passive crossover

Discussion in 'General Electronics Chat' started by hindiikawayos, Jul 8, 2011.

  1. hindiikawayos

    Thread Starter Member

    Jun 8, 2011
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    Hello!
    Can anybody help me how to design a passive crossover? Thanks...
     
  2. #12

    Expert

    Nov 30, 2010
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    Not with the specifications you posted.
     
  3. hindiikawayos

    Thread Starter Member

    Jun 8, 2011
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    I'm sorry! but what specification should I post?
     
  4. Audioguru

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    Dec 20, 2007
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    You need to read the spec's and manufacturer's recommended circuits of the crossover frequencies and circuits for your speakers. Cheap speakers do not have spec's nor recommended crossover circuits.
    Or you can guess wrongly and maybe blow up the speakers.
     
  5. hindiikawayos

    Thread Starter Member

    Jun 8, 2011
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    Thank you!
    Specification from speaker.
    max. input power: 100 watts
    impedance: 8 ohms
    frequency range: 5000 Hz
     
  6. Audioguru

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    Dec 20, 2007
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    A passive crossover network is designed with the detailed spec's of the woofer and of the tweeter. I guess your "100W" speaker is the woofer where it has a peak at 4kHz to 5kHz like most woofers and the crossover filter must reduce this peak.

    The tweeter has a manufacturer's recommended crossover frequency to prevent damage to it caused by low frequencies and to prevent it from resonating.

    The crossover frequency for the woofer must match the crossover frequency for the tweeter.
     
  7. davis.jacobj

    New Member

    Jul 7, 2011
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    Keep in mind that "matching" doesnt necessarily mean set equally. Their acoustic magnitude and phase responses should sum smoothly.

    Some keywords to research would be RC filter, LC/CL filter, impedance, frequency response and phase response just to name a few.
     
  8. davis.jacobj

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    Jul 7, 2011
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  9. Audioguru

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    If the highpass and lowpass filters are both 2nd-order or 4th-order then they make a notch at the crossover frequency. If one driver has its phase connected backwards then instead of a notch there is a boost of +3dB at the crossover frequency.
     
  10. #12

    Expert

    Nov 30, 2010
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    The Linkwitz-Reily equasions (at the linked page) claim to stop the notch problem, but the normal hump in the speaker response might defeat that allegation. Sometimes you have to measure what's really happening to get it just right.

    Hey, it's a start. Fine tuning it is what us nerds do.
     
  11. Audioguru

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    An even-order Linkwitz-Riley crossover also causes a notch when the drivers are in phase (the article says the phase is 180 degrees). But a Linkwitz-Riley crossover has the lowpass and highpass combine at -6dB (not -3dB like a Butterworth) and the phase of one driver connected in reverse then the +3dB boost of a Butterworth is gone.

    The normal hump in a woofer at 4kHz to 5kHz sounds awful (cone breakup that is poorly damped) so it must be filtered out. So the tweeter must operate down to 2kHz to 3kHz. Many little tweeters can't go down that low.
     
  12. #12

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    I've faced that problem. I think it's impossible to get a 1 inch dome tweeter to go down to 2Khz. 5KHz, yes. 2KHz...no.
     
  13. Audioguru

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    I used Philips 1" dome tweeters that go down to 1500Hz or 1800Hz (I can't remember). Their rear chamber was larger than ordinary tweeters that do not go so low.
    My crossover was at 2500Hz. They sound great.
     
  14. hindiikawayos

    Thread Starter Member

    Jun 8, 2011
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    Mr Audioguru that is not a woofer. its a mid range speaker. Buy the way my problem is in Bi-amplification. The tweeter and mid range speakers are connected in one amplifier(high frequency). Can I add a passive crossover between speakers and amplifier? Thanks!
     
  15. Audioguru

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    I quickly copied a Vifa 1" dome tweeter spec sheet and found a Morel with exactly thye same frequency response. They are recommended from 1650Hz to 25kHz.

    They have a 3" dome mid-range recommended from 600Hz to 3kHz and have 4" mid-woofers recommended from 80Hz to 3kHz.

    Of course you can add a passive crossover between a mid-range and a tweeter. The mid-range needs a lowpass filter plus a highpass filter and the tweeter needs a highpass filter.
     
  16. hindiikawayos

    Thread Starter Member

    Jun 8, 2011
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    Can you help me on how to design that kind of passive crossover? Thank you!
     
  17. Audioguru

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    Dec 20, 2007
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    If you have the manufacturer's recommended crossover frequencies and frequency response graphs then you can use an online crossover calculator.
    But frequently the speaker manufacturer has a recommended crossover circuit and even has a recommended enclosure designed.
     
  18. davis.jacobj

    New Member

    Jul 7, 2011
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    I googled and posted a link to the calculators for you :(
    You can use their recommended crossover points to plug into the calculators to get the values you need.
     
  19. hindiikawayos

    Thread Starter Member

    Jun 8, 2011
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    Thank you!
     
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