lrighty.
First things first, the lingo.
Power:
There are tow important types of power in this type of s---, and since you're going into electrical (no?) then you should grasp this fairly easy.
Peak power: This is the maximum amplitude of the sinusoidal waveform, from 0 volts to x volts. Peak-to-peak is twice the peak power, that is, from -x volts to +x volts.
RMS power: root-mean-square. This is the peak power multiplied by 1/root 2, which works out to 0.707. You'll need to know that in life. house power is actually 170v peak, and 120 RMS. The RMS power represents the "average" power.
RMS is what you care about. Neglect anything written on the box of the s--- you're buying but the RMS (sometimes called "continuous") power. If it says A MILLION WATTS PEAK POWER WOWZORS AWESOME" f--- it, its marketing bulls---. You can do whats called "wall socketing" a speaker. You literally plug it into the 120v house outlet, and it will garble for a minute before letting the magic smoke out. This is roughly 14 000 watts, and any speaker will take it for a second or two. Doesn't mean you care. This goes for decks, amps, speakers, anything that reports a wattage.
Frequency:
Humans can hear roughly 20-20000 Hz. A Hertz (Hz) is a unit that means cycles/second. A clock ticks at 1 Hz. In speakers, this describes how many times the speaker is vibrating in a second.
Speakers:
You know. There are low, mid, and high range. This describes what frequency the speakers are good at making.
high range (typically 2000- 20 000 hertz (Hz) - tweeters
mid range (200 - 2000 Hz) - just speakers, mids.
low range (20-200 Hz) - woofers, or subwoofers.
If a speaker is asked to do all three jobs, it typically sounds like s--- because it can't vibrate at so many frequencies at once. This is why having more than one type (than just the stock four cones in the doors) is good. There are two kinds of systems you can get into:
1. Coaxial speakers. Coaxial means they share the same center point, super typical of an aftermarket speaker. This picture is a tweeter coaxial with a mid range:
http://www.o-digital.com/uploads/2226/2 ... _2_449.jpg The term has become abused, and now pretty much refers to any speaker unit that has more than one speaker in it.
2. Component speakers. This means that each range speaker is a separate unit, with separate wiring, mounted in different locations, etc. The benefit to this is primarily sound quality, as the speakers aren't interfering with eachother, and you can tune them by putting them in different locations. Also, they often come with external crossovers for further tunability.
Crossovers:
The audio signal from a normal deck comes out with all the frequencies, 20- 20 000 Hz. Since some types of speakers only want to play a range, they need a way to filter that. Thats where crossovers come in.
A crossover is a device that uses capacitors and inductors (electrical bits that you've likely seen before but haven't put a name to) to filter the signal. Capacitors are usually a high-pass filter, so they let the high frequencies through but block the low ones. Inductors are low pass. There are two types of crossovers, passive and active.
Passive: On a coaxial speaker, a typical one with a mid range (all range, really) and a tweeter, is you'll see a little capacitor before the tweeter, like so:
http://praudio.com/site/wp-content/uplo ... 024-90.jpg. That looks like a home-brew hackjob, but thats the idea. they call it passive because its unadjustable, and works when the speaker works.
Active: This is what you find in your stock deck, when you tune the treble and bass. Its using vaiable capacitors and inductors to change the output. These are also found as little external boxes that split the signal for a component speaker set, or within an amplifier to change the range it amplifies. This is also the principle a radio works on.
Amplifiers:
There are several types of amplifiers, and they all work on the blue smoke majik that is electronics, but this is what you need to know: they make s--- louder.
but, you can make s--- loud and sound like s---, or make it loud and sound like sex. If you like dubstep, you want that second option there.
Loud and shitty: Buy the cheapest amp you can find. That pretty much sums it up.
Loud and sexy: Buy the correct amp for your application. Things to consider:
A) How many speakers are you powering?
-this determines how many "channels" you want to run. A channel is basically a +/- set of wires (two wires) to run to a speaker. So if you're doing 4 door speakers, buy a 4 channel.
-there's a hitch here, you can wire your speakers in parallel or series. Lets say you have 2 speakers.
-- If you wire 2 4ohm speakers in series, you get 8 ohms. you probably know this.
-- If you wire 2 4 ohm speakers in parallel, you get 2 ohms.
Keep in mind you aren't gaining or losing anything doing this, you still use the same net power.
B) What resistance are the speakers you're running?
A lower resistance speaker will take more current, and therefore more power with the same given input from an amplifier. This doesn't mean a 2 ohm sub is better than a 4 ohm one, though. Just know what you're working with, and see where your amplifier is efficient. It will normally list a few different outputs for given resistances.
Side note, what is DVC, Dual Voice Coil. this is a speaker with two internal coils. Marketing BS again, but it gives you the opportunity to run it in parallel or series to change its resistance. ( a 2 ohm DVC sub can be wired for 4 ohms or 1 ohm. )
C) what type of speakers are you running?
there are a few types of amps out there, some are designed for anything, some are designed for subs only, and some are designed for midrange only. Check to see what crossover capabilities they have (low pass filter, high pass filter, adjustable crossover, words like that)
A typical class is a "class D" amplifier. This is a workhorse. Typically sounds like s---, but can pump out the power. Usually this is for subs. If its a single channel, they'll likely call it a "monoblock".
D) What power range your speakers are in
If you want to save money on the amp, ignore this. But if you care how it sounds, buy an amp with 10% or more RMS power than your speakers are rated for.
This is to avoid a phenomenon called clipping. Clipping is when the amplitude of the output exceeds the amplitude the amplifier can provide. Here's a picture, because thats easier to get.
http://www.carstereo.com/help/images/tweak_clipped.gif
Clipping: Clipping sounds like s---, because you're basically feeding the speaker a DC power signal for a short moment, which sounds terrible. If your amp can provide more power than your speakers can take before meltdown, this won't ever happen.
This is also a good way to ensure you never blow your amp.
Bridging: Some amplifiers support what is called "Bridging" which is best described as feeding one channel's output into the amplifier again, to be amplified, and put out in another channels output. So you're combining two channels into one to increase power output. This is handy, but don't use it unless you have to, because its harder on the amplifier.
I think thats about it for amps.
Headunits:
Pretty straightforward. the RMS output of any aftermarket deck likely isn't over 20w/channel. s--- eh? the number they report on the box is peak power, of all channels combined ( 50w x4), so when you see 200W power, read 80W RMS total. Not so sexy anymore eh?
A pre-amp output is pretty much a signal already prepared for a subwoofer. Its fed through a low pass already, and at a low amplitude just like amplifiers like to receive it. This also allows you to adjust your sub from the deck, handy.
RCA inputs: this is how you hook up most aftermarket s---. Its the red/white connectors like on a playstation or N64. (yellow on those is the video)
3.5mm jack: this is the same type of connector that headphones use. Becoming obsolete with bluetooth and usb s---, but still nice option.
USB: you know what this is, any deck with USB will have MP3 support as well.
Bluetooth: If and when you get a smartphone, you can have them connect automatically, no wires, fancy, easy.
Internal crossover. If you like how your music sounds, you want this. Aim for as many channels as you can get.
Am I forgetting anything?
Oh yeah, shapes.
A round speaker sounds best, end of story. Oval speakers are marketing BS, and will make less noise per power input, and sound like s---. Square subs are bulls---. Same with triangles. All bulls---. Buy round speakers.
Also, never mix up the +/- on speakers. Always do it right, or the speaker will play 180ยบ out of phase, which means that it will cancel out the sound waves of the other speakers. You should learn this too in electrical.
Brands to look at:
Pioneer (headunits)
Alpine (eh, not too great actually)
Rockford (amps)
Focal (god,but expensive)
Polk (subs, speakers, amps)
JL Audio (amps, subs)
Clarion (amps)
JBL (speakers, amps)
MTX (subs)
Anything that isn't cheap.
Brands to avoid like the plague:
Most of Sony's stuff from the 90's and early 00's
Pyramid
Pyle
Whatever speakers Kayla has in her car.
Anything you've never heard of and looks sketchy.
