Crossover activo 2 vias

Introduction
The Linkwitz-Riley filter featured here has (almost) perfect phase-coherency, with no peaks or dips at the crossover frequency. The design is adaptable to 2-way or 3-way (or even 4-way) operation, and all formulas are provided below (or use the ESP-LR component calculator program).
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Photo of Completed P09 Rev-B Circuit Board
Please note that the PCB version of the P09crossover is a stereo 2-way design, and has balanced input buffers (unbalanced also available), high and low pass filters, level controls and output buffers for each channel. Each output buffer is configured for variable gain to allow your system to be set up correctly. The suggested power supply is the P05 Rev-B, which also has an auxiliary output suitable for operating muting relays (see below forreasons you may want to include muting).
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2-Way Linkwitz Riley Crossover
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Figure 1A - Stereo Version of a 2-Way LR Crossover
Figure 1A shows the general concept for a full stereo version, with two identical filter sections (but without balanced inputs). With the component values shown, these have a crossover frequency of 310Hz (refer to the article on Bi-Amping to see the reason for mychoice of frequency). This unit will provide a completely flat frequency response across the crossover frequency, with the signal from both filters remaining in phase at all times.
The 2-Way unit is separated into 3 sections per channel ...
• Input Buffer - ensures that all filters are driven from a low impedance source, to prevent frequency and phase shifts
• High Pass - as shown,frequency is approx. 310Hz
• Low Pass - as shown, frequency is approx. 310Hz
It is important with both versions that the filters are properly matched, both within the individual filters, and between channels. While small variations between channels will not be audible, if the high and low pass sections are not accurately matched, then phase and amplitude errors will result.
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3-WayLinkwitz Riley Crossover
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Figure 1B - 3-Way Mono LR Crossover (2 Needed for Stereo)
Figure 1B shows the way to connect a 3-Way crossover. This unit will produce excellent results, with good phase coherency and a flat response across the entire frequency band.
I know the circuits look complicated, but each is basically repetition of a common circuit block - the filter section. Since the opampsare all used as unity gain buffers, the use of premium devices is not really essential, so the TL072 type would be quite serviceable in this role. Needless to say, if you want to use better devices (even discrete opamps) you can easily do so. Make sure that any device used is stable for unity gain - this is not always the case with some devices, especially when external compensation is used. Inthis case, use the manufacturer's recommended value of stability cap for unity gain operation.
|[pic] |Power supply connections (and bypass capacitors) have not been shown, but the diagram shows |
| |the standard connections for a dual opamp. The IC is viewed from the top. The +/-15V power |
| |supplydescribed (see Project 05 - Power Supply For Preamps) is suitable for this crossover |
| |as well. For dual opamps, power is connected to Pin 4 (-ve) and Pin 8 (+ve). |

NOTE: Only one channel is shown for the 3-Way - for a stereo setup, two identical filter circuits are required.
As can be seen, the 3-Way unit is separated into 4 sections ...• Input Buffer - ensures that all filters are driven from a low impedance source, to prevent frequency and phase shifts
• High Pass - as shown, frequency is approx. 3100Hz
• Band Pass - as shown, frequencies used are high pass at 310Hz and low pass at 3100Hz
• Low Pass - as shown, frequency is approx. 310Hz
In 3-Way mode, the bandpass section must have a highpass section whose...