Can blown subs cause Amp problms.

I installed two MTX 12's and wired them parallel to a Lanzar Vibe 1200d.  After about two weeks the amp went into protection. I had the level set high, but at first there were no problems, then the amp started to go into protection when the head unit was turned up.  The subs are rated at 200 rms and I would say I was pushing around 400 rms to them.  Is it possible the subs could have blown and caused the amp to go into protection?Quality Car Audio for Less

Myles Peters (Owner)

Need quality audio equipment for a good price, e-mail me at mjp2424@hotmail.com

Well, I just diagnosed the almost exact same problem today, just with different equipment.  First off, you said your subs are in parallel.  What impedance is the voice coil for each sub?  Are you bridging the amp with both subs in paralell?  If so, then possibly, one sub blew, and the total impedance halved at the amp, therefore causing the amp to go into protection.  Today, I had a customer with two 4ohm Rockford HE subs running in parallel (therefore 2ohms).  He hooked them up bridged so then the amp saw 2 ohms. One sub blew therefore the amp saw 1 ohm.  This is bad for MOST amps.  The majority of the amps out there can only handle a 2 ohm load at the least.  Test each of your subs to see if they are blown and check the impedance level.  Hopefully this will solve your problem.  For my customer, we swapped out his subs for 8 ohm units so that he could safely bridge the amp at 4 ohms.

Hey Xplocivic, thanks for the reply.  My speakers are at a 4 ohm resistance, so I had 2 ohms going to the amp and the amp was a one channel amp, so I had the subs wired parallel to the one channel. Supposabley the amp was supposed to be stable at 1 ohm.  How can you test to see if the speakers are blown and what resistance does a blown speaker show? Quality Car Audio for Less

Myles Peters (Owner)

Need quality audio equipment for a good price, e-mail me at mjp2424@hotmail.com

I ran into the same problem when I had 2 RF eight inch subs running at 2 ohm mono. When I turned the volume up too high my amp would shut down for 15 sec. I changed the wiring to stereo and the problem went away. The amp was rated for 2 ohms mono. As I was running it we put the meter on the subs and measured the resistance as the volume went up and discovered that the resistance was dropping below 2 ohms. As the voice coil in the sub traveled further away from center the resistance got lower, My amp was shutting down because it was going into 1 ohm load mode(the manual said it does this)or it was going into protection. To date I havent quite figured out exactly what was going on, but I will tell you one thing and thats I sold the RFs. We will see what happens with the new subs. Hopefully you didnt damage your amp, but that is what protection mode is for. The situation you are in is exactly the same as mine was I was even overpowering my set. Hope this helps

Myles2424 are you sure you were running a 2 ohm load. Most MTX subs are dual 4 ohm subs. If you were to wire them in parallel and bridge them that would give your amp a 1 ohm load. Now to test the sub you will need a voltage meter. Here is a good tutorial http://www.eatel.net/~amptech/elecdisc/vomillia.htm but to sum it up you set it to ohm mode, and then connect the + test lead to the + terminal on your sub and then connect the - lead to the - terminal on the sub. Do so for each coil, now if each coil is 4 ohm it will not read out 4 ohms it will always be lower. But all the coils should be around the same ohms. If you get a real high reading from one of the coils then you know you have a bad sub. But it is possible that you did blow one of your subs and that can be one reason for it going into protection mode. But what size power and ground cable are you using? Also dose the amp go into protection mode all the or at low volumes?

Hey bberman1, thanks for the link and reply,  the subs are MTX 4000 series at 4ohms, no dual voice coil, the cheap ones. I am using 4 gauge wire to a distribution block and have 8 gauge going to two amps. One of the power wires is going to a capcitor that powers the Vibe 1200D amp.The ground wire is 8 gauge also.  The amp is in protection for good and I sent it back to the manufactuer, but the amp only went into protection when played at high levels.Quality Car Audio for Less

Myles Peters (Owner)

Need quality audio equipment for a good price, e-mail me at mjp2424@hotmail.com

Hey Tcole, thanks for the reply.  Looks like I need subs that can handle more power.Quality Car Audio for Less

Myles Peters (Owner)

Need quality audio equipment for a good price, e-mail me at mjp2424@hotmail.com

No problem, That sounds like exactly what you need.

For future reference, and answering your question on how to test subs.  The easiest way to check a sub is with a digital multimeter.  Connect the meter across the subs terminals and check for continuity, if there is continuity, then the sub is blown.  Also you can check the resistance.  If its a 4ohm sub, then it should read somewhere close to 4ohms, usually 3.7-4.7 ohms indicates a good 4 ohm sub.  If its an 8 ohm sub, then close to 8 is good, so on and so forth.  For DVCs check both voice coils as one could go before the other.  Also when checking the subs resistance, move the cone in and out, the resistance should change, but go back to close to the original value when you are done moving them.  Pretty simple, huh?  Any more questions, feel free to ask.  Good luck on your new subs.  As always, you get what you pay for.  Try to buy from a shop that gaurantees your subs for a few years, that way if they blow then they just get replaced and you don't have to buy new subs, this gaurantee usually costs a little but its not as much as new subs.  Working for Best Buy, our 4 year service plan on a sub is $19.99, well worth it in my opinion.