There comes a time in every car audio enthusiast life where they have stared at their sub(s) and amplifier(s) puzzling over how to wire them together, and which setting to put their impedance to. What is impedance in the first place? Why does it matter? More important than that, does it affect sound quality?
Confusion concerning speaker wiring, watts, amps, and ohms has been around for as long as people have been putting subwoofers in cars. This is especially true with first-time buyers. This confusion is also a likely cause of many blown amplifiers.
Power handling (measured in watts) and impedance (measured in ohms) are entangled in a series of advanced mathematical formulas that link them intimately together such that when one of them undergoes a change in value, the other often does too.
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, “What’s the difference between 2 ohm and 4 ohm?”.
To answer that question, we’ll need to make a few things clear including how impedance works and why does it matter, how to manage the overall impedance load of your subs, how to perfectly match your subs and amps, and how to manage the overall impedance load …etc.
So, without any further ado, let’s dig into the often misunderstood and sometimes puzzling world of speaker impedance.
What is speaker impedance?
Speaker impedance refers to the load a speaker places on an amplifier. Technically speaking, speaker impedance is the “resistance” a speaker offers to the current supplied by an amplifier.
Impedance (like resistance) is measured in ohms, and it’s symbolized by the Greek letter Omega (Ω) for shorthand. Resistance and impedance are relatively similar. However, the latter is constantly changing for different audio frequencies whilst the former is generally constant.
That said, rather than stating a speaker’s impedance for every frequency, speaker manufacturers state the “nominal” impedance, which is sort of the average taken over a wide range of audible frequencies.
To make it easier for you to grasp the concept of “impedance”, we’ll use the analogy of water flowing through a water pipe because it’s an analogy that people can visualize and relate to.
So, think of your amplifier as a pump, your speaker as a water pipe, and your music as water flowing through the pipe.
An audio signal consists of a large number of frequencies that are distributed from the amplifier to the speakers. This process is similar to water flowing through a hose at different pressures.
A larger diameter pipe can handle more volume of flowing water and allows more water to flow through easily. In the same way, a speaker with a lower impedance lets more electrical signal through and allows it to flow more easily.
As a result, a car amplifier rated at 200 watts at 4 ohms impedance load can deliver up to twice that at 2 ohm impedance load. The lower the impedance, the more easily electricity (the signal or music) flows through the speaker.
It must be noted, however, that not all amplifiers are designed to work efficiently with 2-ohm speakers. I mean, think about it, using the pipe analogy mentioned above, you can opt for a bigger pipe, but it’ll only carry more water (audio signal) if you have a pump (amplifier) powerful enough to provide the extra flow of water.
Why does speaker impedance matter?
As mentioned above, speaker impedance determines the current drawn from the amplifier. Remember impedance describes the electrical resistance to an audio signal, so the lower the impedance, the more current can flow. A greater current requires an amp powerful enough to produce more power.
Another way of looking at it is to say the lower the impedance, the higher the load on the amp (and the harder it has to work).
In a nutshell, 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
Looking at the relationships above, it appears that the lower the speaker impedance, the greater the power the amp delivers through that speaker. This is true up to the point when the amp is overtaxed and can not produce anymore current and power. At this point, either the amp fuse will blow, or the amp goes into protect mode to prevent serious damage to its internal components. Therefore, do not run an amp with a load impedance of less than the stated minimum.
In car audio, 4-ohm is the standard. Almost all car amplifiers on the market can drive a 4-ohm load. However, this standard is more of an average impedance for speakers and amplifiers when driven within the part of the audio spectrum for which they are designed.
So, before you buy a 2-ohm or 1-ohm speaker, you need to make sure your amplifier can handle it. You don’t want to purchase an amplifier and a couple of sub(s) to find out that your amp can’t run the subwoofers because wired together, their impedance would be too low for the amp to run without being overtaxed or overloaded.
4 ohm Vs. 2 ohm speakers — What’s the difference?
Well, technically speaking, the only difference between 2 ohm and 4 ohm subs is the level of impedance. In other words, the amount of resistance the voice coils apply to the audio current supplied by the amplifier.
Does low impedance guarantee high quality?
Well, not really. Impedance has nothing to do with sound quality. However, it must be noted that a subwoofer rated at 2-ohm impedance will produce more output than a 4-ohm subwoofer, given similar input wattage, because the resistance is lower.
Why impedance matching is crucial?
First and foremost, it’s worth mentioning that there are several ways to wire subwoofers and amplifiers together. The ideal setup is when your subs’ and amps’ impedances and power ratings are perfectly matched.
Impedance matching is crucial because using mismatched speakers and amplifiers can lead to serious problems (overheating, clipping, damage …etc) when the amplifier is not up to the task. Therefore, the capability of an amplifier should be taken into account before applying a load to it (hooking up a subwoofer). This is not to say that you can only pair a 4 ohm speaker to a 4 ohm amp, or an 8 ohm speaker to an 8 ohm amp.
In theory, an 8 ohm speaker can be hooked up to a 4 ohm amplifier as well. Only then the speaker wouldn’t be able to fully handle the amp’s full power output.
Speaking of subwoofer wiring, it must be made clear that wiring options change a sub’s impedance. In other words, the total impedance depends on how your subs and their voice coils are wired together. This is where all the fun of understanding impedance, parallel and series wiring and their effects, advantages and disadvantages all come into play.
Beware: wiring options change a sub’s impedance
There’s no denying that the impedance world can be hard to grasp especially for beginners. What makes it even more confusing is the fact that in multiple-sub systems, the total impedance changes depending on how the subwoofers and their voice coils are wired together — in parallel or in series, or in a combination of both.
Series wiring means that the devices are wired one after the other — a plus of one to a minus of another.
Adding Speakers in series increases the overall resistance of the circuit. In other words, to figure out the total impedance of multiple subs or voice coils wired in series, you add their impedances together.
For example: Two 2-ohm speakers wired in series have a total impedance of 4 ohms.
Parallel wiring means that the terminals of each device are connected to the same things — plus to plus, and minus to minus.
Figuring out the total impedance of multiple speakers or coils wired in parallel is a bit more involved. When the impedances of all the devices are the same, their total impedance, when wired in parallel, is the impedance value of one of the subs divided by the number of devices.
For example: Four 4-ohm speakers wired in parallel have a total impedance of 1 ohm.