KR20060127108A - First-order loudspeaker crossover network - Google Patents

Abstract

A first-order crossover network having low-pass and high-pass filters to respectively drive first and second loudspeakers in a loudspeaker system is designed such that the phase difference at a crossover frequency between output signals of the first and second loudspeakers is no greater than 60 degrees, so that the output signals are at least partially in phase. Preferably, the phase difference should be about 40 degrees to create a near in-phase effect. The polarity in which the first loudspeaker is coupled to the first-order crossover network is an inverse of the polarity in which the second loudspeaker is coupled to the crossover network. Optionally, the input signals can be equalized to flatten the magnitude responses of the crossover network.

Description

Primary Speaker Crossover Network {FIRST-ORDER LOUDSPEAKER CROSSOVER NETWORK}

TECHNICAL FIELD The present invention relates to the field of speaker crossover networks, and more particularly, to a primary speaker crossover network having some advantages of a secondary speaker crossover network.

Crossover networks are used to separate an input audio signal into multiple frequency bands in a multi-way speaker system, with each band feeding different speakers to an associated frequency band. The frequency of separating one band from another is called the crossover frequency of these two bands. For example, in a two-way speaker system discussed below, the low and high frequency bands are provided to the woofer and tweeter, respectively, and the crossover frequency is the frequency at which the low and high frequency bands are divided.

In a first-order crossover network, such as a first-order Butterworth network, the capacitor is coupled in series with an inherently resistive tweeter to form a high frequency bandpass filter that provides a high frequency band signal to the tweeter, and the inductor is also inherently resistive. It is coupled in series to the woofer to form a low frequency band filter that provides a low frequency band signal to the woofer. At the crossover frequency, the amplitude response of the low pass and high pass filters is about -3 dB (decibels). Since the phase difference between the two networks at this crossover frequency is 90 °, the combined voltage response at the crossover frequency of this crossover network is 0 dB, and no constructive or destructive interference occurs at this crossover frequency.

Although the aforementioned first-order crossover network operates satisfactorily, the low pass and high pass filters are not in-phase. As such, this primary network cannot provide a smoother frequency response due to the following in-phase crossover network benefits: increased stop band rejection and improved polarity operation (robbing, lobing).

In order to have an in-phase response, a secondary or higher order crossover network, such as a Linkwitz-Riley network, must be used. However, secondary or higher order networks require additional capacitors and inductors. For example, a two-way linkwitz-lily crossover network requires additional capacitors coupled in parallel with the woofer to form a low pass filter, and additional inductors coupled in parallel with the tweeter to form a high pass filter. Capacitors and inductors used in crossover networks are typically expensive because of their size, capacity, and power requirements, so these additional components significantly increase the cost of the speaker system.

According to the principles of the present invention, a primary crossover network having low pass and high pass filters for driving first and second speakers in a speaker system, respectively, has a phase difference at the crossover frequency between the first and second speaker responses. Is below 60 ° so that the output signal is at least partially in phase. The response may be electrical or acoustic.

In one embodiment, the low pass filter is formed by an inductor coupled in series with the first speaker with a first polarity, and the high pass filter is formed by a capacitor coupled with a second speaker with a second polarity. The impedances of the inductor and capacitor are chosen so that the phase difference is less than 60 degrees. Preferably, the retardation is about 40 degrees, showing almost in-phase effects.

In another embodiment, the second polarity is reversed to the first polarity to add 180 ° phase shift to the high pass filter.

In another embodiment, the input audio signal is equalized to even out the response of the crossover system. In particular, the level at the crossover frequency rises in the input signal.

1 illustrates an exemplary two-way speaker system including a crossover network in accordance with the principles of the present invention.

FIG. 2 is a diagram of the woofer in the speaker system shown in FIG. 1, where the woofer has a resistance of 8 kW, the capacitor in the high pass filter has a capacitance of 11.5 Hz, and the inductor in the low pass filter has an inductance of 2.2 mH. A diagram showing the response.

FIG. 3 shows that in the speaker system shown in FIG. 1, the tweeter's resistance is 8 Hz, the capacitor in the high pass filter has a capacitance of 11.5 Hz and the inductor in the low pass filter has an inductance of 2.2 mH. A diagram showing the response.

FIG. 4 shows a case in which the resistance of the woofer and tweeter is 8 kW, the capacitor in the high pass filter has a capacitance of 11.5 Hz, and the inductor in the low pass filter has an inductance of 2.2 mH in the speaker system shown in FIG. , Illustrating the combined response.

FIG. 5 shows the woofer in the speaker system shown in FIG. 1, where the resistance of the woofer is 8 kW, the capacitor in the high pass filter has a capacitance of 6.7 kW, and the inductor in the low pass filter has an inductance of 3.8 mH. A diagram showing the response.

FIG. 6 shows that in the speaker system shown in FIG. 1, the tweeter's resistance is 8 kW, the capacitor in the high pass filter has a capacitance of 6.7 kW, and the inductor in the low pass filter has an inductance of 3.8 mH. A diagram showing the response.

FIG. 7 illustrates a case in which the resistance of the woofer and tweeter is 8 kW, the capacitor in the high pass filter has a capacitance of 6.7 kW, and the inductor in the low pass filter has an inductance of 3.8 mH in the speaker system shown in FIG. , Illustrating the combined response.

8 shows that in the speaker system shown in FIG. 1, the resistance of both the woofer and the tweeter is 8 kW, the capacitor in the high pass filter has a capacitance of 6.7 kW, and the inductor in the low pass filter has an inductance of 3.8 mH. A diagram showing the response of the equalizer to be used.

FIG. 9 shows that in the speaker system shown in FIG. 1, the resistance of both the woofer and tweeter is 8 kW, the capacitor in the high pass filter has a capacitance of 6.7 kW, the inductor in the low pass filter has an inductance of 3.8 mH, A diagram showing the combined response where an equalizer is used to equalize the input audio signal.

10 illustrates a method according to the principles of the present invention for generating an output signal from a speaker system having a primary crossover network having a phase difference of less than 60 degrees at a crossover frequency.

1 illustrates a two-way speaker system 100 using a primary crossover network 105 in accordance with the principles of the present invention. The two-way speaker system 100 includes a tweeter 110, denoted by a resistor in FIG. 1, and a woofer 150, also denoted by a resistor in FIG. 1. The tweeter 110 and the woofer 150 each have a positive terminal (shown as "+" in FIG. 1) and a negative terminal (opposite to the terminal shown as "+" in FIG. 1). The input audio signal to the crossover network 105 may be amplified by the amplifier 170. The crossover network 105 is a capacitor 120 that is coupled in series to the tweeter 110 to form a high pass filter for providing a high frequency band input signal to the tweeter, and a woofer 150 that is coupled in series to the woofer 150. An inductor 160 forming a low pass filter provided to 15. The inductor 160 is coupled to the woofer 150 with a first polarity and the capacitor is coupled to the tweeter 110 with a second polarity opposite to the first polarity. In this example, the inductor 160 is coupled to the positive terminal of the woofer 150, while the capacitor 120 is coupled to the negative terminal of the tweeter 110.

According to the principles of the present invention, the capacitance of capacitor 120 and the inductance of inductor 160 are selected such that the phase difference between the response of the high pass filter and the response of the low pass filter at the crossover frequency is less than or equal to 60 degrees. (The crossover frequency is the frequency at which the crossover network 105 divides the audio input signal into high and low frequency bands.) Preferably, the phase difference is about 40 degrees. The inventors have recognized that the response of the two filters is at least partially in phase when the phase difference is less than 60 degrees. As such, the speaker system produces a smoother frequency response due to increased stop band rejection and improved polarity operation. Polarity operation is best understood by looking at the acoustic output graph at the crossover frequency of the combined radiation pattern of the two speakers. Better polarity operation reduces audio degradation for off-axis listeners. If the phase difference is at least partially in phase, the radiation pattern for the mismatched driver is close to on-axis for all frequencies, creating at least partial constructive interference to improve polarity operation. For example, if the phase difference is 60 degrees, the two responses produce at least 50% constructive interference at the crossover frequency. If the phase difference is 180 °, the two responses are completely out of phase, producing 100% attenuation interference, which is of course undesirable. In the case where the phase difference is 90 °, as produced by the first-order Butterworth filter, the two responses are orthogonal and do not produce both constructive and decay interference. In the case where the phase difference is zero, as produced by the second order link-release filter, the two responses are completely in phase, creating 100% constructive interference. The primary crossover network 105 in accordance with the principles of the present invention produces a phase difference very close to zero degrees compared to a conventional primary crossover network.

In the following description of the first and second examples, it is assumed that the internal resistance of the tweeter 110 and the woofer 150 is 8 kHz and the crossover frequency is 1,000 kHz. Since the impedance of tweeter 110 and woofer 150 is treated as purely resistive, the acoustic response of each of tweeter 110 and woofer 150 is equal to the electrical response. The acoustic response of the speaker is the response of the speaker's acoustic output, and the electrical response is the response of the voltage generated across the two terminals of the speaker. In practice, speakers are not purely resistive, but substantially resistive. Thus, the electrical response of the speaker is substantially the same as the acoustic response.

In a first example, the crossover network 105 produces a phase difference of about 60 degrees at the crossover frequency. An example of generating such a phase difference is to select a capacitance of 1.5 mA for the capacitor 120 and an inductance of 2.2 mH for the inductor 160. With this set of values, the low pass filter produces a positive phase shift of about 60 degrees, and the high pass filter produces a negative phase shift of about 60 degrees. However, while the low pass filter is connected to the positive terminal of the woofer 150, the high pass filter is connected to the negative terminal of the tweeter 110, that is, the polarity of the tweeter 110 is the characteristic of the woofer 160 Since it is inverted relative to, the tweeter 110 actually adds a positive phase shift of 180 ° to the high pass filter. Inverting the polarity adds 180 ° to the high pass filter because the incoming signal is necessarily reversed. For example, a positive input will be a negative input and move the diaphragm of tweeter 110 in the opposite direction. Thus, the resulting phase shift of the high pass filter is actually a positive phase shift of about 120 °. Thus, the phase difference between the response of the low pass filter and the response of the high pass filter is about 60 degrees.

In a second example, the crossover network 105 produces a phase difference of about 40 degrees. An example of generating such a phase difference is to select a capacitance of 6.7 GHz for the capacitor 120 and an inductance of 3.8 mH for the inductor 160. With this set of values, the low pass filter produces a positive phase shift of about 71 degrees, and the high pass filter produces a negative phase shift of about 71 degrees. However, tweeter 110 adds a 180 ° positive phase shift to the high pass filter due to the inversion of polarity. Thus, the resulting phase shift of the high pass filter is actually a positive phase shift of 109 °. Thus, the phase difference between the response of the low pass filter and the response of the high pass filter is about 38 degrees.

2, 3 and 4 show the amplitude and frequency response of the crossover network 105 in the first example. 2 shows the response of the low pass filter, FIG. 3 shows the response of the high pass filter, and FIG. 4 shows the combined response. The passbands shown in Figures 2 and 3 are narrower than a typical primary crossover network with a phase difference of 90 degrees. The high pass and low pass filters each have an amplitude response of -6 dB at the crossover frequency and the combined amplitude is about -1 dB.

5, 6 and 7 respectively show the amplitude and phase response of the low pass filter, high pass filter and combined response of the crossover network 105 in the second example. As shown in Figs. 5 and 6, the pass band is narrower than in the first example. The high pass and low pass filters each have an amplitude response of -10 dB at the crossover frequency and the combined amplitude is about -4.5 dB.

It has been found that the individual responses of the high pass and low pass filters should be about -6 dB or less to obtain at least partially in-phase first order network. For example, the individual responses in the first and second examples are about -6 dB and -10 dB, respectively. The midrange dips shown in FIGS. 4 and 7 can be improved by equalizing the input signal before it enters the crossover network 105 using an equalizer (not shown) if necessary. The input signal is preferably equalized before being amplified by the amplifier 170.

For example, in the second example where the equalizer with the response shown in FIG. 8 is used to equalize the input signal before the input signal enters the crossover network 105, the combined response is as shown in FIG. 9. It will be nearly flat as well.

Although described as having a crossover frequency of 1,000 Hz, other crossover frequencies, such as 1,700 Hz, may be used. In addition, although the internal resistance of the tweeter 110 and the woofer 150 is described as 8 kΩ, other resistors such as 6 kΩ may be used, and the internal resistance of the tweeter 110 is different from the internal resistance of the woofer 150. can do. Further, although the low pass and high pass filters have been described to produce phase shifts with the same amount and different directions, the absolute amounts of the two phase shifts may be different. Finally, although described as being used in two-way speaker systems, the principles of the present invention may be used in three-way or other multi-way speaker systems. For example, the principles of the present invention can be used in the design of low pass and band pass filters, band pass filters and high pass filters in a three way speaker system.

10 illustrates a method according to the principles of the present invention for generating an output signal from a speaker system having a primary crossover network having a phase difference of less than 60 degrees at a crossover frequency. In step 1010, the audio signal is sent to a primary passive crossover network having low pass and high pass filters coupled to the woofer and tweeter, respectively. In step 1020, the polarity of the tweeter relative to the woofer is reversed. In step 1030, the individual responses of the two filters are -6 dB or less at the crossover frequency, preferably between -6 dB and -10 dB, and at the crossover frequency between the respective output signals from the low pass and high pass filters. The impedances of the low pass filter and the high pass filter are selected so that the phase difference is less than 60 °. This will produce a low pass phase shift of greater than 60 degrees and a high pass phase shift of less than -60 degrees. With the polarity reversed, the tweeter adds a + 180 ° phase shift to the high pass filter, resulting in an equivalent high pass shift of less than + 120 °. Thus, the phase difference between the low pass and high pass filters is less than 60 degrees, or at least partially in phase, at the crossover frequency. Optionally, in step 1040, a combined response is obtained and the input signal is equalized to compensate for the fall in the region near the crossover frequency.

Although the present invention has been described with respect to some preferred embodiments, those skilled in the art will readily appreciate that many other modes and embodiments may be practiced without departing from the spirit and scope of the invention.

Claims (26)

A primary crossover network that separates an input audio signal from a crossover frequency into high and low frequency bands in a speaker system having first and second speakers having respective impedances, each speaker having positive and negative terminals. as, A first component coupled to the first speaker to form a low pass filter for providing a low frequency band signal to the first speaker; A second component coupled to the second speaker to form a high pass filter for providing a high frequency band signal to the second speaker; The low pass and high pass filters are primary filters, and the impedances of the first and second components are selected such that the phase difference between each response of the first and second speakers at the crossover frequency is less than or equal to 60 °. Crossover network. The method of claim 1, The response is an acoustic response. The method of claim 1, The response is an electrical response. The method of claim 1, The first component is serially coupled to the first speaker in a first polarity, and the second component is serially coupled to the second speaker in a second polarity opposite to the first polarity. The method of claim 4, wherein Wherein the first component is an inductor, the second component is a capacitor, and the impedances of the inductor and the capacitor are selected such that the phase shift for each filter is greater than 60 °. The method of claim 5, And the input audio signal is equalized to smooth the combined response of the first and second input speakers. The method of claim 6, A crossover network in which the combined response at the crossover frequency is raised. The method of claim 7, wherein The combined response at the crossover frequency is raised by about 4.5 dB. The method of claim 1, The combined response of the first and second speakers is less than -6 dB. The method of claim 9, The combined response is at least -10 dB. The method of claim 1, The phase difference is about 40 degrees. As a speaker system, First and second speakers having respective impedances, each speaker having positive and negative terminals, and A crossover network, which is a primary network that separates an input audio signal from a crossover frequency into a high frequency and a low frequency band, The crossover network is coupled to the first and second speakers, respectively, to form first and second low pass and high pass filters for providing a low frequency band and a high frequency band signal to each of the first and second speakers, respectively. A component, wherein the low pass and high pass filters are primary filters, and impedances of the first and second components are phase differences between respective responses of the first and second speakers at the crossover frequency. Speaker system selected to be less than 60 degrees. The method of claim 12, The response is an acoustic response. The method of claim 13, The response is an electrical response. The method of claim 14, And the first component is serially coupled to the first speaker with a first polarity and the second component is serially coupled to the second speaker with a second polarity opposite to the first polarity. The method of claim 15, The first component is an inductor, the second component is a capacitor, and the impedances of the inductor and the capacitor are selected such that the phase shift for each filter is 60 ° or more. The method of claim 16, And an equalizer to equalize the input audio signal to smooth the combined response of the first and second input speakers. The method of claim 17, The combined response at the crossover frequency being raised. The method of claim 18, The combined response at the crossover frequency is raised by about 4.5 dB. The method of claim 14, The combined response of the first and second speakers is less than -6 dB. The method of claim 20, And the combined response is greater than -10 dB. A method of generating an output signal from a speaker system having first and second speakers, the method comprising: Sending an audio signal to a first-order crossover network including low pass and high pass filters, Coupling the low pass filter to the first speaker with a first polarity and coupling the high pass filter to the second speaker with a second polarity opposite to the first polarity; Each filter has a frequency response of -6 dB or less at the crossover frequency, and the impedances of the first and second filters are adjusted such that the phase difference at the crossover frequency of the output signal of the low pass and high pass filters is 60 ° or less. Step to choose How to include. The method of claim 22, Equalizing an input signal to equalize a response of the speaker system. The method of claim 23, wherein The phase difference is about 40 degrees. The method of claim 23, wherein The impedance of the first speaker is equal to the impedance of the second speaker. The method of claim 23, wherein The impedance of the first and second speakers are different.

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