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· Registered
233 Posts
Discussion Starter · #1 ·
"Clipping, by producing harmonic distortion and/or DC, blows woofers."

The idea behind this that a clipped signal contains a heavy harmonic distortion component which can be damaging to voice coils. The problem with this idea is that it's wrong. The harmonic content of the clipped signal is not the culprit at all (the inductance of the woofer pretty much kills any high frequency energy).
DC (direct current) is not to blame either. Modern amplifiers do not produce significant DC when clipped. Even the cheesiest amplifiers to be found at the flea market will not produce a lot of DC.
You may think you can prove this wrong by connecting a multimeter set to DC voltage mode to an amplifier's outputs and measuring "DC voltage" of some value, but the only thing you've proved is that music signals and output stages are not always symmetrical and these asymmetries are misread by the meter as a fluctuating DC value. You're not actually reading DC.
The real villan is dynamic range compression, which refers to an increase in the amount of average energy vs. peak energyof the amplifier's output. signal when it is overdriven (clipped).
When an amplifier clips, the short-duration peaks of the music are "chopped off", but the average level of the signal is allowed to run higher than it would if the amplifier was not clipping. The short duration peaks don't last long enough to worry about in most cases, but the increase in average energy can heat up a voice coil very quickly and are the direct cause of burnt voice coils. A amplifier driven into severe clipping will produce average energy like an amp twice it's rating (a 250 Watt amp like a 500 Watt amp). It's not the clipping that is blowing speakers, it's the old story of too much power.

If you look at the above graph imagine the top and bottom lines represent the maximum output of the amp. Note how long the unclipped sinwave spends on the maximum line. The clipped sinewave spends alot more time along that maximum line. There is a lot more average energy being produced on the right.

· Former '05er
12,590 Posts
Apply a LF square wave to a speaker and watch what happens. Not disagreeing with the analysis, but clipping produces long duty cycle signals. Long duty cycle signals tend to burn up coils of all kinds (even the VSVs in your engine compartment need to be sized to deal with long duty cycle square waves). The graph you tried to link would show this.

I totally agree harmonic distortion doesn't kill speakers. If it did, the stereos of the 50's, 60's, and 70's would have never worked. They had horrible distortion by today's standards.
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