Diagram Guide

The crossover network is intended for use when an existing audio installation is to be extended by the addition of a subwoofer. Often, this additional loudspeaker is one that has been lying around for some time. If its frequency response extends down far enough, all is well and good, but a filter is then needed to cut off any frequencies above, say, 150 Hz. Often, a subwoofer network is an active filter, but here this would necessitate an additional power supply. The present network is a passive one, designed so that the speaker signal of the existing system can be used as the input signal.

Since the bass information is present in both (stereo) loudspeakers, the signal for the sub woofer can simply be tapped from one of them. The network is a 1st order low-pass filter with variable input (P1) and presettable cut-off frequency (P2). The signal from the loudspeaker is applied to terminal ‘LSP’. Voltage divider R1-R2-P1 is designed for use with the output signal of an average output amplifier of around d 50 W. The crossover frequency of the network may be varied between 50 Hz and 160 Hz with P2. The values of R3, P2, and C1, are calculated on the assumption that the subwoofer amplifier to be connected to K1 has a standard input resistance of 47 kΩ.

If this figure is lower, the value of C1 will need to be increased slightly. It is advisable to open the volume of the subwoofer amplifier fully and adjust the sound level with P1. This ensures that the input of the subwoofer amplifier cannot be overloaded or damaged. Make sure that the ground of the loudspeaker signal line is linked to the ground of the subwoofer amplifier. If phase reversal is required, this is best done by reversing the wires to the subwoofer. If notwithstanding the above additional protection is desired at the input of the subwoofer amplifier, this is best effected by ‘overload protection ’ elsewhere in this site.

Author: T. Giesberts Copyright: Elektor Electronics

This is the Simple 3-Way Active Crossover Circuit Diagram with linear phase response. The problems that exist at common crossover schema is known. The low pass filter causes a delay in the signal. Unlike the high-pass filter causes a head in the signal passing through it. Thus the frequency separation created some problems such as:

The crossover schema tries to solve many of the problems mentioned above and based on a study of S. Lipshitz and J.  Vanderkooy, published in the JAES (Journal Audio Engineering Society). A lattice separation uses a linear phase low-pass section with the help of a time delay schema and a schema removal gives the output signal with high-pass filter characteristics. The time delay is not constant over the entire frequency range, but changing very slowly and mainly there are phase differences between signals of the two charges, not even close to the crossover.

The schema consists separation as shown in block diagram [Fig.2] two low pass filters of fourth grade, -24db/oct for a line of low-frequency signals and one for the high frequency separation. In the same frequencies operate both units delay time T1 (for low frequency F1) and T2 (for high frequency F2) and give the same phase characteristics of the low pass section.

The delay schema T1 simulates the time delay introduced by low-frequency filter LPF1, while T2 simulates the time delay introduced by low-frequency filter LPF2 that exists in the line of midrange. Then the signal from the low pass filter removed [IC7A-B] of the signal has been delayed, a clear signal that the characteristics are the same as a signal that has passed through a high pass filter. At the exit of each line is a trimmer with which we can adjust the level between the levels of loudspeakers. The power schema is a well-stabilized voltage + /-15V. The use of meshed split fourth order Linkwitz forcing crossovers be located at-6db [Fig.3].

The above picture shows the main diagram and the necessary formulas for calculating the low pass filters as well as trusses time delay. There is also an example calculation for crossovers and 200IZ 3KIZ that will help calculate and adjust to your needs. The schema derived from a relevant article of the magazine Elektor. 

Components List:
R1,16 = 100Kohms
R2,3,4,5 = 56Kohms
R6,27 = 37.5Kohms[33K+4.7K]
R8,9,12,13,14 = 10Kohms
R10,28 = 75Kohms (150K//150K)
R11,29 = NC
R15 = 56.3Kohms
R17 = 12Kohms
R18,19,20,21,22 = 10Kohms
R23,24,25,26 = 37.5Kohms [33K+4.7K]
R30,31,32,33,34,35,36 = 10Kohms
R37,38,39,40,41,41 = 10Kohms
R42,43,44 = 47Kohms
R45,46 = 47 ohms
TR1,2,3,4 = 47Kohms trimmer or pot.
C1,34,35 = 2.2uF 100V MKT
C2,3,7,8,14,15,18 = 47nF 100V MKT
C4,5,6,9,10,11,16,17 = 10nF 100V MKT
C12,13,20,21,22 = 1nF 100V MKT
C19,23,24,30,31,32,33 = 47nF 100V MKT
C25,26,27,28,29 = 1nF 100V MKT
C36,37 = 1uF 100V MKT
C38,39 = 47uF 25V
IC1 = TL071
IC2,3,4,5,6,7 = TL072,NE5532
All the resistors is 1/4W 1% metal film

Sourced by Elektor