How do Cheap 5.1 kits get away with 1000W ratings!?

Discussion in 'Home Cinema Speakers' started by Richy1984, Aug 2, 2012.

  1. Richy1984

    Richy1984
    Active Member

    Joined:
    Jan 4, 2012
    Messages:
    726
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    28
    Ratings:
    +41
    Simple really,

    A family member was comparing his cheap 5.1 kit to my soon to be rather expensive hi-fi. He asked why its only 70w per channel when his 5.1 kit puts out over 1000w. And I couldnt think of an answer! lol

    So how do they get away with it, because if you can drive a 2grand floorstander with 50-100w of quality amplification then why do these cheap £300 set quote 1000W plus! Surely they arent really that powerfull!?
     
  2. Andy98765

    Andy98765
    Well-known Member

    Joined:
    Feb 15, 2006
    Messages:
    10,474
    Products Owned:
    2
    Products Wanted:
    0
    Trophy Points:
    133
    Ratings:
    +1,367
    In answer to your question, no AIO will ever do 1000watts.
    A. Power consumption usually <200watts, therefore 1000watts breaks the laws of physics.
    B. They are rated along the lines of 6 speakers / 1000watts = 166watts each, therefore 6 * 166 = 1000. BUT only one speaker will ever produce 166watts. i.e. 1 channel driven.
    Low to mid end AV recievers would rate with spare based on 2 channels driven and a lot of high end AV amps would have power supplies rated in excess of the all 5 or 7 channels.
    Example my Cambridge Audio 540R quotes 100watts per channel all channels driven (5) and has a 850 watt power supply. Also my sub attached has its own 200watt amp/power supply indipendant to the AV amp.
     
  3. fayeanddavid

    fayeanddavid
    Distinguished Member

    Joined:
    Sep 23, 2009
    Messages:
    5,655
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    166
    Location:
    Bearsted Kent
    Ratings:
    +2,009
    An added insult is that these grand figures are as you have referred too, are also taken as Peak values and and not RMS, which can boost the interpretation by about 45%
     
  4. Richy1984

    Richy1984
    Active Member

    Joined:
    Jan 4, 2012
    Messages:
    726
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    28
    Ratings:
    +41
    So if I understand correctly...

    Basically if an all in one kit is rating at 1000w its probably around 500w rms, 250 of that may be the sub so that leaves 250w / 5 = 50w.

    But that 50w isnt really a rating of true power for the whole system as only one speaker could be fed that much at once.

    So in effect the 1000w turns into more like 50w + sub.
     
  5. goujam

    goujam
    Active Member

    Joined:
    Sep 25, 2010
    Messages:
    2,235
    Products Owned:
    3
    Products Wanted:
    0
    Trophy Points:
    63
    Location:
    Brierley Hill
    Ratings:
    +187
    Andy98765 has hit the nail on the head, a 1000W power supply on its own would probably be bigger than the All in one is and weight more too! Also as stated above these are peak values so first thing to do is multiply this figure by 0.707 to get the RMS value, divide that by the number of channels which in all in ones includes the sub so in a 5.1 thats 6 channels. This then gives you the Watts per channel, then take into consideration that the all in one is probably using cheap 3 ohm speakers and the value is taken running 1 channel you soon realise that the All in one is probably lucky to get around 30 Watts per channel when all channels are being used. Put some decent speakers on there at 8ohms and you would be lucky to get 10 - 15 Watts and would damage your speakers with clipping.

    But dont get me wrong I have actually heard some very good all in one systems but nothing a entry level seperates system cant beat and is easier to upgrade!
     
  6. PSM1

    PSM1
    Distinguished Member

    Joined:
    Dec 20, 2008
    Messages:
    26,283
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    166
    Ratings:
    +5,439
    As above the way they claim such big numbers is by using low impedance speakers. Hence they will claim 1000W with 3 ohm speakers but most AV receivers will use 6 or 8 ohm impedance for their power. If you convert 1000W at 3 ohms to 6 ohms you get 500W and for 8 ohms this drops to 375W. This then has to power all 6 speakers so gives you 62W per channel at best. If you look at the spec sheet for the all in one unit it will give the power consumption or power supply size. This will be a more accurate value of the power the unit will produce.
    The max power is also slightly irrelevant anyway as it will have no real bearing on sound quality. As long as you have enough power to drive the speakers effectively then you should be more concerned with the TBD/distortion figures etc as these are the things that will affect sound quality. If you can find these values for the all in one system they have you will see a big difference between the 2.
    The best test will be to listen to both and you will find your AV reciever will not only go louder but sound so much better while doing so.
     
  7. Wilseus

    Wilseus
    Active Member

    Joined:
    Jun 21, 2006
    Messages:
    684
    Products Owned:
    1
    Products Wanted:
    0
    Trophy Points:
    28
    Location:
    Northampton
    Ratings:
    +59
    My friend at school (whose father ran a home electronics shop) had a rule of thumb, which, for a stereo system was to divide the quoted figure by 8.
    So if a crappy ghetto blaster/mini "hifi" was quoted at "80W PMPO", it would equate to about 10W RMS per channel into 8 ohms.

    I guess the only answer that the OP has to give to his relative is, simply, "It doesn't."
     
    Last edited: Aug 2, 2012
  8. Wilseus

    Wilseus
    Active Member

    Joined:
    Jun 21, 2006
    Messages:
    684
    Products Owned:
    1
    Products Wanted:
    0
    Trophy Points:
    28
    Location:
    Northampton
    Ratings:
    +59
    Thinking about it further, I think I can work out how he arrived at this figure:

    Take the "real" figures, which as I mentioned earlier with such systems is usually pretty low. Let's assume the real performance is 50W RMS per channel into 8 ohms, all channels driven.

    We can double that value by quoting the peak value as opposed to the RMS, approximately doubling it, so now we have "100W."
    Next, any half decent amplifier can nearly double its output into 4 ohms, so now we have a figure of "200W," perhaps even more if, as someone else said, it uses special low impedance speakers.
    Lastly, they can multiply the last figure buy the number of channels (2 for stereo, 5 or 7 in the case of a home cinema system) giving an impressive sounding 1000W. I haven't factored in a subwoofer, but I'm sure you get the idea.
    Of course that figure is utterly meaningless, but what does that matter if they can sell it to a gullible public? :(
     
    Last edited: Aug 2, 2012
  9. goujam

    goujam
    Active Member

    Joined:
    Sep 25, 2010
    Messages:
    2,235
    Products Owned:
    3
    Products Wanted:
    0
    Trophy Points:
    63
    Location:
    Brierley Hill
    Ratings:
    +187
    Not that its important but RMS is peak multiplied by 0.707
     
  10. Wilseus

    Wilseus
    Active Member

    Joined:
    Jun 21, 2006
    Messages:
    684
    Products Owned:
    1
    Products Wanted:
    0
    Trophy Points:
    28
    Location:
    Northampton
    Ratings:
    +59
    Yes, I know, I was keeping things approximate and simple :)
     
  11. goujam

    goujam
    Active Member

    Joined:
    Sep 25, 2010
    Messages:
    2,235
    Products Owned:
    3
    Products Wanted:
    0
    Trophy Points:
    63
    Location:
    Brierley Hill
    Ratings:
    +187
    Ha ha sorry I had a lecturer who taught me electronic principles that always made us do things exact it must of rubbed off ! He even made us say amperes instead of amps !
     
    Last edited: Aug 2, 2012
  12. BlueWizard

    BlueWizard
    Distinguished Member

    Joined:
    Jun 19, 2007
    Messages:
    22,335
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    166
    Ratings:
    +4,209

    Actually this is the DC equivalent of a Sine Wave Voltage. As it happens, 0.707 is the SINE of 45° (unless my calculator failed me).

    One of the reasons why compact audio, boomboxes, and others can get away with outrageous power ratings is that they are NOT consider High Fidelity systems.

    Only HiFi has to conform to power rating standards. This is one reason why you see non-standard power ratings in AV Receivers, it is because they haven't actually set a standard for rating the power on multi-channel Surround Sound amps yet.

    However, on AV amps, most specifications indicate the limit of the power supply. That is the actual limit of the amp. For example, a 700w seven channel amp might only have a 500w power supply. If so, then 500w is the absolute limit that the amps can draw. Typically the power is rated with two channels driven, then multiplied up to the full seven channels. Again, the power of the amps, can never exceed the power of the power supply.

    Further in an all-in-one 5.1 system, typically for a computer, they are including the power of the Subwoofer which has its own typically larger amp. To illustrate, in a 1000w system, 500w may be the Sub, and the remaining 500w spread among the 5 speaker channels.

    In a more standard component system, the power of the Sub amp is not included in the power rating of the main AV amp.

    Next, in a typical component system the rated distortion levels are in the range of 0.01% to 0.10%. With a cheap overrated boombox, the distortion levels will be about 10%.

    Steve/bluewizard
     
    Last edited: Aug 2, 2012
  13. Weetabix

    Weetabix
    Active Member

    Joined:
    Sep 30, 2005
    Messages:
    238
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    31
    Location:
    Littlehampton, West Sussex
    Ratings:
    +41
    Funnily enough, I had a similar conversation with my neighbour who thought his all-in-one home-theatre-in-a-box Samsung was *super-powerful* until he heard a 75w/channel system.

    I've always understood it that the PMPO (peak music power output) was 4 x the actual RMS output.

    So the equation:

    1000w / 4 = 250w
    250w / 5 channels = 50w

    That could be 50w into a 4ohm load, not an 8ohm load, and perhaps quoted at only one channel driven, and measured at 1kHz only.

    So that's how they get away with it.

    Real hi-fi / home theatre manufacturers tend to quote the power output per channel into 8ohms loads, measured between 20Hz - 20kHz and all channels driven for a more meaningful and truer representation.

    regards
     
    Last edited: Aug 3, 2012
  14. Wilseus

    Wilseus
    Active Member

    Joined:
    Jun 21, 2006
    Messages:
    684
    Products Owned:
    1
    Products Wanted:
    0
    Trophy Points:
    28
    Location:
    Northampton
    Ratings:
    +59
    I think both those things are true, for a perfect sinusoid.

    0.707 is also equal to 1/sqrt(2) and sqrt(2)/2 for reasons that I don't really understand.

    I also notice that 0.707 is the optimum Q for a subwoofer. Coincidence? I don't know.
     
  15. Alan Mac

    Alan Mac
    Active Member

    Joined:
    Feb 13, 2007
    Messages:
    1,459
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    66
    Location:
    Highlands of Scotland
    Ratings:
    +248
    There is no law of Physics which prevents the output power from exceeding the input power. It is possible to devise a machine which can achieve a megawatt output power using a torch battery as the energy source!

    Power is the rate of doing work. It is measured in joules (J) per second (s).

    There is a law of Conservation of Energy. The output energy (measured in joules) cannot exceed the input energy. But there is no reason why the output power cannot exceed the input power.


    Alan
     
  16. Wilseus

    Wilseus
    Active Member

    Joined:
    Jun 21, 2006
    Messages:
    684
    Products Owned:
    1
    Products Wanted:
    0
    Trophy Points:
    28
    Location:
    Northampton
    Ratings:
    +59
    I think we're straying far into the realms of pedantry now! What you say is indeed correct, but we are talking about continuous output power, which cannot exceed the continuous input power. Not for very long anyway! :)
     
  17. Alan Mac

    Alan Mac
    Active Member

    Joined:
    Feb 13, 2007
    Messages:
    1,459
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    66
    Location:
    Highlands of Scotland
    Ratings:
    +248
    Audio amplifiers are intended to be driven with an audio signal.

    When driven by an audio signal as opposed to a sine-wave test signal, the “continuous” power (aka. “average power”) output is very low, typically of the order of 100 milliwatts (mW).

    The peak to average power ratio is large. It makes little sense therefore to use average power as a descriptor of an audio amplifier’s loudspeaker driving capability.


    Alan
     
  18. Ambient Fish

    Ambient Fish
    Active Member

    Joined:
    Apr 28, 2005
    Messages:
    1,645
    Products Owned:
    1
    Products Wanted:
    0
    Trophy Points:
    66
    Location:
    Wishaw
    Ratings:
    +225
    HT Labs Measures

    Five channels driven continuously into 8-ohm loads:
    0.1% distortion at 63.0 watts
    1% distortion at 66.3 watts

    Seven channels driven continuously into 8-ohm loads:
    0.1% distortion at 47.1 watts
    1% distortion at 54.5 watts

    These figures illustrate just how much clean power the Yamaha Z7 can produce and it is no lightweight entry level amp. It has a decent power supply and is 50% efficient it can easily drive my set up to reference levels with minimal distortion (undetectable).

    An easy way to measure your amps maximum output is to mutiply the input voltage by the fuse rating of the fuse in your power cord plug and divide it by the amps efficiency, example - 240 volts multiplied by 5 ampers equals 1200 watts devided by amp effiency 50% = 600 watts divide this figure by the number of channels being driven at full power over the amps frequecy range 600 divided by 7 = approximately 84 watts, this is reduced by various factors in the amps design and construction to the typical figures you see for the Z7, it should be noted that all Class A/B amps are around 50% efficient and the vast majority of AVRs are Class A/B, Pioneer are Class D Digital which are more efficient but are limited by other factors.

    No Amp in the real world is ever driving all channels at full maximum clean power continuosly, if it was the Amp would be like a 3 bar fire with 50% of it's input voltage being dissipated as heat, amps get warm they don't glow red hot and give 3rd degree burns. Truth is that even with all channels being driven at near refence levels whilst watching a movie for example you are using about half to three fifths of the available reserves which is a good thing as it leaves the amp plenty of headroom to cope with extreme moments of peak demand during explosions etc
     
    Last edited: Aug 4, 2012
  19. Thooms

    Thooms
    Active Member

    Joined:
    Nov 24, 2009
    Messages:
    104
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    18
    Ratings:
    +5
    They say it because it makes people buy their stuff. Most people aren't able to test it, so they don't lose anything by it.

    It probably is 1000W for a few microseconds if you put a screwdriver across the decoupling caps in the power supply - maybe that's how?
     
    Last edited: Aug 5, 2012
  20. LJD

    LJD
    Banned

    Joined:
    Jan 3, 2012
    Messages:
    323
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    18
    Ratings:
    +17
    Cables have been getting away with "B/S" for years so why not speakers ? !
     
  21. xedas

    xedas
    Active Member

    Joined:
    Mar 3, 2012
    Messages:
    95
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    11
    Ratings:
    +7
    This subject always makes me smile......the guys from marketing advertise the speakers in their max power abilities ....like they were fuses....one more watt and they blow up.

    And then advertise the peak power in two channel mode and multiply it by 6 (5.1 system with passive sub :rolleyes:).

    God help us all
     
  22. discover

    discover
    Well-known Member

    Joined:
    Oct 14, 2008
    Messages:
    2,725
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    86
    Location:
    Leeds, West Yorkshire
    Ratings:
    +144
    Great thread!
    What about TV Soundbars that have near 200watts RMS? Do these only have one channel or is it the number of speaker drivers the bar has in it?
     
  23. BlueWizard

    BlueWizard
    Distinguished Member

    Joined:
    Jun 19, 2007
    Messages:
    22,335
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    166
    Ratings:
    +4,209
    Again, I remind you that only equipment classified as HIGH FIDELITY is force to conform to power rating standards.

    Compact stereo, all-in-one, boom boxes, and many other components that we assume are high fidelity are not classified as such.

    For the moment, because they are still working out the Standard for Power Ratings on AV Receivers, they are not classified as High Fidelity. Though they certainly are, and most manufacturers make a reasonable effort to give honest power ratings. But you will find may AV amps power rated at 6 ohms, and regardless of excuses or explanation, this is simply a way of inflating the apparent power.

    Usually if power is rated at continuous, FTC (US Federal Trade Commission), or RMS it can be depended on. Many newer, and especially AV amps, are using Digital amps, which means switching amps in the same sense as Switching Power Supplies. These are VERY efficient, and can run off very basic power supplies. Meaning they are also very compact. Initially, most were very skeptical of Digital Amp, but as technology improves, they are becoming the standard for AV equipment.

    Again, if they are using continuous, FTC, or RMS power rating they can be reasonably trusted. However, as in the example of the Sound Bar, is the rated power total or per amp channel? That makes a different. 200w per amp channel is huge. However, 200w total for several amp channels ... not so much.

    Steve/bluewizard
     
  24. Wilseus

    Wilseus
    Active Member

    Joined:
    Jun 21, 2006
    Messages:
    684
    Products Owned:
    1
    Products Wanted:
    0
    Trophy Points:
    28
    Location:
    Northampton
    Ratings:
    +59
    I guess this is how the Lejonklou Tundra manages to drive even very difficult and expensive loudspeakers even though it's rated at only 24W per channel!
     

Share This Page

Loading...