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What will a tweeter do to the impedence?

Discussion in 'Amps and Cabs [BG]' started by Player, Aug 11, 2000.

  1. Player


    Dec 27, 1999
    USA Cincinnati, OH
    I was thinking about adding a Tweeter (x-over @ 2.5k)to my 2-10 cab. How will this effect the impedence of the cab? Can I use an 8 ohm horn with just a x-over cap? What if I use an L-pad? I want to keep the cab @ 8ohms. (I'm thinking I need to cover the 3k htz - 7k range, the 10s go to about 4k). I found one that says "No x-over needed" that's rated at 400w. It's over 1k ohm @ 1khz and over 20ohm @ 40khz. I'm running 2-4ohm 10s in series (8 ohm), if I paralell the tweeter what happens to the impedence of the cab? Any help would be greatly appreciated. Thanks.
  2. Mo' bass

    Mo' bass

    May 4, 2000
    In my Trace Elliot manual it says I can safely add a Horn box to a speaker without worrying about the impedance. I think this is because the Horn box has a very high impedance compared to a 'normal' speaker.

    Let's assume that the impedance of a horn = 1kOhm.
    The formula for calculating the impedance of two speakers in parallel is 1/total = 1/spkr1 + 1/spkr2, so....
    1/total=1/8 + 1/1000=125/1000 + 1/1000= 126/1000.

    TOTAL= 1000/126 = 7,93. That's almost 8 Ohms, so no problem!
    ( if the horn had an impedance of 100 Ohm this numebr would be a little bit lower, but still nothing to worry about.)

  3. Sorry for the delay, Paul, I've been busy.

    Mo'bass is absolutely right.

    I have to add this:

    Nearly every horn has an 8 ohm impedance. Only a piezo crystal horn (the type you guys are talking about) are 1k ohms. They can be parallelled to any woofer without a crossover. However, adding a 33 ohms 5 watts resistor in series (with the horn only), for protection, is often recommended. A standard L-pad cannot be used, since they are designed to deal with an 8 ohms load.

    I, for one, don't like piezo tweeters. They sound harsh and crispy, always too loud. I have found it worth the trouble of putting in a crossover, so I can use a electrodynamic (8 ohms) tweeter.

  4. Player


    Dec 27, 1999
    USA Cincinnati, OH
    Thanks Joris.
    So if I use an 8 ohm X-over and an 8 ohm horn with an 8 ohm speaker load will the cab be 8 ohm?

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