3-Way Active Crossover with Linear-Phase Response

3w_cross_lin_phase_1.gif (16151 bytes)

The problems that exist in common crossover networks are known. The low-pass filter causes delay in the signal. On the contrary the high-pass filter causes be pre-ahead in the signal that it in goes through from this. So, the cross-frequency are created certain problems as 1] the signals of two filters confutation 2] the change of phase between the filters influence axial  3]to axial diagram depend from the frequency. The crossover circuit try it unties many from the problems that report above and are based on research of S. Lipshitz and J. Vanderkooy that was published in the magazine JAES (Journal Audio Engineering Society). A network crossover of linear phase it uses a low-pass department with the help of circuit of time delay and circuit of abstraction it gives in the exit signal with characteristically low-pass filter. This delay time is not constant for entire the area of frequencies, but is altered very late and mainly doesn't exist differences of phase between the signals of two outputs, neither even near in the cross-frequency.


Part List

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

3w_cross_lin_phase_2.gif (6620 bytes)


The crossover circuit is constituted as it appears from block diagram [Fig.2] from two low-pass filters of fourth order -24db/oct, one for the line of low frequency  signals  and one for the high frequency. In the same frequency function also the two delay-time units, T1 (for low cross frequency F1) and T2 (for high cross frequency F2) and give him of characteristically phase with the low-pass part. The circuit delays T1 imitate the delay time that import the filter of low frequencies LPF1, while the T2 imitates the delay time that import the filter of low frequencies LPF2 that exists in the line of mid frequencies. Then the signal that emanates from low-pass filter is removed with IC7A-B, from the signal that has suffered delay, result a signal that his characteristics is same with a signal that has passed in from a low-pass filter. In the exit of each line found a trimmer with that we can adjust the level and  level between the loudspeakers. The circuit supply become from a stabilized voltage +/- 15V. The use of crossover networks of fourth-order Linkwitz heaves the cross-frequencies to find in -6db [Fig. 3].

3w_cross_lin_phase_3.gif (14537 bytes)


In picture [Fig. 4], appear the basic circuits and the necessary types of calculation for the low-pass filters as well as circuits delay time. Also exist an example of calculation for crossfrequencies  F1=200HZ and F2=3KHZ, that it will help in the calculation and the adaptation in your needs. The circuit comes from relative article of magazine Elektor. More theoretical details exist in article, also in relative articles of S. Lipshitz and J. Vanderkooy in the JAES.

  • A Family of Linear-Phase Crossover Networks of High Slope Derived by Time Delay Vol. 31, Number 1 pp. 2 (1983) Author: Stanley P. Lipshitz and John Vanderkooy Abstract: The design of linear-phase crossover networks has until now necessitated the use of crossovers, at least one of whose outputs suffers from either frequency response ripple in the passband or low rolloff rate in the stopband. It may be desirable, at leas

  • Use of Frequency Overlap and Equalization to Produce High-Slope Linear-Phase Loudspeaker Crossover Networks Vol. 33, Number 3 pp. 114 (1985) Author: Stanley P. Lipshitz and  John Vanderkooy Abstract: It has been shown that linear-phase crossovers of high slope can be synthesized by subtracting a suitable low-pass output from a time-delayed version of the input signal. It would be nice to be able to avoid the expense of such an electronic time-delay

  • 2-Way Active Crossover with Linear Phase Response



Sam Electronic Circuits 11/02