Bi-amp = 2 times the power?

Discussion in 'Archived Threads 2001-2004' started by Ken Custodio, Jun 1, 2002.

  1. Ken Custodio

    Ken Custodio Second Unit

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    If you bi-amp a set of front speakers, are you essentially doubling the watts to your speakers or is it the same watts, since one channel goes to the tweeter and one goes to the woofer?
     
  2. RobertR

    RobertR Lead Actor

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    I biamp my front speakers using a 5 channel amplifier. I have a 400 watt channel going to the midrange/tweeter and a 400 watt channel going to the woofers. Yes, that's a doubling compared to connecting a single 400 watt channel to each speaker.
     
  3. Steve Zimmerman

    Steve Zimmerman Second Unit

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    I don't think it's necessarily a doubling of power. First off, you're splitting the pre-amp output and second, and unless you're using two separate amplifiers for the biamping you're still essentially drawing power from the same pool in many cases.

    Even if it *is* a doubling of power, that's only 3dB of extra extension at the highest volume.

    When I bought my first 5-channel amplifier I couldn't stand the thought of "wasting" two unused channels, so I "fool's" biamped for a while. Then I went back to using one channel per and, frankly, I feel rather embarrassed for having spent the extra money on cables and Y-connectors.

    --Steve
     
  4. Wayne_T

    Wayne_T Stunt Coordinator

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    Robert, I agree. Now what happens to the impedance of the speaker? i.e., if I have an 8 ohm speaker, and I remove the bridge from the terminals, do I have two 8 ohm loads? Or two 4s? Or two 16's?
     
  5. Wayne_T

    Wayne_T Stunt Coordinator

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    Steve, if you were connecting two separate channels from your five channel amp to separate terminals on your speaker, then you were biamping that speaker. I don't know why you would call that "fool's" biamping. Please explain.
     
  6. Wayne A. Pflughaupt

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  7. Wayne_T

    Wayne_T Stunt Coordinator

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    Thanks Wayne for the answer on the impedance question. Makes sense to me.
    So "fool's" biamping is an elitist term for what ordinary folks would call passive biamping?
    Steve, I wouldn't dismiss the benefits of passive biamping or be embarassed about doing it. It is strongly recommended in my speaker manuals, and my own experience validates that. I guess it could be somewhat dependant on the internals of the speaker though, so some might benefit more than others. At the very least, you do get double the power which I think is always an improvement.
     
  8. Steve Zimmerman

    Steve Zimmerman Second Unit

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    Wayne_T, I'm no elitist and if it works for you then great.

    However, not all speaker manufacturers think passive biamping is a worthwhile endeavor and you will only get double the power if your amplifier is designed a particular way.

    --Steve
     
  9. RobertR

    RobertR Lead Actor

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    I should mentioned that my speakers use TRUE biamping, as they make use of an electronic crossover and there are two electrically separate terminals for the mid/tweets and woofers. The nominal impedance for each section is 4 ohms. I forgot to mention that the amp delivers 800 watts per channel into 4 ohms, so my front speakers have a whopping 3200 watts available to them. [​IMG]
     
  10. Steve Zimmerman

    Steve Zimmerman Second Unit

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    That's a lot, Robert. Three questions: (1) How far away from the speakers do you sit, (2) What is the efficiency of the speakers in dB, and (3) What is the wattage rating of the speakers?

    10000% of the recommended daily allowance of vitamin C makes for, well, expensive urine.

    --Steve
     
  11. RobertR

    RobertR Lead Actor

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    Steve:
    1. about 11 ft.
    2. 92 dB/1 meter/1 watt
    3. 500 watts for the mid/tweeter section and 500 watts for the woofer section. Since the bass response is rated flat down to 16 Hz, I feel no need for a subwoofer. [​IMG]
     
  12. Steve Zimmerman

    Steve Zimmerman Second Unit

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    Well that means one of two things... No ear drums or a small jock. Ha ha ha. Sounds like some wild speakers.

    --Steve
     
  13. KeithH

    KeithH Lead Actor

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    Biamping does not double the power. Bridging can, depending on the amp design. In bridge mode, an amp is used to drive one speaker, and the power may be doubled.
     
  14. KeithH

    KeithH Lead Actor

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    Regarding bridging, here is what www.whathifi.com out of the UK says:
     
  15. Wayne_T

    Wayne_T Stunt Coordinator

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    Keith, with all due respect biamping does double (or at least approximately double) the power to the speaker. If I connect both sides of a 200W/channel amp to a speaker, it now gets 400W. I will believe that until someone can tell me where the second 200W vanished to.
     
  16. RichardMA

    RichardMA Second Unit

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    True biamping need not mean using a digital crossover.
    You can use an outboard passive crossover with separate
    sections for each driver. My centre is tri-amped,
    the woofer (10") driven by a 100wpc Marantz monoblock,
    the midrange driven by a Antique Sound tube amp and the
    tweeter driven by another identical tube amp.
    The idea of biamping with an electronic crossover at
    the "line level" is that most speakers aren't bi-wirable
    and don't have separate crossovers for each driver. So
    do though. The problem with the line-level electronic
    crossover is (again) the need to split the output.
    But if you tri-amp, you are likely to have to do this too.
    In my setup, I have two centre outputs from my Sony preamp
    and I split one to do the amping to the midrange and tweeter.
     
  17. KeithH

    KeithH Lead Actor

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    Wayne, What Hi*Fi? did a cover article on biamping stereo amps last year. In it, they said that biamping does not double the power as is usually believed. I have the issue in the house and when I find it, I will post their exact statement.
     
  18. Wayne A. Pflughaupt

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  19. Steve Zimmerman

    Steve Zimmerman Second Unit

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