What is system planning? It's the process that keeps you from making costly mistakes and ending up with equipment you don't want or can't use. Here's system planning for most car audio shoppers.
"My friend just got two fifteens for his car and it booms! I just got the same ones he bought but I bought the new gigawatt amplifier I saw in the magazines. I also bought a new head unit but I want to keep my factory speakers because I don't want to spend too much money."
Everything sounds OK until you realize that he drives a Mazda Miata and barely has enough trunk space for a bag of groceries let alone the six cubic feet those two fifteens require. Oh, and he also has a premium sound system that requires an $80 adapter to interface with the factory amplified speakers. Too bad he already opened the boxes and now they're not returnable.
So what could have prevented this? Planning. You need to know four things.
Here's how it should be done.
Now that you know what you want you can figure out how to get it and stay within the set parameters. Here's how to go about it.
Make sure you take into account any vehicle limitations. This includes shallow space in the doors, bottom mount only rear deck speakers, shallow depth head unit, etc. Almost any car audio problem can be solved if you have enough money. Not enough space for large subwoofers? Add more power to smaller subwoofers. No room for a double DIN head unit in your dash? Have the dash reconstructed. If you don't have a lot of money then you need to make better buying decisions. Maybe only one subwoofer instead of two. Maybe a four channel amplifier instead of two stereo amplifiers. A head unit without the dancing lights. One note of caution when budget shopping. Don't skimp on the speakers, especially the front speakers. If there's one thing that should be the best you can afford it's the front speakers. In my experience there is nothing else that can make or break a system like the quality of the front speaker set. The best head unit and amplifiers won't make a difference if you don't have a great front stage. Make sure quality front speakers are a part of your system plan.
In order to get the most out of your custom car audio system you need to do a little planning. Unlike home audio components, car audio components do not have the same connection standards, input levels and output levels. Have you ever connected a home stereo CD player to a home stereo amplifier and then had to adjust the levels to make them work? Of course not. But you will have to in car audio. I won't get into the details of each component right now but I will tell you what to look for in each component in terms of level setting.
This is the term for your in-dash radio source unit, whether it be CD, cassette or whatever. The back of the aftermarket radio should have at least one pair of RCA jacks (shown below).
If it doesn't then you will need a speaker level to RCA (low level) converter such as the one below. Many amplifiers have these built in so you won't need to purchase a separate one. The low-level music signal travels out of the radio through these jacks into RCA cables (shown below), and then on to your next component (equalizer, crossover, amplifier, etc.).
Most car audio components are "unbalanced" and will use these simple cables. The specification you will want to look for on the head unit is the "output voltage". The minimum is usually 0.5 volts but 2 volts and above is common in high end units. More is better in this case. You want a high output voltage to help minimize the noise in your system. A higher output voltage doesn't always mean your system noise will be lower but it helps. I would not consider a low output voltage to be a "deal killer" unless you plan on competing in car audio competitions.
Crossovers, equalizers and other signal processing units will have two specifications. An input voltage and an output voltage. You want to make sure that the input section of your signal processor can handle the output voltage of your head unit. If your head unit output is 4 volts but your signal processor can only accept 2 volts then you might be in for some overload problems. As long as your head unit output voltage is within the voltage that your signal processor can handle you will be OK. Your signal processor input voltage will have an adjustment feature that will help you match the two voltages. The output voltage of the signal processor will be similar to the head unit output voltage. The more the better. It is probably less critical to have high voltage output here if your signal processor is near your amplifiers. This because there will be less chance of noise radiating into the signal cable over such a short distance.
Car audio amplifiers have an input voltage range much like signal processors. Again, you want to make sure that the input section of your amplifier can handle the output voltage of your head unit or signal processor. As long as the input voltage of the previous component doesn't exceed the range of your amplifier you should be OK.
You may also be interested in How to Install Your Own Car Stereo System . It covers many topics including in depth car audio amplifier installation. Click here.