Question on AMPS and SUBS

[1zz-fe ce|ica]

okay i know there is a lot when is comes to hooking up amps and subs ... i've installed a couple of amps into my car and my friends but i never had to deal with ohms .. and wiring in parallel and series ... so that is my question ... how do you determine ohm and how do you wire in series and parallel ... i've read the definitions in crutchfield .. but that doesn't tell me much. most of the systems I put in were a 2 channel amp bridged to one sub. thanks for your help

[S|Lv3rBu||et]

Well, cheer up, its not that bad.
Ohms is the unit for Impedance, or the electrical resistance to an AC flow. Music is an AC signal, so, all speakers have an impedance, measured in ohms, wich is their resistance to the flow of the power coming from your amp. Now, if you have a lower impedance, the amp doesnt have such a hard time feeding power to the speaker, so it can feed MORE power to the speaker.... this is a good and a bad thing. Good cause, well, you get more power.... bad cause, your amp works (about) twice as hard. Thats why amps are rated a minimum impedance (usually 2, or 1 ohms) because, anything below that.... you'll be working them too hard, and they will fry.
How do you figure out your speaker (or network of speakers) impedance? Easy..... if you wire them in series (one after another, negative from one speaker going to positive of the next and on and on), then the impedance is additive. If you wire them in parallel (splitting the wire at the amp, and having a positive and negative go to each sub), the collective impedance is governed by this formula:

1/ (1/X1 + 1/X2 + 1/Xn...)


where x1 is the impedance of the first driver, x2 is the impedance of the next, and so on. Ususally, the impedance of car speakers is either 4, 2 or 1 ohms. So, if you wire two 4 ohm drivers in parallel... you'll have a 2 ohm load. And (basically) youll get twice the power from your amp (if it can handle it). Take those same speakers, and wire them in series... and youll have an 8 ohm load (and about 1/2 the power from your amp). If, say, you wire an 8ohm speaker and a 4 ohm speaker in parallel... you'd have an impedance of 2.666666666666...... ohms. Good rule of thumb: the collective impedance of speakers wired in parallel is always less than the least impedance involved.

Hope this helps!!!
feel free to pm me if I totally confused the sh|t outta you....
:thumbup:

[1zz-fe ce|ica]

wow .. that actually clears up a lot of things.. thanx

[Deftech]

What is "AC Flow" ? Isn't AC Alternating Current. If so Speakers arn't AC units they are DC aren't they. And isn't ohms related to Electrical Current Not specifically AC or DC? Just a question

[SilverRide]

Speakers are DC.

This site explains "OHM`s law" fully:
http://webhome.idirect.com/~jadams/electronics/ohm.htm

[Impulse]

Originally posted by SilverRide
Speakers are DC.

This site explains "OHM`s law" fully:
http://webhome.idirect.com/~jadams/electronics/ohm.htm

No, speakers are not DC. They are linear motors and work via the changing current (i.e. AC) through the voicecoil to induce a changing magnetic field. This induced magnetic field is what either attracts or repels the voicecoil from the permanent magnets at the back of the speaker and causes the cone to move.

[S|Lv3rBu||et]

Couldnt have said it better myself Impulse! :thumbup:

Yes, ohms law ( Voltage = amperage/resistance) is applicable to both AC and DC. But speakers work with AC, the alternations in the phase (+ or -) is what causes the cone to move forward, or backwards, thus exciting the air around them and producing sound.

[RedNOSceli]

I understand that running at a lower OHM load causes the amp to work harder. I know first hand, I ran an amp at 4ohms for a year and then bridged my speakers down to 2ohms and it sounded great and twice as loud and boomy...for about 5mins then the amp, which has never cut out at day in its life, overheated to the point in which I couldnt even touch the heat sync. It was fine after it cooled off, but here's my question...

If having less ohm's, meaning less resistance to the power of the amp, why would that cause the amp to work harder. If 8ohms had more resistance, doent it seem that the amp would work harder at 8ohms instead of 4 or 2ohms?

[Impulse]

The lower impedance allows more current to flow through the amp, which makes it over heat if the components in the amp are not rated for that amount of current.

And S|Lv3rBu||et, it's V=I*R not V=I/R :)

[RedNOSceli]

Thanks much...I assumed as much but my logic made me over think it....