Just need some clarification.

[PatHastings]

One of my friends recently asked me to install subs in their car. He said he was looking at pawn shops for the parts to do it so I'm assuming hes taking whatever he can get.

I have never done any car audio setups before so I have read a few pages on the setup of the amp and it seems pretty basic. Now what I can't seem to get my mind around is wiring the actual subs.

So basically what I understood from various pages is that you want to try to match your subs and amp impedance level as closely as possible. So (to keep it simple) if you have a single channel amp with a 4 Ohm max then you can get a sub with 4+ Ohms, but you could not get a single 2 Ohm sub, but you could get two and wire them in series to match the 4 Ohms on the amp?

Read over ^ and it just sounds wrong... and I went back and found that there are watts too... anyone have any good pages that can explain this to me? Going to keep reading let you know if I get it...

Click to read more...

 

[dumple 5,000+ posts]

bcae1.com basically everything youll need to know

 

[keep_hope_alive Premium Member]

you are correct in your math, but incorrect on some terms.

some quick basics: ohms are a unit of measure for resistance and impedance. resistance is just as the name implies - the resistance to work. resistance is a DC term, impedance is an AC term. both resistance and impedance are measured in ohms. we deal with impedance in audio when talking about speakers because the signal is AC.

relationship between ohms, voltage, current, and power:

amplifiers have a MINIMUM ohm requirement, not maximum. there is no maximum ohms requirement for subs, high impedance from I=V/R you can see as resistance decreases, current increases (if voltage remains constant). amplifiers basically do two things, they increase voltage and they source current. high voltage and high current = high power.

so when you think about what subs to put on an amplifier, you look at it's power ratings. assume a monoblock sub amp is rated for 250W @ 4 ohms and 500W @ 2 ohms. from the manufacturer ratings you can see that this amp can power a 4 ohm load or a 2 ohm load safely. it can also power loads between 2 and 4 ohms, and loads greater than four ohms. another common amp is a multi-channel amplifier in which you bridge two channels into one. many amps have a 4 ohm minimum requirement when bridged, though some can run lower impedance loads.

 

[keep_hope_alive Premium Member]

double post, but i was going to type more anyway. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

power. what is power? it's a complete field of study. i'm an electrical engineer with an emphasis on power systems. we'll keep it simple and not get into complex numbers (not complex as in difficult, but complex as in the square root of negative 1...)

the math for power is above. P=VI or power equals voltage times current. that simple. and you can substitute in resistance or impedance as needed. you only need two variables to calculate the other two.

in car audio we don't have easy ways to measure wattage, current, or impedance, so we focus on measuring voltage and resistance.

wiki can get you started on power, voltage, current, and ohms. bcae1.com is a good site as well. an electronics course would be a great place to start.

installing a car amplifier isn't complex, but it isn't easy either. you're just plugging in wires, but the method of routing, securing, and connecting cables requires experience and skill. most DIY car audio installs are rolling electrical fire hazards. you should understand voltage, current, and resistance in order to properly install an amplifier. that understanding will explain why we do what we do. why do we fuse the power wire at the battery? why do we use grommets when we pass through the firewall? why do we sand away paint when we make ground connections? all answered by electrical theory.

while forums are an easy way to learn, books are better. books have more editing and are usually accurate. forums are filled with bad information. it's tough to tell apart good and bad information when you don't know the answer already.

we're glad you're here asking questions. best way to get a handle on installation is to look at detailed build logs. caraudio.com, diyma.com, sounddomain.com all have build log sections with lots of pictures. forums on your specific car are usually a good place for specific wiring information.

 

[keep_hope_alive Premium Member]

if you give us specific model numbers for the amp and sub(s) we can tell you how to safely wire it. include the head unit and vehicle make/model/year.

for a sub wiring configuration calculator, use this

Rockford Fosgate® - Woofer WiringWizard

 

[PatHastings]

Thanks for all the information. Always wanted to go for electrical engineering, but don't think I have the math skills to do it. Can you recommend a good book to start out with? took a few basic classes in high school, but it was high school teacher didn't have a degree in electrical engineering only a basic understanding.

When I find out the models of everything ill be sure to post (about 2 weeks). I'm sure it will be something cheap that wont last long. Talked to him today said he got a whole kit for something like $100 - $200 so not expecting much. Ill be sure to let you know.

Thanks

-Pat

 

[keep_hope_alive Premium Member]

Books like "The Car Stereo Cookbook"

ISBN-10: 0070580839

ISBN-13: 978-0070580831

And "Auto Audio"

ISBN-10: 0071346899

ISBN-13: 978-0071346894

These are basic, but good for beginners. Your local library system should be able to get them. As far as electrical engineering, you want a Circuits I textbook. Gotta start there and get a command of Ohm's law before you learn anything else.

Here is another resource:

http://www.caraudiohelp.com/

 

[bubbagumper6 5,000+ posts]

Also it was posted earlier but I just wanted to emphasize Basic Car Audio Electronics is a great site to learn on...