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Car Audio


This page is designed to explain car audio to you in a simple direct manner.
  1. What kind of system do you want ?
  2. How much do you want to spend ?
  3. Speaker Terms Explained
  4. Amplifier Terms Explained
  5. Radio Terms Explained
  6. Wiring, Capicitors, and Crossovers
1. What kind of system do you want ?

     Are you just trying to replace factory speakers, want to add a CD player, or just want a louder system ? First you have to decide what you want to do, and what size speakers your car has. Also note that most newer factory speakers sound much better with a higher power radio. Which speakers you want to replace depends on what you want. My car has 3 1/2 speakers in the dash, the 6x9s in the rear deck overpower the 3 1/2s, so I don't see the reason in replacing them. But, even though it seems like the 3 1/2s aren't on, there is a small difference in sound quality.

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2. How much do you want to spend ?

     Also when deciding on what kind of system you want in your car you have to have some idea of how much you want to spend. Most people do not buy everything for their car all at once, I did my car in several different orders. Some people are able to buy one thing and stick with it, to me there is always something new to buy. Here's how I did my car (Not my Mustang):

  1. Radio
    • JVC: Free, gift from a friend
  2. Rear Speakers, and Amplifier
    • Rear Speakers: Sony Xplod (3 Way) 59.99
    • Amplifier: Jensen, 29.99
  3. Subwoofers, Equalizer
    • Subwoofers: 15 inch Subwoofers, 2 tweeters, Box 79.95
    • Equalizer: 10 Band, Level LEDs 19.95
  4. Sub Amplifier
    • Jensen, built-in crossover, bass boost 99.95
  5. New Subwoofers
    • 15 inch Subwoofer, bumped and vented 59.95
    • 15 inch Subwoofer, bumped and vented 59.95
  6. Second Sub Amplifier
    • Jensen, built-in crossover, bass boost 99.95

     As you can see I choose not to spend that much money. Now here is the main difference in the price of stereo items is quality. For example, my Jensen 300s, are rated at 200 watts RMS, now realistically, a Punch 200a will be a whole lot closer to 200 watts RMS than the Jensen. My choice is the Jensen at 99.95, not Punch 200a at 279.95.

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3. Speaker Terms

     To me I could care less if people hear my car coming up the street, I care more about frequency range. Frequencies are measured in Hertz, (Hz). Most people can only hear 20-20,000 Hz. The lower the frequency number is where bass is. Any bass below 20 Hz in general won't be heard, only felt. Most any speaker will have an acceptable higher frequency range, so I tend to pay more attention to the lower number, the lower the frequency range goes, the better your frequency response will be. The frequency response of your speakers depend on where they are installed. In general the more air they have (There are limits) the better your lower frequency response will be, so for example, if you put a 6x9 in a small box, it won't have as much bass, as say a car with a 6x9 in the rear deck. Here are some of the more common speaker terms:
Sensitivity or SPL:This is basically the efficiency of the speaker. The speaker with the higher the number (rated in dB or decibels) will play louder with the same amount of power as a speaker with a lower SPL rating. Lets take two different subwoofers as an example: a Punch DVC 12" sub and a Sony Xplod 12" sub. The Punch sub has a SPL rating of 87 dB while the Sony has a rating of 90 dB. This means that if both speakers are hooked up to a 200 watt RMS amp, the Sony speaker will be louder because of it's SPL (in theory). In general a speaker that is 3 dB higher than it's competitor will take half as much power to produce the same output.
Peak Power Handling:Generally you should not base any decision on this number. This is the maximum amount of power a speaker can handle. As always watch how this figure is worded, some companies rate per speaker, some add both speakers peak power handling together, doubling the peak power output.
RMS Rating:Generally this is the most important figure in all stereo equipment. The RMS rating of a speaker tells how much power a speaker can handle on a continuous basis. Generally you need at least the lowest recommended amount of RMS power to get acceptable sound from a speaker. So if a speaker says it needs 10 watts RMS minimum, make sure it gets 10 watts RMS (at least 10).

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4. Amplifer Terms

     Amplifiers do much more than make your music louder. Amplifiers also make the overall sound of your speakers sound better. First the most commonly asked question, My radio pushes 22 watts RMS and my amp pushes 200 watts RMS, which makes my total output 222 watts RMS, right ?, No, when your amp says 200 watts RMS and it means 200 watts RMS, even if your input is 500 watts RMS, your amp is only going to send 200 watts RMS to your speakers (assuming you don't melt it). Here are some common terms used when talking about amplifiers:
RMS Power:This is the most important number. This is the amount of power the amp can push on a continuous basis. Also on amplifiers look for the voltage that the RMS rating based on. Most amps are rated at 14.4 volts some are rated at 12.5 volts. For example lets say we have two different amplifiers, one rated at 200 watts RMS @ 14.4 volts, and one rated at 200 watts RMS @ 12.5 volts, the one with the 12.5 volt rating will actually make more power than the one with the 14.4 rating.
Peak Power:Generally you should not base any decision on this number. This is the maximum amount of power an amplifier can handle.
Total Harmonic Distortion (THD):This amount of change in the signal sent to the amp. Basically extra noise the amplifier will create. This figure is normally tested at the RMS rating. Anything less than 0.10% is inaudible.
Preamp Outputs:Some amps call this a "Pass." This is just a set of RCA outputs to send an un-amplified signal to another amp. So lets say you need two amps for your rear speakers, this means all you would do is plug inputs into one, and then run the RCA cable to the other amp.
Signal-to-Noise:This tells the difference of your signal and background noise. The higher the value, which is measured in decibels (dB), the less background noise the amp will create.
Built-in Crossovers:This tells you the amp has a built in crossover that can be changed at the flick of a switch. Amps normally have a low-pass and high-pass crossover (and an off position for the crossover). Low-pass means only the lower frequencies will be sent to the speakers (Mostly bass). The High-pass means only higher frequencies will be sent to the speakers (Treble).
Bass Boost:Bass boost is just what you think, it increases the amount of bass sent to the speakers by a set amount, some amps will allow you to choose how much extra bass you want sent to the speakers.
RMS at 2 ohms:This is the output rating in 2 ohms. Normally it is more than the standard RMS rating which is rated in 4 ohms. To keep this basic, to get 2 ohms, you must either use 2-ohm speakers, or more commonly wire two speakers into one output on your amp. In general all car audio stuff runs at 4 ohms (some stereo equipment says up to 6-8 ohm, but with the 12 volt system expect 4 ohm). The 2-ohm rating is a little higher than the 4 ohm rating, but the quality of the sound will normally decrease your sound quality. This change should not be that noticeable though. To sum this up, the lower the ohms the more power your amp will put out (Be careful amps have an ohm limit, go to low and you can melt your amp). Here's the catch, plug two speakers into one amp output, you will notice there seems to be no difference in loudness. Lets use one of my amps as an example, it is rated at 22 watts RMS at 4 ohm, and 25 watts RMS at 2 ohm, but in 2 ohm the amp has to use the 25 watts RMS to power two speakers per channel, instead than one.

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5. Radio Terms Explained

     This section contains terms used when rating tape and CD decks, terms specific to only one type will be noted. Here are some of the more common terms when looking at radio statistics:

Preamp Outputs:This tells you how many RCA jacks the radio has for adding an amplifier. If the radio says 1 set, it means one set for the left and right channel of the rear output. Radios that have 2 sets allow you to have front and rear RCA cables, which will allow you to use your front to rear fade controls. The more expensive radios will sometimes have 3 sets front, rear, and subwoofer. The subwoofer output normally has a low-pass crossover built in the radio. With the exception of a few radios, all radios also have speaker level inputs so you don't have to use RCAs.
FM Mono Sensitivity:This number, rated in decibel femtowatts (dBf), tells how well the radio will pick up weak stations. The smaller the number the better the radio well pick up weak signals. The average is between 8 dBf and 11 dBf.
RMS Power:This is the amount of power the radio can push on a continuous basis.
Peak Power:Generally you should not base any decision on this number. This is the maxiumum amount of power the radio can produce. Let's say a radio claims to be 50x4, this means 50 peak watts per channel, but now let's say another radio says 35x4 and has a higher RMS rating, this means the 35x4 radio in this case will produce more power.
CD Frequency Response:This tells you the range of frequenceies the CD player is cable of reproducing. The average is 20-20,000 Hz.
CD Signal-To-Noise Ratio:This is the measure of the music signal strength compared to the background noise. The higher the rating the cleaner the sound. On average most CD players are rated about 90 dB, some CD players are greater than 105 dB.
Dolby NR:Dolby is a Noise Reduction (NR) system. With this, dolby-encoded cassettes will have less noise. If your cassette player is dolby equipped your siganl-to-noise raio will be higher.
Wow and Flutter:This is the accuracy of the cassette player's playback speed. The average is about 0.10% - 0.11%, the lower the percentage the better.
Tape Signal-to-Noise and Frequency Reponse:These terms are the same as the CD players, only much lower statistics. The average frequency response of a tape player is 30-17,000 Hz. The average signal-to-noise ratio on a tape deck is about 60-65 dB.

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6. Wiring, Capicitors, and Crossovers

  • Wiring
         This section mainly deals with amplifier installation. First thing I want to address your power cable going to the main input of an amplifier. If you have done any amplifier installation you have probably seen the kits that upwards of $95 made by several companies, such as RockFord Fosgate (I have seen "Rampage", and etc. kits for about $20, but they aren't as complete or as nice as the others). Most of these kits have at least 6-gauge cable, if not 4 or 2 gauge cable. This really isn't necessary. Unless you go really extreme you won't need that 4 or gauge cable running from the battery to the amp. In general you can get away with 12-gauge cable, but normally use at least 10 gauge, especially if your amps are going to push more than 300 watts. In my car I ran one 8-gauge cable from the battery to the trunk to power three 300-watt amplifiers, and one 90-watt amplifier and I have never had any problems. Try to use close to, if not the same size ground cable as the power cable. I am not saying don't buy these kits, because they do look nice, and work very well. Mainly I am just giving those who don't want to spend as much money another option. I bought my 8-gauge cable at the local electronic surplus store (MidWest Electronic Surplus). 25 feet of 8-gauge cable cost me about $4.50, that is including the necessary connectors. 25 feet of 6 gauge costs about $6.00, much better than these kits. The only complaint I have had about the power cable I bought from the electronics store, is that the outer covering isn't as thick as nicer cable, so if you do go this route, I recommend covering the cable with electrical tape anywhere it will be rubbed.
  • Capacitors
         Next is Capacitors. First off all a capacitor does is store energy. Capacitors in general will not improve your bass one bit, unless you have a serious power problem. Normally if you have some serious amplifiers running your lights (headlights, dome lights, radio, etc.) will tend to dim or flicker when you hear a low bass note. This is because the amp is taking some power away from the rest of the things running so it can reproduce that note. A capacitor will store enough energy for the amp to play that one note, without it pulling power away from other things running in the car. Basically it will keep your lights from flashing. Normally most car audio stores sell 1/2 farad and 1-farad capacitors (16 volts). The larger the number the more energy the capacitor can store, so the 1-farad would hold more power than the 1/2 farad. These capacitors normally sell from anywhere from $95-$195. Once again most electronics stores carry capacitors but most don't carry anything larger than 1/2 farad, and that's if they have one that large. A 1/4-farad at the electronics surplus store around here costs about $4.00. You can use several capacitors together (put several on the same power line). To me the lights flicking doesn't bother me, so I don't worry about capacitors.
  • Crossovers
         Crossovers are used to filter out unwanted frequencies to your speakers. For example lets say you have some subwoofers in your car, subs can not reproduce treble, so you want them to only get the lower frequencies, for this application you would need a low-pass crossover. Another example would be with tweeters, you don't want your tweeters getting the lower frequencies that they can not reproduce, therefore you would need a crossover to filter out the lower frequencies.

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     I am not responsible for any damage resulting from applying things learned from this site, whether the damage is caused directly or indirectly.
©Copyright 2000, Mike Lee

© 1998 Michael Lee
© 2004 Michael Lee