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Clipping is Really bad.

Posted by BigguyinATL (M) on May 11, 2011 at 08:41:27

And you don't know what it sounds like.

You think, because you have seen the pictures, or maybe even heard a sine wave become squared off, and all the obvious upper harmonics that are present is the sound of clipping. Well it is - but not likely even in a low power amplifier. The peak levels are only 3db higher for a sine wave. A musical instrument or human voice is much different because of the complicated timber of the signal. The peak to average levels will be typically a 4 to 1 (12dB ratio) - and that is when a note is held in sustain (steady). A finger snap or other transient provided a 8:1(18dB) or 10:1 (20dB) or even greater "crest factor". While some of these high crest factors are limited by signal processing during the recording and mastering process, and also in amplified live performaces, a hi-fi reproduction system might not be prepared for the symptoms of clipping. Our ears (and mind) are also forgiving - adding a little more "grit" or "edge" to a saxaphone, the same harmonics are present- only the timber changes - perhaps subtlely - because the artist can also change the timber by altering his playing technique. But clipping can also create other distortion, even in a "well behaved" amplifier. The clipped waveform is assymetrical across the ground reference, producing DC at the output - as much as several volts. The DC voltage will cuase your woofer to displace in or out a bit, causing it to behave non-linearly, so an tenor saxphone playing a loud signal with frequency response in the midrange and tweeter drivers can cause the bass guitar to sound bloated. Lest you tube guys say, "na na nah. we don't pass DC", take caution, that the DC is being passed to the core of your transformer and it too, will cause an increase in distortion, because the DC voltage can cause the core to saturate at an earlier point.

The solution, of course, is to have "enough" amplifier so that it will not clip, while driving the loudspeaker at the desired value - 20dB or more headroom over the RMS values achieved for your sources at typical listening levels.

So if a fortisimo passage is averaging 85dB, and your speakers are 85dB/watt: Add 20dB to one watt and you need 100 Watts peak capability, probably available with a 50 Watt RMS rated amplifier. But for a bit of headroom, a 200 watt amp (6dB) more capability would be more likely meet you needs. Double - or halve - the amplifier requirements if you have less or more rated loudspeaker sensitivity in 3dB increments. My MMG's with an 82dB sensitivity/watt, need 400 watts.





"The hardest thing of all is to find a black cat in a dark room, especially if there is no cat" - Confucius

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