Running sub in car

[spray2000]

Ok, So I'm wanting to run an 8 inch sub in my car it's home theater type sub.. I already have a really good kicker 10 inch sub at my house that actually goes to car which is kind of funny why I don't use that one in the car, But that's mainly because it takes almost 500 watts to run that sub instead of the 8 inch sub I want to run that only run 100 watts.. Now anways in the back trunk there is two stock subs I don't know what size and i'm just wanting to keep them there and just grab the wire and hook it up to the home theater sub red and black, But I don't know if you can use car subs speaker wire or what ever to a home sub..

 

[nukemaster]

A 500 watt sub does not USE 500 watts unless you have the amplifier driving it that hard. Most will make plenty of sound on 100 watts.

Most home subs have a built in amplifier and require 120/240 volts to run. These subs are looking for a rather low voltage input signal not a amplified signal from your cars head unit or another amplifier.

We need more info on exactly what you are setting up.

 

[spray2000]

Umm.. Pretty much I don't want to run an amp or anything but i'm going to be using a 100 watt kenwood Subwoofer 8 Inch in the back of the trunk and just hook it up from the speaker wire that's already there from the stock speakers and hopefully that will work.. I mean this sub is very old and only can run 100 watts which I think is perfect. Now the sub doesn't run from a wall outlet, It use to just run straight to the receiver by speaker wire.. Now what i'm wanting to know is the speaker wire on the stock speakers in my car can I use those wires to hook up straight to my sub in the red and black (Positive and negative) or does it have to be hooked straight up to the actual cone meaning I would have to take it out of the box? And also the car is a montecarlo made in like I think 1997 or something like that so i'm pretty sure the receiver won't put out much power but maybe enough for better sound then what I'm getting with the stock subs..

 

[nukemaster]

Since the speaker sounds passive(does not have its own amp). Yes you can connect it right upto the card amplifier. You do NOT have to open it, inside it just has a short wire from those press clips to the speaker. so + red and - black and you are good to go.

Now for the part that may not be so good.

Many car speakers are 4 ohms and some are even lower(I have seen 8 ohms in a car, but not very often. You can check with a multi-meter). This is done because cars have a lower voltage to work with. Many home speakers are 8 ohm(some may be 6 and older ones may be 16 ohms).

Why does this matter? Because at the same output voltage a 4 ohm speaker will pull 2x the power of an 8 ohm speaker. So if the stock speakers are 4 ohms and getting 40 watts, the 8 ohm speaker will only get 20 watts at the same voltage.

This is because of something called ohms law. This would be a wall of text, but v = current(amps. normally A, but for ohms law it is I) over resistance and wattage is voltage x current(amps)
Here is a cheat.
http/security.livewatch.com/forum-ref/ohms-law-calculator

Speakers are not quite like resistors and audio is rarely running at peak voltage it is all over since it moves the speaker forward and back[it is AC not DC so to speak], but the fact that lower resistance = more wattage still holds true. The 8 ohm speaker would be very easy on your amplifier too since it is made for 4 ohm speakers.

I am not 100% sure how much a home sub like bumps on the road either, but it is a speaker(so it is kind of use to movement).