Installing Car Stereos : How To

How To: Install Car Stereos
Installing a car stereo can be a simple thing. Basically, all one really needs is a wire harness, dash installation kit, and some simple tools. There are so many quick help guides and aftermarket parts a first time beginner can install a stereo easily like a pro.

how to install car stereo


Perhaps the most time-consuming and most important element of a car audio installation is the wiring. There are power cables, ground cables, signal (RCA) cables, speaker wire and more. Then there is the connection of wires to ignition sources, constant 12-volt sources, etc. The process may sound overwhelming. However, if you attack it in small bites, you will find that it is not as difficult as you expect.
Preparing for the Installation
1.  Gather the following tools: knife or wire cutters, solder and solder gun, crimps, stripper, screwdriver, screws.
2.  Plan the installation. Know where you intend to put all the components. For example, the radio is commonly put in the factory opening in the dash, the speakers are put in the factory openings in the front doors, and the rear speakers are put in the factory openings on the rear deck. The equalizer goes in the factory opening below the radio in the dash. An amplifier with built-in electronic crossover usually goes in the trunk. The car's battery, which powers the system, is commonly under the hood, usually on the passenger's side of the car.
Routing Power, Ground and Signal Wires
1.  Route the power cable from the battery through the passenger side of the car to the amplifier in the trunk. This will prove easiest because the battery is commonly on the passenger's side of the car. You will have to feed the power cable through a rubber grommet on the firewall.  (Battery Terminals help with securing a professional connection)  
2.  Route the signal cables (RCA cables) on the driver's side of the car from the head unit to the amplifier.
3.  Ground the amplifier to a clean metal surface on the car's chassis. The ground should be no more than 18 inches from the amplifier. The ground cable must be the same gauge size as the power cable being used.
You don't want to route signal wire next to power wire because that could result in noise entering the sound system. If power cable and signal cable must cross, cross them perpendicularly. If you experience noise you can always get a noise filter
The gauge of the power cable is determined by the specifications of the amplifier you are using. The owner's manual that comes with the amplifier will probably tell you what gauge cable to use. If it does not, consult with a tech advisor from the manufacturer of the amplifier to find out.
Use well-shielded RCA cable. This will help prevent noise from entering the sound system.
Wiring the Radio and Connecting Components
1.  Connect the radio to a constant 12-volt source, an ignition lead, the amplifier turn-on and the antenna. On newer cars, the constant 12-volt and the ignition wire connections can be made through the factory wire harness. On older cars, the fuse block can serve as the constant 12-volt source.
2.  Ground the radio to the chassis.
3.  Connect the antenna to the proper antenna input on the radio.
4.  Connect the radio to the amplifier so when you turn on the radio, you are also turning on the amplifier. Most radios have a power antenna output. This is a 12-volt line that runs the power antenna. When the radio is turned on, the power antenna goes up; when the radio is turned off, the power antenna goes down. Use the power antenna lead to also turn on the amplifier. Use a relay to make the connection, so that the line can run both the power antenna and the amplifier turn-on. Ask a neighborhood car audio retail dealer how to connect the relay. Some radios have a separate power antenna output and a separate amplifier output. If this is the case with your radio, use the amplifier output to turn on the amplifier. Or known as Remote wire
5.  Begin connecting components using 18-gauge or 16-gauge wire on the speakers. The wires run from each speaker to the amplifier. The longer the run, the more resistance on the wire. The larger the gauge size of the wire, the less resistance. Recommend 10-12Ga speaker wire.
6.  Run the speaker wire on the same side of the car as the signal wire. - Which consists of RCA, Remote and Power Wire.
7.  Some installers then Connect the speakers in either a parallel or series configuration. A parallel connection is when you connect each speaker's positives together and each speaker's negatives together. A series hook-up is when you connect one speaker's negative to the second speaker's positive. - DANGER..... this is only needed and used when adding SUBWOOFERS w/ CAR AMPLIFIERS> CAR HEAD UNITS can only be wired individually positive / negative configuration parallel speaker configuration.. Front LF/RF  Rear RR/LR. DO not EVER add more speakers to a HEADUNITs speaker output.... for more info on this please look at hooking up Subwoofers Properly!!!
8.  After connecting the speakers together, run the wires to the amplifier and connect the positive wires to the positive inputs of the amplifier and the negative wires to the negative inputs of the amplifier.
When wiring speakers together and to the amplifier, you need to consider the impedance, or ohms, rating of the speakers as well as the ohms load of the amplifier. Amplifiers are constructed to "see" a certain ohms load. If the load the amplifier sees falls below what it is capable of handling, the amplifier will shut off. Speakers come with various ohms ratings. When speakers are connected together, the ohms rating, or impedance, of the group of speakers that are wired together changes and affects the ohms load of the amplifier. If you wire two 4-ohm speakers together in a series hook-up, you are producing an ohms load of 8 ohms. If you wire two 8-ohm speakers in parallel, you are creating an ohms load of 4 ohms (8 ohms x 8 ohms divided by 8 ohms + 8 ohms = a 4 ohms load on the amplifier). If you connect two 8-ohm subwoofers in a parallel hook-up to an amplifier that is bridged mono, the amplifier will see half of the load because it is bridged. So it will be seeing a 2 ohms load.
Before you do a parallel hook-up on an amplifier, make sure that the amp can take the ohms load that will result. Find out what ohms load the amplifier is stable at and then choose speakers with the appropriate ohms rating, so that the hook-up will ensure that the ohms load is within the capability of the amplifier. Many amps can only handle Bridge Mode in STEREO ONLY. MONO Block amps can handle Most what ya throw at em.
Generally speaking, most midrange, midbass and tweeters you use will be 4-ohm rated. Most subwoofers you use will be 4- or 8-ohm rated. Generally car audio speakers are all rated at 4ohm. So keep in mind, a 4 ohm speaker is twice as efficient as an 8ohm, less power needed to produce big sound.
If you are using passive crossovers with the component speakers in the front and rear of the car, hooking up these crossovers can also affect the ohms load seen by the amplifier. Hooking up the passive crossovers' positive and negative properly can be a concern. Follow the speaker manufacturer's instructions carefully.
If you are preparing to hook up wires to the amplifier and you are not sure which is negative and which is positive, take a 9-volt battery and tap the speaker wire to the positive terminal of the battery. If the speaker first moves forward (or out), then you have touched the positive lead of the speaker to the positive terminal of the battery, and the remaining wire is negative. If the speaker's first move is backward (or in), you have touched the negative wire of the speaker to the positive terminal of the battery.
Overall Warnings:
If you are not comfortable with electrical wiring, do not attempt this installation. Have your stereo installed by your car audio retailer.
Tips from ProShop installers & Users:
Do it once, do it right!
When installing your car stereo, if you really don't want to have it done professionally, don't take short-cuts! I'm a professional and have seen many people run power leads through their door until they short out against the hinge.
Matching amp and sub by Derek dek
If you choose an amp with an average RMS rating above the rating of the sub, you can lower the gain and get better quality sound. Over-powering the sub can occur, but only if you are neglectful and turn the gain up too high. It is much better to run your amp on half gain than full gain. It will increase the life of the MOSFETs and produce better quality sound (won't run into distorted saturation).