What is the difference between 2-ohms and 4-ohms?

Let’s start by saying watts and ohms are all part of a series of mathematical formulas that put them together such that when one of them changes in value, the other often does too.

A brief explanation taken from Crutchfield: 

“Amplifiers provide the electrical pressure in a circuit; ohms measure the resistance, or load, against that pressure; and watts measure how much power is released as work. So, using one of those math formulas, an amplifier that provides 100 watts of power through a 4-ohm speaker, will produce 200 watts through a 2-ohm speaker, because it’s easier to push that reduced load.”

What’s the difference between a 2 ohm subwoofer and 4 ohm subwoofer? Technically, they are different in only a few areas and that is:

  1. How much resistance one can get,
  2. How much power will pass through your subwoofers,
  3. How much dB (logarithmic unit to measure acoustics) they can produce.





What’s the difference between dual 2-ohm voice coils and dual 4-ohm voice coils?


It just gives you two options to choose from when you purchase the subwoofer, each one will be better/worse for a given type of amplifier. Each voice coil has a +/- terminal for wire to plug into, so you wire it sort of like it were two subwoofers .

The question is, do you run the power from the amp, through the first coil, then through the second coil, then back to the amp (wiring in series) or do you split the power wire and run it through both of the coils at the same time (wiring in parallel) . If you wire in series you add the ohms (impedence) of each voice coil to get your total ohms . If you wire in parallel its, often, half of the impedence of a single voice coil that becomes your total impedence . So …

Dual 2 ohm voice coil in series = 4 ohms .
Dual 2 ohm voice coil in parallel = 1 ohm .
Dual 4 ohm voice coil in series = 8 ohms .
Dual 4 ohm voice coil in parallel = 2 ohms .
Since they make two difference versions of the subwoofer, that gives you four options for hooking it up (with one speaker) . To pick which one is best for you, you just compare it to the amplifier that you have, or the one you intend to buy, for the speaker . If your amplifier puts out the most power at 2 ohms, you’ll want the Dual 4 Ohm subwoofer . If you amplifier puts out the most power at 1 ohm or 4 ohms, you’ll want the Dual 2 Ohm subwoofer .
That’s basically all it is, gives you options to make it easier to pick a matching amp .


also impedience is volume/clarity


Does series or parallel affect the sound? Also, what’s a good company to look at for amps? Something affordable


well yes. the higher the ohmage, the better sq. the lower the ohmage, the more volume/power


The Amp runs more efficiently at a higher ohm and sound quality tends to be better. I have a MTX8500 with dual 4ohm coils and i have it wires to 2 ohms and it sounds great. Also, when you half the resistence, you double the power, so if your on a tight buget, you can run a smaller amp, but still bower it to full


Can u explain what it means to have ur amp bridged? What’s the normal wattage of an amp that people buy for their system? Also, can someone explain to me why u actually aren’t getting 1200 watts or whatever the amount is?


If you look at amplifiers online (I like sonicelectronix.com and woofersetc.com ) you’ll see a group of stats like this…

# RMS Power (4 ohms) 70 watts x 2 chan.
# RMS Power (2 ohms) 85 watts x 2 chan.
# RMS Power (1 ohm) Not Stable
# Bridged RMS Power 170 watts x 1 chan.
# Peak Power Output 300 watts

That example is for a two channel amplifier, meaning it has two pairs of positive/negative terminals on the amp to plug a speaker into . You could connect two speakers to the amp by plugging one speaker into each pair of terminals, or you could connect a single dual-voice-coil speaker (remember a DVC speaker have two pairs of terminals on it) by connecting one voice coil to each pair of terminals .
When you “bridge” an amp you basically take two channels and combine them into one extra-powerful channel . This is not necessarily better or worse, it just depends on what sub(s) you’re using .
So in the example above the amp can put out no more than 85 watts if its using two channels, but if you bridge it into a single channel it can put out 170 watts . Since 85wx2=170w you’re basically not getting any more or less power either way, it just depends which type of connection is a better match for the sub you buy .

Mad_Eyes wrote:

What’s the normal wattage of an amp that people buy for their system?

There isn’t any . Generally more wattage = more volume, and more wattage also = more money . So it totally depends on how much a person wants to spend and how loud they want it to be . I’d say for a real entry-level system you’ll want no less than 150w for a subwoofer (that’s real watts) . Some of the real cheap flea-market subs only handle something like 50-75w, but that’s unusually low . Some of the big expensive subs handle 500-1000w, and with competition systems the sky’s the limit .

Mad_Eyes wrote:

Also, can someone explain to me why u actually aren’t getting 1200 watts or whatever the amount is?

There are two different ways you’ll see watts listed . The first is real actual true wattage, which is listed as “RMS” or “continuous” . (See the example above) . Basically this is the number that matters . The other thing you’ll see is “peak” wattage, which will always be higher, usually much higher . Since the peak number is higher, alot of manufacturers will use this number in their advertising to make their amps or subs sound alot better than they are “Wow, a 1000w sub for $65 !” If you see an amp with “3000W !!!!” in huge numbers on the box, or sometimes on the amp itself, its probably the peak wattage and its basically just there to fool people that don’t know better .
Think of it like a lightbulb . I’ve got a 60watt lightbulb in the lamp in here . 60 watts is its true “RMS” wattage . Its just sitting there burning 60 watts continuously while its on . Now maybe when I flip the light switch on, or if there’s a power surge, the lightbulb “peaks” up to 100w for a split second before settling back down to 60w . If the lightbulb handles that little surge without blowing out, you could say its 60w RMS, 100w Peak . But that split second of power surge doesn’t matter to you as the guy trying to figure out which light bulb to buy, and if the light bulb company started printing “100w !!!” on the light bulb box it would make things pretty confusing .

When you’re choosing an amp and sub find the RMS rating for each and match those numbers up . For the most part you can completely ignore peak values .