Myth Busters: 1000W amp is only twice as loud as a 100W amp
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 12th January 2013, 08:33 PM #11 Cal Weldon   Speakerholic diyAudio Moderator     Join Date: Jan 2004 Location: Near Vancouver Think earthquakes. __________________ planet10 needs your help: Let's help Ruth and Dave
Vostro
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Join Date: May 2012
Location: Other side of the fence
Conclusion?
Quote:
 "1000W amp is only twice as loud as a 100W amp"
Twice as loud is alot louder than it sounds

 12th January 2013, 09:42 PM #13 dmills   diyAudio Member   Join Date: Aug 2008 Location: High Wycombe It is a very rough approximation, which depends on frequency and level in non intuitive ways, but remember that loudness (The unit is the Phon) is a perceptual measure where power is a physical one, so the two bearing a non linear (and approximately logrithmic) relationship should not be a surprise. 100W -> 1000W is 10 times the power (+10dB), but perceptually only roughly twice as loud (Highy level and frequency dependent), the power has increased by 10 dB as has the SPL (Ignoring power compression), but the perceived level has only roughly doubled. This is why PA systems become so very large so very quickly. Regards, Dan.
 12th January 2013, 09:43 PM #14 cotdt   diyAudio Member   Join Date: Oct 2005 I actually own a 1000W PA theatre amp and an 10W SET amp. It's true the 1000W amp is about 4 times louder than the 10W amp. It's also true that the 10W amp can still get pretty damn loud. At full blast you want to stand at least 10 feet away from the speakers. In real world use, you rarely use the full output of an amplifier so perception of loudness is simply however high the gain of the amp is set to. Set a 10W amp to high gain, sell it as a 100W amp, and people will never tell the difference unless someone does an actual comparison to a true 100W amp.
 12th January 2013, 09:46 PM #15 cotdt   diyAudio Member   Join Date: Oct 2005 I think the bigger myth is that any hi-fi speaker could actually handle 1000W. You can fry a tweeter with a 5W sine wave (as was demonstrated right here on this forum 2 months ago). Only special PA speakers and subwoofers can handle 1000W.
 12th January 2013, 11:52 PM #16 djk diyAudio Member     Join Date: Feb 2001 Location: USA The contours of equal loudness are only 3dB~4dB apart below 40hz in the 80dB~90dB range. 3dB more down low will sound much louder. However, as the levels go over 100dB the contours become farther apart at most frequencies and it takes over 10dB to sound twice as loud. Power compression only makes things worse. __________________ Candidates for the Darwin Award should not read this author.
 13th January 2013, 12:15 AM #17 dmills   diyAudio Member   Join Date: Aug 2008 Location: High Wycombe Plenty of things willl handle 1000W for a sufficiently short time, there are only really two things that kill speakers, voice coil overheating and exceeding the mechanical limits, and the voice coil has a thermal time constant, so it can make a lot of sense to use an amplifier that can put a huge amount of power into a box short term as long as thermal limits and Xmax are respected. The PA trade has this to a fine art as power is cheap compared to having to truck extra boxes.... Also, the better end of the PA kit sometimes has sense connections to the processing so that speaker protection electronics can model things like voice coil temperature and displacement from amplifier output voltage, means you can use a really big amp with a relatively small driver safely. Think Camco Vortex 6 pushing a Nexo Alpha E 10 inch horn loaded mid/high pack to well over a KW peak, the driver cannot handle anything like that continiously, but it does not matter, because it can use all that power short term, and the protection electronics takes care of the matter. I have used MA5000 (2.5KW/Channel) to drive 10 inch speakers before, it sounded good and worked fine, again, sense connections and a processor with thermal and displacement modelling. The tendency of the hifi world to use amplifiers having only notional headroom (Maybe 3dB on a good day) above speaker continious ratings has always puzzled me, as it implies that either hifi speaker continious ratings are far higher then they need to be, or that people are relying on dynamics crushed in mastering to reduce the need for ability to handle transients. D&B audiotechnik (One of the premier makers of PA speakers in the European market) have an interesting approach, they supply the matching amplifiers for their boxes that have a very much higher short term rating then their continious power rating, this being quite deliberate as it allows the box to actually work somewhat close to its continious rating without clipping the amps on transients. If your SPL requirement is such that you need to run a box close to its continious rating, then the amplifier MUST be capable of significantly more power at least in the short term (Thermal limit can of course be sized for the continious power rating of the speaker), otherwise you cannot get close because there will be no headroom for the crest factor. The saving grace of the hifi scene is that even with the pathetic efficiency levels achieved by most hifi speakers, most listening is done at a tiny fraction of rated power so the speakers and aps are seldom really pushed to the limit, that "double the volume is ten times the power thing works the other way as well", and most hifis play most of the time at very much less volume then pa rigs do.
 13th January 2013, 12:28 AM #18 cotdt   diyAudio Member   Join Date: Oct 2005 PA systems often have to play live music, where you get much higher dynamics, maybe +35dB transients over average levels. Recorded music only has +12dB transients over average level, and often less. Clipping is already built into the recording. There is simply no need for big headroom in hifi. If your average listening level is 0.5W, then just build amps 10W and over. All this talk of 1000W amps belong in the PA scene.
 13th January 2013, 01:55 AM #19 dmills   diyAudio Member   Join Date: Aug 2008 Location: High Wycombe Depends on what recorded music surely, +12 over average might fit quite a lot of pop and rock, but you are going to want rather more then that if orchestral of the purist sort is your thing (And if you have the listening room to take advantage of all that dynamic range). Besides, power is cheap, doubly so if you don't have to do high average power (No thermal issues), think class H with the high voltage rail quite a long way above the low voltage one..... Regards, Dan.
nkolisnyk
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Quote:
 Originally Posted by Amit_112dB If i am putting double the power in a sub then i would expect it to sound twice as loud. How can that sub cheat and eat up all the extra double and give me only little more loudness 10db= 10 times the power, it should be 10 times loud
It's not the amp that's cheating you, it's your ears. We don't hear linearly, but logarithmically. Fun fact: your volume pot is (or is most likely) logarithmic, as to 'sound linear' as you increase it.

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