My Receiver is 75 watts (speaker ?)

Discussion in 'Community Discussion' started by benlee, Jul 30, 2008.

  1. benlee macrumors 65816

    benlee

    Joined:
    Mar 4, 2007
    #1
    receiver is 75 watts per channel and I just bought some cheap Jensen speakers for satellites. Recommended power on them is 15-65 watts.

    Am I going to have a problem?
     
  2. mikeyredk macrumors 65816

    Joined:
    Mar 13, 2003
    #2
    Check the ohms you dont' want to blow out ur speakers or your amp
     
  3. poopyhead macrumors 6502a

    poopyhead

    Joined:
    Jan 4, 2004
    Location:
    in the toe-jam of greatness (Fort Worth)
    #3
    you probably wont have a problem. unless you bought a fairly expensive receiver, your receiver really isnt 75 watts a channel especially with all channels driven as would likely be the case when your surrounds are running
     
  4. benlee thread starter macrumors 65816

    benlee

    Joined:
    Mar 4, 2007
    #4
    the receiver manual says 75 watts per channel rms into 8 ohms, 2 channels driven, 20 Hz to 20 kHz,....

    says can connect speakers with an impedance of between 6 and 16 ohms. Whereas, speaker says Nominal Impedance: 4-8 ohms.
     
  5. CanadaRAM macrumors G5

    CanadaRAM

    Joined:
    Oct 11, 2004
    Location:
    On the Left Coast - Victoria BC Canada
    #5
    Roughly, the watts your amp puts out doubles as the impedance (ohms) is halved. so 75W at 8 ohms, 150W at 4 ohms. Speakers are not uniform in their impedance across all frequencies, yours appear to vary from 4 - 8 ohms depending on the frequency of the tone. Speaker Watt ratings should be comfortably higher than the amp driving them.

    Your amp has the potential to blow out the speakers, so restrict the volume control to half way or under and DON'T crank the bass or engage the loudness compensation switch at high volume.

    The other issue is that inexpensive amps/receivers tend to have a lot of distortion at the higher end of their power range. A distorted signal at 50 watts can do more damage to speakers than a clean signal at 50 watts.
     
  6. MacCheetah3 macrumors 6502

    Joined:
    Nov 14, 2003
    Location:
    Goodyear, AZ
    #6
    Hi
    My normal formula is to match the RMS power of both the amp ( per channel ) to each speaker. Not perfect but rarely it can be...If ever. Matching peak wattage is not a very good idea because, as you pointed out, it is extreme difficult to determine what true efficiency an amp can perform when even getting close to it's tested "peak" power output. Reasonable efficiency to maintain a continuous output power level may drop off after 50% of peak volume or even less on cheaper quality amplifiers / receivers.

    To the original poster. Typically, home audio is rated at 6 or 8 ohms and automotive is rated at 4 but some raise it to 6 ohms.
     
  7. OutThere macrumors 603

    OutThere

    Joined:
    Dec 19, 2002
    Location:
    NYC
    #7
    If your amp is only rated down to 6 ohms and the speakers as low as 4 ohms you risk damaging the amp, as it requires more work from the amp to run low-impedance speakers.

    If you decide to risk it, like others have said, careful with volume, as you could destroy the speakers. I can drive my 110 continuous/440 peak watt rated speakers to damaging levels with my 120w/channel amp pretty easily.
     
  8. Killyp macrumors 68040

    Killyp

    Joined:
    Jun 14, 2006
    #8
    You should be fine, just don't try and get any kind of blistering volumes out of it or else you will end up damaging things (the speakers and the amplifier most likely).
     
  9. benlee thread starter macrumors 65816

    benlee

    Joined:
    Mar 4, 2007
    #9
    why can cheap speakers damage the receiver? Now I don't know if I want to risk it.
     
  10. MacCheetah3 macrumors 6502

    Joined:
    Nov 14, 2003
    Location:
    Goodyear, AZ
    #10
    Hi
    Trying not to ramble. If the resistance ( ohms ) is significantly different, the amp may have to work that much harder. I don't see this being that big of a problem nowadays as most semi-current amplifiers ( including receivers ) have overload and overheating protection that will turn off the amp 99.9% of the time before anything of worry will happen. I also don't see too much with this one but another way is excess energy required by the amp when a speaker is either notably under or over powered, it creates overheating by having the voice coil exceed it's maximum range of motion ( xmax ). The voice coil stops moving forward for a moment, thereby creating heat from resistance and thereby also wear. This also happens again during the same cycle when the voice coil moves backwards and stops. This is what "burns out" a speaker and also causes distortion ( distortion is caused by the speaker not moving fluently ). Prolonging this heat buildup puts extreme wear on the speaker and soon it will not be able to perform properly and will always sound distorted ( at any volume level ). I would think in theory if the overload / overheat protection isn't quite sensitive enough in the amp, that this prolonged slow buildup could possibly damage it though I've never pushed an amp that far ( one or two speakers maybe :) ) to be able to confirm that for you. It's much quicker for a speaker to burn out as the cooling mechanism for the voice coil isn't designed for overheating and only for normal operation. So, it is quite easy to "burn" a speaker.

    Anywho...

    If you do decide to "risk it," I honestly don't see any permanent or otherwise worry-some damage affecting your amp though just listen closely the first time you test this setup for any distortion at your preferred volume level.

    A little end FYI. Proper "break in" of brand new speakers is very important for maximum performance and lifespan. Break in procedures allow the surround and spider to be slowly stretched to full working potential without any tearing of the fibers.
     

Share This Page