3Way Active Crossover with LinearPhase Response 

The problems that exist in common crossover
networks are known. The lowpass filter causes delay in the signal. On the contrary the
highpass filter causes be preahead in the signal that it in goes through from this. So,
the crossfrequency 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 lowpass department with the help of circuit of time
delay and circuit of abstraction it gives in the exit signal with characteristically
lowpass 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 crossfrequency.

R116=100Kohms 
R23242526=37.5Kohms
[33K+4.7K] 
C1213202122=1nF 100V MKT 
R2345=56Kohms 
R30313233343536=10Kohms 
C19232430313233=47nF
100V MKT 
R627=37.5Kohms[33K+4.7K] 
R373839404141=10Kohms 
C2526272829=1nF 100V MKT 
R89121314=10Kohms 
R424344=47Kohms 
C3637=1uF 100V MKT 
R1028=75Kohms (150K//150K) 
R4546=47 ohms 
C3839=47uF 25V 
R1129=NC 
TR1234=47Kohms trimmer or
pot. 
IC1=TL071 
R15=56.3Kohms 
C13435=2.2uF 100V MKT 
IC234567=TL072NE5532 
R17=12Kohms 
C2378141518=47nF 100V
MKT 

R1819202122=10Kohms 
C456910111617=10nF
100V MKT 
All the rsestors is 1/4W 1%
metal film 


The crossover circuit is constituted as it
appears from block diagram [Fig.2] from two lowpass 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 delaytime units, T1 (for low
cross frequency F1) and T2 (for high cross frequency F2) and give him of
characteristically phase with the lowpass 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 lowpass filter is removed with IC7AB, from the signal
that has suffered delay, result a signal that his characteristics is same with a signal
that has passed in from a lowpass 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 fourthorder
Linkwitz heaves the crossfrequencies to find in 6db [Fig. 3]. 

In picture [Fig.
4], appear the basic circuits and the necessary types of calculation for the
lowpass 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 LinearPhase 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 linearphase 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 HighSlope LinearPhase Loudspeaker Crossover Networks
Vol. 33, Number 3 pp. 114 (1985) Author: Stanley P. Lipshitz
and John Vanderkooy Abstract: It has been shown that linearphase crossovers
of high slope can be synthesized by subtracting a suitable lowpass output from a
timedelayed version of the input signal. It would be nice to be able to avoid the expense of such an electronic timedelay
2Way Active Crossover with Linear Phase Response

Sam
Electronic Circuits 11/02 

