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how to add numerical bode results

Discussion in 'Circuit Simulation & PCB Design' started by case-sensitive, Nov 29, 2016.

  1. MrAl

    MrAl Well-Known Member Most Helpful Member

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    Hello again,

    The inductance of the speaker is probably low, but cant be sure without some specs or maybe measurements.

    With a DSP filter you can program any filter shape you want with any phase shape you want. With simple electrical networks this is harder to do. Possibly use the Bessel type with two All Pass filters designed to 'correct' the phase of the output of the low pass and high pass. That would mean the summed output response would be more dependent on just the amplitudes and less on the phase. That might get you there.
     
  2. case-sensitive

    case-sensitive Member

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    just found something that in speakers Bessel should be avoided, Butterworth for uneven and Linkwitz for even orders. This may be more for passive filters. But the simulation for Bessel had the biggest dent at the corner frequency from memory. Luckily in an active filter its easier to change elements. Maybe should wire in potentiometers first and once its sortes, get the proper velues. Otherwise eventually the paths in the PCB bord come unstuck.
    Building digital filters from scratch, hm, maybe can score one on ebay. Changing frequencies would be way easier then. Maybe I have to go for 4th order, 3rd gets 270deg, does not sound like a good plan. The original plan used 24 db filters that can be set via dip switches or so. But I tought 4th order is not that good at the corner frequencies. Some wavieness. Have to find that article and post a scan. Sidetracked with that rebuilding of a house.
     
  3. MrAl

    MrAl Well-Known Member Most Helpful Member

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    Hi,

    The reason i suggested Bessel for your particular case is because it has a more linear phase response which can then be compensated for with the All Pass filter. The other types have a sharper phase transition near the cutoff frequency which would be harder to fix.

    Also interesting is that i have read that Bessel is used for crossover networks, although that is not related to what you are doing here anyway.

    Yeah the DSP type filter would be programmable so everything that changes would be in code not hardware for the most part.
     
  4. dave

    Dave New Member

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  5. case-sensitive

    case-sensitive Member

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    actually not too shabby:
    https://www.minidsp.com/products/minidspkits/2-x-in-8-x-out so this can do stereo crossover for 4 drivers each, USD 275 as kit. Seems its programmed via USB and PC. Somewehere ther was a mention what filters and so on
    http://www.diyaudio.com/forums/mult...ley-whats-difference-whats-your-favorite.html
    one says avoid Bessel, next one says go for it. Guess I have to play with the simulation a little longer.
    There are some other issues with the amps, who knows, may be at the end I have to buy it all ready made or as kits...

    if I was to do it as 4th order it actually come out alright. Lowpass to 241 and highpass to 204 Hz.Most likely they went for Linkwitz.
     

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