What wiring do I need to connect up my amplifier? Is any of it supplied with the amplifier? 

Kenwood amplifiers do not include the wiring necessary to connect them up. However, the wiring required is completely standard and can be obtained from audio shops as well as this website. 

You need enough power cable to run from your car battery's positive terminal through the engine bay to the amplifier. Make sure you fit an in-line fuse or circuit breaker near the battery. Without one, an accidental short circuit could damage your amplifier, not to mention the possible fire hazard. 

You also need another length of the same grade of cable to serve as your earth wire. This should be kept as short as possible by making your earthing point as close to the amplifier as possible.

The final power connection you need is a 'turn-on lead'. This one does not need to be as thick as the power and earth wires (6 amp wire should be fine). It runs from the remote turn-on outlet at the back of your radio to the remote terminal on the amplifier. When connecting these wires, be sure to use crimp-on blade or eyelet terminals to make the tightest, lowest resistance connection. 

The audio signal travels from the back of your radio to your amplifier through an RCA signal cable. Your signal cable should be long enough to reach the amplifier but not too long, as this will tend to become damaged and pick up interference and electrical noise. 

At the output side of the amplifier, you'll need speaker wire. Generally the thicker this wire is, the better. Keep in mind that the thicker the wire, the less of your signal will be absorbed by the copper.

What size power and earth wires do I need for my amplifier? 

Before you can determine the appropriate grade of wire for your system's needs, you need to calculate the current demand of your equipment. 

To do that, you must determine the approximate current draw (in amps) of your amplifier(s). To do this:

• Calculate the total power of each amplifier (multiply the number of channels by the number of RMS watts per channel)

• If you have multiple amplifiers, add up the total power figures for each amplifier to arrive at a grand total

• Next, double this total power figure to arrive at a peak power figure (RMS gives you an average figure)

• Finally, divide by the 13.8 volts of your vehicle's battery - the result is your system's approximate current draw in amps. 

Make sure the cable you use can easily carry the maximum total current drain of your system. 

Where should I earth my amplifier? 

Your earth wire should be of the same gauge as your power wire and must make direct contact with the body of the car. Look for an existing bolt or screw that makes contact with the car body near the amplifier. Remove the bolt or screw, and scrape away any paint or grease.

A star washer will help your earth wire maintain tight contact with the car body. Use a eyelet terminal on the end of the earth wire, to keep it securely fastened to the bolt or screw. 

If you can't find a convenient earth screw or bolt, drill a hole for one. Be careful not to drill into the petrol tank, a petrol pipe, or a brake pipe! 

If you're earthing multiple components, try to earth each one separately, with about a half-inch of space between each of the earthing points. If you'd rather use a single bolt, place the earth for the most current-hungry component (probably the biggest amplifier) closest to the body of the car. Put the earth for the component that draws the least current (probably the electronic crossover) on the top. 

What is a "high-current" amplifier? 

A "high-current" amplifier is capable of passing high current into very low impedances (the speaker's resistance) without overheating or shutting down. In a perfect world with a perfect amplifier, power output would double every time the impedance was halved. For example, a two channel amplifier rated at 50 watts RMS per channel into a 4 ohm speaker load would produce 100 watts per channel when loaded by a 2 ohm speaker load. Unfortunately, no piece of electronics is 100% efficient, and most amplifiers can't do that. 

The best way to identify a high-current amplifier is to look at what happens to the power rating as the load impedance drops. The closer it comes to achieving the perfect world scenario above, the more current it is capable of passing. 

How much power do I need for my subwoofers?

That depends on what sort of bass impact you hope to achieve. If you just want to hear a bit more bass than your normal stereo speakers can put out, you should be satisfied with an efficient 160mm subwoofer driven by as little as 30 watts RMS. On the other hand if you're looking for really big bass sound, you'll need a 250mm or 300mm sub and as much as 150 to 200 watts to drive it. 

Be sure to use the proper box design and volume for the subwoofers you choose. This has a significant effect on bass response. A 250mm sub in the right box with the right amount of power will sound better than a 300mm sub in the wrong box with the right amount of power.