Question about Bridging

Discussion in 'AV Receivers' started by Jason GT, Sep 4, 2003.

  1. Jason GT

    Jason GT Second Unit

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    For the amplification experts here --

    Why is it a bad idea to run a low impedance load on a bridged amplifier? This is something that I've read, and have no reason to really doubt, but there has never been a "why" given.
     
  2. David Judah

    David Judah Screenwriter

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    It cuts the impedance in half. So if you are running a 4 ohm system, bridging takes it down to 2 ohms.

    DJ
     
  3. Jason GT

    Jason GT Second Unit

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    This doesn't make sense (not that I'm doubting you, but it doesn't make sense to me [​IMG] ). Impedance is a characteristic of a load, not a source -- unless I'm missing something.
     
  4. David Judah

    David Judah Screenwriter

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    Try here and here for technical explanations.

    A few highlights:

    "Once you have established that your amplifier is capable of bridging consider the speaker load you will present to it. By bridging an amplifier you essentially halve the impedance it sees from a given speaker so an 8 ohm speaker looks like a 4 ohm speaker to the bridged amp."

    "Connecting the two 8 ohm loudspeakers together in parallel gives you a net load of 4 ohms. The bridged amp will now try to dump 400W into this load (200W to each loudspeaker). Each amplifier section "sees" this as a load of only 2 ohms (half of the 4 ohm net load), which is very nearly a dead short(emphasis mine). The current flow becomes 4 times what it would normally be into a single 8 ohm loudspeaker (one per channel in stereo mode) and the amp tends to heat up trying to deliver this much current."

    DJ
     
  5. Jason GT

    Jason GT Second Unit

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    Thanks DJ, those links were just what I was looking for.
     

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