2ohm, 4ohm? whats the dif?

Shoryuken · 02-29-2008, 09:11 AM

I searched but couldn't find the answer to this question. Probably because its one of those "duh" questions, but here goes.

Whats the difference between 2ohm subwoofers and 4ohm? Is that a primary concearn when I buy, or just a "remember you got 4ohm subs, so you'll need to..."?

Eventually, I'll be using some sort of PC based sound processing (Audigy or some such) before the amp, but for now I'm planning on running the amps out of my sony Xplode.

Thanks for your help

Area3 · 02-29-2008, 09:21 AM

2

Really All it is Voltage...

It Really Boils Down to The Ohms Law..

Ohm's Law defines the relationships between (P) power, (E) voltage, (I) current, and (R) resistance.

Its To Early To Explain But here is a Link that might help

http://en.wikipedia.org/wiki/Ohm's_law

I will further go into Depth if Need Be

kickercivic1 · 02-29-2008, 09:29 AM

No need to know ohms law.lol.... Match up the ohm with your amp... If you have are getting 1OHM stable amp, then get (2) woofers that are dual 4Ohms and you can wire them up to 1 ohm...To figure ou how to wire. check this out..
http://www.rockfordfosgate.com/rftech/woofer_wizard.asp

Shoryuken · 02-29-2008, 09:33 AM

Thanks for the quick reply. I should have been slightly more clear, in that I know (in a vague apprentice-level electrician way) what an ohm is, I'm just wondering how a 4ohm sub sounds as compared to a 2ohm, and more specifically, am I going to need to make sure I get a 4ohm amp or something?

It seems that there would be significantly more heat involved in a 4ohm system, I guess I'm trying to figure out why that would be preferable.

hithere · 02-29-2008, 12:39 PM

Quote: Originally Posted by Shoryuken

Thanks for the quick reply. I should have been slightly more clear, in that I know (in a vague apprentice-level electrician way) what an ohm is, I'm just wondering how a 4ohm sub sounds as compared to a 2ohm, and more specifically, am I going to need to make sure I get a 4ohm amp or something?

It seems that there would be significantly more heat involved in a 4ohm system, I guess I'm trying to figure out why that would be preferable.

Nah...heat varies only linearly with resistance, but with the square of the current. At a given voltage level, a lesser resistance will carry more current, thus giving you a hotter amp and hotter voice coil in the speaker. Also, your speaker is driven by the field set up by current in the voice coil...I'll leave you to guess what lower resistance can do for output and how it all relates. How much power you end up getting out of the amp, tho, is dependent on a little deeper analysis of what the amp is built to match to in terms of impedance.

Shoryuken · 03-01-2008, 06:16 PM

Clearly I'm in WAY over my head. <grin> its amazing the amount of knowledge floating around this board.

So to break it down to the most basic equation that my small brain can comprehend... As a whole (recognizing that the ultimate test is to listen to them) 2ohm subwoofers > 4ohm subwoofers?

Bugbyte · 03-01-2008, 10:23 PM

Try this.

FordNoMore · 03-02-2008, 11:26 AM

Lower resistance (ohms) means that for a particular voltage (i.e. volume knob setting) they'll use more power and be louder. However, you're not going to get 300 Watts out of a 200 Watt amplifier, so your maximum power output (actual volume) is limited by the amplifier power rating, regardless of the speaker. There are some subtleties regarding how efficient the amp is with various speakers but I believe that's more-or-less the story.

400 Watts from a 2 ohm speaker requires about 14 amps of current, but through a 4 ohm speaker requires just 10 amps. (Power = Current^2 x Resistance) Less current means happier transistors in the amplifier, and lower losses from wiring and connections.

Are you looking at bare 2 ohm speakers, or full commercial setups that are rated at 2 ohms? If they're bare speakers, I'm wondering if they're really just intended to be used in pairs (in series) to make a 4 ohm load that the amp is made for.

Slightly related -- Infinity seems to have switched from 4 ohm speakers to 2 ohm and I can't figure out why. Seems like a bad move for quality. All I can figure is that the 2 ohm speakers will sound louder when you compare them to 4 ohm speakers in an in-store display. That's a joke, of course, because they can't actually get louder than 4 ohm speakers, it's just that at the same volume knob setting they'll sound louder. Pretty sad if they only changed them so they'd sound better in comparison displays. I'd love for someone to correct me, because I like Infinity otherwise.

All that being said, kickercivic1 is right... just get what the amp is rated for.

Shoryuken · 03-02-2008, 12:31 PM

Thanks for all the great input. Fordnomore and kickercivic1 may have answered the question I didn't know I was asking. The proverbial which came first, the amp or the speakers question.

That was a great link bugbyte, thanks. Its in my favorites.