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Quick power rating question

Discussion in 'Hi-Fi Stereo Systems & Separates' started by Frazal666, Jan 3, 2005.

  1. Frazal666

    Frazal666
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    Hello, just want to ask, when speakers and stereo amps are rated, it says for example 75 watts RMS. Does this mean each channel/each speaker or in total?
     
  2. eviljohn2

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    Allegedly it's each channel. With some AV amps you need to take this with a pinch of salt though as their output can dramatically drop when more than the standard front 2 speakers are being used. :)
     
  3. karkus30

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    It means very little in the wider context. The rating of an amplifier depends on the sensitivity of the speakers and how difficult they are to drive.

    Some smaller speakers maybe rated at 50W, so you would think a 75W RMS amp would drive them easily, infact you might even think the amp was too powerful for the speakers. But its easy to find amplifiers that are rated much higher struggling to drive the speakers properly.

    This applies in reverse. For instance Naim amplifiers, like a NAP 250 are only rated at 85W, but it has a huge power supply and can continue driving very difficult speakers with ease.

    Its all a bit difficult and after a while you begin to understand which amplifiers are the really powerful beasts and which are clearly overstating their ratings.

    Same goes for speakers, size and power handling mean zip and again the difficult speakers are well known.
     
  4. Frazal666

    Frazal666
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    Ill give you the links. My situation is, I wanted to buy a Mini System - Panny SCAK520 Comet, but I heard separtes sounded better. In Argos, they had a amp, DAB/FM Tuner, CD Player & Speakers for £220. (Get speakers free when brought with rest) link to amp - Argos Separates, but only has 60 watts, compared to 420W with Panny (Unless per channel, but still low). Maybe you can suggest just amp & speakers for under £300. Ill use DVD Player as CD Player using phono lead. Thanks.
     
  5. karkus30

    karkus30
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    The Panny is unlikely to be all that powerful, I just dont know anything about the 101. At £300 you can probably pick up something pretty decent, I cant really advise you on that. Theres probably been loads of posts on best buys at that sort of money, or you could increase your options and buy from a reputable secon hand dealer.
     
  6. Frazal666

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    So is there a way of jugding speakers and amps accuratly? And what do you mean power supply? does get more power from the mains, or does amplifiy with more power, even if the rating is low?
     
  7. bobbypunk

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    To start with you can break down the Panasonic's "claimed" wattages a little:
    High frequency 65 watts per channel
    Low frequency 65 watts per channel - (These do not double output)
    Sub 160 watts
    As far as I understand I think the 10%THD written on their basically means the figure allows quite alot of distortion within the power rating.

    The acoustic solutions amp only claims to be 30 watts running 8 ohms speakers which makes the theory that it will be quieter but the distortion level is only 0.05%.

    There maybe some complicated maths available to work all this out but in general it means seperates will tell the story at least a little closer to the truth!
     
  8. Frazal666

    Frazal666
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    Ok, I think im starting to understand. It sounds like the THD plays a big role in telling how good speakers and amps are. I want a lot of bass, so I want a powerful amp and big speakers, and now, with low distortion. Ill just go to richer sounds and test them there, but I need to know, does the speaker have to match the Ohms of the amp? Or can it bit higher/lower? thanks.
     
  9. cosmicma

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    amplifier power ratings on the cheaper end of the market are just numbers to make them look good

    speaker wattage ratings are usually peak values but saying that a well driven speaker will usually accept more than it given rating without fear of damage but no speaker will tollerate an amplifier driven into distortion for any lengh of time the distorion heats up the voice coils which makes it expand and touch the magnet ( the gap between the coil and magnet is tiny ) which in turn shorts the coil out and cooks it. this is more prominent in the tweeter because the coils are made of thinner wire and the gap is smaller so takes less effort to cook it hence the tweeters are the first to go this is usually down to lack of power rather than too much power from the amp

    when an amplifier is rated there allsorts if things that can be exagerated
    if we take a 10 watt amplifier as an example the rating should be 10 watts rms both channels driven into 8 ohms 20 - 20 khz at 0.05% distortion
    but we can make these figures look a lot more impessive
    if we only drive one chanel ( gives the power supply an easier time ) into 4 ohms and allow 10% distortion we could easilly pump the figures upto 25 watts
    if i then use a peak figure ( x rms value by 1.414 ) vualla i can now sell you a 35 watt amp which in reality is 10

    on the more expensive side of amplifiers the wattage claims are usually true the things to look for are is how close the come to doubling there power into 4 ohms ( krell are good for this ) what the slew rate is ( how fast it can get rid of current this affects the over hang on bass or how tight the sound will be as some may put it ) but these are all fugures on paper and doesn't mean much in the real world the most important thing is to listen before you buy if the overall sound ( character of the music ) pleases you then go for it if it doesn't regardless of reviews or somebody telling how fantastic it might be walk away
     
  10. Frazal666

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    You said that you should hear for yourself. So how do you know if the amp is not powerful Enough? Specs for what I may buy is below, please help. Im sure panasonic will not let thier reputation with such a highly rated system (lowest rating for this system is 4.5/5 so far, but as you said, its down to your own judgment, but its kinda hard, you know). Thanks. Sorrry for all this, and I would really appreciate it if you would just have a look. It is a Panasonic SCAK520.

    Amp@10% THD both channels: Low channel: 1KHZ 65W 6Ohms
    High Channel 10KHZ 65W 6Ohms
    Sub: 80HZ 160W 8Ohms
    Speaker 3 Way 3 speaker : Woofer 16cm Cone
    Tweeter 6cm cone
    Super Tweeter 2.5cm piezo
    Impendance(All woofers/tweeters): 6 Ohms
    Input power Max: 65W (All woofers/tweeters)
    Output Sound Pressure: 83db/W (1.0M)
    Crossover: 2.6 KHZ, 10KHZ
    Frequency Range: 37HZ-23KHZ (-16db)
    44HZ-22KHZ (-10db)
    Sub: 1 Way, 1 Speaker 16cm cone 8 Ohms
    Input Power Max: 160W
    Output sound pressure level80 dB/W (1.0 m)
    Frequency range40 Hz–220 Hz (–16 dB)
    45 Hz–180 Hz (–10 dB)
     
  11. jon_mendel

    jon_mendel
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    Oddly, if you believe the stats then the bass on the panny sub doesn't seem to go that low (my little mission bookshelf speakers go down to 45-50hz...). I guess you could always have a listen to the panny system and see what you think...

    If you don't need tuner, CD player etc. then you're v likely to get a better sound if you just spend your money on an amp and speakers. Richer sounds will have a few amps around the £100 mark (with both amp and speakers, you might get a better deal if you also look at the 'trade counter' refurb stuff they've got) - you should be able to find a Cambridge Audio or Marantz amp that'll give you a decent level of power. If that leaves you a bit under £200 to spend on speakers, you should be able to get something with decent bass; it might be worth looking at a pair of floorstanders as an alternative a sub/bookshelf speakers combi - floorstanders without a sub can also give you a good strong bass (JCW ML710 floorstanders, for example).

    Jon
     
  12. Frazal666

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    Frequency Range: 37HZ-23KHZ (-16db) 44HZ-22KHZ (-10db). doesent this means the speakers go down to 37hz? I have read reviews of this, and all of them mention that the bass is really powerful. One said it managed to make a model ship to fall of a shelf. I would buy seperates, but I need them o be silver, and there are practically no speakers or amps (Good ones anyways) that are silver, unless there £700. (I saw amp & Speakers for £700). I guess the best thing is to try it out. Do they let you try stuff out in Comet? Thanks.
     
  13. cosmicma

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    from what i can see there seems to be a few mini systems that all seem to have the same sort of features and the panasonic scak520 being one of them
    by the looks of it they seem to share the same electronics they only seem to differ cosmeticly and of course the badge
    i havn't heard the panasonic version but i have certainly heard the one sony has to offer ( my son has one ) and also the samsung offering without the sub ( my daughter got that one for xmas ) and for the price their quite reasonable
    if you want something to look fairly impressive with loads of twiddly bits and can be made to sound reasonable ( don't bother switching on the sub ) then go for it the price is good but if your asking what do you think of the sound well in all honesty i have tried to sit in front of my daughters and take it seariously but i can't it's not a piece of hifi
    she loves it by the way and my son is well impressed with his sony and for what there used for ( bedroom ) i think there ideal
    like i said in my previous post forget what i think or what anybody else thinks for that matter we don't have to listen to it if you like it buy it
     
  14. jon_mendel

    jon_mendel
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    Hi,

    looks like I might have misread the stats ;) Anyway, comet should let you have a listen (though you might want to call beforehand to check) or failing that I think they *might* do a 7 day money back offer if you're not happy with the panny when you get it home. It's a good idea to have a listen to an alternative system or two as well, to see how they compare sound-wise - either at Comet or perhaps try somewhere like Richer Sounds to compare it to separates.

    You seem to be getting more silver amps now, but yeah silver speakers might be a problem (I think some of the mordaunt short ones are silver-fronted, if that helps...) Anyway, hope you like what you get in the end.

    Jon
     
  15. Frazal666

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    thanks. I have an idea though. Get this and connect a sepearte amp via the optical out. Than add additional speakers to make some kind of suround extension. Would that work?
     
  16. jon_mendel

    jon_mendel
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    Depends what you mean by work, I guess. I *think* it'd be possible to connect 2 amps up like this, but the optical out from the 2-channel panny amp would just be the same 2 channels you're hearing from the panny's own speakers - in other words, you'd have 2 pairs of stereo speakers. This would be louder than just the panny, and would let you have a pair of speakers in 2 different rooms, but I don't think it'd be surround sound.

    IMO, if you want surround sound you'd probably be better off buying a surround sound amp which also sounds decent in 2-channel stereo. If the aim's to have a louder system, I'd spend what you would spend on the 2nd amp and speakers on buying a single, more powerful set-up (unless you like hearing stereo from 2 pairs of speakers). The 2 amps could be useful if you're likely to listen in 2 rooms at the same time, though...

    Jon
     
  17. Frazal666

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    I dont really need proper surround (ie dolby), just extra channels to add rear speakers(Even if they are in stereo, itll work for me)., maybe wireless speakers, just to make it look even better than it alreay does.
     
  18. jon_mendel

    jon_mendel
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    Fair enough - that would give you the 4 speakers you want.

    If you're using wireless speakers, though, there probably wouldn't be much advantage in having a 2nd amp (unless you want an independent volume control for the speakers - and I think some wireless speakers have their own volume control built-in anyway) as the wireless ones would have their own power supply and built-in amp and would therefore not take any of their power from the 2nd amp.
    What might also be worth looking at is using an adapter that lets you plug the speaker connectors on the panny (or whatever amp you get) into 2 pairs of speakers - richer sounds or Maplin would sell you one for £10 or so (though if you get the panny, be sure to mention that it needs to work for bi-wired speakers) There might even be some way of plugging the panny's optical straight into some wireless speakers?

    Jon
     
  19. Frazal666

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    What do you mean by this?
     
  20. jon_mendel

    jon_mendel
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    Basically, you could get an adapter that would let you run 2 pairs of speakers from the connectors on one amp, rather than buying a 2nd amp for the second pair of speakers.

    The link you posted re. the panny says it has bi-wired speakers - there's different ways of setting this up, but what I'd presume it means is that the panny has 4 pairs of speaker outputs on the back (rather than the usual 2). 2 of these pairs will plug into one of a pair of speakers, 2 into the other (there may also be an output to the sub). This is just something you should bear in mind if you decide to buy such an adapter - after you've seen exactly how the panny does connect to its speakers tell the shop you buy it from about this, and they should be able to suggest the best way of wiring things with the adapter.

    Jon
     
  21. Frazal666

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    Ok, I guess after I get the Hi-Fi, Ill go into Richer sounds and other known shops and ask a bi-wire adapter thing. The thing is, I dont want it to degrade the quility of the front tweeters (Because of less watts) as according to reviews, the tweeters are what make the Hi-Fi really good. Will this adapter put 65 Watts to each channel? or will it divide the power to each speaker? Thanks
     
  22. jon_mendel

    jon_mendel
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    Interesting question... There's arguments about whether using switches can degrade the sound quality - IMHO, if you use a decent quality switch and haven't got high-end kit you're unlikely to hear any significant difference (I certainly don't on my hi-fi).

    If you wire the amp up to a 2nd pair of wired (and 'passive') speakers, the power will be divided between the 2 pairs of speakers. If you use a pair or wireless speakers tbh I'm not quite sure - as they should take *very* little power from the panny I wouldn't think the power would be divided, but maybe ask at comet (they may be able to sell you wireless speakers, too)...

    That said, I've just noticed that - according to its stats - the panny apparently can give a kind of surround sound if you connect it's optical output to a decoder :blush: I guess you could then feed this into a surround sound decoder/amp... tbh, I'm not sure how this would work or how much benefit you'd get from it - so far as I know, CDs only carry 2 channels of music...

    Jon
     
  23. tom_nieto

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    For £300 you'd be absolutely mad to go for that panasonic system. You can get a decent setup from richer sounds for that sort of cash (http://ws4.richersounds.com/information.php?cda=static&cst=hifisystems). The marantz hi-fi system 3 I'm sure can come in either a silver or gold finish (not sure which though). I think the Cambridge Audio stuff comes in silver too.

    If not, this amp is good http://ws4.richersounds.com/showproduct.php?cda=showproduct&pid=CAMB-A5-SIL

    Which leaves you enough cash for these speakers http://ws4.richersounds.com/showproduct.php?cda=showproduct&pid=MISS-M73I-BCH

    And just a little bit left for connecting cables.

    The A5 and m73i combo will absolutely without a shadow of doubt wipe the floor with that mini system. If the watt ratings are really of interest to you, the CA amp is 60W and probably rated with a much better distortion figure at higher impedance.
     
  24. Frazal666

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    Could any of you reccomend me a pair of surround speakers? Ill look in dealtime later on. Ill probaly end up getting wired surrounds, but ill see if wirless speakers are worth what they cost. As for The cambridge A5 it has no remote control (And being the couch potato that I am, its a must). The mission speakers are floorstanders, and I need something small, and not take much room. In English, I have an old Aiwa mini given by my mother years ago, and I want to put whatever I get in the same spot, next to my Tv. Floorstanders just wont do, unfortunatly. (Although my mother wouldnt mind them...Easter pressie!). The option 3 just wont do as its black, and the speakers brownie colour. I think Ill just test the Panny and see what I think of it. It always have a 14 Day return thing so... Thanks for the suggetions, as my mother likes listening to music, I could buy her the option 3 thing, she'll like it.
     
  25. Frazal666

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    By the way, if I connect a pair of active speakers, will it use any of the pannny's power? I know passive will...
     

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