From MP3Car.com Wiki
[edit] Onboard Sound
[edit] Internal card
[edit] PCI Card
[edit] Consumer level
[edit] Professional level
[edit] PCIMIA
[edit] Consumer level
[edit] Professional level
[edit] External Cards
[edit] Consumer Level
[edit] Professional Level
[edit] Firewire
[edit] Consumer Level
[edit] Professional Level
[edit] Crossovers. Active vs Passive
The reason the terms active and passive exist is because no 1 speaker can produce the entire range of audio. Obviously a subwoofer isnt going to produce high notes like a tweeter, and vice versa. So every speaker has a frequency range that it produces the best and with the least amount of distortion, and if you try to play a different frequency through it then you'll get crappy sounding music.
So that's why we need multiple speakers. We break the audible range of sound up into a few different parts. Normally it's three parts, one for the low frequencies (subwoofer), one for the middle frequencies (woofers/speakers that go in the door/mids/whatever you want to call them), and the tweeters. This way, each speaker has its own range of frequencies it can focus on to provide you with the best sound!
You will get crappy sound if you use a speaker to play a frequency that it wasnt designed for? Well we need to send only the frequencies that we want each speaker to play to each speaker. That's what crossovers are for! There are two types of crossover -- active, and passive.
Passive crossovers are the most common and easiest to set up, because speaker component sets already come with them. Just wire them in between the amp and speaker, and go! Active setups are a little harder, though. Rather than filtering out the frequency range for each speaker after the amp, an active setup filters it out before via hardware or software (well in our case anyway, since we conveniently have a computer already in the car).
The reason this causes more complication is because you have to have as many channels in your amp as you have speakers, since you need a dedicated channel for each speaker. You also have to tune your crossover yourself, but that can be a good thing because you'll get to tweak it more to your liking. Active crossovers are also nice because they don't suck power like passive crossovers do.
[edit] Troubleshooting
[edit] Getting rid of that whine or buzzing noise in you speakers
So, now you've installed your PC and hooked it up to your stereo. It rocks! Except for the fact that there's this "buzzing" noise, or "whine" coming through your speakers! It may seem to pick up when you accelerate and slow down when your rpms go down, or it may just be a persistent buzzing noise. Either way, it's ruining your install! What's up and how do you get rid of it?!
The noise is nearly always caused by improper grounding of your system. According to the wikipedia, a ground loop is caused by an unwanted current that flows between a conductor at two points that have nominally the same potential.
Wha?! Here's what's happening. The chassis of your car serves as a ground. Often when installing PC's and amplifiers, they are located in different parts of the car. The ground wire for both units is often grounded in different spots on the car. While the metal chassis is a decent conductor, it isn't perfect and there can be a difference in electrical potential between the two grounding points. The result is a buzzing noise, or a whine, often coming from the alternator, which accounts for the change in the sound as the alternator spins faster and slower with engine rpms.
There are some things you can check for.
1. A loose audio connection between your PC and amp, or PC, head unit, and amp (depending on your install) can cause a constant buzzing sound. Often the Y-adapter connecting the sound card is not pushed in fully.
2. Sometimes buzz or hum can come from an unmuted MIC or Line-In on your sound card.
3. Make sure your groud points are clean. That means sand/grind off all paint and such so you get a clean metal on metal connection.
4. It's also possible that the RCA cables are too close to power cables. While most proper setups would ensure that power cables do not run near or beside audio cables. Move the power cables further away from the audio cables until there was no "whine".
5. Background noise can get higher in volume substantially if your battery is low. This happens if you are using more current than the alternator can provide, therefore the battery eventually discharges and needs manual charging. When it's very low, the whining noise can be simply horrible to a point where you can't hear anything. But as soon as the battery is charged to 50% or above the noise is removed completely.
6. You could be using a cheap inverter or badly made components. Cheap inverters are not always a good clean source of power. They were not specifically designed to power a PC and could be the cause of unwanted noise.
7. Ground all components to the same point. This will reduce the potential and should greatly reduce any noise.
8. Try mounting your PC or amplifiers on wood or plastic. The whine could be coming form the fact that there is an earth loop in the case of the PC of amp.
9. Use a "ground loop isolator", available at nearly all electronics stores, or car audio suppliers. This device prevents a direct electrical connection between the two sources and will usually fix the ground loop. This is more of a band aid than a fix. you should try to solve the problem rather than cover it up. But if this is your last resort and it works, use it.
The source of the whine can be mysterious and very difficult to track down even if you perform 1 & 2, above.
For more information, search on terms: "Ground loop", "alternator whine", or "buzzing".
Useful threads:
[1]
[2]
[3]
[4]
[5]
