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Can You Replace 2 Ohm Speakers with 4 Ohm Speakers

We all know that speakers have many different ratings including: Size, power handling, frequency response, impedance…etc. All these are intuitively simple except for impedance.

The concept of speaker impedance is in fact one source of confusion we frequently run across. This confusion is also a likely cause of many blown amplifiers and speakers.

Speaking of confusion, every now and then We get e-mails and comments from readers who like to get some help with their car audio setups. One recent one asked, “Can I replace 2 speakers with 4 ohm speakers?”.

To answer this question, we’ll need to make a few things clear first including what impedance means and why does it matter, how to manage the overall impedance load of your speakers, how to perfectly match your speakers and amps.

What is Speaker Impedance?

To put it simply, impedance refers to the load a speaker places on an amplifier. Technically speaking, it’s the “resistance” a speaker offers to the current supplied by an amplifier.

Impedance (like resistance) is measured in ohms, and symbolized by the Greek letter omega (Ω). However, unlike resistance which is generally constant, impedance changes for different audio frequencies.

Since the audio signal from an amplifier is a mixture of all types of sounds (music, voice, speech…etc) with lots of different frequencies, the speaker impedance is constantly changing. So, instead stating the impedance for every frequency, speaker manufactures state the “nominal” impedance, which is an average taken over a wide range of audible frequencies.

To help you fully grasp the concept of “impedance”, think of your loudspeaker as a water pipe, and your amplifier (or receiver) as a water pump.

The bigger the pipe, the more easily water can flow through it. Bigger pipes also handle more volume of flowing water. This is a low impedance situation: the large pipe does not impede the large flow of water.

So, a speaker with a lower impedance is like a bigger pipe in that it lets more electrical signal through and allows it to flow more easily.

A pipe with a small diameter on the other hand allows less water to flow through it. This is a high impedance situation: the small pipe impedes the flow of water, keeping it small.

But where is the water coming from? It’s being pumped out of your amplifier (or receiver), which is going to work really hard to generate and maintain the desired amount of water pressure needed to fill up that pipe, regardless of whether it is big or small.

These general relationships can be summarized by:

  • Lower the impedance → more current → greater load → increased power
  • Raise the impedance → less current → smaller load → decreased power

So, if you choose a low impedance (aka large pipe) speaker, you need to make sure that your amplifier is capable of putting out the amount of current the low impedance speakers demands. Otherwise, the amp fuse will blow, the amp will shut itself off temporarily or the protection circuit in the amp will kick in and turn the amp off.

For this reason, it’s highly recommended to not run an amp or a receiver with a load impedance of less than the stated minimum (normally 4 ohms).

Why Does Speaker Impedance Matter?

Speaker impedance matters for two reasons:

  1. If you connect an amplifier to the wrong speaker impedance, you risk damaging the amp. So, before you buy a speaker, you need to make sure the amplifier or receiver can handle it.
  2. The amplifier will deliver maximum power to the speaker when the speaker impedance matches that of the amplifier. A low impedance will result in a weak output. On the other hand, if the speaker impedance is higher than that of the amp, its power output will again be less than it’s capable of.

All amplifiers (and receivers) will feature a rating which will usually look something like this.

  • 50 Watts x 2 @ 4 Ohm
  • 100 Watts x 2 @ 2 Ohm

This rating is really important when purchasing speakers. To get the maximum output out of the amplifier rating listed above you want to make sure your speakers are wired at 2 Ohm load. If you run the same amplifier at a 4 Ohm load, you’ll end up with a 50% loss in potential power.

Additionally, you would not want to run this amplifier lower than a 2 Ohm load, otherwise you’ll put a lot of strain and overtax the amplifier, which can potentially burn it up since it would be running at twice the recommended power rating and capabilities.

2 Ohm Speakers Vs. 4 Speakers — What’s the Difference?

Well, technically speaking, the only difference between 2 ohm speakers and 4 ohm speakers is the level of impedance. In other words, the amount of resistance a speaker’s voice coil applies to the audio current supplied by the amplifier.

A lower impedance speaker will accept more power. For example, a 2 ohm speaker will extract more power from your amplifier than a 4 ohm speaker, about twice as much.

In theory, if the two speakers have the same sensitivity (dB/W/m), but one is 4 ohm while the other is 2 ohm, the latter will sound 3dB louder. However, there is no direct relationship between impedance and sound pressure per Watt.

Can You Replace 2 Ohm Speakers with 4 Ohm Speakers?

Most car headunits and amplifiers can easily handle 4 ohm speakers.

So, the answer is Yes. You can replace 2 ohm speakers with 4 ohm speakers without any problem. However, the new 4 ohm speakers might not play quite as loud unless they are more efficient. But you might not notice any significant difference.

Keep in mind that while it’s usually fine to replace a speaker with one of higher impedance, it is not usually good idea to replace your speakers with lower impedance speakers. The difference is that the amp (either external or built into the head unit) may not be stable at the lower impedance; It will eventually overload and fail.

Why Impedance Matching is Crucial?

As mentioned above, an amp’s outputs have an impedance rating just as a speaker does; This is the reason why 2 ohm speakers should be used with the 2-ohm speaker outputs of an amplifier, and 4-ohm speakers should be used with 4-ohm amplifier outputs. A mismatch of speaker and amplifier impedances can put the amplifier’s circuits at risk of failure; it also results in distortion and poor sound quality. This is especially true when you crank it up, as the demands on the amplifier for power are greatest at high loudness levels.

Beware: Wiring Options Change Speakers’ Impedance

Speaker impedance is a complex subject. What makes it even more confusing is the fact that in multiple speaker systems, the total impedance changes depending on how the speakers are wired together — in parallel or in series, or in a combination of both.

Series Wiring

A series arrangement means that the devices are wired one after the other — a plus of one to a minus of another.

Speakers wired in a series arrangement combine their impedance; for example, two 2-ohm speakers wired in series add up to 4 ohms total.

Parallel Wiring

Parallel wiring refers to connecting the “plus” wire of one speaker to the “plus” of the next, and “minus” of one to the “minus” of the other.

Figuring out the total impedance of a set of speakers wired in a parallel is a bit more involved.

For two speakers, you multiply together each individual impedance, then divide the result by the sum of the impedances. For example, two 4-ohm speakers in parallel are (4 * 4) / (4 + 4) or 2 ohms total.

 

 

Alex Brown

Hey There, my name is Alex Brown, I'm an LA-based sound engineer with over 10 years experience installing, troubleshooting, and repairing commercial, automotive, and household sound equipment. I've installed highly competitive car audio systems, and everything from navigation systems to full car stereo systems, remote starters, alarms and beyond. I enjoy creating solutions and simplifying everyday needs. I also love helping people get great sounding gear, thereby, saving the world from bad sound one customer at a time.

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