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In my day I have seen many car audio systems. I have seen the best, and some
of the worst. If there is one corner which gets cut more often than proper
fusing, it is probably propping a speaker in the back deck so that it can
hit you in the head the first time you stop short! :-) But fusing (PROPER
FUSING) is often overlooked, or worse yet, skipped or bypassed for
convenience. It is one thing I see over and over again in bad installs. You
know the type, the type of install done in a driveway with a bunch of
teenage friends who are all TRYING their best. But they just don't know any
better!
Hopefully, we will educate you a little here. The most vital item in a
car audio system that uses amplifiers is the fuse. NOT the fuse in the AMP,
the fuse by the BATTERY! You don't have one? YOU better GET one! Look, even
the automotive companies haven't figured out how to cut the corner of using
a fuse (or fusible link) in a car. If they can't, we can't. A fuse needs to
be placed on the positive line coming from the battery, as close as
possible. I will say within 1 foot, but it should really be closer. If there
is any possibility of the wire making contact with ANY metal BEFORE the
fuse, the fuse needs to be moved back! Not just under normal circumstances.
Picture the car in an accident, and the hood caved in, or the front smashed
up, or a side impact to the fender next to the battery. Imagine the worse
case scenario. Are you protected??? Imagine a loose wire from the battery
flapping around full of current, sparking on everything after an accident.
Now picture a broken FUEL line at the same time. If that doesn't make you
put the fuse in the right spot, nothing will.
Next, keep in mind this fuse is meant to protect the vehicle, and the
occupants. This is NOT the protection for your amplifier(s)! MOST amps have
internal fuses for that already, OR are supplied with inline fuses to
protect the amp. Use the inline fuse, or use a fused distribution block NEAR
the amplifier(s). Fused distribution blocks are very convenient if you have
multiple amplifiers.
OK, what size/type fuse do we need? On the market there are many types of
fuses. Up to 60 Amps you can use AGU glass fuses. They are inexpensive, and
they work fine. If you need more than that, you will probably need to go to
a "MAXI-FUSE" or Wafer type fuse, which are more expensive. But they go up
to 250 amps or so. There are also the inline -cheapo style- fuses that
usually come in ultra cheap amplifier kits. The fuse is very small, exactly
the same type as found in most car fuse boxes. We do not recommend these in
any application larger than 1 amp, up to about 250 watts. The following is
just my opinion, but I feel very strongly about this. Lastly, there are
"circuit breakers". Circuit breakers are considered by many to be better.
They are convenient, if it trips, you just reset it! No fuse to buy....
HOWEVER, once a circuit breaker is tripped the first time, it can never be
as accurate again. It may well take twice the amperage to trip it the next
time! or maybe HALF. Those are extremes, but still possible. Worse yet, I
have seen circuit breakers WELD SHUT were they could NOT be tripped, there
was no way to stop the power from going through until they actually melted!
Nice way to have a fire..... So in general, we do not suggest circuit
breakers. Use a fuse holder, and carry several different sized fuses with
you, just in case.
NEVER under ANY circumstances bypass or alter a
fuse or circuit breaker that is blown!!!
The fuse blew for a REASON most of the time, although they can sometimes
just fail. Just because you don't feel like driving home without your music,
there is NO REASON to override a MAJOR safety feature! I don't want to tell
you how many times I saw people using pieces of speaker wire, or tin foil
wrapped around a fuse because they were too cheap, or didn't have a spare
fuse. If you absolutely feel you MUST override a fuse, override one near the
AMP, NOT the one BY THE BATTERY!!! That fuse is protecting EVERYTHING!
OK, I think we got across the importance of having,
and KEEPING the fuses. So what SIZE fuse do you need? How do you calculate
that? For the MAIN fuse (again, the one by the battery) use this procedure:
Add up all of your amplifier(s) power output in wattage. So if you have a
4x75 watt RMS amp, and a 600 watt RMS sub amp, you have 900 watts total
system power (RMS). Divide that number by your cars voltage (avg. is
about 14 volts). Use a fuse similar in size to that number, and 90% of the
time, you will not have any problem. This is just a rule of thumb guide, but
it works pretty well overall... Using this math on the above amps, you would
get 64. I would suggest a 60 amp fuse in that case. In fact on systems up to
about 1000 RMS, I usually suggest 60 amps. Only on systems over 1000 RMS do
I suggest going to larger than 60 amp fuses. That is not to say you could
not BLOW a 60 amp fuse with a 1000 watts system, you could. But it is
unlikely with normal day to day operation. Lets leave extreme use and
competition use out of this.
For the record, for the hard
core crowd who REALLY need to know what the proper calculation is:
Total RMS power x 2 = Total power
usage
Total power usage/battery voltage =
Current draw
Add about 10% and use the closest
fuse size.
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