Audio Systems: subwoofers, impedance mismatch, amp off

Question
QUESTION: I have two Alpine types R's and I hooked up an amp to them, and they work for a little bit then all the sudden they'll stop, but the beat still goes, then they'll work again, then stop, ect... do you know what the problem is?

ANSWER: Here are the possibilities (I cannot give you a more specific reply without knowing the make and model number of speakers and amplifier and the wiring method you have employed).


ONE:  If the impedance of the speakers presents a load to the amplifier that is lower than the rating of the amplifier it will go into thermal or overcurrent condition.  For example, if your speakers are 4 ohm coils in parallel giving a 2 ohm load to the amp and your amp is rated for 4 ohm minimum load it would cause amp problems.

TWO: If the speakers are defective, such as a shorted voice coil, it will place a heavy load on the amp and cause it to burp.

THREE:  If you are overdriving the amp and the heat dissipation is causing the temperature to rise inside the amp it will cause this.

The condition you are experiencing is what we call "activation of the protection circuit".  When excessive current drain from the power supply is detected by the protection system it shuts the amp down; when the temperature of the outputs or their heatsinks get low enough it will turn the amp back on.

So, you will need to do some elementary troubleshooting to find out what is going on.  If it is an impedance mismatch you will need to rewire or change out either the speakers or amplifier. If it is overdrive you will have to be satisfied with lower power input to the woofers. If it is a bad voice coil you will need to get it repaired or  replaced.  And so on.


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---------- FOLLOW-UP ----------

QUESTION: When I hook one type R up to the amp, it works fine, but then when I hook the other one well, and as soon as I get it hooked up to the amp, it shuts the amp off so im woundering if it is the activation of the protection circuit, then I unhook it, then the other sub works again, ect...so would I just have to turn the power down on the amp?

Answer
You did not give me the model numbers.  I can only guess that you are connecting the speakers in parallel and placing a load on the amp that is too low for its driving capability.  It will eventually blow the amp and you will have to replace it if you continue this mismatch.

You must either put the speakers in series or add another amp to drive the second one OR just get by with one speaker.

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