So, you're looking to buy a new car stereo huh?  You're not quite sure what to buy, but you don't want to trust that rude salesman at the audio store either, right?  Well, you picked up the right paper.  After reading this, picking out the right stereo should be easier than changing your oil (which really isn't that hard...).
    First off, you should probably decide what kind of stereo you need.   The kind of stereo you need (or want) can depend on many things, but mainly on these two themes: how do you like to listen to your music, as quiet background or as loud overpowering tunes? What kind of music do you listen to? Rap, country, rock, classical? Now, once you know this, it's easy to figure out what kind of system you need.  If you like it loud, you're going to need some power behind that music.  Some quality amplifiers will help in this area.  You're also going to need speakers that can handle the power.  If you like nice background music, but enjoy cranking up Beethoven occasionally, or simply love full bass and crisp highs, a light to medium power amp and some quality speakers will take care of your needs.
    Now that you've got the kind of system that you want in mind, how on earth do you go about choosing the right components?  When exactly do you need an amp?  What the hell is a crossover?  Why do you need to know what Hz means?  Well, unless you want that sales person to see a sucker coming a mile away, you need to know at least a little about these items.  First, you need to learn the numbers and how they apply to your stereo.  By "the numbers" I'm talking about those complicated looking specs that you sometimes see printed on the back of your speakers and stereo components.  The reason these are important is that they can tell you with just a glance of what the speaker is capable of.
    First off you should know what Hz stands for.  Hz is the technical abbreviation for Hertz, which is used to measure the frequency of a sound.  Frequency is how many times, or cycles, a sound wave vibrates in a second.  So, something that is said to have a frequency range of 20-500 Hz is capable of vibrating between twenty and five hundred times a second.  Now, translated to the real world, the lower the hertz (Hz), the lower the sound, and vice versa.  To put it all in perspective, the human hearing range can pick up sounds between 20 Hz and 20,000 Hz.
    Now, how does this apply to your speakers?  Well, with simply looking at these numbers you can tell the quality of the speaker you're buying.  The tweeters in your car handle the high frequency sounds, such as cymbals, and should be capable of reaching 20,000 Hz.  The woofers or sub woofers handle the low bass, and should typically be capable of at least hitting the 40 Hz mark.  Now, if you listen to a lot of rock and roll, you don't really need a speaker capable of sounds that low.  Rock sounds fine on a speaker that can only go down to 100 Hz.  But, if you want that extra depth to the music, you ideally want your speakers to cover every frequency from 20 Hz to 20,000 Hz. This is why most cars and home stereos have multiple speakers.  There is no one speaker that can do this, since the larger the speaker the slower it will vibrate.  So, a half inch tweeter cannot go down to even 100 Hz, and a twelve inch sub woofer cannot go up to 5,000 Hz.
    Of course, for all the sounds between the woofer and the tweeter, we have the midrange speaker.  In cars, this is typically a five to six-inch speaker mounted either in the front doors or the rear seating area.  This speaker should have a frequency range that overlaps your woofer's frequency on the low end and your tweeter's frequency range on the high end.  Doing this will give you full coverage of the entire range of human hearing, making for a great sounding system that will add amazing depth to any CD you own.
    Now, how loud do you want your music?  You need to think of two different things when considering this.  First off, if you like really loud music, you need to pay attention to the spl, or efficiency, of the speaker.  This is measured in decibels, abbreviated Db.  The higher the decibel rating, the louder the speaker can play without distortion.  If you don't like your music loud, this spec shouldn't concern you too much because you won't be pushing the limits of your stereo.
    The second item to consider when thinking of loudness is of course power.  Nothing is more important than power.  This is provided by an amplifier, or amp, which takes the signal coming from your radio or cd player and gives it an extra wham! before it reaches your speakers.  Once you find a set of speakers that suit your needs, you need to look at the RMS power rating, measured in watts.  This should be listed on the papers that came with your speakers, or printed on the speaker magnet.  Some speakers may also list a maximum power rating.  However, the maximum power rating is entirely irrelevant and is mainly there to make the speaker look better than it really is, so ignore it entirely.
    The RMS is the minimum power required to drive the speaker efficiently.  If you don't need loud music, an amp with an RMS rating similar to your speaker will suit your needs just fine.  If you entirely enjoy maxing out your cd players volume control, then you want more than just the minimum.  The RMS rating is usually a range, such as: RMS power range (watts): 50- 250.  In this example, the most powerful amp you would want to buy would be a 250 watt (RMS) unit.  Make sure that you are reading the RMS number and not the Peak Power Rating numbers on both the amp and the speaker, or you'll be highly disappointed.
    Personally I like to get an amp somewhere in the middle of the power range.  For instance, if I had just purchased the speaker given in the example above, I would look for a 150- watt amp.  This way I know that I'm not overloading the speaker and risking blowing it, nor am I under powering the speaker, and putting it at an even higher risk of damage.  Yep, that's right.  Never, never under power your speakers.  The chances of harming them is greater when they are under powered then when the speakers are overpowered, believe it or not.
    Now, you may be asking yourself, if I don't listen to loud music, why do I need to spend all this extra money on an amp?  Well, the main reason is clarity.  First off, you must understand that size limits car audio. Your dash mounted cd player has enough room to accommodate the electronics for the radio and cd player, but with all that jammed in there, there isn't much room for an amp to boost the signal to the speakers.  Now, if you want a demonstration of what I'm saying, go home and unplug your home theater speakers and hook them up to your walkman.  You can imagine the difference.  No matter how good the speaker, it can only operate to its fullest extent under the proper power.  Basically what I'm telling you is by simply purchasing a small fifty watt amp for your car you can sharpen your music's high's and deepen the bass, making for a much more enjoyable sound.
    Now, the one final thing we need to cover is the confusing topic of crossovers.  A crossover is the electronic device that filters out certain frequencies and allows others through to be played on your speaker.  This is necessary to keep your tweeters, with a frequency range of 7,000-20,000 Hz, from trying to play the 200 Hz frequencies.  Since they are incapable of playing below 7,000 Hz, a 200 Hz signal would cause distortion and possible damage to the speaker itself.  Now, there's no use in putting all this money into your stereo and then having it distort worse than your factory installed system.  Crossovers are the final link in setting up a beautiful stereo system.  Fortunately, most amps come with crossovers built in.  All you have to do is pay attention to the crossover points on the amp you're buying.  For instance, you don't want to amp your tweeters using a unit with only a low crossover point of 500 Hz.  This isn't as complicated as it sound, really!  Usually low powered amps have high crossover points for tweeters, and vice versa.
    I recommend you get a mail order catalog such as Crutchfield simply to browse over the numbers and get a good feel for what the numbers mean and how they relate to speaker size and sound quality.  Once you are comfortable with the numbers, you can go and confuse the hell out of that rip-off sales person with questions like "So if I buy this amp, can I hook it up to a speaker with a 50-200 watt RMS power range and a frequency range of 20-800 Hz, or will the crossover point be too high?"  If that gets him scratching his head, I'd suggest going to another store.  At least now you can be confident that you won't get taken for your money.  Remember one thing though, if the speaker is cheap and the numbers look to good to be true, they probably are.  The numbers are not always 100% accurate, but the lies become obvious once you began comparing speakers.  Now, sit back, forget all those stinking numbers, and enjoy your new stereo!

    Notes: This paper was done as a non research informative essay for College English 10001, taught
               by Prof. Laura Dolan.  The statements made in this paper are fact as I know them but
               not necessarily 100% accurate (It was a requirement that we not research for this paper).
               All papers on this site are copyrighted and should not be reproduced with out permission
               from the author.  Please contact Blonde Rock at [email protected] for details.
               Thank You.