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How do I work out which power speakers are appropriate to the amp?

Discussion in 'Hi-Fi Stereo Systems & Separates' started by Stevie G, Apr 4, 2004.

  1. Stevie G

    Stevie G
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    Ie, if I get a 25 per channel (rms) amp, what so sort of rated speakers should I go for, or if I went for a 50w one, etc.

    Thanks.
     
  2. karkus30

    karkus30
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    Ah, how many Watts :laugh: the age old question......right here we go.

    Firstly, dont get too concerned with power ratings. If your buying a good quality amplifier then it should drive most speakers that you will find in your average hi fi/ electronics store. Check what impedance the amplifier will drive, its usually 8 ohms, just to make sure your not getting hoodwinked. You will see speakers with 100w 150w or more a decent amp will have no problems driving these speakers.

    The exception to this rule are speakers that are difficult to drive and these are usually in the higher price bracket, starting around £600.

    The shock is finding that an amplifier with a very low output, say a minidisc player which could only output a few fractions of a watt, is very likely to cause damage to a speakers rated at much higher wattages.

    This can is also a problem with amps that are rated for PMP (peak music power instead of RMS) it might say 400 watts, but just looking at some of those cheap amps tells you they wont deliver that for very long. Conversley a quality amplifier rated at 100watts is unlikely damage a 30Watt speaker.

    If you are intrested in delving a bit deeper, then you might find it interesting to know that the power of an amplifier is not really related to how loud it is: For instance you might think a 50 watt amp was twice as loud as 25 watt amp, but you would be wrong. To get around twice the volume takes around 10 times as much power, so you'd need a 250 watt amp.

    Lots of high end amps are rated around 25-40 watts and can drive even difficult loads. Thats because they have very careful design and large power supplies that allow the amp to deliver huge amounts of current with ease.

    Finally there a thing called speaker sensitivity, its usually quoted in db. Anything around 89dB and above will be fine. If you see anything in the low 80s and below, beware, these require amplifiers that are able to output large currents. Even some quality amplifiers may struggle with speakers that are very inefficient.

    Hope thats not confused you too much, I ve generalised as much as possible.
     
  3. Stevie G

    Stevie G
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    Crikey, nice and easy then....!

    The one I'm looking as it only a fairly cheap system, a Hitachi mini system with DAB, but the speakers don't look very powerful so I thought perhaps I could replace them if they don't sound too good. I don't know what the impedance is on them, as I can't find them on the Hitachi web site (it's this one here http://www.currys.co.uk/martprd/sto...dfjcflgceggdhhmdfho.0&page=Product&sku=961329 )
     
  4. karkus30

    karkus30
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    With a mini system its probably best to stick to the speakers that come with the unit. Small amps like these rarely have the power to drive anything difficult. Higher wattages on speakers dont make them more powerful/louder. I have seen people add things like Wharfedale diamonds to mini systems with reasonable results.

    I couldnt find the system you mentioned as the site was just a log out page.
     
  5. Stevie G

    Stevie G
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    Sorry, if you go to http://www.currys.co.uk it's got the link on the from page - this weeks hot offer, £189.

    I don't want anything too powerful, just with a better range with three way speakers that are rated higher.
     
  6. karkus30

    karkus30
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    Better range ? 3 way speakers dont have a better range, just more drive units. The speakers that come with the system are pretty much designed to take advantage of the system 'as is'.

    When you start talking of better sound quality, then every part of the system would need improving. Power is not the issue with improved sound quality.

    At this stage its 'welcome to the wonderful world of hifi' , its not a hobby, its a lifestyle :)

    I would suggest you started looking at hi- fi separates if its sound quality your after. It can still be reasonably priced if you use places like Superfi or Richer Sounds etc or even better if you buy second hand.

    There are of course the usual constraints, space, asthetics, cost. But if you really want a great sound (that doesnt mean powerful), then separates are where its at. If your interest grows, then you can start up-grading, a component at a time. This way your system grows with you.
     
  7. Stevie G

    Stevie G
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    I know what you're saying, but I'm only after a decent little stereo for occasional use, not a fully specced system. I've already got a pretty good surround system with a Marantz amp, but for listening to the odd cd or the radio it's too powerful. We've got an old couple living downstairs and I feel too consious to be able to enjoy it properly when the floor vibrates!

    This caught my eye because it's very small and looks nice, and also has dab, but I just thought the single drive speaker (sorry, I think what I meant by range was one with bass, mad & treble of some description).

    This specific purchase is just for something that looks nice, subtle and sounds good, not a fully fledged system.

    Thanks!
     
  8. karkus30

    karkus30
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    As I said, you dont need a three way speaker (woofer, mid and tweeter), most speakers these days are just two way designs (some have the tweeter in the centre of the woofer, so you wouldnt recognise them as two separate drive units).

    The speakers that come with your system will be fine for the use your going to put them to. A better speaker would probably need to have the volume raised to get it working properly.

    I wouldnt waste your cash changing the speakers, but its your choice.
     
  9. Stevie G

    Stevie G
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    OK, thanks for the advice! :)
     
  10. Stevie G

    Stevie G
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    I just had a look at it in a store and it's 8ohms.
     

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