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How To Wire a 4 Channel Amp to 6 Speakers

Every now and then We get e-mails and comments from novice car audio enthusiasts who want to pick our brains on different car audio setups. One recent one asked, “How can I wire a 4 channel amp to 6 speakers?”.

Well, there are many ways to wire speakers and amplifiers together. The ideal setup is when the number of channels on an amp matches the number of speakers you have. That said, wiring up 6 speakers to a 4 channel amplifier can seem counter-intuitive (or even impossible) for non-experienced fellas, but It’s doable.

To thoroughly answer this guy’s question, we’ll need to make a few things clear, including but not limited to what speaker impedance means, how it works, why it does matter, how to manage the overall impedance load of your speakers, and how to perfectly match your speakers and amps…etc.

So, without any further ado, let’s get started.

What is Speaker Impedance?

We all know that car speakers have a few different specs including power handling, size, frequency response, and impedance. All these ratings are intuitively simple and easy to understand except for impedance, which is often presented as a complex subject making it ignored or misunderstood at the very least.

Simply put, impedance refers to the load a speaker places on an amplifier. In other words, it tells you basically how much current will flow through a speaker at a certain voltage.

Impedance (like resistance) is measured in ohms, and is symbolized as (Ω) for shorthand. Technically speaking, speaker impedance is the “resistance” a speaker offers to the current supplied by an amplifier. However, unlike resistance, which is generally constant, the speaker impedance is constantly changing for different audio frequencies.

That said, instead of stating the impedance for every frequency, speaker manufacturers state the “nominal” impedance, which is sort of the average of the lowest values of the speaker impedance taken over a wide range of audible frequencies when both your speakers and amps are driven within the part of the audio spectrum for which they are designed.

All pretty simple, right?

Well, if you find it hard to get your mind around impedance, here’s a metaphor example:

We’ll use the analogy of water flowing through a pipe because it’s an analogy that most people can easily visualize and relate to.

So, think of your speaker as a pipe, and the audio signal as the water flowing through that pipe. If the pipe is big, a greater volume of water can flow through it. If it’s small, less water can flow through it. 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.

That said, a speaker with a low impedance will accept more power. For example, a 4 ohm speaker will draw more power from your amp than a 8 ohm speaker, about twice as much.

In a nutshell:

  • Low impedance → more current → greater load → increased power
  • High impedance → less current → smaller load → decreased power

But where is the water (electrical signal) coming from? It’s being pumped out of your amplifier, and your amp is going to work really hard to generate the water pressure you need to fill up that pipe, regardless of whether it is big or small. Therefore, do not run an amp with an impedance load that’s less than the stated minimum (normally 4 ohms).

Another way of looking at it – using the pipe analogy – is that if you choose a low impedance (aka bigger pipe) speaker, you need to be sure that the amplifier is powerful enough to provide the extra flow of water to fill it up. Otherwise, the amp (or the speaker) will eventually overload and fail.

Why Do I Need To Know About Speaker Impedance?

You need to make sure the impedance of any speaker (or speakers) connected to an amp is within the capabilities of the amp. Therefore, a basic understanding of speaker impedance is quite important when connecting a speaker to an amplifier – this is especially true when hooking up multiple speakers to an amplifier.

I mean think about it, you don’t want to buy a couple of subs or speakers, only to find out that your amplifier can’t run them because wired together, their overall impedance would be too low for the amp to run without overheating, constantly turning off, or going into protect mode.

Most car amplifiers in the market are designed for a speaker load impedance of 2-8 ohms. This means the minimum speaker impedance is 4Ω. Therefore if you have a speaker with a rated impedance of 2Ω, 4Ω, 6Ω, or 8Ω, your amp will work just fine. The lower the impedance, the greater the current flowing through the speaker and the greater the power available. But, don’t use a speaker (or speakers) with an impedance below 2 ohms.

This is a real concern when you hook up multiple speakers to one amplifier. For example, four 4Ω speakers wired in parallel have a total impedance of 1 ohm – way too low for your amp. In this case you should consider using 1 ohm stable amplifier.

Beware : Wiring Options Alter Amp’s Impedance

There’s no denying that impedance can be a bit challenging and abstract to get one’s head around. And to add insult to injury, in multiple-speakers systems, the total impedance changes depending how the speakers are wired together — in parallel or in series, or in a combination of both.

Series wiring and parallel wiring refer to two distinct ways of routing the speaker wires to your speakers to properly manage the overall impedance load. Whether you need to use a series wiring configuration, parallel wiring, or a mix of both, the wiring diagrams blow will show you exactly the best way to wire your speakers.

Parallel Wiring

In parallel wiring we combine all speakers positive leads together, and all negative leads together – plus to plus, and minus to minus. Parallel circuits are quite easy and simple to wire because all it takes to add an additional speaker for example is to connect the new speaker positive lead to the speaker wires of the other speakers and the negative lead to the connection of the other Speakers.

The best thing about parallel wiring is that if one of your speakers goes out, it doesn’t affect the other speakers. Only the failed speaker stops producing sound.

It must be noted, however, that adding speakers in parallel arrangement causes the overall resistance of the circuit to drop, as resistance drops, the current must increase according to Ohms Law.

To figure out the total impedance of multiple speakers wired in parallel, 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.

In other words, when the speakers have the same impedance, their total impedance, is the impedance value of one of the speakers divided by the number of devices.

For example: Four 4-ohm speakers wired in parallel have a total impedance of 1 ohm.

Series Wiring

In series wiring we wire the speakers one after the other — a plus of one to a minus of another. When speakers are wired in series, you add their impedances together to figure out their total impedance.

Adding speakers in series increases the overall resistance of the circuit. For example, two 4-ohm speakers wired in series add up to 8 ohms total.

Unlike in parallel wiring, the main disadvantage to series wiring is that if one of your speakers goes out the other will as well due to the way they’re connected.

How to Wire a 4 Channel Amp to 6 Speakers?

There’s a wide variety of ways to hook up 6 speakers to a 4 channel amplifier. Each of which depends on a set of parameters including your overall setup, what amp you have and how many ohms the speakers are, not to mention the way you want to do the wiring …etc.

So, let’s imagine that you have a set of 5.25″ speakers in the doors, a set of 4 inch speakers in the dash, and a set of 6×9 speakers running in the rear deck. All of which should be hooked up to a 4 ohm 4 channel amplifier that’s stable down to 2 ohms.

On a side note, the easiest way to have all these speakers up and running would be to wire the weakest speakers in terms of power handling (dash speakers in our case) directly to the headunit, and connect the remaining ones to the amplifier.

 

A great way to connect all the speakers to one 4 channel amp is to have the rear deck speakers on two separate channels, and the front four speakers wired up running to the amp where the front left speakers are on the same channel, and the front right ones are on the same channel.

You can also put two pairs of 4 ohm speakers on a 4 channel amp (in parallel) giving it a 2 ohm load, and leave the remaining speakers as a 4 ohm load. Or the other way around – Pair up rear deck speakers in parallel (4 ohm load), and put the 2 pairs on the front ( 2 ohm load).

6 speakers to 4 channel amp wiring diagram-1

Another way to hook up a 4 channel amplifier to 6 channel speakers, is to bridge it into 2 channel mode, and run 3 speakers on the right side in series per channel, and run the other 3 speakers on the left in series per channel. This way you’ll end up with 12 ohms of resistance at the speakers, but by switching the amplifier into 2 channel mode, you cut that load in half to 6 ohms, which should give you an effective amount of power and keep the heat down at the amp.

Furthermore, you can run 2 pairs of speakers in parallel which would be 2 ohms then the other Pair of speakers can just be run normally off of the other channel.

As a general rule of thumb, always check the impedance on the speakers and the minimum impedance on the amp. If the latter can support the overall impedance load of your speakers when wired together, then you’re good to go.

P.S: It must be noted that if all of your speakers are 2 ohms you would definitely need an additional amp since if run in parallel they would bring it down to 1 ohm, and that would ruin the amplifier.

 

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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