How to Wire 2 Subwoofers to a Mono Amp
What happens when you want more bass, but your monoblock amp already runs a subwoofer? If your amplifier can handle the total RMS of 2 subs, wiring them to a mono amp can be done, allowing you to double the bass reproduction of your car stereo system.
Running 2 subwoofers isn’t for everyone, of course, but if you really want that extra bass, it will shake the car seat you spend so much time in and turn heads as you drive by.
However, it’s important to note that a dual subwoofer setup is only functional as long as you wire it correctly, because if it’s not done right, it could end up very costly for you.
There are many configurations, and before you start you have to know the amplifier can handle the total RMS and impedance of both of your subwoofers.
So, before you start you have to do a bit of math to make sure the amp and subs can work together. Then make sure you wire the 2 subs to your mono amp correctly, so you can enjoy that extra umph in your lower frequencies for many moons to come.
Things to Know before Wiring 2 Subs to a Mono Amp
Before thinking about wiring 2 subs to a mono amp you have to know how many voice coils both your subwoofers have, because there are many ways to skin this cat.
Whichever way you choose to wire them, remember your amplifier must be able to handle the same impedance load your wiring circuit will produce. But before we get going let me explain exactly what you need to know.
When running any subs and amplifier, it’s important to match the RMS. For any subwoofers to sound their best, you need an amp that can power them, and this means your amp’s RMS should match or even better exceed the total RMS of your subwoofers.
So, if you’re wanting to wire 2 300W subs to a mono amp, your amplifier should be at the very least 600W RMS. Also, remember if you’re changing the impedance of your subs, the RMS of your amp will change, too.
Impedance of the subwoofer load helps the amplifier determine how much of a power load the subs can handle. This is typically measured in ohms, and the amp will supply the amount of power that it detects the subwoofer can handle.
A lower impedance means that there will be more power flowing from the amplifier, whereas a higher impedance speaker will have less power flowing from the amplifier.
Mismatching the impedance between amplifiers and speakers can damage your equipment, so make sure you get this right before you start.
Every subwoofer has an impedance rating, but of course you intend to wire 2 subs to the same mono amp, so that extra device has to be taken into account when working out.
The impedance load of your subwoofers must match what the amplifier can handle, and whether you wire them in a series or parallel wiring circuit, you can either multiply or cut the impedance load.
Choosing The Right Wiring Set Up
Choosing the right wiring set up also depends on how many voice coils your subwoofers have. They can either have one (Single Voice Coil – SVC), or 2 voice coils, which is known as a Dual Voice Coil (DVC).
If you’re not sure which type of subwoofers you have, look at the back and if there’s one set of connector terminals (+ -) it is an SVC. Whereas, if it has 2 sets of terminals it means it’s a DVC.
Neither is better than the other, but a DVC will give you more wiring options, and you’ll be able to configure your impedance load in more ways than you will with a pair of SVC subs.
Subwoofer Wiring Circuits
As already mentioned above, depending on the way you wire your subs, determines the overall impedance of your set up. You can wire them in a series or parallel circuit, or even a combination of both if you have to, and either way makes sense for certain set ups.
Series wiring is akin to running a relay. The series wiring set up will run from Amplifier positive (+) to Subwoofer A +, and the Subwoofer A negative (-) to Subwoofer B +, and the Subwoofer B – to Amplifier – , so it all makes a big loop, or as I say like completing the relay.
To work out the total impedance of this Series wiring set up, you need to add the total impedance of your subs, so if you’re wiring 2 x 4-ohm subs to a mono amp, you will have an 8-ohm load.
The other way to wire your subwoofers is to run a parallel wiring circuit, and this is the best way for wiring 2 subs to a mono amp.
In parallel wiring, the terminals of each subwoofer are connected to the same terminals: positive to positive and negative to negative.
As opposed to series wiring, parallel wiring actually divides the impedance load, but working it out is a bit more complicated than series wiring.
Basically, when the impedances of all the subs are the same, their total impedance is that value divided by the number of voice coils.
For example, 2 x 4-ohm SVC subwoofers wired in parallel have a total impedance of 2 ohm. If you have the same set up, but with 2 x 4 ohm DVC subs, however, you will end up with a 1 ohm impedance load.
With that said, let’s look at a few different ways of wiring 2 4-ohm subs to a mono amp that can handle 1 or 2 ohms.
How To Wire 2 Subs To 1 Mono Amp
Wiring 2 x SVC 4-Ohm Subs to a Mono Amp – 2 Ohm Load
For the first example, I will start with the easiest dual sub and monoblock wiring set up: Wiring 2 x 4 Ohm SVC subs to a mono amp.
A wire will run from Subwoofer B positive terminal (+) to Subwoofer A +. And another wire will run from the same positive terminal in Subwoofer A to the positive terminal in the mono amp.
And for the negative terminal, you will run exactly the same with the negative terminals (-): Subwoofer B – to Subwoofer A – and Subwoofer A – to mono amplifier –.
Wiring 2 x DVC 4-Ohm Subs to a Mono Amp – 2 Ohm Load (4 Ohm Load Needed)
If you have 2 x 4 ohm DVC subwoofers, the wiring gets a little more complex, and you can’t actually wire this load down to 2 ohm, so you have to run at at 4 ohms. You should still wire it in parallel circuit, but because you have twice as many terminals on your subwoofers, you need more wiring connections.
First run a positive wire from Subwoofer B + to Subwoofer A + on the left side terminals. Then run another positive wire from the same terminal in Subwoofer A to your positive terminal in the back of your mono amp.
Do the same for the negative terminals, but you have to use the terminals on the other side of your DVC sub. So, if you ran the positive wires on the left side, run the negative wires on the right sided terminals.
For example, run a negative wire from Subwoofer B – to Subwoofer A – and then from that same terminal to the back of the Amplifier – terminal.
Now you still have a + and – terminal on each side of each subwoofer free. For these you need to run what’s known as a bridged wire between each one. But the difference with the bridged wire is that you run a short one from the + to – terminal on the same sub. And of course do the same on the other sub.
How to Wire 2 Subs to a Mono Amp Stable at 1 Ohm
If you want your mono amp to run at 1 ohm, you can wire 2 subs, but you have less options. For this you can only run 2 x 2 ohm SVC subs, or 2 x 4-ohm DVC subwoofers. So, with that said, let’s look at the wiring for these set ups.
Wiring 2 x SVC 2-Ohm Subs to a Mono Amp – 1 Ohm Load
For this set up, it’s the same as the first example above: wiring 2 x 4-Ohm SVC subs to a mono amp that’s stable at 2 ohms.
Basically, run a positive wire from Sub B + to Sub A + and from that same terminal to the mono amp +. And do exactly the same for the negative terminals: Sub B – to Sub A – and then from that same Sub A – terminal to the amplifier’s negative – terminal.
Wiring 2 x 4-Ohm DVC Subs to a Mono Amp – 1 Ohm Load
Wiring 2 4-ohm subs to a mono amp running at 1 ohm is the most complex wiring circuit, and this can’t be done with SVCs.
It’s similar to running 2 x 4-ohm DVC subs to an monoblock amp at 2-ohm, but you need to get the impedance down further, so there’s a bit more wiring to do.
Firstly, you should run a wire from the left side positive terminal + of Subwoofer B to the left side positive terminal + of Subwoofer A. Then from that same terminal, run a wire to the positive terminal + in the back of your mono amp.
Do the same with the negative terminal, but on the right sided terminals: Sub B – to Sub A – to Amplifier – all of which is the same as above.
As already mentioned, you need to get your impedance down further with this set up, so the bridging wires is different to wiring them into a mono amp at 2 ohms.
Instead of bridging A+ to A- and B+ to B- as in the above example, you need to bridge the unused + to the + terminal of the other side of the DVC sub. And do the same with the negative terminals.
Wiring 2 Subs to a Mono Amp
So there you have it. Wiring 2 subs to a single mono amplifier isn’t as difficult as it seems, it just takes a bit of patience, research and math for getting the right wiring set up.
When choosing an amplifier, the most important thing is to get one that can handle the power for your subs. Most mono amps are 2 ohms or 1 ohm, and they’re designed specially to run a subwoofer, or 2, but they also need to be able to handle the total RMS.
Running 2 subs adds a bit more complexity to the wiring and the math you need to do beforehand, but as you know it can be done. And once you have them up and running, you will make such a difference to the bass output in your car.