Crushed Voice Coil

My brother is having trouble keeping his subs from blowing.  It seems that everytime he cranks his system he manages to crush his voice coil.  The manufacture told him that he needed to break in the speaker before turning it up and he waited little over a month and the voice coil crumbled once again.

He tried the KICKER L7'S and they seemed ok for until he started to really turn it up.

His amp pushes 1200 rms @ 1 ohm and the subs are http://www.cadencesound.com/action.lasso?-Database=Products&-Table=WEB&-ResponseAny=drivers_detail.html&-token.sub=WB&-token.comps=&-KeyField=ID&-KeyValue=122&-search.

Forbidden the box is approx .55 to .6 what was recommended by cadence.  The CD player is a Alpine CDA 7995.  All power cables are 4 gauge with a 2 farad cap.  The ground wire from the battery to the chasis has been upgraded also.  The amp is a Ultimate DD1-1200 and the crossover is a coustic.  The gain on the amp is about 1/4 the way with the sub sonic filter set to the minimum. 

I know that distortion will fry a coil.  But what would cause one to crush.  He never has been able to turn the system up real loud with his subs.  Could it be the subs.  He currently has my orions which are 12's and has not had any trouble.  I know that this sounds like the answer to my question it's the subs but the cadences are suppose to hold 600 rms and the amp is pushing 1200/2.

Much appreciated info. Send me the link to the Ultimate web site. To cause a subs voice coil to crush could mean a loss of control of the motion of the driver, in other words throw a hotdog down a hallway. If the amp has lost control of the motion of the driver, the voice coil former may be making contact with the bach of the magnet structure (pole piece). This also can be an indication that the gain is still too high on the amp, a bass boost cicuit is turned on on either the cd or the amp, the cd you are playing may have (if burned) distortion recorded on it. Get yourself a line driver, I am a firm beleiver that the alpine is not actually producing a 4volt non clipping preout. If the audio signal is clipped (distorted) at the output stages of the cd player (present at higher volume levels) the signal given to the amp is a distoreted signal to begin with, the amp says OK here you go and passes it on to the sub which says OMG you want me to do what and we end up with damaged speakers. Turn your subsonic filter up a bit, a sealed box is probably starting to roll off around the 50hz mark, that filter may keep out some of the damaging energy.

Next, if you have a meter - set it to measure risistance, we want to measure the resistance of your amps ground. Take one side of the meter and hook it up to the battery ground, take the other side of the meter and (first disconnect the ground from the amp) and connect it to the ground wire itself. This should give yu a measurement in ohms. If it is above .5 ohm, ground the amplifier directly to the battery, make sure of this.

I need some more info on your amp to check it out as well. I won't be able to get back to you until tomorrow.

Sorry for taking so long I was out frying my woofers so I can have a reason to upgrade.

Ketel the amp is only a 1/4 up you think that's too much.  I will tell him to try lowering it.

Forbidden here is the link to the amp. The amp is the DD1-1200    http://www.ultimate-sound.com/technical/technical.html

Ultimate is also affiliated with the auto sound competition industry.  Two of their decision makers come from well known companies. MB Quart and Lighting Audio.

I will e-mail him your comments tonight and have him to start the process tomorrow. 

He is using the crossover that is built in on the Radio.  He has two 2ohm subs.  I was wonder if because the amp is rated at 1200 rms into a 1 ohm load could this be causing the subs to blow by over powering them.  I have read reports that this amp actually puts out more than 1.3 kilowatts or over 1300 watts.

I know that a lot of subs claim to be able to handle a certain amount of power but can't even come close.  Is Cadence one of those companies.