First thing's first. Disconnect the negative battery line.
Depending on your amp and subwoofer specs you may need to consider the
gauge of the wire you are running to supply power. 8 gauge is typically
fine for most single amp setups. Personally I wouldn't run anything
smaller than 8 for a single amp. Most likely you will be putting the
amp/speaker in the trunk/hatchback area, and the length of the wire
directly coresponds to resistance and heat build-up. The bigger the wire
the better. I'd opt for a 4 gauge wire if you can afford it. You can
always get a distribution block later to fork several 8 gauge wires to
different amps if you want to expand.
Get an inline fuse for the main power line and place it somewhere near
the battery terminal. Your amp probably has a fuse but just to be safe
put one where it counts. Those extra few dollars could save your entire
There are several ways to run the wire. I'll give you one that I use.
First you're going to need to fold back the carpet on the passenger's
side. Near the ECU cover there should be some wires going into the
engine compartment, and this area is sealed with a rubber seal. You can
see it better from the engine compartment. It's a bitch to take the seal
off and put it back on because it's really tight in there. So, what I
usually do is put a TINY hole in the rubber and force the end of the
wire thru it so it expands to the size of the wire. You can always
spread a little RTV on it later. I don't bother removing the seal and
have to hassle with trying to put it back on. Don't connect the wire to
the battery just yet. Also note to be very careful not to cut any of the
car wires when you're making the hole. You're going for a tiny hole
anyways, so you can use something blunt like an allan key to make the
Now that you have one end of the wire inside the car running from the
engine compartment, you can remove the lower side panels (not the door
panels) and conceal the wire behind them. They are connected by metal
male/female clips and the edges are folded over the framing. If you
think you're pulling hard enough to break it or you're bending it a LOT
you probably are going to break it.
Run the wire all the way back to the trunk/hatch area. You're going to
want to ground the amp to the body of the car. I usually go for a
seatbelt bolt hole. If you don't have a hole like this or you want
something else, you're going to have to drill and tap a new hole, but
I'd be careful back there and avoid puncturing the fuel tank. If you do
drill/tap a new hole, make it at least 8mm to 12mm. MAKE SURE YOU SAND
THE AREA THAT YOU'RE GROUNDING TO to a bare metal finish to get a good
Connect the wires to the amp. Connect the negative wire to the car body
somewhere near the amp. USE THE SAME OR LARGER GAUGE WIRE AS THE
POSITIVE. Connect the positive wire running from the trunk to the engine
compartment to the positive battery terminal. You may need a
distribution connector for the batter terminal; or you can go ghetto and
braid the end of the wire and put it inside the battery cable connector
before you screw it on. After you're all done connecting the amp wires
and speaker, you can reconnect the negative battery line.
I'd make sure the amp is secured and screwed down so it doesn't fly
around and short one of the connections.
Oh I almost forgot; don't use the connection wires you get with your
subwoofer. They usually supply wire that is way too thin. You'll get an
overall better signal if the wire is thicker, like 16 gauge.
And if you hear a strange high-pitch noise that seems to match the
frequency of your engine sound, that's the sound of your alternator. If you
hear this, you probably have a shitty ground connection. Other causes could
be that you're running the wire too close to other power lines or the
alternator itself. You may need to experiment with the path of the wire if
you have this problem.
*sigh* More stuff I forgot to mention:
I'm not sure how experienced you are with stereo equipment so I'll just
say this for good measure. You said you are getting a subwoofer; just
one. A lot of subwoofers have dual voice coils (DVC) and can only be
wired for 2 or 8 ohm operation. Most stereo amps cannot support a 2-ohm
mono load, so unless you bought a monoblock amp you're probably (99%
chance) going to have to wire it for 8ohms. If your sub is a single
voice coil 4ohm then you have nothing to worry about. Most stereo amps
can safely bridge into a 4ohm mono load. If you do have a DVC sub, see
this paper for more info:
Also for load handling, you can't rely on the speaker's MAX wattage
rating. You'll want to pay close attention to RMS value. Generally
you'll want your amp's wattage ratomg to be close to (preferably exactly
or above) your speaker's RMS value. Otherwise the sound may be distorted
and you could melt the voice coil or overheat the amp. The RMS wattage
is typically half of a speaker's MAX wattage rating, but I'd look at the
manual for specifics.
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