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Thread: Altec 846A Valencia 8 or 16 Ohms?

  1. #1
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    Altec 846A Valencia 8 or 16 Ohms?

    Hello,

    I am aware that my speakers are rated at 16 Ohms but the rear panels say "Designed to operate from 8 Ohms to 16 Ohms". Any chance I can use them at 8 Ohms?

    Please advise.

    Cheers.
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    Administrator Mr. Widget's Avatar
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    Impedance is not a fixed number, it is a curve that varies with frequency. Typically an impedance number is based on the lowest impedance a speaker hits however this spec is rather arbitrary. It is possible for an "8 ohm" speaker to actually dip below 8 ohms at some point and be above 10 ohms most everywhere else. For example let's say you have two 8 ohm speakers that dip to 7 ohms at 125Hz. If you run two in parallel then at 125Hz, the combined impedance will be 3.5 ohms... could be a problem with some amplifiers and absolutely of no consequence with others.

    In most cases you really don’t need to worry about this spec. It only matters when combining multiple speakers on a single amp or in choosing taps on a tube amp. Even there when choosing taps on a tube amp, there is no “wrong” answer. You can compare the sound of the different taps and use the one that sounds best to you. You will not damage anything.


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    According to my approximate calculations an amplifier rated at 45W/Ch RMS into 8 Ohms would deliver 33 Watts. How wrong am I?

    Cheers,

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    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by f456gt View Post
    According to my approximate calculations an amplifier rated at 45W/Ch RMS into 8 Ohms would deliver 33 Watts. How wrong am I?

    Cheers,
    It isn’t that simple. The current capability of the power supply and other design aspects of the amplifier will determine the actual power capability at different impedances, but as I mentioned earlier, speakers are not resistors, and vary widely with frequency. The bench tests you see in magazines are with high power resistors and are not directly representative of the real world.


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