Car Stereos: smoked subwoofer problem, ohm subs, loudness controls

Question
hi
I installed sound system by expert hands shop , but after 2 month my 2
subwoofer was burned up they talled me the sub was damaged and they don't
know why!!

2 sub sony xplod 1100 watt
http://www.sony-mea.com/product/xs-gtx120lt

connected to 1 amp kenwood 2400 watt
http://ae.kenwood.com/Car_Entertainment/Power_Amplifiers/KAC-X11D

they ignore my problem and i want to prove to them that was their problem
so i ask you to get help :)

the 2 sub was smoked in one time the amp in good condition as they say..

thank you brian

Answer
Hi,

According to the links you provided, it looks to me like the amplifier is simply far too powerful for the subwoofers.

When comparing amplifier and subwoofer power specs, you should always look at the RMS or "rated" power, and ignore "max" or "peak" power.  Your amplifier is rated for 1200 watts into a 2-ohm load.  When you combine two 4-ohm subs, then the impedance at the amplifier is 2 ohms.  The power produced by the amplifier will be divided evenly between the subs, so at full rated power, each of your subs would be getting 600 watts--twice their power rating.  This could easily overheat the subwoofers' voice coils and damage the subs.  An amplifier with this much power doesn't have to be malfunctioning to overpower and damage these subwoofers.

In theory, one could adjust the amplifier's gain control to reduce its power output below the level that the subs can handle safely.  In practice, though, this isn't easy or foolproof--one certainly can't set the amp by ear in a case like this.  You'd have to use a voltage meter to monitor the amp's output power while playing a test track.  However, you could still exceed the maximum safe power level if you played a source track that was recorded at a higher level than the test track, or if you turned up the bass boost or loudness controls on the head unit, or adjusted the volume past the point that the installer used as the normal maximum listening level.

Ultimately, I think your problem was caused by a mis-match in the power rating between the amplifier and the subs.  You simply have too much power for your subwoofers, and in a case like this, it doesn't require negligence on the part of the installer to damage the subs.

Brian