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promitheus 2nd July 2001 05:04 PM

HI everybody !!
I need some help. There is this design of active crossovers using time shift filters. This crossover has no difference in phase between high and low frequencies. There used to be an article in the Elektor magazine. But I canīt find any info anymore. If anyone knows a link or something please post.
Thanks, Ilias.

jam 2nd July 2001 06:22 PM

Phase Linear Cross-Over

Elector published a book High-end Audio Equipment in 1995 and the article you want ( Active phase-linear cross-over net network) is in that book.

If you have any problems finding it please e-mail me.


P.S. Nelson Pass also published an article on subtractive (linear phase) cross-overs and I believe this is available on the Pass Labs web site.

[Edited by jam on 07-02-2001 at 12:25 PM]

Alex M 3rd July 2001 09:54 AM

A further possibility for linear phase filters is that of
filler (Baekgard) drivers.

You can do a Web search for Baekgard for more information. I
have written a short note on this at


promitheus 3rd July 2001 02:13 PM

Thanks a lot for all the help.
If anybody has a link or file of the elektor active crossover I would really be interested in having a copy.
Thanks again

ALW 3rd July 2001 03:07 PM

Phase coherent crossover
There's 2/3 way 24dB/oct Linkwitz-Riley design at

Spice model I did looks good, phase coherent at the crossover point.


Alex M 3rd July 2001 03:22 PM

Ah, but there's a difference between a crossover which is
"linear phase" and one that's "phase coherent at the
crossover point". The first reproduces (at least in theory)
a transient perfectly, while the second simply ensures that
the two drivers are moving in the same direction at the
same time at the crossover frequency. Linkwitz Riley
crossovers are in the second category; here (I think!) we
are talking about the first kind, which is much harder to
put into practice.


[Edited by Alex M on 07-03-2001 at 09:24 AM]

promitheus 3rd July 2001 08:28 PM

The circuit I am talking about that ws published in the Elektor magazine is an active crossover that has the smae phase in all the drivers for every frequency not only at the cross over point.

ALW 4th July 2001 09:19 AM

Phase coherent
The design above is almost perfectly phase coherent across most of the audio band (there's some minor deviation at very low frequqncies). The only reason for specifically mentioning crossover point was this is often the worst area.

Worth a peek.


promitheus 4th July 2001 10:36 AM

Yeah it looks good. Itīs a little different than the one I read before but I will test it out too on simulation.
Thanks again.

ALW 4th July 2001 12:45 PM

Helpful software

Since you're obviously into SPICE, you may find the following application useful. It's 'Filter Wiz' available in LE or Pro versions (

There are partly working demo's available, its' a very easy to use wizard-style application, that allows the design of active filters in Butterworth, Chebyshev, Inverse Chebyshev, Elliptic or Bessel / Thompson alignments.

One can force filter orders, or define by pass / stopband performance. It's great for creating crossovers, since one can easily prototype a design, fine tune in SPICE modelling and just build the final design.

Saves a lot of time with a soldering iron!


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