hypothetical question about power

I was reading through the thread about how someone's battery keeps dying from their system.  I was wondering if this is a consistant problem with people that install a car audio system.  I will be installing shortly a 1100 watt sony mono sub amp and 2 sony 10's.  The amp should be delivering around 200 watts rms at 2 ohms I believe to the subs, each.  The new stereo I am putting in should not draw any more power than the old one I believe.  So really the only new drain on the battery and in turn the alternator is the amp.

I have already replaced the alternator in my car once (it died about 6 months ago, car is 1995 and had not been replaced yet), and I do not feel like doing it again.  So what I want to know is this:

1)  Is this a common problem?  If so is it only among high power systems, of which I don't think mine is one.

2)  What can I do to keep it from happening?  If i turn down the gain on the amp, lowering the wattage?, then would that in turn keep it from drawing so much from the battery?

just some input, if yall would, thanks

1.  Yes, it is a common problem, especially with novices or people who do not understand that car audio is manipulating electricity, and that the alternator is the SOLE source for electricicty in a running vehicle.  It is not only with high-powered systems (although it is certainly more common the higher system power is taken.)  It can happen in any car with any additional electrical load added.  It is especially more common in newer cars which are often designed with just enough electrical capacity for the loads of the car and nothing else.  Car makers do this to save costs and to improve gas mileage.  That's also why cars use the absolute smallest gage wires possible: to save costs and improve gas mileage.   So, no matter how big your system is, you run the risk of overloading and burning out your alternator.  That's why I suggest an altrnator upgrade quite often.

2.  Turing down your gain will NOT, repeat NOT limit the power your amplifier can produce.  Your amplifier will retain its ability to produce maximum power and to draw maximum current with any gain setting.  Gain is not a volume control nor a power limiter.  It simply matches the input capability of the amp to the output voltage capability of the head unit.  That's ALL.

Determining how many amps an amplifier will draw is easy.  Look at the fuse on the amp.  It cannot draw more than that or the fuse would blow.  Always use RMS power ratings at 12 (or 12.5) volts.  All other ratings are for marketing purposes only.  A mono amp and a stereo amp with the same power ratings will draw the same current from the electrical system.  I believe an Explorer comes with Ford's 130 amp alternator, and your vehicle under normal operating full-load conditions should use less than 80 amps.  So on a truck you do have some headroom.

Is your new amp a Sony Explode XM-D500X?  This amp is actually rated at 250 watts RMS and will draw about 20 amps, so you should be fine.

By the way, if you do run into power problems, short of a new alternator there is no real solution.

Yes, you have it exactly.  And it works or they wouldn't do it.  It's like PT Barnum said... a sucker born every minute...

Input gain control is not the same as volume.  But yes, if you never turn the volume on your HEAD unit up past half, then the equipment will in theory operate at about half its power ratings.  Gain is completely different.  People often mis-use it thinking it is a volume control, and end up blowing amps and speakers.

RMS is the maximum safe normal operating rating.  Peak means the equipment is capable of hitting, but not sustaining, that rating for a very short period of time.