Reducing power output

Discussion in 'The Projects Forum' started by saja, Aug 5, 2011.

  1. saja

    Thread Starter New Member

    Aug 5, 2011
    3
    0
    Hi,
    I have a siren driver that I wish to use in a promotional vehicle for fundraising purposes, the unit is from an ex Police vehicle, it is a 12v unit and its output is 100w. I do not know what the average impedence of a police siren speaker is, 8-10 ohm?
    My question is I have a new 40w 8 ohm horn speaker, what is the best way to reduce the power output from the siren unit to match the 40w speaker?

    Many thanks SAJA.
     
    Last edited: Aug 5, 2011
  2. JingleJoe

    Member

    Jul 23, 2011
    185
    10
    my first thought is to add a resistor in series with the speaker
     
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  3. #12

    Expert

    Nov 30, 2010
    16,284
    6,797
    Another way is called a "pad" with resistor in series and resistor in parallel. Not knowing the impedance is what is stopping a good answer here.

    ps, Is that Johnny Depp from the chocolate factory?
     
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  4. hgmjr

    Moderator

    Jan 28, 2005
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    I have locked this duplicate post. You can find the original here.
     
  5. saja

    Thread Starter New Member

    Aug 5, 2011
    3
    0
    Sorry, new to this.

    SAJA
     
  6. hgmjr

    Moderator

    Jan 28, 2005
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    No problem. Duplicate threads tend to be confusing with some members replying to one and other member replying to the other. The continuity of discussion is lost when this happens.

    hgmjr
     
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  7. iONic

    AAC Fanatic!

    Nov 16, 2007
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    PWM at 40% dutycycle at 12V should reduce the 100W horn to 40W.
     
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  8. RRITESH KAKKAR

    Senior Member

    Jun 29, 2010
    2,831
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    I was also thinking this ....
     
    Last edited: Aug 7, 2011
  9. Audioguru

    New Member

    Dec 20, 2007
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    Your "40W" speaker might be rated in Watts or rated in phoney Whats.
    Many cheap speakers are rated in Peak Watts which is the real power number doubled.

    A speaker is usually rated for music or speech which have intermittent power, not continuous power from a siren so maybe you should reduce the power into the "40W" speaker to 10W or less.

    An amplifier's output power is reduced when its supply voltage is reduced.
     
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  10. JingleJoe

    Member

    Jul 23, 2011
    185
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    No, it's me!
     
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