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Thread: phase shift

  1. #1
    Newbie
    Join Date
    Aug 2008
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    6

    phase shift

    Hello,


    I have Pioneer P9 + Processor, VRX amp and Hertz Mille MLK3 component speakers.
    In my older setup I used the P9 Processor crossover and used the following crossover
    configuration for the MLK3:

    Woffer - 80hz/12db, 1.25Khz/12db
    Mid - 1.25Khz/12, 5Khz/12db
    TW - 5Khz/12

    when used with all crossovers slope 12db/oct I had to reverse the phase of the Mid (it's written in the P9 manual pioneer says -

    "When the values of the slope at the crossover point are set at 12 dB/oct. or 36dB/oct. for both filters, the phase reverses 180 in the cut-off frequency of the filter. In this case, setting to reverse improves the connection between sounds."

    and it's indeed sounds better!

    now, I want to bypass the P9 crossover and use the VRX 6 built-in analog crossovers (becuase he sound is more nature, less bright and synchronization in approved between speakers). all the VRX6 crossovers are 12db/oct slope.

    my question is - do I need to reverse the phase of the Mid's also in this configuration? is it work differently with those analog crossovers?

    it is difficult to hear diffrences when you should always go to the trunk in order to reverse the phase, so becuase of that I want to know exactly the way it works.

    Thanks

  2. #2
    Car Audio Moderator durwood's Avatar
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    Chicagoland (St. Charles,IL)
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    Unless the filter is of linear phase type (it will specifically say this or say FIR), then it is an analog mathmatical model even if it's implemented digitally.

    -Passive uses inductors, capacitors and resistors in between the gain stage and the speakers so it will create a phase shift due to inductance or capacitance.
    -Active uses capacitors and resistor components + opamp circuit as a buffer in between the source and the gain stage and allows you to have a variable type. It also creates the phase shift due to the capacitance.
    -Digital IIR crossover is done via the math behind the passive OR the active model (linkwitz, butterworth, etc) and therefore it still has the phase shift occuring
    -Digital FIR crossover is done via convolution and it creates linear/minimum phase crossovers so there is no phase shift at the crossover frequency.


    For every 6db/octave there is a 90 degree phase shift at the crossover frequency.
    6 = 90
    12 = 180
    18 = 270
    24 = 360
    ....

    So it should work the same in your case since it is nothing more than a basic active analog model.

  3. #3
    FLAC WuNgUn's Avatar
    Join Date
    Sep 2007
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    1,351
    Dammit! I need to find a nice, easy to use, FIR VST plugin crossover!

    Durwood, aren't you using the RubberFilter plugin's?

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