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  1. #1
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    Power stereo speakers with surround amp?

    Hi all. I'm new to the forums here and fairly new to home audio stuff.
    I just picked up a pair of used speakers in great condition (Pioneer CS-C9900) and I need to buy a receiver/amp for them. These speakers are 150W max, 6 ohm. I'm on a limited budget so I need to get something used. On craigslist I see a lot of 5.1 receivers, but they're all 80W or 100W per channel. I don't really care about surround sound, so my question is this:
    Is it possible (and if so, how) to bridge 2 channels of the surround amp to power one speaker? For example, let's say the amp has 5x 80W. I want to bridge (L+Ls) and (R+Rs) and ignore the center, thus having 2x 160W, which I think would be good for my speakers.
    Any help would be much appreciated. Thanks.

  2. #2
    Suspended markw's Avatar
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    Generally, bridging amps on receivers will release forever to the ether the magic smoke that makes them work.

    Just look for used/vintage stereo units or be satisfied using only one channel per speaker..

  3. #3
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    OK Thanks. I won't do that then.
    I found a great deal on a Pioneer VSX-D509S receiver so I bought it and it has been sounding great for the few minutes I've had it on so far.
    Here's what its manual says:
    Continuous average power output of 100 watts* per channel, min., at 8 ohms, from 20 Hz to 20,000 Hz with no more than 0.2 %** total harmonic distortion (front).
    Continuous Power Output
    Front................... 100 W per channel (1kHz, 0.8 %, 8 Ω)
    Center....................................100 W (1kHz, 0.8 %, 8 Ω)
    Surround.............. 100 W per channel (1kHz, 0.8 %, 8 Ω)

    Since my speakers are 6 ohm, 150W max, what does this mean? Will I ever have a problem since the ohms don't match?

  4. #4
    Phila combat zone JoeE SP9's Avatar
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    There should be no problem. If you are concerned, check the temperature of the receiver periodically during the first week or so while it's being used. As long as it's not too hot to touch it will be OK. Excessive heat is a sure sign of an amp being pushed too hard.
    Does the receiver have a 4 Ohm power rating? If it does, it will have no problem with most any speaker.
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  5. #5
    Suspended markw's Avatar
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    I gotta wonder what impac those little asterisks have on the power ratings of a unit.

    Quote Originally Posted by spookybathtub
    OK Thanks. I won't do that then.
    I found a great deal on a Pioneer VSX-D509S receiver so I bought it and it has been sounding great for the few minutes I've had it on so far.
    Here's what its manual says:
    Continuous average power output of 100 watts* per channel, min., at 8 ohms, from 20 Hz to 20,000 Hz with no more than 0.2 %** total harmonic distortion (front).
    Continuous Power Output
    Front................... 100 W per channel (1kHz, 0.8 %, 8 Ω)
    Center....................................100 W (1kHz, 0.8 %, 8 Ω)
    Surround.............. 100 W per channel (1kHz, 0.8 %, 8 Ω)

    Since my speakers are 6 ohm, 150W max, what does this mean? Will I ever have a problem since the ohms don't match?
    100 is a "magic number" that many manufacturers strive for ans many will stoop to various ways of stating the power output of their units to achieve it for marketing purposes.

    Most rate amps at 20 - 20 khz or the like, not at 1 khz, which produces a higher, less real-world, number.

    ...but it should work.
    Last edited by markw; 08-31-2009 at 04:46 AM.

  6. #6
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    Ah I see. Well that's kind of a bummer.
    My thinking was this:
    The speakers are 150W max, so they're probably about 75W RMS. Therefore 100W per channel on the amp is a good number. And I think 100W at 8 Ω is a bit more than 100W at 6 ohm, right? Does anybody know the equation to find that?
    Now I realize it's actually a bit less than 100W per channel, but I suppose it's still in the right ballpark. Thanks guys, for the reassurance that it will work.

    The receiver's manual does say to "use speakers with a nominal impedance of 8 Ω to 16 Ω. No mention of 4 Ω.

    Oh yes, and I forgot to include the asterisk definitions:
    * Measured pursuant to the Federal Trade Commission’s Trade Regulation rule on Power Output Claims for Amplifiers.
    **Measured by Audio Spectrum Analyzer.

  7. #7
    Shostakovich fan Feanor's Avatar
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    See my remarks in context, below ...

    Quote Originally Posted by spookybathtub
    Ah I see. Well that's kind of a bummer.
    My thinking was this:
    The speakers are 150W max, so they're probably about 75W RMS. Therefore 100W per channel on the amp is a good number.
    The "maximum power" rating of speaker is generally irrelevant for in-home use -- you don't need to have an amp that puts out that much power. ('Sensitivity' is the more useful specification.)
    And I think 100W at 8 Ω is a bit more than 100W at 6 ohm, right? Does anybody know the equation to find that?
    There is no useful formula. If an amp were perfect, it would deliver twice the power into 4 ohms it does into 8, but there are very few amps that will do this because they don't have a large enough power supplies to supply the current and/or they can't handle the extra heat that would be produced.
    Now I realize it's actually a bit less than 100W per channel, but I suppose it's still in the right ballpark.
    Sure, you won't have a problem.
    Thanks guys, for the reassurance that it will work.

    The receiver's manual does say to "use speakers with a nominal impedance of 8 Ω to 16 Ω. No mention of 4 Ω.
    Aren't your Pioneers actually 8 ohm? If so you have no problem. If they were 4 ohm you'd be very ill-advised to use them with that receiver.

    Oh yes, and I forgot to include the asterisk definitions:
    * Measured pursuant to the Federal Trade Commissionís Trade Regulation rule on Power Output Claims for Amplifiers.
    **Measured by Audio Spectrum Analyzer.

  8. #8
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    My speakers are 6 Ω.

  9. #9
    Shostakovich fan Feanor's Avatar
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    Quote Originally Posted by spookybathtub
    My speakers are 6 Ω.
    Ah! My apology: you did mention that. Then if your receiver is rated for 8 - 16 ohms, 6 ohms is a potential problem; watch for it getting overly hot in which case discontinue use.

  10. #10
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    The speakers you have are great speakers! U used to have the same ones and they can handle a lot of power with a lot of bass! 100W for them will be great!

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