From Crutchf
I worked for a High End Audio Store [22 years] and dealt with this problem many times. Visited many top quality speaker manufactures where the engineers/designers actually demonstrated the problem described below.
Fom Crutchfield;
Underpowering your subwoofer — Pop and Sizzle
Underpowering a subwoofer isn’t inherently bad for the sub. Not giving it enough power just means that the music will sound weak and lack detail.
The danger is when that power is coming from an amplifier that's being overworked and sending out a clipped signal. The clipped signal tries to make the sub do things it's not designed to do, which leads to it tearing itself apart or overheating and burning out.
First, what’s a clipped signal?
Clipping a signal, or squaring its waveform, occurs when the volume of a source signal exceeds the electronic capability of a circuit. Let's say our amplifier can't play a signal more powerful than what voltage V1 can produce. If we tried to increase the volume at the source, the amplifier wouldn't produce more voltage, it would distort the signal, eventually into the form of a square wave.
Pop: A clipped signal tries to move the cone too quickly
You will notice that the sides of the clipped signal are vertical. That means that the signal will try to move the sub's cone from all the way forward (point E) to all the way to the rear (F) in zero amount of time, travelling at the speed of infinity. Nothing travels that fast, and the sub either tears itself apart trying, or the flapping cone wobbles just enough to jam the coil in the magnet's voice coil gap, killing the sub.
Sizzle: A clipped signal also tells the voice coil to hold still and heat up
The other parts of a square wave, the top and bottom, are horizontal lines that represent the times the signal is telling the cone to stay all the way forward or all the way back. Current flowing through a stationary coil only heats up the coil, which doesn't even benefit from a cooling breeze due to movement. The coil usually burns through one or more of its windings, or heats up enough to deform its shape so that it jams in the magnet's voice coil gap.
There's another, more complex reason voice coils burn when subjected to over-driven, clipped signals. A square wave carries twice the RMS power of a sine wave of the same amplitude (height). So not only is the signal telling the voice coil to pop into a position and sizzle, it's doing it with almost twice the power of the sub's maximum capacity. Usually, it's the glue holding the coil wire to the former that first melts under all the heat, and the coil crashes in its gap.
Distortion is the sub killer
Low power and low volume will not hurt a sub – but distortion will. A clipped signal is a sub's worst enemy. It isn't loudness that destroys an under-powered sub, it's trying to get bass volume by turning up a distorting signal that does it.
Subs are made to withstand a lot more than their specified RMS ratings, so giving them a little more than their highest RMS rating is safe, as long as it's clean and distortion-free.
How to not blow your subwoofer — match the RMS power ratings
Ignore all "peak" and "maximum" wattage ratings, and use only RMS ratings. They may be harder to find, but RMS ratings are the only power ratings you should use. To safely drive a subwoofer, use an amplifier that can give it no less than 75% and no more than 150% of its highest RMS power rating.
I worked for a High End Audio Store [22 years] and dealt with this problem many times. Visited many top quality speaker manufactures where the engineers/designers actually demonstrated the problem described below.
Fom Crutchfield;
Underpowering your subwoofer — Pop and Sizzle
Underpowering a subwoofer isn’t inherently bad for the sub. Not giving it enough power just means that the music will sound weak and lack detail.
The danger is when that power is coming from an amplifier that's being overworked and sending out a clipped signal. The clipped signal tries to make the sub do things it's not designed to do, which leads to it tearing itself apart or overheating and burning out.
First, what’s a clipped signal?
Clipping a signal, or squaring its waveform, occurs when the volume of a source signal exceeds the electronic capability of a circuit. Let's say our amplifier can't play a signal more powerful than what voltage V1 can produce. If we tried to increase the volume at the source, the amplifier wouldn't produce more voltage, it would distort the signal, eventually into the form of a square wave.
Pop: A clipped signal tries to move the cone too quickly
You will notice that the sides of the clipped signal are vertical. That means that the signal will try to move the sub's cone from all the way forward (point E) to all the way to the rear (F) in zero amount of time, travelling at the speed of infinity. Nothing travels that fast, and the sub either tears itself apart trying, or the flapping cone wobbles just enough to jam the coil in the magnet's voice coil gap, killing the sub.
Sizzle: A clipped signal also tells the voice coil to hold still and heat up
The other parts of a square wave, the top and bottom, are horizontal lines that represent the times the signal is telling the cone to stay all the way forward or all the way back. Current flowing through a stationary coil only heats up the coil, which doesn't even benefit from a cooling breeze due to movement. The coil usually burns through one or more of its windings, or heats up enough to deform its shape so that it jams in the magnet's voice coil gap.
There's another, more complex reason voice coils burn when subjected to over-driven, clipped signals. A square wave carries twice the RMS power of a sine wave of the same amplitude (height). So not only is the signal telling the voice coil to pop into a position and sizzle, it's doing it with almost twice the power of the sub's maximum capacity. Usually, it's the glue holding the coil wire to the former that first melts under all the heat, and the coil crashes in its gap.
Distortion is the sub killer
Low power and low volume will not hurt a sub – but distortion will. A clipped signal is a sub's worst enemy. It isn't loudness that destroys an under-powered sub, it's trying to get bass volume by turning up a distorting signal that does it.
Subs are made to withstand a lot more than their specified RMS ratings, so giving them a little more than their highest RMS rating is safe, as long as it's clean and distortion-free.
How to not blow your subwoofer — match the RMS power ratings
Ignore all "peak" and "maximum" wattage ratings, and use only RMS ratings. They may be harder to find, but RMS ratings are the only power ratings you should use. To safely drive a subwoofer, use an amplifier that can give it no less than 75% and no more than 150% of its highest RMS power rating.
