Quote:
Originally Posted by Gir
How can under powering a sub hurt it? People say this, but it makes no sense.
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It's not under powering it that causes the problem, it's driving an amp too far that hurts the sub. With a more powerful amp, as the desire for more volume increases you turn up the volume, the input wave form to the amp gets larger, the output wave form gets larger, and the wave shape stays the same. This is what you want.
But with an "under powered" amp. as the input goes up the output quickly gets to a point where the peaks are as high as the rail voltages and can't go any higher. From that point on as the input amplitude gets higher the output amplitude stays the same, but the wave forms square off. These new corners in the wave happen much too fast for the driver to respond to, so the volume doesn't get any/much higher. BUT, the squared off waveform actually transmits MUCH more power. This power has to be dissipated by the voice coil as heat. This heat can cause the voice coil to overheat, warp, or just expand to the point that it hits the side walls of the magnet. When that happens, you have a blown speaker on your hands. Not because it was under powered, but because it was over powered due to improper use of the amplifier.
The problems is that it's hard to hear when this starts to happen, and even harder to resist the urge to turn the volume up just a little more. I know when I'm setting up a system for someone else that isn't going to touch their own gains, I try to set it so that the sub amp can't get to this point and then level match the other drivers to that. The problem is, that invariably leaves more room to go, but it's safe.
Now, should you spend more money and get the bigger amp? Well, something will always be the weak link in the system and the sub will almost always be the one being punished for that weak link. If you over power the sub with nice smooth wave forms, the voice coil will still fail, BUT you'll be able to reach higher volumes before that happens. Also, many class D amps are more efficient when not run near their limits. Meaning a more powerful amp, say a 1000 watt amp, being used to output 300 watts will be using less power then another amp that's at it's limit to output that same 300 watts. This will put less strain on the cars charging system. My recommendation is to run the larger amp and under use it vice running a smaller amp and possibly over using it.
YMMV