It can be hard for people who aren't car stereo fanatics to understand, but the car stereo field is extremely complicated. Are you a nonbeliever? Consider the evidence:

Even a simple system runs off a car's electrical system, which is anything but child's play. If compact discs are involved, the system works with digital signals that are manipulated by what amounts to a computer. Those signals will probably pass through an amplifier that's juiced by an ingenious device called a switching power supply. Finally, these amplified electrical signals have to be transformed into sound by another ingenious contraption called a speaker, which uses things like paper, plastic, and magnets to do the trick.

And that's just the most obvious stuff. Believe me, it gets a whole lot deeper and heavier. But the subject of car stereo systems does not have to remain a mystery for beginners. That, in essence, is what this story-and the "Cool School" columns that will follow in subsequent issues-is all about. Think of it as your passport into the wide, wild world of car stereo.

KNOW THYSELF

The first thing you need to do, even before you walk into a car stereo shop, is determine what you want your system to do. Ask yourself-and answer-some basic questions.

What type of music do I like? Rap? Metal? Country? Pop? Jazz? Classical? A combination of some or all of the above?

At what volume do I usually listen to music? Soft? Loud? Really loud?

How concerned am I about bass reproduction? Is it a big concern? Should it be accurately reproduced, the way the musicians and producers intended it to be heard? Or should it be big, fat, ground pounding bass-the kind that you can hear from a quarter-mile away?

What music sources are important to me? Cassette? CD? MD? DCC? Radio? If I had to rate each one with a percentage figure that represents how much of my total music-listening time is spent listening to it, how would it rate?

Do I want to show my system off, or do I want to keep it hidden? A system that looks impressive will probably score points with my friends, but a hidden system won't draw the attention of thieves. . . .

How much can I really afford to spend on my system?

Armed with the answers to these questions, you can discuss what you want and what you're able to afford with a professional system designer and/or installer. At that point, they'll be able to make specific recommendations that take these prime factors into account.

The answers are all up to you, of course, but the one place I'd like to step in involves price. You can get a car stereo system for $100, but my guess is that you won't like the way it sounds. In general, the kinds of basic systems that we'll be discussing here start at about $1,000 and run up to $1,500 installed with name-brand gear. For that kind of money, you should be able to put together a system that'll let you enjoy accurate-sounding music and do so at volume levels that will be satisfying (if not absolutely deafening).

SHOP SHOPPING

Before you discuss anything with anyone, though, you need to find a shop that's manned by professionals-people who know about electrical systems, physics, and acoustics as well as have a lot of experience performing installations. The following will help you separate a good installer from a chop shop:

Make sure the shop is authorized by the various equipment manufacturers to sell the gear it sells. That way you're assured of getting new equipment with a full warranty. Most authorized shops are riddled with stickers and displays bearing the manufacturers' logos, but that's no guarantee; a call to the manufacturer(s) in question will clarify things.

Check to see that the shop offers at least four or five separate lines of name-brand merchandise in each product category (amps, speakers, and head units, for example). This will help ensure that the shop is aware of all the latest developments and options in the car stereo field and will therefore be able to really recommend the best gear for you.

Take a tour of the shop's installation bay and see if it's in good condition. While most install bays don't look like hospital operating rooms, utter chaos in a bay could result in utter chaos in your car. The same goes for the appearance of the person who'll be doing the install. He or she doesn't have to look like a soap-opera star, but you don't want a sloppy worker getting grease all over your upholstery, either.

Good shops display trophies they've won, copies of magazine layouts that feature their handiwork, certificates from manufacturers or the MECP (an installer certification program), or letters from satisfied customers.

Check to see that the shop has numbered sales invoices, which are a sign (but not a guarantee) of legitimacy. If it doesn't, get out of there fast.

THE HOST

Now that you know who you want to talk to, it's time to start talking. And once you've told a shop's design team all about yourself, the place to start is with your vehicle. Think about it: They're as different as the people who drive them. Some are big, while others are small. Sedans have trunks, but wagons, hatchbacks, and pickups have less in the way of rear space. Some have a stock sound system that has some parts that are good enough to keep; in others, the stock system should simply be removed and hurled against a convenient concrete wall ... er, I mean replaced.

Your vehicle has to be examined for several reasons: You need to decide whether any of the stock components are worth keeping. You need to determine the amount of space it offers for car stereo components. And your installer needs to know what kind of acoustics it offers; in this regard, your vehicle is just like a concert hall. And believe it or not, it matters whether the vehicle was built after 1992.

The vehicle's year matters because those made after 1992 come with pretty good speakers, and they're often located in places where they'll contribute positively to the system's sound. So if you have a limited budget, you can use some or all of the stock speakers for reproducing the mids and highs, adding a special "subwoofer system" to cover the low end.

You should also tell the design team whether you own the vehicle or are leasing it . If it's leased, you'll want two things: The system can't disrupt the stock condition of the car, or you'll violate the conditions of' your lease. And you'll want a system that can be removed easily, so you can yank it out and use it in your next vehicle when the lease runs out.

THE SPEAKERS

Once you've determined what you want from your system, laid out your general budget, and walked the design team through your vehicle, you should start to discuss specific components. While it might seem logical to start with the cassette deck or CD player (the "head unit," as it's generally known). it's best to proceed by putting together a basic system (see FIGURE 1) that you can build on, or "upgrade." And speakers are the main consideration here. To be as generic as possible, I'll proceed on the assumption that we're working on a system for an owned (not leased) late-model sedan; future columns will cover the bases in terms of different vehicle types.

When designing a basic system for this kind of car, my first recommendation would be to have the design team evaluate the stock front and rear speakers. If it's decided that they're usable, I'd recommend that they be tied together using the -parallel" wiring configuration; your design team will know what this means and should be able to handle it. Wiring the speakers in parallel is one of the best ways to accomplish our basic goal-but it isn't the only way. If the shop you've chosen has another strategy, make sure they can justify it to your satisfaction. And don't worry if your car only has front speakers, since it's no trouble to add rear speakers.

  The next step is to filter out the very low frequencies that each set of speakers would otherwise be asked to reproduce; a little device called a "capacitor" or "cap" will restrict these speakers to delivering only mid and high sounds. A 200-microfarad cap (that's its electrical value) will set the "cutoff " for each speaker at 200 Hz. We do this because the mid and high speakers can't safety reproduce anything lower.

If the design team thinks the stock speakers aren't usable, replacing them with "coaxial" speakers front and rear is a good starting point; a coaxial, or coax, combines a woofer with a tweeter in one round or oval frame. A better option, at least in terms of the system's sound, would be to choose "component" or "satellite" speaker sets, each of which consists of two separate woofers and tweeters. There are plenty of companies that build both types of speakers. My recommendation is to stick with a name that you know and trust. Most good shops will let you "A/B" the speakers sitting in their sound board. If they don't. demand a good explanation; if they can't give you one, find another shop. Cost: about $90 for a pair of coaxes and about $225 for a component set.

The nice thing about component speakers is that the installer can position the separate tweeters high in the vehicle's doors or dash, which generally results in the best sound. Component sets also come with "passive crossovers," which act like the capacitors mentioned above (they typically use caps, in fact) and protect the set's tweeters. The set's woofers also need filtering, though, since even they can't handle the lowest frequencies; in this case, a 200-RF capacitor will do the trick.

Note that the front speakers are the main producers of sound in any good system, since that mimics the situation that occurs at a live music performance. This being the case, it's almost always a good idea to stay with the stock rear speakers when money is especially tight-rear speakers don't have to do that much (at least when a subwoofer system is onboard), so they don't have to be ultra-hi-fi models.

A SUBWOOFER

Even systems designed around the tightest budget need a subwoofer system. For our purposes here, a sub system can he defined as any speaker-"enclosure" combination that employs a woofer whose cone diameter measures 8 inches or larger; the enclosure, typically, takes the form of a fiberboard box or the sedan's trunk. As mentioned, you need the larger driver to reproduce those very low frequencies.

Since we're talking about an inexpensive system in a late-model sedan, you could opt to use a single 10- or 12-inch woofer in a "free-air" configuration. In this scenario, the woofer is bolted to a sheet of fiberboard that's sized to seal the area between the vehicle's trunk and rear seat; the woofer's cone-side fires into-and through--the rear seat. If metal or some other type of material resides between the speaker and the back seat, it will need to be removed. Warning: Retaining the vehicle's structural integrity and getting a tight sea] is critical. (Now you know why an experienced design team is critical.) Cost: about $200 including installation.

Another option is to have the design team build a ported or sealed subwoofer box. The box should sit in the trunk, with its woofer firing at the rear seat; again, any material that obstructs the sub system's output will have to be removed. If a ported box is used, the ports should be aimed at the sedan's rear deck; this will help maximize the sub's performance If you're willingr to trade trunk space for big bass, this is a great way to go. Cost: about $500 including installation.

In either case, the woofer should be rated with an "impedance" of 4 ohms. This type of woofer will get twice as much power as the system's other speakers when we wire and power it in a special way (more on that in a moment).

As with the stock or satellite speakers, a passive crossover will be required to filter the signal that's destined for the subwoofer system, In this case, though, we want to filter out high frequencies; one little "coil (a 6.4-mH device) will filter out everything above about 100 Hz.

Woofers aren't universal, though. Some do a great job in free air, some are built specifically for use in big or small sealed boxes, and others work best in big or small ported boxes. Don't get too antsy when the design team recommends a specific woofer for your needs; if they've earned your trust up to this point, you should rely on their expertise.

THE AMP

When dollars are tight and/or you want your system to be as simple as it can be, it's possible to design one using only a single "two-channel" (stereo) amplifier, and that's what we'll do here. An amp has to be built extremely well in order to drive multiple speakers, though, so any old bargain model taken off the clearance rack just won't do.

You need a high-quality amp that uses a "MOSFET" power supply, and it has to be able to handle "loads" of 2 ohms. The MOSFET designation means that the amp is made with high-quality components that should be able to withstand the rigors of powering multiple speakers, while its 2 ohm ability means that the amp can run very efficiently and with double the power output. Efficiency is key, since an inefficient amp will produce a lot of heat, and heat shortens an amp's lifespan.

In terms of power, go with a model that's rated by its manufacturer to deliver more than 25 watts continuous into each of the two channels and into a load of 4 ohms. This should be enough power to run the system to your satisfaction. The exception is if you're really into big, loud bass; in that case, go with an amp that delivers 100 watts total into the subwoofer.

In addition to that MOSFET power supply, features should include "low-level" (also called "line-level") inputs, which let you pipe in the high-quality signals output by better head units. Again control will let you, match the signal level of the amplifier to that of the head unit. Gold-plated connectors will offer connections that resist corrosion and the distortion it produces. Finally, the speaker and power terminals should be sturdy. Cost: from $300 to $500, depending on your bass needs.

The amp can be mounted under the driver's or passenger's seat, next to the subwoofer system, or, if a sub box is being used, on the actual box itselt

THE HEAD UNIT

The last item on your list should be a head unit. All the head unit really has to do is provide a high-quality signal to the rest of the system. You also have to be able to use it, of course, so ergonomics are important, and there may be some special features that you want. Both of these things are up to you, naturally.

You can go as skimpy or as extravagant as your budget will allow. You may even want to hold onto the stock head unit and put in a really great amp and speaker set behind it; stock heads have gotten much better in the last few years, and a head-unit upgrade is the easiest one going. Whatever you do, don't blow all of your funds on the head unit right out of the gate. You can still get great sound out of this system with a lower-end head unit.

The main criteria for the head unit, besides picking one that plays the kind of software you own or plan to use, is that it must have at least two line-level outputs. These outputs will let you use a common RCA cable to link the head unit with your high-quality amp-without degrading the signal in any way. Cost about $300 to $450.

WIRING

There's no reason not to use the stock wiring that came with the vehicle, even if you've replaced the stock speakers. The sub system will need its own wiring, of course, since it wasn't stock. Use fairly hefty 12-gauge speaker cable (about $1 a foot) to feed the sub system. The installers should solder all of the new connections that are made; this will protect against corrosion and accidental disconnections.

A power cable (about $1.25 a foot) needs to be run from the amplifier straight to the positive post on the vehicle's battery; this cable is what delivers juice to the amp (ask the design team, or see what the amp's manufacturer says, when determining the gauge of the cable). Two fuses should be used--one should go near the battery, the other near the amp. The amp's owner's manual will list the proper fuse values.

When the wire is run throughout the vehicle, make sure that the installer puts the power cable and the signal-carrying RCA cables and speaker wires on opposite sides of the vehicle. This will help eliminate noise and interference.

And as far as those RCA cables are concerned, you don't have to bother with expensive, super-high-end models. In most cases, the basic models from a brand-name cable company will suit your needs just fine-and save you some cash. Gold-plated connectors and a shielded design, which help reduce amplified engine noise and ensure a durable connection, are almost industry-standard now, but check that your cables have them just to be sure.

The actual wiring process is straightforward (again, see FIGURE 1): A set of RCA cables (stereo left and right) run from the head unit's line-level outputs to the amplifier's line-level inputs. The amp has four speaker terminals-plus and minus for each of the left and right channels. We're going to run three sets of speaker wire from these terminals: one to the speakers on the left side of the car, one to those on the right, and one to the sub system. In addition, another set of speaker wires will be used on each side of the car to connect the rear speakers to the front speakers. Soldering is the best connection method here. Before the wires are connected to any of the speakers, however, the passive crossovers need to be spliced into the plus or "positive" wires. Again, a 200-uF cap is used for each woofer and a 6.4-mH coil is tapped for the subwoofer.

IF YOU AND THE DESIGN TEAM follow this plan and use solid, name-brand components, you'll be amazed by how good this system sounds. Even if all you've done is tied a beefy amplifier and a well-designed subwoofer system to the stock head unit and satellites, you'll be in for a terrific surpfise. That's what a smart system design will do for you-and that's what "Cool School" is all about.