Subwoofer amp confusion?

Discussion in 'Archived Threads 2001-2004' started by Chris Shelly, Jan 6, 2002.

  1. Chris Shelly

    Chris Shelly Second Unit

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    Hello,

    I have been looking at several 12 inch powered subwoofers. Most are within the same price range and have very close specifications. I am a little confused about the amplifiers though. Some brands say they use 120W amps into 4 Ohm speakers. Others say they use 240W or 250W amp but then they don't say what Ohm the speaker is. I suspect these subwoofers actually have the same power but each manufacture words it different depending on what the marketing department feels is best. If you take a solid 120W amp that can handle a 4 Ohm load then you will double the amplifier power if the amp is 120 at 8 Ohm. So for example Acoustic Research could rate the amp for its S112PS at 240 Watts if the wanted to and not say what the impedence is. Could someone please clarify this observation for me?

    Chris
     
  2. Barry BB

    Barry BB Stunt Coordinator

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    A decreased ohm rating requires more power from an amp. The ratings are a measurement of the power that the amp is required to push out for the ohm load of the sub.

    Basically as you halve the ohm load you double the amount of power required for the amp to drive that load. So if you have an amp that is rated at 120 watts into an 8 ohm load and you connect a 4 ohm sub to that amp then the amp will be required to push out 240 watts. You run the risk of overheating the amp if you do not match a sub to its rated ohm load.

    This stuff confuses me also so I'm sure someone will jump in to correct any incorrect statements that I made.
     

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