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What's speaker impedance all about ?

Discussion in 'Home Cinema Speakers' started by Ray, Mar 8, 2005.

  1. Ray

    Ray
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    Hi.

    I'm planning to get a set of Cantons. On the website they are all rated the same 'nominal impedance of 4-8 ohms' . Why is there a range of values ? Why aren't they rated as 4 or 6 or 8 ohm ?

    The amp I'm looking at getting requires the centre and surrounds to have at least an impedance of 6 ohm. Presumably the Cantons will be ok.

    I don't want to blow any speakers so how accurate are these ratings ?

    Thanks

    Ray :)
     
  2. Dune

    Dune
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    Speaker impedance varies with freqency so the figures (4 or 8 ohm etc) are known as "nonimal". I think (though I am not certain) that if a speaker is rated at 8 ohm then it its impedance isn't supposed to drop much below that over the entire frequence range.

    So when they say 4 - 8 ohm they are being a bit perverse IMO as it will vary anyway.

    Loweer impedance speakers can be harder for amplifiers to drive. They draw more current from the amp but if it hasn't got the current to give then it will sound awful as it struggles to drive the speaker.

    Some amps are better than others at driving low impedance loads. Hi-Fi amps like Naim are renowned for being able to drive difficult loads and can sound louder than amps rated with higher watts per channel when driving such loads.

    Dave
     
  3. avanzato

    avanzato
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    The impedance quoted is an average figure. So an 8 ohm rated speaker will almost certainly drop to 4 ohms (or lower) at some frequency and go up to 12 ohms+ somewhere else. The Germans are just being more 'accurate' about it. You shouldn't have any trouble running the Cantons on your amp.
     
  4. Ray

    Ray
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    Thanks guys. Still not sure I completely understand it but I'm happier now that I won't be running into a serious problem.

    Cheers

    Ray :)
     

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