Impedance Matching

Discussion in 'General Electronics Chat' started by trainman, Sep 9, 2010.

  1. trainman

    Thread Starter New Member

    Sep 9, 2010
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    Impedance Matching Question: I bought a Sony receiver which calls for 8 ohm speaker impedance. I was going to hook it up to my current speakers but noticed they are rated at 6 ohms. What problems will I encounter if hook them?
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
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    The amp will have to deliver more current to reach any given power level. 2 ohms is not as bad as 4, but 6 ohms is an odd value.

    Worst case is blowing the output transistors when playing material with the volume cranked up. Sony is probably better than some years ago when the heat sinking was really poor.
     
  3. marshallf3

    Well-Known Member

    Jul 26, 2010
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    6 ohm speakers are becoming very common in home audio and generally considered as safe for use with either 4 or 8 ohm output amplifiers.
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
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    Shows you how plugged into the audio trends I am. Everything was 4 ohms last time I checked.
     
  5. lmartinez

    Active Member

    Mar 8, 2009
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  6. marshallf3

    Well-Known Member

    Jul 26, 2010
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    Yea, and now car sub amps tend to be rated into 2 or even 1 ohm.

    Used to be 8 ohms was the standard, then they came up with amps that were stable into 4 ohms so they were labeled as 4 or 8 ohms. I've seen the 6 ohm convention used on home speakers for quite a few years now.

    And we aren't talking about off-brando's either, even $1,000 apiece Infinity Sudio Monitors are often rated at 6 ohms.
     
  7. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    Unless your amp has a heatsink that is WAY to small or other problems like inaudible oscillations are happening, you won't have any problems with a 6 Ohm speaker and an amp rated for 8 Ohm impedance. CRank it uP, you've got lots of hearing left to lose and tinnitus is such fun...DAMHIK :)
     
  8. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    I didn't mean anydisrespect to you trainman. I just wanted to tell you that, as I shouldn't have said anything about you giving yourself hearing damage. That was not what I intended by my post. Just that I have damaged my hearing long ago and meant it as a warning to all people reading this post- loud noise causes tinnitus and I don't wish that curse on anyone.

    Don't Ask Me How I Know - DAMHIK

    Sincerely,
    Kermit
     
  9. t_n_k

    AAC Fanatic!

    Mar 6, 2009
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    I don't believe modern semiconductor based audio systems use maximum power transfer matching of amplifier to speaker.

    Amplifiers generally have very low output impedance - probably in the order of 10's of milli-ohms.

    Impedance matching was (is?) important with amplifiers having a valve (vacuum tube) output stage.
     
  10. marshallf3

    Well-Known Member

    Jul 26, 2010
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    tinnitus, loss in hearing sensitivity, (especially in certain frequency bands) and hearing distortion when there really isn't any are just some of the results of being exposed to jhigh volume levels for a brief period of time or even moderate levels over the long term.

    I'm also a victim and as someone who values music as much as I occasionally do it's a pain in the rear - especially the distortion part. Over the years I've learned to tune some of it out but I'll never be able to appreciate the finer points as well as I used to since the damage is usually permanent.

    Whenever I "hear" a car from a block away with subs that almost blow the glass out I cringe, knowing darn what those kids can expect not too many years from now. Then again, it's obvious they all they're interested in at the momemnt is being louder than their friends and that may never change.
     
  11. marshallf3

    Well-Known Member

    Jul 26, 2010
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    There's still a limit as to how much current an output stage was meant to drive and most modern protection circuitry can't compensate fast enough. Although less sensitive to it and better protected I still wouldn't run a 2 ohm speaker load on an amp that was only rated to drive no less than 4 ohms.

    If run without a speaker a semiconductor amp is still better off with no load and a tube amp with a dead short.
     
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