Subwoofer On/Off Switch?

Another tip, if you do put a simple switch inline (like a dipswitch, or circuit breaker type, toggle whatever) I recommend that you have either your stereo off prior to switching, you may find that it causes your amp to "chop" (lack a better term, it causes feedback and is hard on your speaker and amplifier).

Craig

Because your still sending a signal through the RCAs, also depends on if you have a good filter built inside the amp.  Some amps will pop the speakers if you turn the car off prior to turning the radio off.  But consider this, you have a relay inside the amplifier, well when you switch, your switch (that is inline), the relay will eventually realize that there is not a +V and will switch, well there is a delay to that switch (since it is not instantanious), also the active elements inside the amplifier (op-amps, IGBT's Transistors SCR bridges and what not) all suffer from this delay, so if a filter is not installed inside the amp to deal with the "delay periods" the signal will be cut off, but the other portion of the amplifier that is trying to send an output to your speakers will experience a pulse that is that "pop" you may experience.  I know this is kind of a crappy way to explain it, but without going through the circuit and showing you step by step and doing the math, I cannot provide a better answer. 

Hope this helps

Craig

hey guys thanks for the feedback. well after reading this awhile ago i went on to install the switch. it took less than 10 minutes. works great, and there doesn't seem to be any "pops". the only thing i couldn't figure out was that the indicator light in my switch won't work. used the same kind of switch when i installed a rear foglight on my car. it would be cool if the switch would light up everytime the sub is on. thanks again for the replies

'92 325i

Lighted switches have three terminals, 1 ground and two switch leg terminals.  Try swapping positions on the two switch terminals, you probably installed them backward, which doesn't hurt anything, it just doesn't allow you to have the switch lighted when it's turned on.  Remember, it'll only be lit when the the switch is turned on and the HU is on.  If it still doesn't work then it's likely that your amp turn on lead doesn't send enough power to operate that light in the switch, but I doubt that'll be the case. 

Thanks ccroush. I think I see somewhat of what you're saying. But what would normally prevent this from happening in a standard turn off situation (HU relay goes off, cuts 12v to remote)? Wouldn't it be identical to using the switch? Unless the amp has some sort of signal sensing technology on the RCA in's (which I have yet to hear of on standard car amps), you would get the same pop and damage/wear on components whether you turn the amp off with the HU or the switch. It is a mark of a quality amp that it has a good filter and does not pop on turn off, yes, but how is it different when it is the HU turning it off or an outboard switch? The amp is going to see the exact same signal (12v being cut at remote terminal) whether it is the HU’s relay or the switch cutting power. The only difference is the RCA’s still having signal, and I don’t believe many amps have a signal sensing shutoff as well as a 12v lead off. When you say “ well there is a delay to that switch (since it is not instantanious), also the active elements inside the amplifier (op-amps, IGBT's Transistors SCR bridges and what not) all suffer from this delay, so if a filter is not installed inside the amp to deal with the "delay periods" the signal will be cut off, but the other portion of the amplifier that is trying to send an output to your speakers will experience a pulse that is that "pop" you may experience.”

This is undoubtledy true, I have experienced it myself. I think it is one of the differences between, say, a JBL1200.1 and a Jensen xxxxx. The nicer amp will have the circuitry to compensate for the delay and such. But it shouldn’t matter whether the 12v signal is being cut by the HU or the switch would it? The only thing I can think of is a slight continuing of sound coming out as the supply rail caps continue to power the amp as they drain because ethe RCA’s still have signal, but this would happen even if there weren’t a signal. Perhaps there is some way the switch changes it, but I can’t seem to see it. Could you enlighten me?

Well, if the relay that turns the amp on and off (connecting the remote) does not have a good regulation filter on it, what I described above can occur.  You get the "popping and what not" now I only experienced this in substandard amplifiers, and I haven't really seen it in some of the newer ones that I have worked with.  Now to answer your question.  well when the head unit cuts the signal it also cuts the RCA signal as well, so you are shutting everything "except the constant 12V source" the amp will not suffer as bad from this delay problem.  Now you are correct about cap discharge, and if you only cut the remote, and leave everything else problem you have a A*e^(-tRC) discharge rate that occurs and since you have a signal but you do not have the remote turn on, and the other components are not "turned off" due to the delay time k, you can experience a discharge to the output that causes this noise, or popping to occur.  The theory behind this is pretty icky, its nasty regulation and switching problems that occur, but can easily be dealt with by implemenation of good filters in the system.  I used to see this happen a lot when ppl would have their radios up really loud and then just shut off their car, even some of the best filters cannot prevent the popping in that case (higher currents and thus higher power out) causes all kinds of problems.  But none the less, a good book in power electronics may clear up some of these concerns, but typically if you have a good amp (not prymid or targa or something) you shouldn't ever run into this problem.  I was just gave my 2 cents, because I didn't know what type of amp or anything that was being used in this situation.

Craig