can someone please explain this to me please. what are ohms and how do i use them. on this rockford fosgate amp that i am looking at it says 4 ohms 50x4 or 2 ohms 100x4. how do i get my speaker to run 2 ohms and whats the difference of 4 and 2 ohms thanks

 

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You-can't-"make"-your-speakers-run-at-2ohms-unless-you-run-them-mono(which-would-both-sound-like-***-as-well-as-make-any-Fosgate-amp-run-VERY-hot,probably-shutting-it-down-or-frying-it-eventually)or-parallel-wire-your-rearfill-speakers-with-the-Quarts. Basically,"ohms"=resistance,or-the-degree-of-which-your-speakers-resist-the-flow-of-electricity.Almost-all-component-or-coaxial-speaker-sets-are-going-to-be-4-ohms.If-you-want-to-get-the-most-power-to-your-front-speakers,I-would-recommend-bridging-two-channels-of-the-amp-to-their-own-speaker-while-running-rearfill-off-of-your-head-unit.This-would-give-your-quarts-about-150watts-per-side-as-well-as-maintain-the-best-possible-soundstage-(I-would-never-recommend-sending-the-same-amount-of-power-to-rear-speakers-as-the-front).If-you-must-wire-rearfill-to-the-amp,I-would-look-into-purchasing-"Orion-HCCA-5S"-or-"Image-Dynamic-Chameleons",each-being-very-good-2ohm-component-sets-which-would-get-those-100watts-per-channel-you-were-looking-for.

 

The explanations for amplifier power ratings and speaker impedance are covered by lots of electronic variables, and lots of mathematic equations. Without going into too much detail or math lets just say that amplifier power (P) is derived from the amount of voltage (V), that the system is operating at multiplied by the current (I) that the system is flowing, so in math terms P=I*V. Current (I) is determined by system voltage (V) divided by system resistance (R), or your speakers, so, I=V/R. Using basic math it's easy to see that if you reduce R, from 4ohms to 2ohms, current will increase. Because current increases, power will increase. Again, this is a very basic explanation, and does not take into account frequency response, vehicle voltage fluctuation, amplification factors, distortion levels, or other variables.

Ok, so how does this answer your question? Well it's hopefully an insight. Industry standards have been established that rate and list the capabilities of car audio components. It is generally accepted that an amplifiers maximum output is derived using a load of 4ohms. However, lots of companies have over built their amps to be able to run on a 2ohm load. This means that the amp has to be able to run at higher currents, which will cause heat, without shutting down. Having said that, most auto speakers are rated at an industry standard 4ohms, which is what the amplifier sees as a load. The only real way to change what the amplifier sees is to combine speakers in one of two configurations, series or parallel.
View a speaker as a piece of wire. If you connect another wire to the end of the first piece (making it longer), you have connected these wires in series. Doing this with speakers means you add the value of each speaker toghether, so 4 + 4 now give you 8ohms. This has the effect of reducing the power output of the amp, so it won't play as loudly. On the other hand, running speakers in parallel has the opposite effect. Using the wire analogy again, picture laying two wires side by side, and connecting the end of each piece to the end of the piece lying next to it. Doing this gives the signal a choice of paths to take, and effectively reduces the load the amplifiers sees by half to 2ohms, causing the amplifier to play louder.
Generally, the only speakers you combine are subwoofers, there are exceptions to this of course, so unless you are talking subwoofers, I wouldn't try combining speakers to reduce the resistance. Gene or Percy are very good with specific models of amps and speakers, so with more information I'm sure they can tell you what your options are. I hope this helps, cause it sure gave me hand cramps typing...

 

Simplified terms.

Parallel. Hooked up + to + to +, that is positive from the amp goes to positive terminal on the speaker and positive on other speaker in question. Same goes with negative.

Series. Speakers are hooked up from + on one speaker to - on the other speaker. Looks like a +/-/+/- chain for the speakers. The end of the chain, in this case, + and -, is hooked up to the respective amp terminals.

For figuring out series ohms is easy. Just add the impedance together. (4 ohm + 4 ohm) = 8 ohm.

Now for parallel it gets a bit tougher. 1/ ((1/r1 + 1/r2)). With two speakers at 4 ohms it knocks down to 2 ohms. With three speakers it gets a little more difficult.

Percy