Does a clipping amp damage speakers? |
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Blaize110
Young Croc Joined: 11 May 2010 Location: Gloucestershire Status: Offline Points: 673 |
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Hmm, just my musings here but:
Surely in a sine wave, the cone is moving the same distance as it would during a square wave of the same amplitude, simply in a slower and more constant manner. Whereas with a square wave, it makes the entire distance move almost instantly. Assuming that the cooling is proportional to the total distance moved by the cone, then both sine and square waves should provide the same amount of cooling when averaged out. The other factor I guess it would come down to, is could the coil cope with not being cooled during that fraction of a second that it is being 'stopped'. Taking the example of a 50Hz wave, a sine wave is causing the coil to be moving all of the time, therefore providing cooling of some sorts. But a square wave cause the cone to be 'stopped' for 0.01s before moving it again. I don't know the relevant equations, but would guess it's not enough to cause complete thermal overload in that time. (Quotes on 'stopped' due to the fact that the cone wouldn't instantly stop as it would have some intertia) However, even if both waves provided equal cooling, then the square wave would ultimately carry more power and so require more cooling to prevent thermal overload.
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BUZguy
Registered User Joined: 17 November 2011 Location: South Wales Status: Offline Points: 478 |
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you could look at it like this - say you had a 100w rms speaker and run it with a 100w amp unclipped. then suppose you run the amp so hard into clip that it produced, say 200w of distorted power. let's say that the driver worked for a few mins and then burned the voice coil out. this happens because 200w of thermal power dissipated in the coil was enough to take out the driver. if you took a 2nd amp, say capable of 500w and run this at exactly 200w, if 200w is the power at which the voice coil has reached its limit of temp, then similarly this would burn up at 200w too. the 2nd amp was not clipping but it still killed the driver. so it is power overload that kills speakers, whether the high power came from a clipped amp or not.
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nomercy82
Registered User Joined: 06 April 2011 Location: Pittsburgh PA Status: Offline Points: 265 |
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I'd go with a resounding yes. Clipping an amp does cause damage, as to the specifics If I recall it sends the drivers to or past xmax, causing them to move in a non linear motion. Leading to mechanical failure.
If clipping didn't damage speakers there wouldn't be anything like a compressor. |
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Building a system in Pennsylvania.
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Conanski
Old Croc Joined: 26 January 2006 Location: Ottawa, Canada Status: Offline Points: 2545 |
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Like what 1 or 2hz? What has that got to do with audio? At any audible frequency the amount of time a driver spends "stationary" with a square wave input signal is inconsequential and even if this does happen it's not going to significantly factor into the stress levels experienced by the driver, no damage will result if the signal is within the power handling capacity of the driver. |
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soulray2
Registered User Joined: 02 January 2011 Location: Glasgow Status: Offline Points: 332 |
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No, this is rubbish! Only way too much power, (for a given enclosure, that is!), can cause mechanical failure, due to exceeding Xmax. It has nothing to do with clipping, which may cause failure due to overheating the VC, but that's really again because of excess power over a given period! |
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"Moderation in all things, particularly moderation!"
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audiomik
Old Croc Joined: 06 April 2010 Location: Bath, UK Status: Offline Points: 2962 |
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Hmmmm! Plenty of assumptions that an Audio program signal is entirely symmetrical.
Unfortunately this isn't the case. Now lets consider the signal with say an asymmetry with more positive half cycle duration than negative. The current output of the Amplifier moves the coil forward (convention) in the magnet gap. Should this exceed the Xmax value of the 'Speaker being driven then the loss of magnetic field from the poles means a change in the impedance of the coil and a reduced cooling effect. Thus exceeding the 'Speaker's rating and will overheat the coil. In more extreme cases, exceeding Xmech, this will damage the mechanical structure of the 'Speaker. So when you overdrive your 'Speaker, the Current - this is the component of the Power being applied which actually moves the coil - behaves something like this in this 'Scope pic: The sinewave signal is the Amplifier Voltage output and the clipped waveform in the center is the Current. Now should anyone then apply a clipped source signal to this same situation, especially one which is asymmetric, then you can easily see the effect which the current will have on the coil of the 'Speaker. At the point of destruction when the Amplifier Output was increased in the test result above, the current increased dramatically but unfortunately not for long enough to take a pic of the results before the 'Speaker coil failed completely. Please note: no I'm not going to deliberately wreck any more 'Speakers to get more results unless that is if someone else wants to provide them FOC for destruction! So, in answer to the Thread Title: "Does a clipping amp damage speakers?" then yes it certainly can, as does over-driving with an un-clipped signal above their rating in either case. And to comment on the content of earlier posts in this thread relating to Harmonics, it is the RMS Current applied directly to the coil which is the issue! Mik Edit: correction of parameters Edited by audiomik - 14 May 2012 at 1:57am |
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nomercy82
Registered User Joined: 06 April 2011 Location: Pittsburgh PA Status: Offline Points: 265 |
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The reason may not be as important as the result. Drive your amps into the clip range and just watch better yet listen to what happens to sound quality, and eventually your drivers.
A 50 watt amp driven into clipping will eventually cook a speaker even if the speaker is a 100 watt rms speaker. |
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GEB
Old Croc Joined: 13 November 2009 Location: East Midlands Status: Offline Points: 1993 |
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Lot of differing 'facts' here! Problem is, who is correct? Is this Bill F experienced enough to provide this statement, or do the people opposing this out-qualify him?
It was just a search for the truth really, not people's personal 'myths', or what they've 'read' on internet or been told by a 'mate' sort of thing! Some of which are obvious to everyone, even me!
Edited by GEB - 14 May 2012 at 10:11am |
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swannie
Registered User Joined: 15 March 2008 Location: WEYMOUTH Status: Offline Points: 276 |
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Ok, not a technical answer, but one thing i would say after years of soundsystem install, hire & play..
If going by the red clip lights on amps, which is the only real way on the night at a gig weather the amp is clipping.. Many amps seem to be calibrated or set up differently. Some amps are happy to flash there red lights all night, with no bad issues.. (mild flash we are talking about) where as others (with the same paper/power spec) will crunch, pop & give the speaker a hard time under mild clipping. Also reading up on various amp test's it seems that many amps have different clip behavior dependent on design. One thing has to be said is that red lights are there for a reason.. bit like a rev counter on a car.. Always better to be running at 75% rather than 100% if you want it to live longer. as mentioned above, the most important factor.. Quality of sound. I always opt for amps at least 20% more power than i need, then limit the output via a compressor or speaker management system to avoid clipping of amps & over power of speakers, and giving enough headroom to cope with input voltage difference(220-240v), cable length & thickness & temp of the rooms its operating in. All of those factors can effect output power of amp, SPL you hear & weather the said amplifier is really 'clipping at 500w' lets say.. Edited by swannie - 14 May 2012 at 10:15am |
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GEB
Old Croc Joined: 13 November 2009 Location: East Midlands Status: Offline Points: 1993 |
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Seems the correct information from what I can gather from those who are not talking out their bottoms is that clipping does not cause damage to speakers, but a clipping amp 'may' deliver too much power into the speaker and cause it to fail, in which case it would happen on a more powerful amp regardless. If it were true guitar speakers would fail left, right and centre. There is not DC present in a clipped signal, people are confusing themselves because of the square tops of the signal, were as DC wouldn't be made up of + & - element components in the first place. And the coil doesn't stand still and effect cooling as no sound would come out of the speaker in the first place if it was still!
Is that the general jist of it?
Edited by GEB - 14 May 2012 at 10:43am |
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audiomik
Old Croc Joined: 06 April 2010 Location: Bath, UK Status: Offline Points: 2962 |
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Re: "Lot of differing 'facts' here! Problem is, who is correct?"
The best way to find out is to read up on the Theory and then run some practical tests of your own to see the results..... A good starting point will be the Science of Moving Coils in Magnetic Fields - Faraday's Laws are a good starting point Mik |
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clvrdck
Registered User Joined: 31 August 2009 Location: geneva Status: Offline Points: 11 |
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if you had real DC going to your cones, you'd know about it.
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