JP5656421B2 - Crossover frequency determination device and sound field control device - Google Patents

Description

  The present invention relates to a method for setting a crossover frequency in a sound field control apparatus.

  In audio products, home theater products, etc., systems capable of reproducing 5.1 channel audio signals are known. Such a system is connected to a plurality of speakers such as left and right front speakers, a center speaker, a surround speaker, and a subwoofer. In this case, when the low-frequency reproduction capability of each speaker such as the front speaker, the center speaker, and the surround speaker is not sufficient, the low-frequency component of the signal of the channel corresponding to those speakers is converted into a sub-frequency reproduction capability. It is preferable to distribute and distribute to a woofer or other speaker. For example, if the center speaker is a speaker with insufficient low-frequency playback capability and the left and right front speakers are speakers with sufficient low-frequency playback capability, the low-frequency component of the center channel signal is distributed to the left and right front speakers. May play. Further, when all speakers other than the subwoofer are speakers with insufficient low-frequency reproduction capability, the low-frequency component of the signal of the channel other than the subwoofer may be distributed to the subwoofer for reproduction. In such a case, in the sound field control device, it is important to appropriately set the crossover frequency between the subwoofer and the other speakers.

  In many conventional sound field control devices, the user manually operates the crossover frequency of each speaker. On the other hand, Patent Document 1 discloses a method in which the system automatically determines the crossover frequency.

Japanese Patent Laid-Open No. 2005-253001

  In the method of automatically setting the crossover frequency, such as Patent Document 1, the crossover frequency is set based on the low frequency reproduction capability of each speaker connected to the system. However, if the crossover frequency is simply set based on the low frequency reproduction capability of each speaker, the setting may be such that the user feels uncomfortable in terms of localization of the sound image.

  Examples of problems to be solved by the present invention include the above. An object of the present invention is to automatically determine a crossover frequency so that a user does not feel uncomfortable from the viewpoint of localization of a sound image.

The invention according to claim 1 is a crossover frequency determination device used in a sound field control device connected to a plurality of speakers, which outputs a test signal from each of the plurality of speakers and collects sound with a microphone. A temporary determination means for determining a temporary determination value of a crossover frequency for each of the plurality of speakers, and a channel to which a speaker having insufficient low-frequency reproduction capability is connected based on the configuration of the plurality of speakers. Low-frequency supply destination determination means for determining whether or not the low-frequency component of the signal is supplied to the channel to which the low-frequency dedicated speaker is connected, and when the low-frequency component is supplied to the low-frequency dedicated speaker, when the low-frequency supply destination determination means determines to output the value limited by the first upper value determined tentative decision value in advance as the determination value of the crossover frequency, the low frequency component is low pass When the low-frequency supply destination determination unit determines that the speaker is not supplied to the connected channel, the temporary determination value is limited to a predetermined second upper limit value that is a frequency higher than the first upper limit value. Crossover frequency determining means for outputting the determined value as a determination value of the crossover frequency.

It is a block diagram which shows the structure of the audio system to which this invention is applied. It is a figure which shows the example of arrangement | positioning of each speaker. It is a figure which shows the example of a speaker structure. It is a block diagram which shows typically an example of the process by a signal processing circuit. It is a flowchart of a crossover frequency determination process. It is a flowchart of a sense of incongruity prevention process and a low-frequency range amount emphasis process. It is another flowchart of a sense of incongruity prevention process and a low frequency range feeling emphasis process.

  According to a preferred embodiment of the present invention, a crossover frequency determination device used in a sound field control device connected to a plurality of speakers outputs a test signal from each of the plurality of speakers and collects sound with a microphone. A temporary determination means for determining a temporary determination value of a crossover frequency for each of the plurality of speakers, and a channel to which a speaker having insufficient low-frequency reproduction capability is connected based on the configuration of the plurality of speakers. Low-frequency supply destination determination means for determining whether or not the low-frequency component of the signal is supplied to the channel to which the low-frequency dedicated speaker is connected, and when the low-frequency component is supplied to the low-frequency dedicated speaker, A crossover cycle for outputting a value obtained by limiting the temporary determination value with a predetermined first upper limit value as a determination value of the crossover frequency when the low frequency supply destination determination unit determines And a number determination means.

  Various speakers such as a front speaker, a surround speaker, and a subwoofer are connected to the sound field control device. Among these, speakers with sufficient low-frequency reproduction capability, such as low-frequency dedicated speakers such as subwoofers, and speakers with insufficient low-frequency reproduction capability are included. In the crossover frequency determination device, first, a test signal is output from each speaker, and by analyzing the frequency characteristics of the signal obtained by collecting the sound with a microphone, a temporary determination value of the crossover frequency of each speaker is obtained. Desired.

  On the other hand, the sound field control device, based on the presence or absence of a speaker connected to each channel, and the characteristics of each speaker, the low-frequency component of the signal of the channel to which a speaker with insufficient low-frequency reproduction capability is connected, It is determined in advance to which other speakers having sufficient low-frequency reproduction capability to supply and reproduce. The low frequency supply destination judging means refers to this information. When the low frequency component of the signal of the channel to which the speaker having insufficient low frequency reproduction capability is connected is supplied to the channel to which the low frequency dedicated speaker is connected, the provisional determination value is determined in advance. A value limited by the first upper limit value is output as a determination value of the crossover frequency. This crossover frequency refers to the crossover frequency between the low-frequency dedicated speaker and the other speakers.

  Here, the first upper limit value is set in the vicinity of the lower limit of the frequency that changes the localization of the sound image when reproduced by the low-frequency dedicated speaker, and is preferably set to about 100 Hz. As a result, when the low-frequency component of a channel connected to a speaker with insufficient low-frequency playback capability is distributed to the channel to which a low-frequency dedicated speaker is connected and played back, up to a very high frequency component is installed. As a result of reproduction from a low-frequency dedicated speaker whose position is not clear, it is possible to prevent a problem that the localization of the sound image becomes unnatural and the user feels uncomfortable.

  In one aspect of the above crossover frequency determination device, the low frequency supply destination determination means determines that the low frequency component is not supplied to the channel to which the low frequency dedicated speaker is connected. In addition, a value obtained by limiting the temporary determination value with a predetermined second upper limit value is output as a determination value for the crossover frequency. The second upper limit value is preferably set to a frequency that is lower than the lower limit of the frequency corresponding to the human voice or a slight margin. As a result, it is possible to prevent a problem that a human voice is heard from a strange direction when the low frequency component is distributed and reproduced to speakers other than the low frequency dedicated speaker.

  Another aspect of the above crossover frequency determination device is a speaker configuration for determining whether the configuration of the plurality of speakers includes only a low-frequency dedicated speaker and a speaker with insufficient low-frequency reproduction capability. When the speaker configuration determination unit determines that the configuration of the plurality of speakers further includes only a low-frequency dedicated speaker and a speaker with insufficient low-frequency reproduction capability, the crossover frequency determination unit includes: Regardless of the temporary determination value, the crossover frequency is set to a predetermined fixed value. When the configuration of a plurality of speakers includes only a low-frequency dedicated speaker and a speaker with insufficient low-frequency reproduction capability, it can be estimated that the user is a type that places little importance on the directionality of the sound image. Therefore, in this case, the crossover frequency is set to a fixed value, and reproduction is performed with sufficient power from the low-frequency dedicated speaker up to a certain high frequency band.

  Another aspect of the above crossover frequency determination device further includes speaker configuration determination means for determining whether the configuration of the plurality of speakers is a configuration not including a surround speaker, and the configuration of the plurality of speakers is When the speaker configuration determination unit determines that the configuration does not include a surround speaker, the crossover frequency determination unit determines a value obtained by limiting the temporary determination value with a predetermined third upper limit value as a crossover frequency. Output as a value. The third upper limit value is preferably set to a frequency that is lower than the lower limit of the frequency corresponding to the human voice or a slight margin. As a result, it is possible to prevent a problem that a human voice is heard from a strange direction when the low-frequency component is distributed to the low-frequency dedicated speaker or other speakers and reproduced.

  In another aspect of the above crossover frequency determination device, the temporary determination unit determines a maximum value of the temporary determination values obtained for each of the plurality of speakers as a temporary determination value for all of the plurality of speakers. And As a result, the signals of all the channels are processed by the same band limiting filter, and the phase characteristics can be made uniform, so that it is possible to prevent a sense of incongruity in hearing during reproduction.

  In another embodiment of the present invention, the above-described crossover frequency determination device and setting means for setting a determination value of the crossover frequency in a band limiting filter provided in each of the channels of the plurality of speakers are provided. A sound field control device can be configured.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

(System configuration)
FIG. 1 is a block diagram showing a configuration of an audio system which is an example of a sound field control device to which a crossover frequency determination device of the present invention is applied.

  In FIG. 1, an audio system 100 includes a signal processing circuit 2 to which digital audio signals SL, SC, SR, SLS, SRS and SSW are supplied from a sound source 1 such as a CD player or a DVD player through a signal transmission path of a plurality of channels. A measurement signal generator 3 is provided.

  The audio system 100 includes a signal transmission path of a plurality of channels, but in the following description, each channel may be expressed as “L channel”, “R channel”, or the like. In addition, when referring to all of a plurality of channels in the representation of signals and components, the suffixes of reference numerals may be omitted. Further, when referring to signals and components of individual channels, subscripts for identifying the channels are attached to the reference numerals. For example, “digital audio signal S” means digital audio signals SL to SSW of all channels, and “digital audio signal SL” means digital audio signals of only the L channel. .

  Furthermore, the audio system 100 includes D / A converters 4L to 4SW that convert the digital outputs DL to DSW processed for each channel by the signal processing circuit 2 into analog signals, and these D / A converters 4L to 4SW. Amplifiers 5L to 5SW for amplifying each analog audio signal output from. The analog audio signals SPL to SPSW amplified by these amplifiers 5 are supplied to a plurality of speakers 6L to 6SW arranged in a listening room 7 as illustrated in FIG. 2 and reproduced.

  The audio system 100 also includes a microphone 8 that collects reproduced sound at the listening position in the listening room 7, an amplifier 9 that amplifies the collected signal SM output from the microphone 8, and an output of the amplifier 9 that is digitally collected. And an A / D converter 10 that converts the sound data DM and supplies the sound data DM to the signal processing circuit 2.

  As shown in FIG. 2, for example, as shown in FIG. 2, the speakers are arranged in front of the listening position RV in front of the listening position RV with two left and right front speakers (front left speaker, front right speaker). ) 6L, 6R and a center speaker 6C are arranged. In addition, two left and right channel surround speakers 6LS and 6RS are arranged behind the listening position RV, and a subwoofer 6SW dedicated to low frequency reproduction is arranged at an arbitrary position. The audio system 100 supplies analog audio signals SL to SPSW in which the frequency characteristics, the signal level of each channel, and the signal arrival delay characteristics are corrected to the six speakers 6L to 6SW and causes them to ring, thereby providing realistic sound. Realize space.

  The signal processing circuit 2 is formed by a digital signal processor (DSP) or the like, and receives digital audio signals of a plurality of channels from a sound source 1 that reproduces a CD, DVD, and other various music / video sources. The digital output signals DL to DSW are output by performing frequency characteristic correction, level correction and delay characteristic correction for each channel.

(Speaker configuration determination processing)
Now, before actually reproducing the signal from the sound source 1 as described above, the audio system 100 needs to be set in advance. Specifically, after the user connects a plurality of speakers as described above to the audio system 100, the audio system 100 first executes speaker configuration determination processing.

  When the user connects each speaker to the audio system 100 and inputs an instruction, the audio system 100 automatically executes speaker configuration determination processing. Specifically, the audio system 100 generates pink noise and other measurement signals from the measurement signal generator 3, and the measurement sound from the speaker 6 via the signal processing circuit 2, the D / A converter 4, and the amplifier 5. To the listening room 7. The output measurement sound is collected by the microphone 8 and sent to the signal processing circuit 2 via the amplifier 9 and the A / D converter 10. The signal processing circuit 2 determines the characteristics such as the presence / absence of connection of each speaker and the reproduction band of each speaker based on the frequency characteristics of the sound collection data DM obtained through the microphone 8, and thereby the audio system The configuration of a plurality of speakers connected to 100 is determined.

  An example of speaker configuration information obtained by the speaker configuration determination process is shown in FIG. FIG. 3 illustrates three cases as a speaker configuration.

  Case 1 is an example in which a front speaker, a center speaker, a surround speaker, and a subwoofer are connected to the audio system 100. Based on the reproduction band of each speaker, the front speaker and the surround speaker are determined to be large speakers, and the center speaker is determined to be a small speaker. In case 2, it is determined that the front speaker and the surround speaker are large speakers and the center speaker is a small speaker, and the subwoofer is not connected. In case 3, it is determined that the front speaker is a large speaker, the center speaker and the surround speaker are small speakers, and a subwoofer is also connected.

  “Large speaker” refers to a speaker having sufficient low-frequency reproduction capability, and includes so-called low-frequency speakers and full-band speakers. On the other hand, the “small speaker” refers to a speaker with insufficient low-frequency reproduction capability, and includes a so-called middle / high-frequency speaker. As described above, the distinction between the large speaker and the small speaker is based on the degree of the low-frequency reproduction capability, not the size of the speaker itself. Moreover, the “low-frequency dedicated speaker” refers to a speaker that handles an extremely low frequency range of about 20 to 100 Hz that cannot be sufficiently reproduced by a normal speaker, and is a subwoofer, for example.

  Further, when the audio system 100 determines the speaker configuration in this way, the audio system 100 automatically determines a low-frequency component distribution method based on the result. Here, “low-frequency component distribution” means that the low-frequency component of the channel signal to which a speaker with insufficient low-frequency reproduction capability is connected is supplied to another speaker having sufficient low-frequency reproduction capability, Say playing from that speaker. Specifically, based on the result of a prior experiment or the like, a low-frequency component distribution method is determined in advance for each combination of the presence / absence and characteristics (low-frequency reproduction capability) of each speaker connected to the audio system 100, and the audio Stored in system 100. The audio system 100 determines a low-frequency component distribution method in the case of the speaker configuration based on the presence / absence and characteristics of the speaker indicated by the speaker configuration obtained by the speaker configuration determination process.

  In the example of FIG. 3, in case 1, since the center speaker is a small speaker, the low frequency component of the center channel is distributed to the left and right front speakers and reproduced. In Case 2, since there is no subwoofer, the low frequency component of the center channel is distributed to the left and right front speakers and the left and right surround speakers and reproduced. In Case 3, the low frequency components of the center channel to which the small speakers are connected and the left and right surround channels are distributed to the subwoofer and reproduced.

  As described above, the audio system 100 determines the speaker configuration by performing the speaker configuration determination process, and the low frequency component of the channel to which the small speaker having the low frequency reproduction capability is connected is determined by any other It is also automatically determined whether to distribute to channels.

(Crossover frequency judgment processing)
(I) First Example Next, a first example of the crossover frequency determination process will be described. First, the crossover frequency will be described. FIG. 4 is a block diagram schematically showing a low-frequency component distribution process performed by the signal processing circuit 2. Actually, the signal processing circuit 2 is configured by a DSP or the like, and the low-frequency component distribution processing is performed by digital signal processing. FIG. 4 schematically shows this by a circuit diagram.

  FIG. 4 shows a low-frequency component distribution process when all five speakers other than the subwoofer are small speakers. The signals SL to SRS of the channels of the five speakers other than the subwoofer are supplied to the corresponding high-pass filters (HPF) 22L to 22RS, respectively. The signals SL to SRS of these five speaker channels are added to the subwoofer channel signal SWF through the adder 21 and supplied to the low-pass filter (LPF) 22SW.

  The controller 20 determines the crossover frequency Fx and supplies it to the high-pass filters 22L to 22RS and the low-pass filter 22SW. The crossover frequency Fx is set as a cutoff frequency of each of the high-pass filters 22L to 22RS and the low-pass filter 22SW. As a result, the signals DL to DRS output from the high-pass filters 22L to 22RS include only components in the higher frequency range than the crossover frequency Fx, and are reproduced from the corresponding small speakers 6L to 6RS. On the other hand, the signal DSW output from the low-pass filter 22SW includes components lower than the crossover frequency Fx of the signals of the six channels, and this is reproduced from the subwoofer 6SW. In this way, the low-frequency component of the channel to which a speaker having insufficient low-frequency reproduction capability is connected is distributed to the speaker having sufficient low-frequency reproduction capability and reproduced.

  FIG. 4 is merely a typical example of a method for distributing low-frequency components. Actually, as shown in FIG. 3 as a method of distributing the low frequency components, the low frequency components are distributed by different methods depending on the speaker configuration obtained by the speaker configuration determination process. For example, in case 1 in FIG. 3, since the center channel signal is distributed to the left and right front channels, the center channel signal Sc is added to the left and right front channel signals SL and SR, unlike the example of FIG. It will be. In the case 3, the center channel signal SC and the surround channel signals SLS and SRS are added to the subwoofer channel signal SWF. Unlike the example of FIG. 4, the front channel signals SL and SR are subwoofer signals. It is not added to the channel signal.

  Next, the crossover frequency determination process for determining the crossover frequency will be described. FIG. 5 shows a flowchart of the crossover frequency determination process. This process is executed by the audio system 100, particularly the signal processing circuit 2. Note that at the time when the crossover frequency determination process is executed, the above-described speaker configuration determination process is completed, and a plurality of speaker configurations connected to the audio system 100 and a method of distributing the low frequency components have already been determined. .

  First, the signal processing circuit 2 performs provisional determination of each speaker crossover frequency (step S10). Specifically, first, pink noise is generated from the measurement signal generator 3 and output to the listening room 7 is collected by the microphone 8, and the signal processing circuit 2 acquires the sound collection data DM. By adjusting the amplification degree of each of the amplifiers 5L to 5SW based on the sound collection data DM, the signal processing circuit 2 sets the speaker volume in all bands to a predetermined reference power (for example, 75 dBspl) for all the speakers. Next, pink noise is generated again from the measurement signal generator 3, which is band-limited by a 200 Hz low-pass filter and then output from each speaker. The output measurement sound is collected by the microphone 8, and the signal processing circuit 2 measures the power measured when the band is limited to 200 Hz or less (hereinafter referred to as “measurement power”) for each speaker.

  Then, the signal processing circuit 2 determines a temporary determination value of the crossover frequency of each speaker excluding the subwoofer by comparing the measured power and the reference power when the band is limited to 200 Hz or less. For example, if the difference between the measured power and the reference power is less than 6 dB, the signal processing circuit 2 sets the provisional determination value of the speaker's crossover frequency to 80 Hz. In addition, if the difference between the measured power and the reference power is 6 dB or more and less than 12 dB, the signal processing circuit 2 sets the provisional determination value of the speaker crossover frequency to 100 Hz. Furthermore, if the difference between the measured power and the reference power is 12 dB or more, the signal processing circuit 2 sets the provisional determination value of the speaker crossover frequency to 150 Hz. Thus, the signal processing circuit 2 outputs the temporary determination values FxL to FxRS of the crossover frequency for all speakers other than the subwoofer. The method of provisional determination of the crossover frequency described here is merely an example, and the provisional determination value of the crossover frequency may be obtained for each channel by another known method.

  Next, the signal processing circuit 2 acquires the maximum value Fxmax among the obtained temporary determination values FxL to FxRS of the crossover frequency (step S20). Next, the signal processing circuit 2 refers to the current speaker configuration, which is the determination result of the speaker configuration determination processing that has already been performed (step S30), and determines whether or not the current speaker configuration is a predetermined speaker configuration. Determine (step S40). Specifically, the signal processing circuit 2 determines whether the current speaker configuration corresponds to either (A) a configuration including only a subwoofer and a small speaker, or (B) a configuration not including a surround speaker. Determine whether.

  When the current speaker configuration does not correspond to the predetermined speaker configuration (step S40: No), the signal processing circuit 2 executes a discomfort prevention process (step S50).

  FIG. 6A shows details of the discomfort prevention process. The signal processing circuit 2 refers to the low-frequency signal distribution method based on the current speaker configuration, and determines whether or not the low-frequency component of the channel to which the small speaker is connected is distributed to the subwoofer (step S51). . For example, Case 3 shown in FIG. 3 corresponds to the case where the low frequency component of the channel to which the small speaker is connected is distributed to the subwoofer.

  When the low frequency component of the channel to which the small speaker is connected is distributed to the subwoofer (step S51: Yes), the signal processing circuit 2 sets the upper limit value Flimit of the crossover frequency to the first upper limit value 100Hz, and the crossover Return to the frequency determination process. On the other hand, when the low frequency component of the channel to which the small speaker is connected cannot be distributed to the subwoofer (step S51: No), the signal processing circuit 2 directly returns to the crossover frequency determination process.

  Then, the signal processing circuit 2 determines the crossover frequency Fx (step S70). Specifically, the maximum value Fxmax of the temporary determination value of the crossover frequency obtained in step S20 is limited by the upper limit value Flimit, and the crossover frequency Fx is determined. Therefore, when the upper limit value Flimit is set by the discomfort prevention processing, the crossover frequency Fx becomes the upper limit value Flimit if the maximum value Fxmax is larger than the upper limit value, and the crossover frequency Fx becomes the maximum value Fxmax if smaller than the upper limit value. Become. On the other hand, when the upper limit value Flimit is not set by the discomfort prevention process, the maximum value Fxmax determined in step S20 becomes the crossover frequency Fx.

  As described above, the reason for limiting the upper limit value of the crossover frequency by the discomfort prevention process is as follows. Basically, according to the low-frequency component distribution method described above, the low-frequency component of a channel connected to a speaker with insufficient low-frequency reproduction capability is distributed to other speakers with sufficient low-frequency reproduction capability. It is preferable to do. However, in general, in comparison with left and right speakers, low-frequency dedicated speakers such as subwoofers have a characteristic that their installation positions vary depending on the user and are not clear. Therefore, if the low-frequency component of a small speaker with insufficient low-frequency reproduction capability is distributed to the subwoofer and played, the low-frequency component is allocated to the subwoofer up to a very high frequency. Therefore, the localization of the sound image becomes unnatural and the user may feel uncomfortable. Specifically, if a component in a band higher than about 100 Hz is distributed to the subwoofer, for example, when the subwoofer is located at the corner of the listening room, the sound image moves there, and the user You may feel uncomfortable. Therefore, when discomfort prevention processing is executed and the low frequency components are distributed to the subwoofer, the upper limit of the low frequency components allocated to the subwoofer is limited so as not to cause the above-mentioned sound image discomfort. -ing On the other hand, if the low-frequency component is distributed to speakers other than the subwoofer, that is, speakers composed of left and right pairs such as left and right front speakers and left and right surround speakers, localization of the sound image may not be unnatural. Because there is no, it does not limit the upper limit of the low frequency component that can be distributed to the subwoofer.

  The first upper limit value “100 Hz” set as the upper limit value Flimit in step S52 is merely an example, and the application of the present invention is not limited to this. That is, the lower limit of the frequency band that affects the localization of the sound image or an arbitrary frequency determined by adding a slight margin can be set as the first upper limit value.

  Now, returning to the crossover frequency determination process shown in FIG. 5, when it is determined in step S40 that the current speaker configuration corresponds to the predetermined speaker configuration (step S40: Yes), the signal processing circuit 2 performs the low sound volume sense emphasis process. Is executed (step S60).

  FIG. 6B shows details of the low-frequency range emphasis processing. First, the signal processing circuit 2 determines whether or not the current speaker configuration includes only a subwoofer and a small speaker (step S61). In the case of a configuration with only a subwoofer and a small speaker (step S61: Yes), the signal processing circuit 2 forcibly sets the crossover frequency Fx to a fixed value of 150 Hz, and returns to the crossover frequency determination processing. On the other hand, when the configuration is not only the subwoofer and the small speaker (step S61: No), that is, when the current speaker configuration is only the front speaker without including the surround speaker (including the case where there is a subwoofer and the case where there is no subwoofer) The signal processing circuit 2 returns to the crossover frequency determination process as it is.

  In the crossover frequency determination process, the crossover frequency Fx is determined in step S70. At this time, when the crossover frequency Fx is forcibly set to a fixed value of 150 Hz in the low-frequency range emphasis processing, the crossover frequency Fx is 150 Hz as it is. On the other hand, in the case where the crossover frequency Fx is not forcibly set in the low frequency range emphasis processing, the signal processing circuit 2 sets the maximum value Fxmax of the temporary determination value determined in step S20 as the crossover frequency Fx. .

  Next, the reason why such low sound volume sense emphasis processing is performed will be described. As determined in step S40, when the speaker configuration is (A) a configuration including only a subwoofer and a small speaker, or (B) a configuration not including a surround speaker, the user selects a sound image. It can be assumed that the user is a type of user who does not care much about the direction of the user. Therefore, in the case of such a user, it is not necessary to prevent the sense of incongruity of the sound image as in the discomfort prevention processing, but the low-frequency volume is prioritized and the low-frequency component is sufficiently obtained through a speaker having sufficient low-frequency reproduction capability. It will be played back.

  Specifically, when the speaker configuration is only a subwoofer and a small speaker, as shown in step S62, the crossover frequency Fx is forcibly set to a fixed value of 150 Hz, and the low frequency component up to 150 Hz is subtracted. Play low frequency sound sufficiently by playing with a woofer. On the other hand, if the speaker configuration does not include surround speakers, the user can guess that the directionality of the sound image is not so much, but in this case, the low-frequency component of the small speaker channel is assumed to be the front. Since there are cases where reproduction is performed from a speaker and reproduction from a subwoofer, low frequency components are not necessarily distributed to the subwoofer. Therefore, the crossover frequency Fx is not forcibly set to a fixed value as in the case of the configuration with only the subwoofer and the small speaker.

  As described above, according to the crossover frequency determination processing of the present embodiment, when the low frequency component of the channel to which the small speaker is connected is distributed to the subwoofer based on the speaker configuration, the discomfort prevention processing is executed. Therefore, it is possible to prevent the user from feeling uncomfortable with the sound image. If the speaker configuration includes only a subwoofer and a small speaker, the user presumes that the volume of bass is more important than the directionality of the sound image, and the crossover frequency Fx is forcibly fixed to a higher frequency. Then, play the bass from the subwoofer enough. As described above, in this embodiment, the low frequency component can be reproduced by setting the crossover frequency by an appropriate method according to the configuration of the speaker connected to the audio system 100.

(II) Second Example Next, a second example of the crossover frequency determination process will be described. As described above, it is preferable that the low-frequency component of a channel to which a speaker having a low-frequency reproduction capability is basically connected is distributed to other speakers having a sufficient low-frequency reproduction capability. However, if the low-frequency component distributed to other speakers includes a very high frequency, an undesirable result occurs. Usually, the low-frequency component of a channel to which a small speaker such as a center channel is connected is distributed to a pair of large speakers arranged in front of the user, a pair of large speakers arranged behind the user, or a subwoofer. Will be played. Here, when the low frequency component distributed to the subwoofer includes a frequency corresponding to a human voice or the like (generally referred to as a frequency from about 150 Hz to a high frequency), the low frequency component is forwarded to the user's front. The user does not feel uncomfortable when distributing to the pair of large speakers located in the position, but when playing by distributing to the pair of large speakers or subwoofers located behind the user, the human voice is It can be heard from a pair of speakers located behind the subwoofer or a subwoofer placed in the corner of the room, and the user may feel uncomfortable.

  From this point of view, in the second embodiment, when a low frequency component of a channel to which a speaker with insufficient low frequency reproduction capability is connected is distributed to another speaker with sufficient low frequency reproduction capability, The upper limit of the crossover frequency is limited so that human voice is not included in the low frequency component. This prevents the user from feeling uncomfortable by hearing a human voice from a strange direction such as behind the user or a corner of the room.

  The main routine of the second embodiment of the crossover frequency determination process is the same as that shown in FIG. 6, and the details of the discomfort prevention process and the low sound volume feeling emphasis process are different from those of the first embodiment. FIG. 7A shows a flowchart of the discomfort prevention process according to the second embodiment, and FIG. 7B shows a flowchart of the low sound volume feeling emphasis process according to the second embodiment.

  First, the discomfort prevention process will be described. As shown in FIG. 7A, step S53 is added in the discomfort prevention process of the second embodiment. That is, in step S51, when it is determined that the low frequency component of the channel to which the small speaker is connected cannot be distributed to the subwoofer (step S51; No), the signal processing circuit 2 determines that the upper limit value Flimit of the crossover frequency. Is set to the second upper limit value 130 Hz (step S53). Accordingly, the crossover frequency Fx finally determined in step S70 is limited to the second upper limit value 130 Hz or less.

  This second upper limit value is determined as a frequency lower than the lower limit of the human voice frequency band, that is, about 150 Hz. In other words, if the lower limit of the human voice frequency is 150 Hz, and if some margin is given to this and the low frequency component of 130 Hz or higher is not distributed to other speakers, the human voice is behind the user. In addition, it is possible to prevent inconvenience that sound is heard from a direction with a sense of incongruity such as a direction in which the subwoofer is arranged. The frequency of 130 Hz is merely an example, and application of the present invention is not limited to this. That is, the second upper limit value in this case can be set to an arbitrary frequency that is lower than the lower limit frequency of the human voice by a predetermined margin. For the above purpose, the second upper limit value is set to a frequency higher than the first upper limit value set in step S52.

  If it is determined in step S51 that the low-frequency component of the small channel is distributed to the subwoofer, the upper limit value of the crossover frequency is limited to 100 Hz in step S52, so that the human voice is uncomfortable. The problem of hearing from a certain direction does not occur.

  Next, the processing for emphasizing the low range feeling will be described. As shown in FIG. 7B, step S63 is added in the low-frequency range emphasis processing of the second embodiment. That is, when it is determined in step S61 that the speaker configuration is not a configuration including only a subwoofer and a small speaker, that is, a configuration including no surround speakers (step S61; No), the signal processing circuit 2 determines that the crossover frequency The upper limit value Flimit is set to the third upper limit value 130 Hz (step S63). Thereby, the crossover frequency Fx finally determined in step S70 is limited to 130 Hz or less. Therefore, as in the case of the above-described discomfort prevention processing, it is possible to prevent a problem that a human voice is heard from a direction with a sense of discomfort, such as the user's back or the direction in which the subwoofer is arranged. The third upper limit value is normally set to the same value as the second upper limit value described above, and is set to a frequency higher than the first upper limit value.

  On the other hand, if it is determined in step S61 that the speaker configuration is only a subwoofer and a small speaker, the crossover frequency Fx is forcibly set to a fixed value of 130 Hz in step S62. There is no inconvenience that the voice can be heard from an uncomfortable direction.

  As described above, in the second embodiment, it is possible to prevent the inconvenience that the human voice can be heard from a direction with a sense of incongruity while maintaining the advantages of the sense of incongruity prevention processing and the low-frequency range emphasis processing.

(Modification)
In the embodiment of the above crossover frequency determination process, the signal processing circuit 2 determines the maximum value Fxmax among the temporary determination values FxL to FxRS of the crossover frequency obtained for each speaker in step S20. Based on this, one crossover frequency Fx is determined in step S70. Therefore, a unique crossover frequency Fx is set for all channels. However, the application of the present invention is not limited to this. That is, the process of step S20 may be omitted, and the crossover frequency Fx may be determined individually in step S70 for the temporary determination values FxL to FRS obtained for each speaker. Further, only one crossover frequency may be set for speakers constituting the pair, for example, left and right front speakers, left and right surround speakers, and the crossover frequency Fx may be determined individually for the other speakers.

  However, when different crossover frequencies are applied to each channel individually, different band limiting filters (HPF and LPF) are applied between the channels. Therefore, since the phase characteristics between them are different, there is a possibility that interference between channels occurs and the audible characteristics during reproduction deteriorate. In this respect, when a common crossover frequency is applied to all channels as in the above-described embodiment, there is an advantage that such a problem does not occur.

DESCRIPTION OF SYMBOLS 1 Sound source 2 Signal processing circuit 3 Signal generator for measurement 4 D / A converter 5, 9 Amplifier 6 Speaker 8 Microphone 10 A / D converter 20 Controller 21 Adder 22L-RS High-pass filter 22SW Low-pass filter

Claims (6)

A crossover frequency determination device used in a sound field control device connected to a plurality of speakers,
A temporary determination means for determining a temporary determination value of a crossover frequency for each of the plurality of speakers by outputting a test signal from each of the plurality of speakers and collecting the sound with a microphone;
Based on the configuration of the plurality of speakers, it is determined whether or not the low frequency component of the signal of the channel to which the speaker having insufficient low frequency reproduction capability is connected is supplied to the channel to which the low frequency dedicated speaker is connected. A low frequency supply destination determination means to
When the low-frequency supply destination determination unit determines that the low-frequency component is supplied to a low-frequency dedicated speaker, a value obtained by limiting the temporary determination value with a predetermined first upper limit value is determined as a crossover frequency. When the low-frequency supply destination determining means determines that the low-frequency component is not supplied to the channel connected to the low-frequency dedicated speaker, the temporary determination value is set to a frequency higher than the first upper limit value. And a crossover frequency determination means for outputting a value limited by a predetermined second upper limit value as a determination value of the crossover frequency. The crossover frequency determination device according to claim 1, wherein the second upper limit value is a frequency lower than a lower limit frequency of a human voice by a predetermined frequency . Speaker configuration determination means for determining whether the configuration of the plurality of speakers is a configuration including only a low-frequency dedicated speaker and a speaker with insufficient low-frequency reproduction capability;
When the speaker configuration determining unit determines that the configuration of the plurality of speakers includes only a low-frequency dedicated speaker and a speaker with insufficient low-frequency reproduction capability, the crossover frequency determining unit determines that the temporary determination value is Regardless of this, the crossover frequency determination device according to claim 1, wherein the crossover frequency is set to a predetermined fixed value. Speaker configuration determination means for determining whether the configuration of the plurality of speakers is a configuration not including a surround speaker;
When the speaker configuration determining unit determines that the configuration of the plurality of speakers does not include a surround speaker, the crossover frequency determining unit is a value obtained by limiting the temporary determination value with a predetermined third upper limit value. The crossover frequency determination device according to claim 3, wherein the crossover frequency determination value is output as a crossover frequency determination value.   5. The temporary determination means sets a maximum value among the temporary determination values obtained for each of the plurality of speakers as a temporary determination value for all of the plurality of speakers. 6. The crossover frequency determination apparatus according to claim 1. The crossover frequency determination device according to any one of claims 1 to 5,
A sound field control device comprising: setting means for setting a determination value of the crossover frequency in a band limiting filter provided in each of the channels of the plurality of speakers.

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