building speakers, i need help with ohms..

Discussion in 'Home Theater Projects' started by Jeff:L, Jul 2, 2004.

  1. Jeff:L

    Jeff:L Auditioning

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    I would like to build some bookshelf speakers or maybe floorstanding speakers. I know that my receiver puts out 85 watts at 8ohms. Well one midrange is 8 ohms, and one tweeter is 8 ohms. So I can wire them to get either 4 ohms or 16 ohms right? So how can I get my bookshelf speakers to have the correct ohms? (8ohms)?

    Imagine if I wanted two midrange and one tweeter (all 8 ohms).. how would I get 8 ohms out of that? Any help is appreciated... thanks!
     
  2. Dave Poehlman

    Dave Poehlman Producer

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    Well, I believe the filter circuit (crossover) splits the power so you still wind up with roughly an 8 Ohm loudspeaker with an 8 Ohm tweet and 8 Ohm mid.

    Now, if you threw another mid into the equation, those would be wired in parallel and give you an end result of 4 Ohms on the mid side, while the tweeter would still give you 8 Ohms. So, the total would be sort of an average somewhere around 6 for the whole speaker.

    Most modern receivers are capable of handling a 4 to 8 Ohm load, so as long as you're within that range, you're fine.

    Does that make sense?
     
  3. Rory Buszka

    Rory Buszka Supporting Actor

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    Since the bass range makes the greatest current demands on the reciever's amplifiers, I would get an amp that can support a 4 ohm nominal load if your midbass or bass section is going ot be nominally 4 ohms. It is not a perfect averaging since the demand on the amplifier in the treble range is less than 20% that of the demand of the bass section.
     
  4. ThomasW

    ThomasW Cinematographer

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    Regardless of what the crossover does, the impedance of the woofer is the impedance of the system.
     
  5. Dan Wesnor

    Dan Wesnor Second Unit

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    Actually, the crossover can raise the impedence of the system above that of the woofer, but only if the designer knows what he is doing.
     

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