The following was submitted by your fellow member, cargodz

Lately we have had many individuals wanting to install there own amplifier(s) and subwoofer(s), which is great, although they may lack the general knowledge of what this entails. For this reason I have laid out the fundamentals of amplifier wiring.

Before you even begin thinking about doing this yourself, make sure to pick out the right products. This means that you must have an amplifier that meets the needs of your speakers/ sub(s). For example: if you choose 2- 12-inch subs with dual 2ohm voice coils and an amp that only puts out 2ohm stable power then you will not be able to run your subs at full efficiency. To have your system run at full efficiency you will need to have the impedance of your amp match a configuration of your sub(s). Also make note that power requirements are a must and many manufacturers place maximum wattage labels on their products to entice the unknowing public. Maximum wattage labels should always be ignored and system(s) requirements judged by the RMS values of the products (so make sure that you don’t get an amp that may very well overpower your sub(s).
The last piece of the puzzle is the power and wiring itself. Make sure that you are providing enough power for your system. Check here:
In some cases with smaller amplifiers you may be providing enough power from your stock alternator (vehicle specific), and with some a small capacitor may be required to assist in current draw, with most larger systems though an upgrade of the entire charging system will most likely be required (larger higher amp alternator, battery(s), motor – chassis ground, alternator – battery positive, battery negative – chassis ground).
Now that you have the proper pieces we are ready to begin.

Always start by disconnecting your negative battery cable.

Next figure out where to mount your amplifier example: back of seat, under seat, trunk floor, on subwoofer enclosure (last one not recommended with high powered systems as the added vibration may lead to amplifier internals coming apart) Note: try to keep your amp located near a good grounding point (solid metal frame or attached cross member).

Now you will need to run a length of power wire from your battery (POS.+) to the amplifier. Do NOT connect to battery yet. This is generally done by feeding the wire through the engine compartment, (most vehicles) through an existing grommet in the firewall. If a proper grommet cannot be found you will have to drill a hole.
If drilling is required: First make sure that you are drilling into a clear area and not into vital vehicle components. Next after drilling your hole, mount a rubber grommet into the hole so the metal does not cut through your wiring (as a good idea you may want to coat the open metal area with silicone before installing the grommet to keep the area from rusting).
Once through the firewall, continue running wiring to along one side of vehicle under the vehicles carpet (you’ll probably have to remove some trim pieces) and up under or along side of the back seat (if applicable) to amplifier positive.

Next install the fuse holder (block) between 3 to 12-inches away from your positive battery terminal end connection in your power wire and connect to battery positive (Do NOT install the fuse itself yet).

Now go back to amplifier location and measure out length of ground cable to good grounding location (you should have already located earlier). Try to keep ground wiring as short as possible (premium being under 16-inches).
Clean all paint away from grounding point for a good connection (in some cases drilling may be required if a suitable hole or bolt cannot be found as grounding point). Connect wire to grounding point (bolt or ground connector preferred) and then to amplifier negative.

You will now work your way back into the cabin of the vehicle and remove the head unit/ stereo (assuming you have an aftermarket unit with RCA connections, if not please skip this step and see note below). Choose the proper RCA connectors on the back of the head unit (if more than one set) for desired application and connect RCA cables. For this demonstration we will assume the installation of subwoofers.
Now at the back of your head unit, connect the remote lead wire to the remote wire in harness (usually blue or blue w/ white stripe wire).
Feed RCA cables and remote wire behind dash and then under dash to the opposite side of the vehicle of the power wire (by keeping these apart it will avoid possible unwanted engine noise through your speakers). This will be done in the same manner as the power wire, just on the other side of the vehicle.
Once you have your RCA cables and remote wire run back to your amplifier, connect in appropriate connections.
Note: If you do not have a head unit/ stereo with RCA connections an adapter that is to be spliced into the speaker wires will be required to complete the install.

Now that you have this done, you are ready to hook up your speakers/ sub(s). Run speaker wire from the connections on the amplifier in the desired configuration, in example Mono (1-channel.), 2- channel, 4- channel, etc. to your speakers/ sub(s).
The sub(s) may be able to be connected in either parallel or series. Check Here:

For connecting your sub(s) from the amp in an enclosure: It may be done either by connecting to an external box mounted set of terminals, small hole drilled in enclosure and direct to sub(s) (fill with silicone to avoid wire rubbing), or through the enclosure port(s) (if applicable).

Now that you have all of your connections complete: At the front of the vehicle under the hood, install the fuse in the holder (block) and connect negative battery cable.

Before you power the system up, make sure all gains on amps are turned completely down. You may now power the system up and adjust accordingly, either with an o-scope, digital multi-meter, or by ear.

Congratulations you have now installed your new amplifier(s)!

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