Butterworth, Linkwitz, Chebyshev, 2nd 3rd 4th order etc....what???

Discussion in 'Home Theater Projects' started by Anthony_I, Oct 7, 2003.

  1. Anthony_I

    Anthony_I Stunt Coordinator

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    can someone please point me in the direction of a website that will explain all this stuff to me and what the differences are.

    Its all so bloody confusing.

    Thank you
     
  2. John Garcia

    John Garcia Executive Producer

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    Are you designing your own speakers?

    Basic overview of Linkwitz-Riley and Butterworth:

    http://www.trueaudio.com/st_xov_1.htm

    Excellent book to pick up is the Loudspeaker Design Cookbook.
     
  3. Anthony_I

    Anthony_I Stunt Coordinator

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    not designing my own speakers, just trying to better understand how things work.

    but i barely understand a word that page is talking about.
    I was looking for something more along the lines of definitions of each type sort of thing.

    But i will read that page over a couple of times.
     
  4. Neil Joseph

    Neil Joseph Lead Actor

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    [​IMG]

    This belongs it the DIY/Advanced area.
     
  5. ThomasW

    ThomasW Cinematographer

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    All those are the last names of people that have invented different types of crossover designs.

    The 'orders' are how fast the XO (crossovers) stops the frequencies so

    1st order = 6db/octave of roll-off
    2nd order =12dB/octave of roll-off
    3rd order =18dB/octave of roll-off

    Roll-off means that the frequencies are decreased by the filter at the roll-off rate. So a 1st order XO centered @100Hz means that the frequencies will be 6db lower at 50Hz, 12dB lower at 25Hz and so on.

    This is really only important to know if you plan on designing your own speakers.

    For something like a subwoofer the best XO is 4th order (24dB/octave) Linkwitz-Riley
     
  6. BruceD

    BruceD Screenwriter

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    ThomasW,
     
  7. ThomasW

    ThomasW Cinematographer

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    Bruce

    Yes, IMO symetrical 24dB/octave is optimal for the sub/main XO. To obtain this I use the Marchand XM9 active XO's, not the sub out in my pre/pro

    The nice about using 24dB L/R for the sub/main XO, is that it keeps the phase correct, and provides a steep roll-off slope. This helps prevent smearing of the stereo image with HFE 'leakage' into the sub, and prevents the mains from working to low.

    I don't bother with any so called 'standards' (ie THX), my recommendations/experience is based on 3 decades of building and using subs
     
  8. Anthony_I

    Anthony_I Stunt Coordinator

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    So why should i use a 4th order linkwitz instead of a 4th order chebyshev or butterworth?? whats the difference?
     
  9. Richard Little

    Richard Little Stunt Coordinator

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  10. Patrick Sun

    Patrick Sun Studio Mogul

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  11. Richard Little

    Richard Little Stunt Coordinator

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  12. ThomasW

    ThomasW Cinematographer

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  13. BruceD

    BruceD Screenwriter

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    Thomas,

    Yes, as a matter of fact, like you, I also use a Marchand XM-9 between the mains and sub and don't use the sub-out on the processor (directing all bass to the main L&R).

    This then allows me to use a parametric EQ only on the output of the XO to the sub to correct for room modal peaks.

    I could never get a clean integration between the sub and main speakers with the processor's XO. I assumed this was because the high-pass and low-pass slopes of the processor's XO were mismatched.

    I guess if you only have bookshelfs with limited low-frequency capability, today's THX 80Hz XO in the processor may be OK, but I sure wish they also provided a symmetrical high-pass and low-pass 4th order L-R option.
     

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