For almost every speaker we can buy, we’ll find a specification for impedance, measured in ohms (or Ω). But they never explain what impedance means. But let me explain as to what a difference it would bring to final amplified output.
Now let’s see what impedance means and what impact it brings to the speakers.
It is just like water flowing through a pipe. When talking about things like watts and voltage and power, a lot of audio writers use the analogy of water flowing through a pipe. Why? Because it’s a great analogy! That’s why I’m going to use it here instead of coming up with something more original.
Think of the speaker as a pipe. Think of the audio signal (or, if you prefer, the music) as the water flowing through the pipe. The bigger the pipe, the more easily water can flow through it, and the more water can flow through it. A speaker with lower impedance is like a bigger pipe. It lets more electrical signal through, and lets it flow more easily.
This is why we’ll see an amplifier rated to deliver, say, 100 watts into 8 ohms impedance and maybe 150 or 200 watts into 4 ohms impedance. The lower the impedance, the more easily electricity flows through the speaker.
So does that mean we should buy a speaker with lower impedance? Not at all, because a lot of amplifiers aren’t designed to work with 4-ohm speakers. Think back to that pipe carrying the water. We can put a bigger pipe in, but it’ll only carry more water if we have a pump powerful enough to provide all that extra water.
But will the difference in impedance have an impact on the quality of sound
Take almost any speaker made today, connect it to almost any amplifier made today, and you’ll get more than enough volume for your living room. So what’s the advantage of, say, a 4-ohm speaker versus an 8-ohm speaker? And I would say none.
The impedance of a speaker has no relation to the quality of the speaker. Then why do speakers come in 8 ohm and 4 ohm versions? Many manufacturers of speakers offer a choice of impedance… 8 ohms or 4 ohms.
The reason for offering two versions is for special applications. For example, in a speaker system with dual woofers, two 4 ohm woofers can be wired up to form an 8 ohm system. More power can be driven into a 4 ohm speaker as compared to an 8 ohm speaker (assuming the same driving signal!).
Let us see about using a 4 ohm speaker? 4 ohm speakers place a significantly heavier demand on power amplifiers as compared to 8 ohm speakers. Because of their lower impedance, twice as much current will flow through a 4 ohm speaker (as compared to an 8 ohm speaker) for a given volume control setting (assuming the amp can keep up). This translates to amplifiers getting significantly hotter (and heat is among the top enemies of electronic devices!).
If we use 4 ohm speakers, our speaker wiring will have to be (or should be) larger. This is because the resistance of the speaker wires becomes more significant with respect to that of the speaker. The result is that more power is “wasted” (in the form of heat) in the wires leading to the speakers! Amplifier power is relatively costly, so it does not make sense to waste that power in the lines leading to the speakers.
But there is one more thing that will should concern us is that will the system handle the difference in impedance efficiently
If we do choose a 4-ohm speaker, we need to make sure our amplifier or receiver can handle it. How do we know the handling capacity? Sometimes it’s not clear. But if the amplifier/receiver manufacturer publishes power ratings into both 8 and 4 ohms, we’re safe.
A 4-ohm speaker draws more electric current through our AV receiver’s output transistors, and since more current equals greater power, 4-ohm speakers tend to have greater dynamic range and play louder more easily than 8-ohm speakers.
In car audio, 4-ohm speakers are the norm. That’s because car audio systems run on a 12 volts DC instead of a 120 volts AC. A 4-ohm impedance allows car audio speakers to pull more power from a low-voltage car audio amp.
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