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-   -   General car audio questions for a newB (http://www.diyaudio.com/forums/car-audio/85170-general-car-audio-questions-newb.html)

rocko1290 22nd August 2006 10:54 PM

General car audio questions for a newB
 
Hello all. I am new to the forum, and a new driver, but I am now ready to put a system in my car. I am pretty familiar with home audio, but I do not know a whole lot about car audio since I haven't been driving for very long. I just have some general questions to clear some stuff up.

--Do aftermarket head units (stereo decks, CD players) generally have crossovers built into them?

--I am aware that a home audio subwoofer can be tuned/calibrated. Can the same be done for a car audio subwoofer? If so, how?

--I have heard of people having an amplifier for their speakers...what advantage does this have?

--Is it common to have ported enclosures in cars?

--What is sound damping, and what does it do? I have heard of ported enclosures being "lined" and sealed enclosures being "stuffed".

--Since the air pressure inside a subwoofer enclosure is higher than outside, how can I determine how low of frequency response my sub(s) are giving me?

--Generally, what kind of wires are used from the car battery to the amp, and is there a fuse required?

--Generally, what kind of wires are used from the amp to the sub(s)?

--Sometimes, there are little knobs on car audio amps. What are these knobs for? Can they aid in calibrating/tuning the subwoofers?

--I know in home audio, you can make it virtually impossible to blow your subwoofers by installing a rumble filter on the amp...is there a way to eliminate (or greatly reduce) the possibility of blowing your car audio subwoofers?

Sorry for so many questions. If you cannot answer ALL of these questions, that is fine. Just please answer what you can!

Any help appreciated!

--Thanks :)

rocko1290 23rd August 2006 02:05 AM

Also--what is "F3"?

And in head units, how many discrete channels do they output? I know they normally output 4 channels, but how many of those channels are discrete? Are they all stereo?

And what is an equalizer, and what does it do?

rocko1290 24th August 2006 01:51 AM

Disregard my last posts!
 
After some research, I answered a few of my own questions. I have some left though. Please help answer what you can! :)

--Do aftermarket head units (stereo decks, CD players) generally have crossovers built into them?

--What is the advantage of having an amplifier for your speakers

--Is it common to have ported enclosures in cars?

--What exactly does sound dampening do? Is it spelled damping dampening? I have heard both terms.

--Sometimes, there are little knobs on car audio amps. What are these knobs for?

--Is there a way to eliminate (or greatly reduce) the possibility of blowing your car audio subwoofers?
--How many discrete channels do head units usually output? I know they usually output 4 channels, but is it a stereo signal?

Any help appreciated!

--Thanks :)

sr20dem0n 24th August 2006 02:11 AM

--Do aftermarket head units (stereo decks, CD players) generally have crossovers built into them?

Most of the mid level and higher ones do, some have 3-way (or even 4-way) crossovers built in, powerful enough to run a fully active system by themselves (with enough amps)

--What is the advantage of having an amplifier for your speakers
More output before distortion


--Is it common to have ported enclosures in cars?
Unfortunately, yes ;)


--What exactly does sound dampening do? Is it spelled damping dampening? I have heard both terms.
It's referred to as damping and dampening, they're pretty interchangeable. Anyway, it has multiple uses depending on where you put it. When placed on the rear deck or trunk lid it reduces rattles. When placed on the doors it's used to seal up the baffle for the front speakers to reduce cancellation and increase midbass response. When placed basically anywhere else it's used to reduce road noise.


--Sometimes, there are little knobs on car audio amps. What are these knobs for?
Gain, EQ (frequency and/or boost level), and crossover frequency are the most common


--Is there a way to eliminate (or greatly reduce) the possibility of blowing your car audio subwoofers?
Yes, keep your amp out of clipping and listen to your subs, if they start distorting then turn the volume down, that's the best way to save them. Also, if they're ported then using a subsonic filter set about 5Hz below the box's tuning frequency is a very good idea (if it's tuned above 30Hz, since frequencies below ~30Hz are pretty rare).


--How many discrete channels do head units usually output? I know they usually output 4 channels, but is it a stereo signal?
2, car audio is only stereo, the 2 channels are just mirrored on the back. There is a fade control to adjust the relative output of the front/back, but they're still playing the same thing.

rocko1290 24th August 2006 03:08 AM

Thanks for the response.

--What's the difference in a 3-way and 4-way crossover?

--What do you mean by the amp "clipping"?

--I know what the tuning frequency is, but how can you tell what frequency your subs are actually producing?

--Where can you get a subsonic filter, and where are they generally installed? Sounds like they are the same thing as a rumble filter for home audio.

--How do you tune/calibrate your subwoofers and speakers?

--You were talking about the crossover knob on the amp...this cannot control the frequencies that are sent to the speakers, can it?

--How do you know what to set your crossover at on the amp and on the stereo deck?


Appreciate it!

rocko1290 24th August 2006 03:08 AM

Oh yeah--and what if the sound dampening is inside the enclosure...what does it do then?

Thanks

sr20dem0n 24th August 2006 03:29 AM

--What's the difference in a 3-way and 4-way crossover?
A 3-way has support for a highpass on one pair of channels, bandpass on another pair of channels, and lowpass on another pair of channels. Typically it highpasses the "front" outputs for use with a tweeter, bandpasses the "rear" outputs for use with a midbass, and lowpasses the "subwoofer" outputs for use with a sub. A 4-way crossover is the same but with another bandpass thrown in there for a midrange. The only headunit I know of with a 4-way crossover built in is that crazy Clarion (forgot the model). Several units have 3-way crossovers built in, Alpine, Pioneer, and Eclipse all offer their own.

--What do you mean by the amp "clipping"?
That's what happens when you try to push an amplifier beyond its limits. The top and bottom of the wave (which looks somewhat like a sine wave) get cut off. The first figure on this page has a nice graphical representation of the results of clipping.

--I know what the tuning frequency is, but how can you tell what frequency your subs are actually producing?
They're producing whatever they're being fed. There are several ways to check this, but the easiest would be to generate a frequency spectrum plot, which shows the frequency content of the song. There are several ways to get this, if you have a good mathematics program (matlab, maple, etc) you can just take the discrete fourier transform and plot the results.

--Where can you get a subsonic filter, and where are they generally installed? Sounds like they are the same thing as a rumble filter for home audio.
They are, but normally at a higher frequency. Most mono car amplifiers have them built in.

--How do you tune/calibrate your subwoofers and speakers?
By ear, unless you have access to an RTA and mic

--You were talking about the crossover knob on the amp...this cannot control the frequencies that are sent to the speakers, can it?
Yeah, it's an adjustable highpass or lowpass filter (highpass for the front speakers, lowpass for the sub)

--How do you know what to set your crossover at on the amp and on the stereo deck?
80Hz is a good starting point, but you have to adjust by ear from there.

sr20dem0n 24th August 2006 03:30 AM

Quote:

Originally posted by rocko1290
Oh yeah--and what if the sound dampening is inside the enclosure...what does it do then?

Thanks

The wavelengths the sub is reproducing are very very long, standing waves aren't an issue in this case so that's not something you have to worry about. The most it would do is help keep the box's panels from vibrating, but I doubt it would do much, and I highly doubt it would be audible, especially in a car.

rocko1290 24th August 2006 08:58 PM

Quote:

--Where can you get a subsonic filter, and where are they generally installed? Sounds like they are the same thing as a rumble filter for home audio.
They are, but normally at a higher frequency. Most mono car amplifiers have them built in.
[/B]
How do you know what they are set at, and can you adjust them?

sr20dem0n 24th August 2006 11:48 PM

If it's built into the amp then you can normally adjust it anywhere between ~15hz and ~50hz


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