to the signal reproducing devices 160, there will be a sound path length difference for the audio signal reproduced by Device A, 402a, Device B, 402b, and Device C, 402c, which generally results in a sound phase difference. By precompensating for this phase difference by applying a device-specific audio correction in the form of a variable phase delay, this effect may be minimized for a selected listener position or listener direction. I.e. by instructing Device A to apply the largest phase delay and Device C to apply the least phase delay or even no phase delay, the sound signals from the three devices will arrive at the listener position 404 with a minimized phase difference. In the case where the arrangement is a vertical stack of signal reproducing devices 160, this compensation may be applied to account for a relative, average ear height of the listeners compared to the position of the system. In the case of a horizontal stack, it may be desirable to compensate for a direction to a preferred listening area, which is non-normal to the stack. An example of use of this embodiment is beam-forming, wherein the combined audio output from the group of signal reproducing devices 160 is predominantly directed in a desired, relatively narrow, direction.

Figure 4c illustrates a sound reproducing system 100 corresponding to the one shown in figure 4a, but arranged horizontally on a floor surface 400. Each of the sound reproducing devices 160 in this example comprise an accelerometer for determining a device orientation, as indicated by the arrows 406. As the sound reproducing devices 160 are all at the same level with regards to the floor 400, the compensation to account for proximity to the floor, as described for fig. 4a is not relevant in this configuration. Thus, by using the device orientation 406 input from the accelerometers, the device-specific audio signal compensation may be better optimized for the particular configuration of the system.

Figure 4d left and right illustrates another example of using the device orientation 406 input for establishing an improved device-specific audio signal compensation. In this case, only one signal reproducing device 160 is shown, but the principle also applies for multiple devices. The signal reproducing device 160 is here shown to be a two-way speaker unit, i.e. by comprising both a treble speaker 408 and a bass speaker 410. An optimum device-specific signal compensation will be different depending on whether the signal reproducing device is oriented such that the bass speaker 410 is located towards the floor 400 (as illustrated in the left figure), or towards the top (right). Thus, an improved compensation is achieved by sensing the device orientation 406 of the signal reproducing device 160.

Figure 5 illustrates a signal flow 500 useful in combination with the method and the sound reproducing system 100 according to the invention. The signal flow 500 prescribes the data communication from the transmitter side 502 device to the receiver side 504 device, over an air gap 506 as provided by the free-space optical connectors as described above. On the transmitter side 502, system data 508 and audio data 510 are multiplexed in a multiplexer 512 before being transmitted by the optic transmitter 514. On the receiver side 504, the optic receiver 516 receives the multiplexed optical data stream, which is then demultiplexed in a demultiplexer 519 to reproduce the system data 518 and audio data 520.

Figure 6 schematically shows an example of the sound reproducing system 100 according to the invention. In this embodiment, the system comprises three signal reproducing devices 160, i.e. devices having a loudspeaker 130: the first audio device 110, the second audio device 120, and the third audio device 600. Each signal reproducing device 160 comprises a digital to analog converter (DAC) 602 and an amplifier (AMP) 604 to supply the loudspeaker with an analog sound signal to reproduce. According to an example, the logic circuit 606 of a first audio device 110 may receive an optional digital first input audio signal 608, for instance from an external signal generating device or an analog input signal received through an analog to digital converter (ADC, not shown), and transmit this audio signal via its first optical connector 142 to the second optical connector 152 of the second audio device 120. Since the first audio device 110 is not connected to anything on its second optical connector 152, it may deduce that it is an outer-most device in the arrangement, i.e. the bottom device in this case. The logic circuit 606 of the second audio device 120 mixes the audio signal received from the first audio device 110 with an optional second input audio signal 608 that the second audio device 120 may receive from another source. This combined audio stream is then transmitted via the first optical connector 142 of the second audio device 120 to the second optical connector 152 of a third audio device 600. Since the first optical connector 142 of the third audio device 600 is not connected to any other device, the third audio device 600 is able to deduce that it is the last audio device in the chain of connected audio devices 110, 120, 600. The logic circuit 606 of the third audio device 600 may again receive an optional third input audio signal 608 from e.g. a signal generating device, and mix this third input audio signal with the audio signal received from the second audio device 120. Being the last device, the third audio device 600 now has mixed the master audio signal that is to be played by all the signal reproducing devices 160. Therefore, the master audio signal is now transmitted back through the chain from the third audio device 600 to the second audio device 120 and to the first audio device 110. Pending any individual device modifications or adjustments of the audio stream, each of the signal reproducing devices 160 now reproduces the master audio stream simultaneously. According to the inventive method, a device-specific audio signal correction is established for all three signal reproducing devices 110, 120, 600. In some embodiments, it is the device itself that will calculate this correction, while in other embodiments it would done by one device for all signal reproducing devices 160 in the system 100.

Figure 7 illustrates the mixing in a sound reproducing system. Device A in the bottom receives only input stream A, and therefore mixes stream A alone as a sole contribution to the combined audio stream A for transmission to device B. Device B receives the combined audio stream containing A from device A, and input stream B. Device B then mixes those two streams into a combined audio stream A+B and transmits that stream to device C. Device C additionally receives an input stream C, and therefore mixes the combined audio stream A+B+C. As device C is the last device in the sequence, the combined audio stream A+B+C is the master audio stream, which is therefore distributed back to devices B and A for reproduction.

Although the present invention has been described in connection with the specified embodiments, it should not be construed as being in any way limited to the presented examples. The scope of the present invention is set out by the accompanying claim set. In the context of the claims, the terms "comprising" or "comprises" do not exclude other possible elements or steps. Also, the mentioning of references such as "a" or "an" etc. should not be construed as excluding a plurality. The use of reference signs in the claims with respect to elements indicated in the figures shall also not be construed as limiting the scope of the invention. Furthermore, individual features mentioned in different claims, may possibly be advantageously combined, and the mentioning of these features in different claims does not exclude that a combination of features is not possible and advantageous.

LIST OF REFERENCE NUMBERS

100 sound reproducing system 110 first audio device

120 second audio device

130 loudspeaker

140 first housing

142 first optical connector

144 first optical transmitter 146 first optical receiver

150 second housing

152 second optical connector

154 second optical transmitter

156 second optical receiver

160 signal reproducing device

170 signal generating device

302, 304, 306, 308, 310, 312, 314, 316 method steps

303 digital input audio stream

400 floor/ground

402, 402a, 402b, 402c sound path

404 listener position

406 device orientation

408 treble speaker

410 bass speaker

500 signal path

502 transmitter side

504 receiver side

506 air gap

508 system data

510 audio data

512 multiplexer

514 optic transmitter

516 optic receiver

518 system data

520 audio data

600 third audio device

602 digital to analog converter (DAC)

604 amplifier

606 logic circuit

608 input audio signal

A, B, C, A+B, A+B+C audio streams

Claims

CLAIMS . Method of controlling a sound reproducing system, wherein the system comprises a plurality of audio devices, which plurality of audio devices comprises two or more signal reproducing devices, wherein each signal reproducing devices comprises: a logic circuit and a loudspeaker arranged in a housing, wherein the loudspeaker is arranged to receive an audio signal for playing from the logic circuit via digital to analog converter, DAC, and an amplifier, each signal reproducing devices further comprises a first and a second optical data connector, the first and second optical data connectors being in data communication with the logic circuit and being arranged on different sides of the housing, optionally, an additional optical data connector, the additional optical data connector being in data communication with the logic circuit, and wherein the two or more signal reproducing devices are configured to be mutually arrangeable such that the first optical data connector on one signal reproducing device is connectable directly with the second optical data connector on a proximal signal reproducing device in an arrangement to establish a bidirectional data communication link between the logic circuits of the signal reproducing devices, the method comprising: arranging the two or more signal reproducing devices in sequence in an arrangement to establish the bidirectional data communication link, for each of the two or more signal reproducing devices in the sequence, o if one or more digital input audio streams are received via the first, second, and/or additional optical data connector(s), mix the one or more digital input audio streams into a combined digital audio stream, o if there are additional signal reproducing devices in the sequence, transmit the combined digital audio stream as a digital input audio stream to a next signal reproducing device in the sequence, else transmit the combined audio stream as a master audio stream to all of the two or more signal reproducing devices in the arrangement for reproduction, determining a stack position of the two or more signal reproducing devices arranged in the arrangement, establishing a device-specific audio signal correction for each of the two or more signal reproducing devices in the arrangement, wherein the devicespecific audio signal correction is based on the stack position of the specific signal reproducing device in the arrangement, preparing a device-specific output audio stream from the master audio stream by applying the device-specific audio signal correction for each of the two or more signal reproducing devices, reproducing the device-specific output audio stream via the DAC, amplifier, and loudspeaker of each of the two or more signal reproducing devices. The method according to claim 1, wherein the method comprises the step that if the first signal reproducing device receives no digital input audio stream, it transmits an empty stream to the second signal reproducing device in the sequence. The method according to any one of the preceding claims, wherein the devicespecific audio signal correction comprises a phase correction for compensating a sound path length difference to a listener. The method according to any one of the preceding claims, wherein the devicespecific audio signal correction comprises a correction for a communication delay between the audio devices in the sound reproducing system. The method according to any one of the preceding claims, wherein the devicespecific audio signal correction comprises a volume attenuation of at least a part of the frequency spectrum for compensating for proximity effects from a wall or floor. The method according to any one of the preceding claims, wherein the devicespecific audio signal correction comprises an equalizer compensation. The method according to any one of the preceding claims, wherein one audio device of the sound reproducing system determines the device-specific audio signal correction for the two or more signal reproducing devices. The method according to any one of claims 1-6, wherein the device-specific audio signal correction is determined individually by each signal reproducing device, based on the stack position of said signal reproducing device. The method according to claim 8, wherein the device-specific output audio stream for a particular signal reproducing device is prepared by said signal reproducing device from the master audio stream and the device-specific audio signal correction. 16 The method according to any one of the preceding claims, wherein the devicespecific audio signal correction for a specific signal reproducing device is further established based on device capabilities of said signal reproducing device. The method according to any one of the preceding claims, wherein the devicespecific audio signal correction of a specific signal reproducing device is further established in response to a device metrics of said signal reproducing device. The method according to any one of the preceding claims, wherein at least one of the two or more signal reproducing devices further comprise an accelerometer for determining a device orientation, and wherein the method comprises further establishing the device-specific audio signal correction based on the device orientation. Sound reproducing system, wherein the system comprises a plurality of audio devices, which plurality of audio devices comprises two or more signal reproducing devices, wherein each signal reproducing device comprises: a logic circuit and a loudspeaker arranged in a housing, wherein the loudspeaker is arranged to receive an audio signal for playing from the logic circuit via digital to analog converter, DAC, and an amplifier, each audio device further comprises a first and a second optical data connector, the first and second optical data connectors being in data communication with the logic circuit and being arranged on different sides of the housing, and wherein the two or more signal reproducing devices are configured to be mutually arrangeable such that the first optical data connector on one signal reproducing device is connectable directly with the second optical data connector on a proximal signal reproducing device in an arrangement to establish a bidirectional data communication link between the logic circuits of the signal reproducing devices, wherein the logic circuit of each of the two or more signal reproducing devices are configured to perform the method according to any one of the preceding claims. The sound reproducing system according to claim 13, wherein at least one of the two or more signal reproducing devices comprise an additional optical data connector, the additional optical data connector being in data communication with the logic circuit. 17 The sound reproducing system according to any one of claims 13 or 14, wherein the signal reproducing devices further comprise an accelerometer for determining a device orientation.