Why did my speakers blow?

Dual 4 Ohm Subwoofer

I hear this all the time from customers.  There’s a big misconception when it comes to understanding why speakers blow.  Many people think that too much power damages speakers.  And that’s true to an extent, but I’d say 95% of the time it happens because of the exact opposite.  Sometimes my customers dreamily reminisce about the system their friend had and how loud they played it and they describe to me that it was “So loud, the speakers couldn’t handle it”.  And really that is not the case at all!

So why do speakers blow?  Speakers are easily damaged from a LACK of power.  Distortion happens when you run out of power.  The speaker starts breaking up and you hear fuzzy and garbled sounds, sometimes crackling and gritty noises.  This is actually the sound of the amplifier clipping.  Whether it’s the amp built into the radio or it’s a separate amp that you’ve powered up with a thick power wire coming from the battery, you will run into the point where the amp runs out of power and starts clipping.  That is when you start to hear distortion.  And over time, distortion will cause the voice coil in the speaker to heat up and break apart and shortly thereafter, it stops making contact completely and thus you have blown speakers.

So how do you prevent this from happening?  It’s all about the power.  If you like it loud, you need the power to back it up.  You need the right amplifier and you need to supply it with the proper power wire.

But what if you have a 1600 watt amplifier and a 1200 watt subwoofer and you still manage to damage your subwoofer?  This can happen due to a number of reasons, and I see it happen often enough that I feel I need to explain this.

Typically when a customer comes into my store and relays this dilemma to me, I immediately ask them if they know the RMS rating of the amplifier and the subwoofer.  They usually repeat to me what they originally told me: they have a 1600 watt amp and a 1200 watt subwoofer.  So I ask to see this 1600 watt amp and this 1200 watt subwoofer and I can quickly see that these are the numbers largely plastered on the equipment.  They are not the true power rating, but simply a peak power rating which is the number that grabs everyone’s attention.

After closer inspection, I see the amplifier has two 25 amp fuses and there is 8 gauge wire ran to it.  If this amp was really capable of 1600 watts, it would need a much larger gauge wire like 2 or 0 gauge.  However, with two 25 amp fuses, I can tell right away this amp is really only putting out about 350 watts RMS.  And the subwoofer?  After looking the model # up on the internet we find it’s rated at 600 watts RMS.  So what does all this mean?

We are under powering the subwoofer and pushing the amp into clipping which is distorting and damaging the speaker.  If we really wanted to use the 600 watt subwoofer, we would need to supply it with an amplifier pushing out about 600 watts RMS.  And that’s not the only problem here.  To really pull that amount of current, you need to use 4 gauge wire.  You could get away with 8 gauge, but 8 gauge is only capable of pulling so much current, about 500 watts safely.  At some point, you will end up starving the amp for power.  That means you’re not getting your full 600 watts out of your amp, which means you’re once again, under powering your subwoofer and running the risk of damaging it.

So here are the key factors to keep in mind so you can avoid damaging your speakers:

1) Always check the RMS rating of your speakers and make sure it matches or is close to the RMS rating of your amplifier.  Don’t pay attention to peak power ratings, they are very misleading.  Companies use this number to grab your attention and sell you on their product.

2) Always make sure you are running the proper gauge power and ground wire based on the RMS rating of the amplifier.  If you don’t trust the rating on the amplifier, check the fuses on the amp and use an amps to wattage calculator to determine the true output.

3) Never play your car stereo speakers with distortion.  Remember, distortion is what damages speakers.

I’d be happy to answer any questions anyone may have and post any comments.  Thanks for reading my tips.  I’ll be back next week with a post about how important it is to have the proper box for your subwoofer with tips and tricks on building it.