View Full Version : 4 ohms vs 2 ohms
09-03-2006, 12:20 PM
Im new to this and about to purchase a 5 channel amp for my limo,Ive notice there are always 2 ohm ratings and 4 ohm ratings listed wit different wattage .Whats the difference and when u buy a sub does it matter which sub u buy since Ive notice they have different ratings to?Do u have to use a specific sub ie: only a 2 ohm if thats the hook up ur going to use?
09-03-2006, 12:27 PM
09-03-2006, 12:28 PM
have fun with it, It doesnt really matter, higher ohms is more resistance, which usually puts alot less stress on the amp.
It does matter which sub/speaker/amps u buy, because there's alot of differnet quality builts. For amps look for low THD which would be most useful for SQ (sound quality) setup. Which I am thinking u will be diong since its a limo.
U can wire speakers/subs together to one channel on an amp for a differnt load, ie. check the differnet setups with the link I provided. Say if u have a dual 4ohm subwoofer u can wire it to 2 or 8 ohm load on the amp. Usually on speakers its single voice coil, so if ur planning to hook just that speaker up to the amp it will be whatever ohm load it says on the speaker (4 ohm speaker hooked onto an amp will be getting the 4ohm power out from the amp).
Thats the basics of it, if u look around the forums I think u'll find alot of other useful information.
09-03-2006, 12:32 PM
if you want a final 2 ohm load, you would need a Dual 4 ohm subwoofer. Amps "usually" make more power at the lower ohm load(less resistance = more power) The exception being amps that make the same power at 1-4 ohms( PG xenon, JL, JBL Crown's etc). Amps usually run hotter and pull more current at lower ohm loads and sometimes are less efficient.
To answer your question, You need a Dual 4 ohm sub to get a final load of 2 ohms to your amplifier. And most amps make more power at 2 ohms vs. 4 ohms.
09-03-2006, 02:15 PM
If you are new to this, then I would suggest sticking with simplicity until you fully understand all the ins and outs of ohms and current flow.
Almost everything in car audio is based on 4 ohms. About all the speakers you will see are 4 ohms and a lot of subs are too. If you are trying to match a speaker to an amp, look to see what ohm load the speaker is(probably 4 ohms) and then see how much RMS or continuous power it can take. Then get an amp that puts out that RMS(continuous) power at the 4 ohms. That's pretty easy.
It works the same for 2 ohms too, but lots of times a speaker doesn't come already 2 ohms. It will either come with multiple voice coils that can be wired together parallel to get 2 ohms, or you would have to use two regular single voice coil speakers/subs that are 4 ohms each and then wire them parallel to get 2 ohms. Then if you do that, the amp's output at 2 ohms(say 100 watts) will be divided to each speaker equally(50 watts per speaker). One other thing is, I read above where someone said amps make more power at 2 ohms usually. Yes they do, and sometimes this is what you want or need, but also the distortion factor rises some at 2 ohms. On subs this may not matter much, but on interior speakers, it can make a difference.