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Can an amp be too powerful for a speaker?

Discussion in 'Home Cinema Speakers' started by tjobbins, Aug 11, 2005.

  1. tjobbins

    tjobbins
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    Not sure if this thread belongs in speakers or amps, it's more a general/theory question.. it probably does belong in Power Amps, but that forum seems to receive a lot less attention than Speakers, so hope it's ok here..

    I must admit to having close to 0 understanding of the technicalities behind watts, amps, etc. So apologies if this is a dumb question:

    Is it possible for an amp to be 'too powerful' for a speaker? I am looking at a used NAD S200 power amp, dual monoblocs with 250W into 8ohms, 400W into 4ohms. It can be bridged to a monobloc to provide a massive 700W into 8ohms.

    I am upgrading my amps at the moment - getting separate monoblocs for my fronts at least, but I would also like to get a monobloc for my Dynaudio Contour Centre which is 4ohm. I could therefore use the above amp, bridged, and provide up to a massive 1400W into 4ohm (I assume).. but is that too powerful? would that mean that if I cranked the volume all the way to maximum, the speaker would blow up? :) Not that I ever would, but I wouldn't want to think that it could happen.

    Again, apologies for a question which may be completely flawed. If anyone knows of any good articles/sites that can provide a basic grounding on all this, that would be appreciated too (e.g. I dont understand why 2*250W monoblocs bridged = 700W..)


    Tom
     
  2. Astaroth

    Astaroth
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    It would only be too powerful at higher volumes. As long as you are running them at sensible volumes then there wouldnt be any issue - whilst I wouldnt consider myself a total expert either, it has frequently been stated on here that running an amp that isnt powerful enough for your speakers is more likely to cause damage than the other way around.

    The other issue with speakers and amps is that there is little (particularly with speakers) standardisation on how to measure these statistics they quote and so you always need to take them all with a pinch of salt.

    The speaker (unfortunately) will not actually blow up but if you ran them too high for too long then you can potentially cause perminant damage to them (as well as your ear drums)
     
  3. roversd1

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    Its a tricky one to explain - an amplifier of 1 watt can 'fry' a speaker quite as easily as a 100 watt amp.

    There are many low wattage speakers that benefit from being driven by big amps.

    Speakers have a sensitivty rating - usually from about 86 db (decibels) upwards

    This measurement is when the speaker is fed one watt of signal and measured at 1 metre distance. (so different speakers with different efficiency ratings will sound louder/ quieter when fed a signal)

    Then next is the power rating, how much signal will the speaker take before the voice coils within the drive units overheat and melt?

    Then, how much is the minimum power handling before the speaker cuases distortion from the amplifier (the amplifier being over driven/ the speaker is drawing too much current)

    So you end up with a minimum/ maximum power handling plus sensitivity specifications for a speaker.

    Impedence is the resistence load thatthe speaker presents the amplifier - the lower the impedence the more current is required to make the speaker go loud - the amp has to work harder for a 4ohm load than it does a 8 ohm load

    Large power amps enable a speaker to cope with large dynamics/ transients, ie, when there are big changes in the music from quiet to loud etc.

    Smaller amps can struggle with these at high volumes.

    Amplifier/ speaker designs have been around for nearly 90 years so theres not alot to worry about.

    Big amplifiers tend to be used with multiple driver /ineficient home cinema speakers that require huge amounts of current to drive the mainly low frequency driven audio tracks.

    Your choice of amp when matched up with pretty much any mainstream speaker will be fine.
     
  4. tjobbins

    tjobbins
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    Thanks Astaroth, that's very helpful.

    I've just had a dig around the Dynaudio site, and thoughtfully they keep an archive of all their speaker specs so I've found the specs for mine.

    They provide 'IEC Long Term Power Handling' ratings, which for both my fronts and centre are '> 150W'
    (http://www.dynaudiousa.com/products/archive/contourarc/13/con13spec.htm)

    It does say more than 150W, but it does make me wonder what 'more than' means. I don't think I'll be going for that bridged Nad, but all of the amps I have so far looked at would provide more than 150W. E.g. Tag McLaren 125M monoblocs will provide around 250W into 4ohms.

    Would you say there's any risk of damage, or does this still only apply at very high volume levels?

    Naturally I wont be running them at those sort of levels - but I do worry what might happen if I accidentally dropped something heavy on the Volume Up button on my remote, or something similar :)
     
  5. roversd1

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    250w into 4 ohms is an absolute maximum - you'll be suprised to learn that even at fairly loud volumes, the average speaker will bearly draw more than about 55 watts
     
  6. tjobbins

    tjobbins
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    Thanks rover for all the info, very interesting. And yes you're right, I am surprised.

    So am I worrying too much about this? Can I assume that any amp rated at 100W (I havent looked at any lower than that) or above is going to be fine for my Dynaudios?
     
  7. roversd1

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    From memory, most Dynaudios are around 4 ohm which means they will draw alot of current from the amp. But, if the amp has a whacking great power supply, it shouldnt be a problem.

    You can always try something bigger to make them sing.
     
  8. Reiner

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    That should be fine, just don't exaggerate into either direction - there is e.g. no point in driving a 150W speaker with a 1000 Watt amp and as it has been stated a low-powered amp, when driven hard, can damage a speaker, too (so-called clipping).
    I guess an amp with 100-200 Watts would be a nice match for the Dynaudios, but make sure it's power stable as the Danes are demanding.
     

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