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Speakers in series - capacitor

Discussion in 'Audio' started by cero10, Oct 19, 2020.

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  1. cero10

    cero10

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    Oct 12, 2020
    Hello guys. I read about speakers in series (especially high frequency ones) need bidirectional capacitors not to blow up.
    So my question is: in case of connecting four 2-ohm speakers in series(total 8 ohms) do I need a single capacitor parallel to the last speaker? or three capacitors parallel to the 2nd, 3rd and 4th speakers?
     
  2. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    Neither nor. You need a single capacitor anywhere in series. Usually one would place the capacitor at one end of the series connected speakers.
     
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  3. cero10

    cero10

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    Oct 12, 2020
    Simple as that huh...thank you for the quick reply. So the capacitor rating should be halved from 2 speakers in series to 4 speakers in series, if I want to keep the same cutoff frequency right? [we are talking about the same speakers]
     
    Last edited: Oct 19, 2020
  4. Audioguru

    Audioguru

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    Sep 24, 2016
    Why do you use four 2 ohm tweeters in series instead of one 8 ohm tweeter? To make the sounds go left, right, front and back?
     
  5. cero10

    cero10

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    Oct 12, 2020
    Because I have them lying around..this is part of a portable speaker build and it being portable already poses some challenges. So I am trying to look at the little discrepancies before they blow.
     
  6. Harald Kapp

    Harald Kapp Moderator Moderator

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    How about a complete schematic diagram of your circuit for inspection and possible hints?
     
  7. bertus

    bertus Moderator

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  8. cero10

    cero10

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    Oct 12, 2020
    This is the complete schematic.
    whole circuitry.png


    I think all of those project are going for clear sound, while I am going for portable. I checked out some of them, and they are using filters?? (inductors/resistors) for each of the speakers. I have not read about those at all.
     
  9. bertus

    bertus Moderator

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  10. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    These capacitors are not connected in series. This is how a series connection looks like:
    upload_2020-10-20_15-56-1.png
    You would need a capacitor for the subwoofer, too.

    BUT: Inspect the circuit board of the amplifier. Most likely there are already the required capacitors installed and you will not need extra capacitors. Otherwise you would find these capacitors loosely mouinted in the original speaker cabinet which is most unlikely as they can much better be fitted to the PCB.
     
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  11. cero10

    cero10

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    Oct 12, 2020
    They were indeed mounted inside the speakers but not in the arrangement you imagine. It is connected like this: satellite speaker.jpg

    Why would I need a cap on the sub as well? I am a newbie and do not understand the logic behind it.
     
  12. cero10

    cero10

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    Oct 12, 2020
    Last edited by a moderator: Oct 20, 2020
  13. bertus

    bertus Moderator

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    Hello,

    C1, C2 and L1 make the highpass filter for the tweeters.
    L2 and C3 make a low pass filter for the low range speaker.
    Rp1 and Rp2 make an attenuator to balance the volume between low and high.
    Req en Ce make a correction for the impedance of the low speaker.

    Bertus
     
  14. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    In this case the capacitor bypasses one of the two speakers for high frequencies. This is kind of a simple crossover network to account for the different power content of different frequencies so that the total of the acoustic output of all speakers sums up to a pleasant listening experience.
    To protect the speaker from DC components in case of a failure within the amplifier. DC can quickly destroy the speaker. The capacitor for the subwoofer needs to be of a mucj higher capacitance than the ones you use for the tweeters.
    That is a true 2-way crossover to separate the bass and lower midtones (speakers f5) from the upper midtones and treble (speakers sd1.1). Crossover frequency in this example is 4000 Hz, but that i not always the case.Bass speakers cannot reproduce treble and vice versa treble speakers (tweetes) cannot reproduce bass. By separating the frequency ranges the speakers are operated in their optimum frequency range for best sound quality.

    Matching speakers, crossover frequencies and crossover circuit as well construction of the speaker housing is a science per se (see e.g. here). It requires some math and lots of experience, not to mention the technical equipment (test tone generators, spectrum analyzers) and a good sense for sound quality to build a well soundig speaker.
     
  15. Audioguru

    Audioguru

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    Sep 24, 2016
    Your high voltage battery will be too big and heavy to be portable. 22.2V is six series 3.7V lithium cells that produce 4.2V each when fully charged then the total is 25.2V for each battery. Why bother stepping them up to 26.4V? You will need 24 18650 Lithium battery cells for the amplifier to play loudly for 1 or 2 hours, or four large 12V car batteries.

    A tweeter MUST have a series capacitor to block low frequencies from blowing it up. A woofer needs a series inductor to block its shrieking cone breakup mid-high frequencies.
     

    Attached Files:

  16. cero10

    cero10

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    Oct 12, 2020
    1) what is the equation that keeps the higher than 4000Hz frequencies between C1,C2 and L1?
    2) what is the equation for keeping the lower than 4000Hz part of the signal between between L2 and C3?
    3) does this work like a constant potentiometer?
    4) so does it increase or decrease impedance?
    Sorry for the multiple questions?
     
  17. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    Kalimera Cero:

    1 and 2) These are LC filters. The basic LC filter equation is of not much use as the other components including the frequency dependent impedance of the speakers have to be accounted for. The design of crossover filters for well sounding speakers is a little science per se (see for example here)
    3) No. A potentiometer is a voltage divider, ideally independent of frequency. A filter like this is a frequency divider, ideally independent of voltage.
    4) What do you mean by that? If well designed the impedance as "seen" by the amplifier is the same as for a single speaker.
     
  18. bertus

    bertus Moderator

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  19. cero10

    cero10

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    Oct 12, 2020
    1) So one of the speakers is playing the full range of signal and the other above 1200Hz? or both play above 1200Hz?
    2) I know that the z2300 amp has a low pass filter of 150Hz, I am assuming I still need the cap, so my question is how big should the cap be not to impede the signal of <200Hz?

    I got this frequency cutoff calculator online, is this legit?
     
  20. cero10

    cero10

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    Oct 12, 2020
    In my case the z2300 has those on its pcb, but I am keeping the: capacitors cut lower frequencies and inductors cut higher frequencies.
     
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