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well i was happy with my old setup i had. i had an alpine CDA-9851 head unit with an alpine MRP-F240 4/3/2 channel Amp, which was then connected to a Rockford Fosgate P2 sub. it sounded so nice but i wanted something a little more, and i wanted to amp my speakers to i decided to get a new amp, in which id need a new sub.

anyway getting to the point of this post. i changed over to an alpine MRP-M450 mono sub, connected to a new Rockford Fosgate P3 sub. sounds awesome but i then decied to change over to the stock head unit as im looking to go back to stock and just amp everything. any who i added in a line out converter and it sounded awesome. well the subs did. if i turned off the car and back on again the subs came back to life. but then i put it all back together and i realized when i turned it off the subs seemed to shut off.

i thought maybe it was the line out converter. so i got tired of messing around with it, it was getting late so i just put the alpine deck back in and called it a day. then the same thing happened with the alpine. sitting it sounded nice but when you drive you turn it up and then the subs to just shut off in the middle of a song. so id turn off the deck and back on again and like before. the subs worked again. until the volume was turned up. and it wasn't like i was basting it...

any idea why this is happening? i do plan on putting back in the stock cd player when i get my new ipod adapter for my cd changer input and then fire it all through the amp. but right now any input would be great.


PS. its also a dual voice coil sub, so im told. it has 2 inputs on the sub. + and - on both sides. my friend had a setup that you just connected them through each other. ex. the box to one side then another set of wires going to the other side with the appropriate polarities.

 
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Well it could be any number of things, but usually when something like this happens, it means your amp is going into protection mode. This could be caused by a drop in voltage from your cars electrical system to the amp, meaning that your battery or alternator is not suplying enough power. It could also be that you have your sub wired up wrong and it is present an impedence that is too low for that alpine amp to handle. I see that it is rated down to 2 ohms, so if your sub is wired to a lower impedence, your amp is not going to like it and it will either overheat/fry itself or shut down. Is the amp actually shutting down (turning off) or is there just no sound coming out of the subs? If it is just no sound and the amp is still on, it might be that you have a problem with your line out converter and the amp is not getting an audio signal. Could be many things, you really need to post more info. Is there an indcator light on that amp, is it flashing or changing colors when the sound goes off? Does the amp get really hot when the sound stops? Do you hear popping or crackling through the sub before the amp cuts off? etc..

 
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Try turning the gain down on your amp.

 
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seems like the amp isnt getting enough power, or overheating. is your power wire big enough for the amount of watts youre running?

 
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It sounds like your having the same problem i did when i first started in the ice category... your amp might be to big for your lil alternator so when u asking for big bass(more power) it will shut off with that being said it might be get new amp or new HO alternator.. i didnt check out the parameters of your amp so its just a guess also it just might be like 85gp4 said lower ur gains on your amp and see what happens

 
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There is a member on this forum who was running near or over 1000rms watts on the stock alternator without a problem.

I also think you should try to lower the gain setting on your amp.

 
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what guage of power wires are you running for both the positive and the grounds? what is the ground going from your battery to the chassis? if that's still stock, you need to upgrade that. anyone with a system should definitely do the "big 3" upgrade. if the voice coils are 4 ohm and you've got them in parallel, you'll still be at 2 ohms, so your amp should be fine. does the line out converter have an adjustment on it? i know some do. if the voltage out of the converter is too high going in to the amp, it could also cause the amp to go in to protection and shut down.

does the amp completely shut down the output where there's nothing out of the sub or is is just muted some?

 
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use bigger power wire...check voltage.....if yur 4 gauge try 2 or 0....if yur 8 go to 4 gauge so on.......um....might be overheating so put it in a more open air location. new battery and such....capacitor....dont know wut to tell ya man

 
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With that amp, he should be more than ok with 4ga wire. To be honest, 8 ga would work as well, because it only has 2x20 amp fuses, which means that that amp is never going to draw near 40 amps and 8ga or 4ga can handle that easily. You definatly do not need a new battery unless your old battery is bad and as for a cap....dont get me started....just dont buy one .

 
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Oh and check where your amp is grounded to the chassis, make sure that the area that the ground wire is attached to is bare metal and is unpainted or sanded off. A good place to ground is the selt belt bolts under the rear seats. If your ground is loose or not good, your amp will cut off.

 
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well thanks for all the input. well alot of you were correct. it was going into protection mode. i had it at 2 ohms and i changed it to 4 its was running at 440 RMS and now its down to 220 RMS which really helped. it wouldn't shut down till the subs got low, so im guessing the sub was drawing too much bass for the amp to handle, if thats possible. i changed it over just now and it sounds awesome. i just have to do some final tweaking but over all its 100% better.

 
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If you have it wired at 4 ohms right now and it is working, then it was a resistance issue. Most people dont realize that when the music is on and the sub is drawing power, the resistance is in constant flux. You should try hooking up a multimeter to the amp when the music is playing and you will see that it is most definatly not a constant 4 or 2 ohm connection. When a really low/deep bass note hits, the subwoofers magnets use more power to increase the magnetic force needed to cause the motor structure to excur. When this happens, the amp has to output more power and as such the resistance (ohms) naturally dip lower. When you had it wired for 2 ohms, Im sure it was trying to dip down to at least 1 ohm or maybe lower and your amp could not handle that.

 
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Quick question, how can a DVC sub be wired to both two or four ohms unless one of the voice coils isn't connected?

And I know RF isn't making a dual 3 ohm sub so don't even try that, lol!

 
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This is how I thought a speaker worked:
When the voice coil draws in more power it's magnetic field becomes larger. Therefore the magnetic field opposing/attracting the magnet becomes larger. This larger magnetic field results in greater displacement of the cone/spider in either direction. The motor structure in a loudspeaker is fixed!

 
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yeah.

the resistance doesn't change. the resistance is a fixed, physical attribute. only voltage and current change which is what creates the wattage. the voltage and current is dynamic and relative to the fixed impedance of the sub.

 
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Well it looks like school is in session today.

The below plot is from an Aperion Intimus 533-T loudspeaker as reviewed by Stereophile. Note how impedance (solid line) changes with frequency (frequency is the x-axis, impedance is the left y-axis). Impedance also changes with things like enclosure type, voice coil temperature, and so on.



Resistance is a static DC measurement. Impedance is an AC measurement of resistance, inductance, and reactance. Since loudspeakers deal in AC signals this is why impedance is a more relevant concept.

Any questions?

 
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interesting. been a few years since my electro-magnetic theory classes.

 
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I'm reading 'The Electric Life of Michael Faraday' right now. It's a good book for the real dorks out there, lol.

 
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Oh how correct you are. Forgive me for not clarifying and going into more detail, I consider the magnet and what I call (rather simply) the piston, to be the motor "structure". The changing power level and pursuant change in magnetic fields is what propels the "piston" up and down through the larger magnet that is the boot of the sub. I use the fictional verb "excur" to describe the process of excursion, which encompasses this all and simplifies it for those who have no idea what makes their sub beat. Sorry for the confusion.

 
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sooo....just listen to chrismaspie...

he knows his ****.

 
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X2!

 
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Im having a similar problem with my amp. I recently lost my starter and got it replaced and now my subs arent working, and my buddy says the amp is getting no power. It was cutting out before and now it isnt working at all. Any suggestions guys? is my amp blown?

 
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if the amp isn't getting power, the power fuse is probably blown, not your amp. starter problems shouldn't have anything to do with it unless they disconnected your amp power wire for some reason.