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  1. #1
    Roysen
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    DC-moduler til passive høytalere.

    Jeg poster denne her også - det ikke sikkert man trenger å være så teknisk skolert for å vite hva dette dreier seg om: http://www.hifisentralen.no/forum/in...c,13937.0.html

    Mvh
    Roysen

  2. #2
    Overivrig entusiast
    Ble medlem
    Jul 2006
    Innlegg
    844
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    DC-moduler til passive høytalere.

    Tipper at det dreier seg om dette:
    Faseforskyving med kondensatorer, her er et skjema.
    Forklaring finner du ved å lete litt i linken:

    http://www.speakerbuilding.com/conte.../crossover.gif

    Litt service:

    First of all I optimized the Sunshine for a listening distance of 2 meters. This covers the problem of aligning the acoustical centres of the woofer and the tweeter. It works in the way explained in the drawing above.

    Because I do not like tweeters connected in reversed polarity to restore the phase alignment of the drivers, I use a phase control circuit. The tweeter connected in reversed polarity does not really restore the phase alignment of the drivers anyway. Only the average sum of the tweeter and the woofer, the amplitude answer will look OK. In reallity the tweeter will begin a half period earlier than the woofer to radiate a special frequency and, of course, the woofer will end to radiate a special frequency a half period later. The phase control circuit slows down the tweeter. This means, that there is no phase shift at very low frequencies and 180 degree phase shift at very high frequencies.

    As you can see on the schematic Fig. 5. Response of the phase control circuit I designed the circuit to have a corner frequency around 500 Hz. That means a phase shift of 90 degree ( 1,57 ) at 500 Hz. Like I mentioned before I slowed down the tweeter. Therefore the real phase shift is in the negative direction ( The possibility with the to big and to expensive condensators and inductors described below will alter the shape of the curve, but not the corner frequency ).

    Dimensioning the phase control circuit
    If you look at the crossover schematic you will find the phase control circuit behind the filter condensator (L2, L2', C3, C3'). To provide perfect working conditions for the circuit, you have to take care for a linearized tweeter impedance. Also the 6dB filter will love the linearized tweeter impedance. The linearized tweeter has an average impedance around the DC resistance of the tweeter voice coil. This DC resistance will be the starting value for calculating the phase shift circuit. First step now is, to choose a corner frequency: Lets take 500 Hz like in the design of the Sunshine. The second step is to calculate an inductor and a condensator which have the same resistance like the DC resistance of the tweeter at the corner frequency. The calculating formulas are:


    C = 1 / (2 * PI * corner-frequency * DCR-tweeter)
    L = DCR-tweeter / (2 * PI * corner-frequency)

    With this formulas and a DCR of the tweeter from around 5,3 Ohm you end up at a value of 60 uF for the condensator and a value of 1,68 mH for the inductor. For the Sunshine I chose 60 uF and 1,5 mH for the part values. You can design the circuit with the inductor and the condensator having only the half value of the DCR of the tweeter, but then you will end up with 120 uF condensators and 3,4 mH inductors. This seems to be a little bit to expensive, even for me, and a little bit to big too.
    Radionette Kurer

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