well i just hooked up my friends new subs, and when he shuts the car off, the subs release a few thumps....I don't know if this is normal or not? maybe they are just releasing the extra signal, or even air that was in the sub...? do any of you know what the thumping after the car is turned off could be?

 

it's called a thump. they probably do that too when u turn them on. makesure the rca's are away from the power cable and that grounds are good.

 

ok i will check that. if that is the case, will it cause any damage to the subs, amp, or cd deck? or even the rest of my car?

 

could be the amp as well

what type of amp do you have, most decnety ones have delayed turn on to prevent this thump

 

The amp is staying on longer than the source...ie deck or eq. This means the signal from when deck or eq turning off, is getting amplified by the amp that is still powering down.


2 ways to fix it.

1. Put a switch on the turn on led of the amp, and shut off the power before you turn of the car.

2. get a timmer (can't remember the technical name fo it) that automatically mutes the input leads to the amp, so that there is no singnal for the amp to amplify.

There is also one other problem I have come across over the years, but I'll with hold this info.......I don't want to confuse you with it yet.

 

BTW, what components are in this system, and who did the install?

 

Pulovr is 100% accruate. The thump is from your power source delay (amp). If it is not too loud, I would just ignore it. I'm curious as to what amp you are running?

 

It can also be the deck's fault.

 

that's ghay, shouldn't the remote B off the deck cut power to the amp before the deck shuts down?? I think it would help to know what components you are running in this system.

 

yup, we need to know the conponets b4 anyone can help.

 

well its typical, I make a forum sticker about helping others solve your problems, and hardly anyone follows, no wonder people complain.

 

here's whats happening for an electronic point of view...

first PULOVR is 100% correct the deck is shuting off before the AMP

but the big question is why does this cause thumps?

here's why. when the Deck turns off the signal wires are not at 0 volts or "ground" they actually are allowed to float the deck is not grounding them out which in fact it should not have to.

now is floating voltage bad? not really since it's a steady voltage, steady voltages or rails as they are called by electronics guys d cannot be amplified by the amp, all classes of amps kill rails in their very design.

your now asking how much crack I've had today? arn't you? here I start by saying it's floating voltage and then I state steady floating voltages don't cause it. Yup I must be on crack.

while there is steady floating voltages there is another thing at work and thats Noise or floating AC voltages. this noise is constantly changing... constantly changing signals are what all classes of AMPS amplify. this is the cause of the thumps.

now why is it the thumps stop? simple it's because the amp stops amplifying once it's drained it's capacitors and any power capacitors you've added into the system.

now all AMPs even threatre amps have Capacitors that have to be drained once off...ussually this results in threatres the power off cycle being AMP then everything else...

in a car you don't want to have to deal with a separate switch. so what to do?

well if you have a crappy deck it could be the decks fault because the deck sends the remote signal to the amp to tell it on or off so if it tells the amp off before muting it's signal lines the amp will thump...... so it could be the deck

it could be the wires.... bad signal wires = noise

but wait your thinking you'd hear thumping all the time if it was the wires. wrong... there is something in amps calls a noise supression system. this system cancels out the noise when there is a stronger audio signal.

the way a noise supression system works is it "sees" the signal from the amp which is ussually a much much much much stronger voltage then the noise and smooths the signal out removing the noise. basically when you turn the system off and the deck stops sending a signal well the noise is the only thing on the line now and is the strongest signal so the noise supression system goes to work smoothing out the curves of that signal but not eliminating all noise and you still have an amp that magnafies the noise.

you could try to ground the signal wires to get rid of the noise.

OK YES TO ANSWER ALL YOUR QUESTIONS NOW THAT ALL THE AUDIO GURUS HAVE I AM ON CRACK

I know your saying you can't do this. but yes you are audio gurus and I am an electronics dude.... ok so you can't connect the signal wire straight to ground. but what can you do?

you use a resistor I believe 75 ohms is the correct one to use and you want to use one thats rated at the same resistance as an inifinate length of the wire you are using. (it should be on the wire covering) you connect one end to the signal wire and one end to the ground.

IT IS VERY IMPORTANT THAT IT IS THE SAME RESISTANCE AS THE SIGNAL LINE OR YOU WILL CAUSE ELECTRICAL FEEDBACK AND HARMONICS AND FUNKY STUFF....

now if you buy a good amp most will state the required signal input line resistance required... this is because they are internally grounded just as I've shown you here...

anyways I'm going back to the performance forum where I belong

 

I just lock all the ones I get that I think are poorly thought out.

 

good idea

 

ummm i dont know if u guys are aware but all amps turn off after the HU is off. i've had about 20 diff systems in my car and every time the amp turns off some ( 1 or 2) seconds after the deck. it's faulty deck, or bad ground on the deck. it is not caused by the amp in any way.

 

if u want to be 100% sure if it's cause by the deck or by the amp do this:
turn your system on and have it playing at a regular volume. then while its playing unplug the rca's out of the amp.......if it thumps then it's the amp....... if it doesnt thump then turn your deck off while the rca's are still unplugged, if there is no thump then it's not the amp and the cd player for sure.

 

Where does it state that I said the amp is a problem Soundscare?

I've been doing this since I was 15. I'm now in my 30's (gee, that makes me old, doesn't it? )


I said the amp is amplifing a signal from a deck, that has not muted the signal yet. I never said the amp was at fault.


And if I recall, I also said the deck might be the problem.


Some decks use a really shitty cheap remote output transiter, that over time, starts to go south. There isn't much you can do, except send it in to get fixed, or just use a simple switch to cut power to remote turn on lead of the amp.

There is also one other advantage of doing it this way. If you run a real fused 12v power souce to the switch, and then run it to the remote turn on lead of the amp, then you can run more things off this remote wire....and as long as it's fused properly (something you say you don't do......and after I heard that, I have no faith in what comes out your mouth anymore), then you can run almost any 12v thing you want (within reason).


Things you can hook up to turn on with the switch....

1. the amps first and foremost.......and you can also hook up more than 2 or 3 without worring about blowing the decks remote lead output.

2. fans for the amps

3. neons

4. whatever else you want to hook up, as long as it doesn't exceed the wires power/amperage handling, as well as the fuse's rating's.


You can use the remote lead from the deck to do all of this, but you must use a 12v relay. If you don't, the decks remote output, will be toast in a few seconds.


There are still other little things that might be the problem, but without knowing the compents in the audio chain, or actually seeing the system in person, then all I can really do is give susgestions to the guy.

With over 18 years of installing systems and alarms, and I have come across quite a few weird and fuqked up installs. Ex....lamp cords that were used to supply power to the amp, because the guy was too cheap to get a real power cable and fuse..... is just one example. Another guy was using the remote lead of the deck, to power his little neon light under the dash. The guy returned 4 decks, until he brought the car to me to find out what might be wrong.





That's why I said I also wanted to know who did the install.

BTW, your way of testing the amp, by pulling out the rca's, is not a safe way of doing it. There are also instances that even doing this will not pinpoint the problem. I once found a guy had hooked up the power and ground ok, but had accidently hooked up the remote power lead from the AMP, to the power distributon block that powered all the amps. He did this to test the amp to make sure it would turn on. Well, the guy forgot to hook it up to the deck, and left it connected to the 12v block. Over the next few days, he had a constant turn on/off thump, and then after all of this, the battery would go dead overnight. DUH, of course the battery would go dead, the amps never turned off. Also, because they never turned off, it was amplifing the signal from the deck. He had NO idea why all of this was happening. He must of checked and rechecked the systen at least a dozen times, and reintalled and checked the deck too.......but for some reason, he never noticed that the amps never turned off. I found the problem in about 10 minutes. You should of seen his face.



and some people wonder why they have noise, and problems with thier systems.



90% of the time, it's the install that's the problem.

 

I have a stock deck, and a crappy amp. But the amp is wired independantly of the deck. If I turn the deck of first, the sub thumps. So I think Jason's noise suppression theory is correct. At least in my setup! So I've resorted to killing the sub first if needed. Regardless, when the car turns off, everything powers off, but the amp still delays over the deck, so thumps are heard.

 

Im a pro

I use telephone wire for power ground and remote
run grounds outside and overtop my hood
run speaker wire out the door sil not even in the rubber boot to the doors

 

I should give you this..... , But I'm pretty sure everone knows you are joking. (or I at least hope they do)



You also forgot how to hook up a regular TV (120v), dirrectly to the car's battery. One problem, it will only be 1/10th as bright as to would be at home.....which is not a problem if you watch it only at night. Right Matt?