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All Forums  Cool Edit  Is CLIPPING bad for speakers??

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AusRob Location: Australia Posts: 78	Posted - Mon Aug 26, 2002 9:15 pm  Most definitiely, severe clipping may damage speakers, as the "flat top" of the signal simulates a DC signal, for which speakers are not designed. Cheers, ROB _________________ "I'd give my right arm to be ambidextrous...."
mjb Posts: 167	Posted - Tue Aug 27, 2002 1:14 am  Quote: the "flat top" of the signal simulates a DC signal, for which speakers are not designed. Your amplifier can pass DC? Wow! Where can I get one of those bad boys, and a DC sub? :) Seriously, there's more risk from the sudden increase in HF content (the harmonics that give that flat top its nice sharp corners and flat top) at the point of clipping. This will increase the power going to the tweeter: This is bad for the health of the tweeter, which is usually a much lower power handling rating than the main drivers.
SteveG Location: United Kingdom Posts: 6695	Posted - Wed Aug 28, 2002 4:55 am  Well you're nearly there... Yes, a lot of HF will blow out your tweeters. No question. But the bass end? Well there are a couple of things to say about this. Firstly, although some power amps most certainly can pass DC, it's a seriously bad idea to pass it to the speakers. For a start, there's not a room around that can reproduce frequencies anywhere near that low, and any small DC offset in the amp output will cause a permanent deflection (although this is usually pretty small) in the resting position of the cone. So AC coupled speakers are a good idea, because with DC coupled ones, the slightest fault will take out the speaker cones, and even if you have switch-on transient supression, this won't protect your speakers from the inevitable damage that an amp fault will cause. But the biggie, and the one that seems to be most misunderstood, is the power handling one. Let's just consider first what happens when an amplifier clips at a level below the speaker power handling limit - the under-powered amp situation. The speaker cone has mass, which means that it takes time to accelerate. When your amp output clips, the cone will continue to travel in the direction that it was going, even though it's not supposed to. Not only that, but it generates what's known as a 'back emf' in the form of an error signal, which will actually be reflected in the amp's output. What happens at this point varies rather, according to what type of amp you've got, but it ain't good, and it sounds dreadful, however you look at it. But the real problem is that it's actually not too good for the voice coil. Coil wants to stop, cone is going to keep travelling... Pretty soon, as they try to part company, this will loosen the windings, and this is when you get 'grating' noises from your speaker. So what about the other way around? Plenty of output from the amp, which isn't going to clip yetawhile. And the speaker cone suspension will hit the end stops, where it will promptly make a horrible clicking noise that you really won't like. But with modern-day speakers, you have to do this for quite a while before damage actually starts - unless of course you overdrive so severely that you rip the cone straight out of the speaker. Yes, the voice coil will warm up, and eventually burn out, which is another good reason for not continuing this for too long. But believe it or not, this is actually less likely to damage your speaker than the underpowered situation will. And it will sound better, too. If you run an amp up to its clipping point, it's going to produce far more distortion during the peaks than a relatively underdriven but more powerful amp will. So the general rule is (if you want to play safe, and have good sound) that if you've got 50W rated speakers, run them off a 100W amp, and use a bit of common sense about the levels. So, you run your underpowered amp into clipping a lot of the time, thinking that your much more powerful speakers will handle it okay, and actually, they're not handling it very well at all! Quote: I hope this isn't a dumb question:o) Not at all. This is in fact a very good question! Steve _________________
post78 Location: USA Posts: 2887	Posted - Wed Aug 28, 2002 5:34 am  Quote: generates what's known as a 'back emf' Isn't this only a problem with passive monitor systems? _________________ Answer = 1. Probably.
SteveG Location: United Kingdom Posts: 6695	Posted - Wed Aug 28, 2002 6:02 am  Quote: Quote: generates what's known as a 'back emf' Isn't this only a problem with passive monitor systems? Strictly speaking, no, since all speakers have an amp driving them! There have been speakers designed in the past which have attempted to use the back emf to alter the driver behaviour by utilising the fact that it is an error signal, as a part of a feedback loop - this is one way of achieving Motional Feedback, which can tidy up the bass end of your speaker system quite well, up to a point. What makes it more complicated with passives is that you also have to take account of the resistance of the speaker cables and crossover (usually the worst offender), which will screw up the ability of the amp to 'damp' the speaker. The huge advantage of active speakers is that you can virtually eliminate these features from the equation, and therefore the amp gets to 'control' the voice coil rather more directly, and therefore accurately. It's a bit like the difference between having a fish on the end of a long line, or a really short one. With the long one, the fish can still swim about rather more... So yes, the back emf is always at a lower level with actives, because it's reflected back into a really low impedance. But if you put an output coupling capacitor into the circuit, you lose any advantage you've gained completely. I'll freely admit that this is a bit 'swings and roundabouts', but I'm wary - I've seen enough large cones get wrecked completely by amp faults that wouldn't touch an AC coupled system to think that some of the advantages around the DC point are rather over-rated. It is perfectly possible to get around this quite adequately in a designed system (which is basically what an active speaker is), but I suspect that a lot of them are actually DC-coupled. And it is certainly true that DC coupled square waves fed to a bass unit (higher mass) even at low level are going to tax the coupling between the coil and cone, however they are caused. Steve _________________
post78 Location: USA Posts: 2887	Posted - Wed Aug 28, 2002 8:15 am  Ahh, I see. I'm guessing that virus is going away? _________________ Answer = 1. Probably.
SteveG Location: United Kingdom Posts: 6695	Posted - Wed Aug 28, 2002 3:14 pm  Quote: Ahh, I see. I'm guessing that virus is going away? It's much better in the mornings than the evenings. Much to my family's relief I think, it's taken my throat right out... but thanks for the thought! Steve _________________
teflon20 Location: Australia Posts: 474	Posted - Wed Aug 28, 2002 6:11 pm  Quote: Can digital clipping(aka volume exceeding 0db threshold) do any type of damage to the speakers that are playing it?? THANKS I hope this isn't a dumb question:o) Try it out for yourself with a crappy speaker. Use at your own risk. I will not be responsible for any damages.
DLEA Posts: 8	Posted - Wed Aug 28, 2002 6:31 pm  Yes. It is bad.
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