Loudspeaker box for cardioid radiation

Abstract

A loudspeaker box (1) for cardioid radiation is described, comprising a loudspeaker enclosure (5) having a front (F), a rear (R) diametrically opposite the front (F), and side walls (S) connecting the front (F) and rear (R). The loudspeaker enclosure (5) has a front loudspeaker chamber (7) terminated at the front (F) by a front loudspeaker (6), wherein a resonance channel (2) opens from the front loudspeaker chamber (7), and wherein the loudspeaker enclosure (5) has a rear loudspeaker chamber (8) terminated by a rear loudspeaker (3). The loudspeaker enclosure (5) has a side channel (4) opening at the side wall (S), and the rear loudspeaker (3) radiates laterally out of the side wall (S) via the side channel (4).

Description

[0001] The invention relates to a loudspeaker box for cardioid radiation with a loudspeaker enclosure having a front, a rear diametrically opposite the front, and side walls connecting the front and rear, wherein the loudspeaker enclosure has a front loudspeaker chamber closed at the front by a front loudspeaker, wherein a resonance channel opens from the front loudspeaker chamber, and wherein the loudspeaker enclosure has a rear loudspeaker chamber closed by a rear loudspeaker. The front loudspeaker chamber is separated from the rear loudspeaker chamber by an intermediate wall.

[0002] DE 10 2023 121 413 B4 discloses a loudspeaker system comprising a front loudspeaker enclosure with at least one first loudspeaker and a rear loudspeaker enclosure with at least one second loudspeaker. The rear loudspeaker enclosure is a bandpass enclosure with at least one first chamber and at least one second chamber. The first chamber has a first sound outlet, and the second chamber has a second sound outlet. The first and second sound outlets are offset from each other with respect to a main radiation direction of the front loudspeaker enclosure. The rear loudspeaker enclosure is implemented as a bandpass enclosure with two chambers and two offset sound outlets to improve directivity over a wide frequency range.

[0003] EP 3 229 488 B1 shows a loudspeaker system with a front enclosure containing one front loudspeaker and a rear enclosure containing two rear loudspeakers and an opening. The rear loudspeakers are located in the side walls of the rear enclosure and are oriented towards the sides of the loudspeaker system. An opening is positioned in the center of the rear wall to maximize the distance to the front of the loudspeaker system. The radiation pattern of the entire sound system can vary depending on the positions of the loudspeakers and the opening. The sound wave path from the front loudspeaker to the opening of the horn section and the sound wave paths from the rear loudspeakers to the opening of the horn section are each spaced at λ / 4.

[0004] US 10,123,111 B2 discloses a passive cardioid acoustic system that generates a relatively high low-frequency sound intensity in the forward direction. This is achieved by an acoustic circuit that modifies the strength and phase of the sound radiated from the inside of one or more vibrating diaphragms and combines it with the sound radiated from the outside of the diaphragms to cancel out some of the back radiation and enhance the forward radiation.

[0005] DE 2 100 884 A discloses a loudspeaker arrangement with a cardioid directional characteristic comprising at least one cone loudspeaker arranged at the front of a nearly closed housing, wherein at least one slot-shaped opening is provided in at least one of the side walls of the housing, which crosses the axis direction of the loudspeaker at nearly a right angle in a longitudinal extent.

[0006] DE 10 2019 108 423 A1 discloses a loudspeaker box with improved self-cooling, comprising a loudspeaker enclosure and a loudspeaker. For cooling, a metal section connected to the loudspeaker's flange ring projects into the enclosure and forms a channel wall of an air duct for heat dissipation.

[0007] DE 196 22 307 A1 discloses a low-frequency loudspeaker box that combines two separate transmission units, a woofer and a subwoofer unit, in a common enclosure. The subwoofer unit is implemented as a compound bandpass system in a push-pull configuration, while the woofer unit operates according to the bass-reflex principle.

[0008] DE 1 291 790 A discloses a loudspeaker box in which the rear of one or more loudspeakers is connected to sound outputs via sound passages. The sound passages are directed obliquely outwards with respect to the direction of sound radiation and terminate in outputs arranged on the front or side of the box.

[0009] US 7,551,062 B2 discloses a directed acoustic device comprising at least one transducer for generating at least two wave trains. The wave trains are guided by at least one waveguide along different paths to achieve directed radiation by destructive interference in directions greater than ninety degrees from the acoustic axis.

[0010] DE 20 2012 000 148 U1 discloses a loudspeaker arrangement comprising a cylindrical bass loudspeaker enclosure, a bass loudspeaker, and a central bass reflex port. At the end of the arrangement, a circumferential bass reflex slot open to the atmosphere is formed, connecting the bass reflex port to the end of the loudspeaker enclosure.

[0011] US 2005 / 0178611 A1 discloses a low-frequency loudspeaker enclosure (subwoofer) with at least one pair of loudspeakers mounted in the same enclosure, facing in opposite directions. The front loudspeaker is surrounded by side ports, while the rear loudspeaker radiates into a chamber that also has side ports.

[0012] The object of the present invention is to create an improved loudspeaker box in which the cardioid radiation is improved and the acoustic backward cancellation in the low-frequency range is extended to a larger frequency range.

[0013] The problem is solved with the loudspeaker boxes having the features of claim 1 and claim 8. Advantageous embodiments are described in the dependent claims.

[0014] In a first embodiment, the loudspeaker housing has a side channel, and the rear loudspeaker radiates laterally along the side wall via the side channel. The side channel is preferably limited by the rear wall.

[0015] It is proposed that the rear of the loudspeaker enclosure has a rear wall designed to deflect the rearward sound pressure of the diaphragm of the rear loudspeaker into the side channel, the rear wall having an opening in the area adjacent to the diaphragm for direct rearward sound radiation.

[0016] In another embodiment, it is proposed that the rear loudspeaker chamber is divided into a first and second rear loudspeaker chamber, which are closed off on two opposite side walls by rear loudspeakers whose diaphragms radiate laterally, wherein the first and second loudspeaker chambers are each connected to a side channel, which radiates laterally from the side wall next to the associated rear loudspeaker.

[0017] A bass reflex port is therefore present, featuring a lateral section in the form of a side channel through which bass reflex sound waves are radiated laterally outwards in the rear of the speaker enclosure. This broadens the sound wave cancellation caused by the resonance port over a wider frequency range and also becomes effective in the transition from the low-frequency to the mid-frequency range at approximately 200 Hz. This is achieved by positioning the Helmholtz resonator laterally via the side channels closer to the front-facing sound radiation, resulting in an improved cardioid directivity pattern of the speaker.

[0018] The resonance channel can exit on either side of the front speaker at the front of the speaker enclosure. This improves the effect of the front-facing Helmholtz resonator on the primary front-facing sound level.

[0019] The rear speaker chamber can be closed off by the rear speaker. In the first embodiment according to the invention, the rear of the speaker housing has a rear wall designed to deflect the sound pressure directed towards the rear from the diaphragm of the rear speaker into the side channel. This means that the resonance chamber of the rear speaker is not used for the sound energy of the side channel, but rather the sound energy radiated directly from the speaker diaphragm via the diaphragm's radiation plane in the direction of radiation from the rear speaker. This sound energy is deflected through the side channels by means of the at least partially closed rear wall.

[0020] The rear wall is open in the area adjacent to the membrane for rearward sound radiation.

[0021] A rear opening in the back panel adjacent to the diaphragm allows sound energy to be utilized in addition to rearward radiation. The speaker cabinet can still be placed close to a wall without affecting the diaphragm, particularly without causing it to tear, as the sound energy from the rear speaker is dissipated via the side channels. Utilizing the primary sound energy of the rear speaker ensures that a very high sound pressure level is radiated through the side channels to prevent cancellation.

[0022] The side channel can exit from the side walls on either side. This allows for symmetrical sound radiation.

[0023] The rear loudspeaker chamber can be enclosed at the rear by several rear loudspeakers. Therefore, when the present application refers to "one loudspeaker" and "one channel," this does not preclude the presence of further corresponding elements. Using multiple loudspeakers allows the loudspeaker box's performance to be increased and the radiation pattern to be more precisely adapted to the loudspeaker box's design and the surrounding environment.

[0024] The rear speakers can be positioned at an obtuse angle to each other with their diaphragms radiating towards each other. Alternatively, the rear speakers can be positioned at an angle away from each other. This allows each rear speaker to drive its own side channel, with each of the two side channels facing in opposite directions being driven by one of two rear speakers positioned at an angle away from each other.

[0025] In a second embodiment according to the invention, the rear loudspeaker chamber is divided into a first and a second rear loudspeaker chamber, which are closed off on two opposite side walls by rear loudspeakers whose diaphragms radiate laterally. The first and second loudspeaker chambers are each connected to a side channel bounded by the rear wall, which radiates laterally from the side wall in addition to the associated rear loudspeaker.

[0026] The side channels can also have opposing bypass channels for rearward radiation from the rear. This means that the side channels not only radiate outwards laterally, but also, via the bypass channels, towards the side wall opposite the first lateral outlet. The outlets of the bypass channels of the opposing side channels are directed towards each other. The sound energy exiting via the bypass channels is redirected, for example with the help of an optional additional deflection element, to exit towards the rear of the loudspeaker enclosure. This further improves the cardioid directional characteristic. The rear loudspeakers couple with a wall located behind the loudspeaker enclosure in the hemisphere, resulting in only a slight increase in the sound pressure level for the rear loudspeaker, but not for the overall system.The side channels of the rear speakers can be the same length as the bypass channels. However, it is particularly advantageous if the bypass channels are shorter than the side channels.

[0027] This means that the bass reflex port not only has the section radiating outwards to the side (the side port), but also an additional section radiating inwards or to the rear (the bypass port). A bass reflex port is thus divided into a section opening outwards to the side (the side port) and a section opening in the opposite direction, or towards the rear (the bypass port).

[0028] The front speaker chamber can be enclosed at the front by several front speakers. This can further increase the performance of the speaker box.

[0029] The front speakers can be positioned at an obtuse angle to each other with their diaphragm radiation plane. This further improves the directional characteristic, resulting in a more point-like sound pressure radiating forward, and the cardioid directional characteristic caused by resonance cancellation.

[0030] The at least one rear speaker and / or front speaker can be, in particular, a woofer. The woofer range is defined by the upper limit of 200 Hz at the transition to the midrange.

[0031] The invention is explained in more detail below with reference to the accompanying drawings and exemplary embodiments. These show: Fig. 1 - Sectional view of a loudspeaker box with front resonance channels, rear speaker for rear radiation with deflection into side channels; Fig. 2 - Sectional view of a conventional loudspeaker box with front resonance channels and rear speaker for rear radiation; Fig. 3 - Exemplary frequency responses of the loudspeaker boxes from Fig. 1 and Fig. 2; Fig. 4 - Sectional view of a loudspeaker box with rear speaker and a wall adjacent to the back; Fig. 5 - Exemplary sound level of the frequency response of the loudspeaker box Fig. 4; Fig. 6 - Sectional view of a loudspeaker box with side-firing rear speakers for the rear speaker chambers and with side channels; Fig. 7 - Exemplary frequency responses of the loudspeaker box Fig. 6; Fig. 8 - Sectional view of a loudspeaker box with side-firing rear loudspeakers for the rear loudspeaker chambers and with side channels with additional bypass channels for rear radiation; Fig. 9 - Exemplary sound level of the frequency response of the loudspeaker box Fig. 8; Fig. 10 - Exemplary frequency responses of the loudspeaker box Fig. 8.

[0032] Fig. Figure 1 shows a sectional view of a first embodiment (LP-1) of a loudspeaker box 1 with front resonance channels 2 and a rear loudspeaker 3, which spans a rear (virtual) diaphragm radiation plane M for the radiation of a rear sound wave RP for the rear radiation of sound energy (i.e. rear sound level), which is also deflected into side channels 4.

[0033] The loudspeaker box 1 has a loudspeaker enclosure 5 with a front F, a rear R diametrically opposite the front F, and side walls S connecting the front F to the rear R. A front loudspeaker 6 is arranged at the front F within the loudspeaker enclosure 5, enclosing a front loudspeaker chamber 7 and defining a front (virtual) diaphragm radiation plane M for radiating a front-facing sound wave FP (forward-directed sound pressure level). The front loudspeaker chamber 7 forms a resonance chamber that vents through the front resonance channels 2 to form a Helmholtz resonator.

[0034] For cardioid radiation, the loudspeaker enclosure 5 has a rear loudspeaker chamber 8, which is sealed off from the rear loudspeaker 3. The loudspeaker enclosure 5 has a side channel 4, bounded by a rear wall 9, which opens at the side wall S. The rear loudspeaker 3 radiates laterally out of the side wall S via the side channel 4. This provides a lateral sound wave SC for cancellation in a cardioid radiation pattern, which interacts with the front sound wave SF with a phase shift due to the distance, similar to a Helmholtz resonator. The distance between the opening of the side channel 4 and the front opening results in a time-of-arrival shift between the front sound wave SF and the lateral sound wave SC.

[0035] The lateral radiation of the sound wave SC generated by the rear loudspeaker 3 shortens the sound path towards the front sound wave, thereby making cancellation effective in higher frequency ranges up to the midrange. The sound pressure level can thus be reduced as desired, as uniformly as possible, to a predetermined level of preferably more than -15 dB over a wider low-frequency range down to 200 Hz.

[0036] The front resonance channels 2 are bounded by inner channel walls 10 in the front loudspeaker chamber 7. Front resonator sound waves FR emerge from the resonance channels 2, which interact with the front sound wave FP in the manner of a Helmholtz resonator and improve bass reproduction.

[0037] The front loudspeaker chamber 7 is separated from the rear loudspeaker chamber 8 by a partition wall 11.

[0038] The front and rear loudspeakers 3, 6 each have a diaphragm 12 which is electromagnetically driven by a loudspeaker driver in a known manner.

[0039] The rear wall 9 can have a central opening O that aligns with the radiation direction of the rear sound wave RP defined by the rear loudspeaker 3. The rear wall 9 partially covers the diaphragm area of ​​the diaphragm 12 in order to deflect part of the rear sound wave RP, radiated directly from the diaphragm 12, into the side channel 4.

[0040] It is evident that the side channel 4 opens into opposite sides on the side walls S on both sides. Thus, functionally, there are two side channels 4, or rather, two oppositely oriented sections of a common side channel 4.

[0041] Fig. Figure 2 shows a sectional view of a conventional, state-of-the-art loudspeaker box 1 (LP-SdT) with front resonance channels 2 and a rear loudspeaker 3 for rearward radiation. In contrast to the embodiment according to [reference missing]... Fig. 1. Side channels 4 leading to the side walls 2 are missing. This results in the sound path of the rear sound wave RP being lengthened to the front sound wave FP, and in addition, all the rear sound energy being radiated to the rear. This can lead to undesirable reflections at the rear wall surface if the distance is close, and at very short distances to an overload of the diaphragm 12 of the rear loudspeaker 3.

[0042] Fig. Figure 3 shows exemplary frequency responses of loudspeaker box 1. Fig. 1 and Fig. 2.

[0043] The goal of the improved speaker box 1, for example, is to... Fig. 1 is to extend the reverse cancellation of at least -15 dB (or more) in the range from 35 to 200 Hz.

[0044] The measurements for the conventional loudspeaker box 1 according to Fig. 2 (LS-SdT) exhibit a maximum reverse cancellation of -23 dB at approximately 85 Hz. The distance between the front and rear ports is 1 / 4 of a wavelength at 85 Hz, which corresponds to 1 m. Below and above 85 Hz, the triggering efficiency gradually decreases. This illustrates the nature of conventional cardioid loudspeaker designs 1, which operate within a limited frequency range dependent on the distance between the sound sources. The conventional loudspeaker 1 (LS-SdT) offers a reverse triggering efficiency of -15 dB (or more) in the range of 35 to 160 Hz.

[0045] To increase cardioid efficiency in the higher frequency range, the resonator sound waves of the rear loudspeaker 3 are radiated laterally by the loudspeaker box 1. Fig. 1 (LS-1), which has the side channels 4. This achieves a similar suppression in the lower frequency range (35-70 Hz) as with the conventional loudspeaker box 1 (LS-SdT) according to Fig. 2. However, the reverse rejection is extended in the upper frequency range. For example, an additional rejection of 3 to 4 dB can be achieved from 80 Hz upwards to reach the target reverse rejection of -15 dB in the 35-200 Hz range. This is because the additional rear connections, i.e., the outlets of the side channels 4, are located closer to the front connections, i.e., at the front F.

[0046] Fig. Figure 4 shows a sectional view of the first embodiment (LP-1) of a loudspeaker box 1 according to Fig. 1 with a rear speaker 3 and a wall W adjacent to the rear R. Therefore, reference is made to the explanations regarding Fig. 1 referred.

[0047] The speaker box 1, which can be operated as a cardio subwoofer, can be placed directly on the wall W. This offers additional flexibility for the user and the advantage of a higher sound pressure level – more headroom, since the rear speaker 3 operates in half-space. This can increase efficiency by, for example, +6 dB. This is particularly useful in permanent installations (e.g., in discotheques and nightclubs) where conventional cardio subwoofers struggle with placement flexibility. The conventional speaker boxes 1 according to Fig. 2. Space is needed between the subwoofer and the wall for the rear speaker. 3.

[0048] Fig. Figure 5 shows an example frequency response of loudspeaker box 1. Fig. 4 with wall W placed directly against the rear wall and a distance of one meter between wall W and rear wall 9. Positioning the rear wall R approximately one meter away from wall W is a typical placement for a conventional subwoofer, which requires some distance from wall W.

[0049] Measurements taken with the loudspeaker enclosure 5 positioned close to wall W (rear panel 9) show a more linear frequency response without room reflections from the rear wall, as well as a higher sound pressure level, since the rear loudspeaker 3 is coupled to wall W and operates in a half-space. This results in a 6 dB higher sound pressure level compared to a greater distance between the rear panel 9 and wall W. This additional 6 dB of sound pressure level applies only to the single rear loudspeaker 3, not to the entire system.

[0050] If, however, wall W is located at a greater distance, e.g. 1 meter, as in the example measurement, rear room reflections occur in the low-frequency range, leading to frequency gaps.

[0051] Fig. Figure 6 showed a sectional view of a second embodiment (LP-2) of a loudspeaker box 1 with laterally oriented rear loudspeakers 3 for the rear loudspeaker chambers 8 and additional resonator side channels 4 extending from the rear loudspeaker chambers 8 in the manner of a Helmholtz resonator. This amplifies the sound waves SP radiating directly from the sides by the lateral resonator sound waves SC from the side channels 4.

[0052] In this embodiment, there is no rear radiation. Therefore, the loudspeaker box 1 can be positioned independently of the characteristics of the space behind it.

[0053] The front speaker chamber 7 extends to the rear wall 9 of the speaker enclosure 5. This allows for a very large bass resonance chamber. The laterally arranged rear speaker chambers 8 are separated from the front speaker chamber 7 by diagonal partitions 11. The laterally arranged rear speaker chambers 8 contain inner channel walls 14, which extend laterally from the respective rear speaker 3 towards the side wall S. The inner channel walls 14, together with the rear wall 9, define the laterally exiting side channel 4.

[0054] For example, two front loudspeakers 6 are located on the front F, their diaphragm radiation plane M positioned obliquely towards each other. This angle can be, for example, in the range of 90° to 140°, and preferably 120° ±10°. This achieves a better forward radiation pattern, especially when additional horn drivers 15 for the midrange and treble frequencies are arranged in front of the front bass loudspeakers 6.

[0055] A suspension element 16 for attaching the speaker box 1 can be provided on the rear wall 9.

[0056] Fig. Figure 7 shows exemplary frequency responses of loudspeaker box 1. Fig. 6.

[0057] Modern high-performance line arrays must provide controlled dispersion from 35 / 40 Hz to 20 kHz. The range from 35 to 200 Hz, with wavelengths up to 10 m, is particularly critical. An additional cardioid section can help in this area. The problem with the conventional placement of the cardioid attenuator is that its range is limited to 1 to 1.5 octaves. This may be sufficient for subwoofers, but it is not wide enough to cover the larger frequency range (2.5 to 3 octaves) required for the lower end of full-range systems.

[0058] It is evident that with the second embodiment according to Fig. 6 (LS-2) also provides attenuation in the higher frequency range between 200 and 300 Hz compared to the first embodiment ( Fig. 1 and Fig. 3) can be achieved. The attenuation in the lower frequency range can be further increased using the bypass channels 17 of the third embodiment (LS-3), without significantly reducing the attenuation in the higher frequency range between 200 and 300 Hz.

[0059] This also makes it possible to achieve an improved cardioid radiation pattern for loudspeaker boxes with wider bandwidth 1.

[0060] Fig. Figure 8 shows a sectional view of a third embodiment (LP-3) of a loudspeaker box 1 with side loudspeakers for the rear chambers and side channels 4 with additional bypass channels 17 for rear radiation.

[0061] The construction of speaker box 1 is essentially the same as the construction of the one in Fig. The embodiment shown in Figure 6 is comparable. The rear side channels 4, bounded by the rear wall 9 and opening in opposite directions at the side walls S, are additionally opened towards the opposite side wall S by bypass channels 17. This allows part of the resonator sound wave to be radiated as a lateral resonator sound wave SC and another part as a rear resonator sound wave RR.

[0062] The cardio section of this third embodiment is designed as a bass-reflex enclosure with two front openings and three radiating areas FP, SP, RR, in which microphones M1, M2, M3 can be located for capturing and controlling the emitted acoustic waves. The microphones M1, M2, M3 are in the Fig. 7 is shown only for the lower (left) side of loudspeaker box 1, but can equally well be present additionally or alternatively on the upper (right) side. For the other embodiments, microphones M1, M2, ... are preferably present at the sound outputs of the rear or side loudspeakers, respectively, but are not shown for clarity.

[0063] The three radiation zones FP, SP, and RR are located at different distances from the front zone. The sound emitted by the diaphragm of the rear side loudspeaker 3, which is picked up by the first microphone M1, radiates the upper frequency range and is located closer to the front F. The rear side channel SC, picked up by the second microphone M2, radiates the lower frequency range and is located farther from the front F. The rear bypass channel RR radiates the lower frequency range, which is picked up by the third microphone M3 and corresponds to the frequency range of the side channel, and is located furthest from the front F. The side channels SC and bypass channels RR can be manufactured with the same length or, preferably, with different lengths as shown.

[0064] The suspension element 16 on the back of the rear wall 9 is located in the sound path of the towards each other rear resonator sound waves RR of the bypass channels 17 and at the same time forms a deflecting element for the sound waves.

[0065] The speaker boxes 1 after Fig. 6 and Fig. 7 have a broadband cardioid radiation pattern, which can be used particularly for line arrays or full-range loudspeakers that require a cardioid radiation pattern.

[0066] Fig. Figure 9 shows exemplary sound levels in decibels (dB) of the frequency response of loudspeaker box 1. Fig. 8 in the cardio range from 30 to 300 Hz. The sound recorded by the first microphone M1, which is directly radiated from the diaphragm of the side loudspeaker 3 in the lateral radiation range SP, the sound recorded by the second microphone M2, which is radiated from the longer rear side channel 4 in the radiation range SC, and the sound recorded by the third microphone M3, which is radiated from the shorter bypass channel 17 in the radiation range RR, are plotted as sound levels dB against the frequency.

[0067] The measurement is based on the bass reflex enclosure 1. Fig. 8 with two ports SC, RR of different lengths and the same resonant frequency Fb of approximately 43 Hz. The upper frequency range (above 80 Hz) is primarily radiated by the diaphragm of the side rear loudspeakers 3 (picked up by the first microphone M1), while the lower frequency range (from 30 Hz) is radiated by the rear ports SC and RR (side channel 4 and bypass channel 17). Although the frequency spectrum of the side channels with the side resonant sound waves SC and of the bypass channels 17 with the rear sound wave RR is identical, the shorter bypass channels 17 with the rear sound waves RR radiate more energy than the longer side channels 4 with the side resonant sound waves SC.The higher energy radiated by the shorter bypass channel 17 with the rear sound waves RR provides an additional rear cancellation of 3 to 4 dB in the lower range (30 to 115 Hz), as the distance from the rear sound waves RR to the front FR is greater. The cancellation in the upper range is mainly achieved by the energy radiated by the side loudspeakers 3 with the side resonance radiations SP (recorded by the first microphone M1), but is somewhat less, since the longer side resonance sound waves SC, which are closer to the front F, radiate less energy.

[0068] Fig. Figure 10 shows exemplary frequency responses of loudspeaker box 1. Fig. 8. The upper frequency response represents the case where the length of the side channels 4 is equal to the length of the bypass channels 17 (SC = RR). In the lower frequency response, the side channels 4 are longer than the bypass channels 17 (SC > RR).

[0069] Broadband reverse cancellation is achieved when the two ports SC and RR, i.e., side channels 4 and bypass channels 17, have approximately the same lengths. This ensures that side channels 4 and bypass channels 17 have the same resonant frequency Fb and the same frequency spectrum, and radiate the same energy.

[0070] If ports SC and RR, i.e., side channels 4 and bypass channels 17, have different lengths, and port SC is longer than port RR, the shorter bypass channels 17 radiate a rear sound wave RR with more energy than side channels 4 with their lateral resonant sound waves SC. Both ports SC and RR have the same resonant frequency (Fb) and the same frequency spectrum.

[0071] If the length of the bypass channels 17 is equal to the length of the side channels 4, the reverse cancellation in the lower frequency range can be extended in a sub-range, such as from about 120 to 180 Hz as shown, compared to different lengths SP > RR, while reducing the cancellation of the upper frequency range.

[0072] If the length of the bypass channels 17 is greater than the length of the side channels 4, i.e., the SC connection is shorter than the RR connection, the shorter side channels 4 radiate more energy with the lateral resonant sound waves SC. The side channels 4 and bypass channels 17, i.e., the SC and RR connections, have the same resonant frequency Fb and the same frequency spectrum. This allows the rear cancellation to be extended in the upper frequency range, while reducing the cancellation in the lower frequency range.

[0073] Therefore, three scenarios are conceivable: 1. SC = RR: The side channels 4 and bypass channels 17 have the same length • SC and RR have the same resonant frequency (Fb), the same frequency spectrum and emit the same energy. • Offers broadband reverse cancellation. 2. SC > RR: The side channels 4 and bypass channels 17 have different lengths, with the side channels 4 being longer than the bypass channels 17. • SC and RR have the same resonant frequency (Fb) and the same frequency spectrum, but the shorter RR connection radiates more energy. • Extends backward cancellation in the lower range, but may reduce cancellation in the upper frequency range. 3. SC < RR: The side channels 4 and bypass channels 17 have different lengths, with the side channels 4 being shorter than the bypass channels 17. • SC and RR have the same resonant frequency (Fb) and the same frequency spectrum, but the shorter SC terminal radiates more energy. • Extends backward cancellation in the upper range, but may decrease cancellation in the lower frequency range.

[0074] This means that the space required between the SP, SC, and RR radiation zones can vary considerably depending on the system's size and frequency range. The cardio zone, with three (or more) FP, SP, and RP radiation zones located at varying distances from the front F, offers additional flexibility, as multiple ports emitting the same or different energy can be positioned to achieve broadband rear cancellation in the desired frequency range. Reference symbol list 1 speaker box 2 front-facing resonance channels 3 rear speakers 4 side channels 5 speaker enclosures 6 front speakers 7 front speaker chamber 8 rear speaker chamber 9 Back panel 10 inner channel wall 11 Partition wall 12 Membran 14 inner channel wall 15 horn drivers 16 Suspension element 17 Bypass channel F Front M Membrane radiation plane O Opening R Back S side wall SC lateral resonance sound wave SF frontal sound wave SP Side Resonance Radiation SR rear sound wave RR rear resonator sound wave

Claims

[1] Loudspeaker box (1) for cardioid radiation with a loudspeaker enclosure (5) having a front (F), a rear (R) diametrically opposite the front (F) and side walls (S) connecting the front (F) to the rear (R), wherein the loudspeaker enclosure (5) has a front loudspeaker chamber (7) closed off at the front (F) by a front loudspeaker (6), a resonance channel (2) opens out of the front loudspeaker chamber (7), the loudspeaker enclosure (5) has a rear loudspeaker chamber (8) closed off by a rear loudspeaker (3), the front loudspeaker chamber (7) is closed off from the rear loudspeaker chamber (8) by an intermediate wall (11), the loudspeaker enclosure (5) has a side channel (4) opening out of the side wall (S) and the rear loudspeaker (3) radiates laterally out of the side wall (S) via the side channel (4), characterized by, that the rear (R) of the loudspeaker housing (5) has a rear wall (9) that is at least partially closed and is designed to deflect the sound pressure directed towards the rear (R) of the diaphragm (12) of the rear loudspeaker (3) into the side channel (4), wherein the rear wall (9) has an opening (O) in the area adjacent to the diaphragm (12) for direct rearward sound radiation. [2] Loudspeaker box (1) according to claim 1, characterized by , that the side channel (4) is limited by the rear wall (9). [3] Loudspeaker box (1) according to claim 1 or 2, characterized by , that the resonance channel (2) opens on both sides next to the front loudspeaker (6) at the front (F) of the loudspeaker housing (5). [4] Loudspeaker box (1) according to any one of claims 1 to 3, characterized by , that the side channel (4) opens out of the side walls (S) on both sides. [5] Loudspeaker box (1) according to any of the preceding claims, characterized by, that the rear speaker chamber (8) is closed off at the rear (R) by several rear speakers (3). [6] Loudspeaker box (1) according to claim 5, characterized by , that the rear loudspeakers (3) are positioned at an obtuse angle to each other with their diaphragm radiation plane (M). [7] Loudspeaker box according to claim 5, characterized by , that the rear loudspeakers (3) are positioned at an angle away from each other with their diaphragm radiation plane (M). [8] Loudspeaker box (1) for cardioid radiation with a loudspeaker enclosure (5) having a front (F), a rear (R) diametrically opposite the front (F) and side walls (S) connecting the front (F) to the rear (R), wherein the loudspeaker enclosure (5) has a front loudspeaker chamber (7) closed off at the front (F) by a front loudspeaker (6), a resonance channel (2) opens out of the front loudspeaker chamber (7), the loudspeaker enclosure (5) has a rear loudspeaker chamber (8) and the front loudspeaker chamber (7) is closed off from the rear loudspeaker chamber (8) by at least one partition (11), characterized by, that the rear loudspeaker chamber (8) is divided into a first and second rear loudspeaker chamber, which are closed off on two opposite side walls (S) by rear loudspeakers (3) whose diaphragms (12) radiate laterally, wherein the first and second loudspeaker chambers are each connected to a side channel (4) which radiates laterally from the side wall next to the associated rear loudspeaker (3). [9] Loudspeaker box (1) according to claim 8, characterized by , that the side channels (4) are limited by a rear wall (9). [10] Loudspeaker box (1) according to claim 9, characterized by , that the side channels (4) continue to have mutually directed bypass channels (17) for rearward radiation from the rear (R). [11] Loudspeaker box (1) according to any one of claims 8 to 10, characterized by , that the front speaker chamber (7) is closed off at the front (F) by several front speakers (6). [12] Loudspeaker box (1) according to claim 10, characterized by , that the front loudspeakers (6) are positioned at an obtuse angle to each other with their diaphragm radiation plane (M).

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