Some people like to have more than one subwoofer in the car, and if you’re one of those people, you may be wondering how to wire two subs to one amp.
Connecting two subwoofers to one amplifier can be confusing for beginners, so I will show you how to do it step-by-step.
Generally, two SVC subwoofers can be connected to the amplifier in either parallel or series. Depending on their impedance, two DVC subs can be connected to the amplifier in either parallel-series, parallel-parallel, or series-series.
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Tip: If you want to wire two subwoofers to one amplifier, you must ensure that the amplifier can handle the extra load. Most of today’s amps can take the impedance of 4, 2 and 1 ohm, so the connection is simple.
An excellent example of such a monoblock is my favourite Skar Audio SKv2-4500.1D (link to Amazon) which supports 1,500W RMS at 4 ohms up to 4.500 W RMS at 1 ohm.
In this article, I’ll walk you through the steps involved in wiring two subs to one amp in different configurations.
Can Two Subwoofers Run With One Amplifier?
You can use two subwoofers in the car and connect them with one amplifier. In fact, it’s a pretty standard setup for people who want to add a little more bass to their car audio system.
When connecting two subwoofers to one amplifier, you need to consider a few things.
#1. The Wattage Rating of the Amplifier.
Make sure that the amplifier can handle the extra load of two subwoofers.
Most amplifiers are designed to run one subwoofer, which is the most common combination, so you’ll need to ensure that your amp is powerful enough to run two subs.
#2. The Impedance of the Subwoofers.
Another thing to consider is the impedance of all subwoofers. In any case, the amplifier should be able to support the subs’ impedance. Otherwise, it can be overloaded, which can cause its clipping or overheating.
For example, if you already have an amplifier that works only at 4 ohms, you’ll need to ensure that your subwoofers are 4 ohms, or you will have to make different than standard wiring combinations to make the total impedance of 4 ohms.
#3. Wire Gauge.
Although it does not directly affect the connection of two subs, the wire gauge must be large enough to handle the amperage of two subwoofers, especially if you connect them in parallel.
Most subwoofers will work with 10AWG, but it depends on the total load and whether you have a parallel or serial connection type.
I always recommend having more resistance safety in the system, which means you will do better to go for a larger diameter than for too small.
Why Wire Two Subs to One Amp?
For me, the reason for connecting two subs with one amplifier is simple. With the one amplifier, I spend less on the car audio setup and will also save some space in the trunk.
In most installations, you can wire two subwoofers to one amplifier and get the same or even better results than with two amplifiers.
The main advantage of using one amplifier is that you’ll save money and space, so if you’re on a budget or don’t have a lot of room in your car for extra equipment, wiring two subwoofers to one amplifier is a great option.
Another advantage of using one amplifier is that it’s easier to wire everything up.
If you’re unfamiliar with car audio wiring, having two amplifiers can be a little confusing with double power wiring, connecting distribution blocks, etc.
Wiring two subwoofers to one amplifier is a pretty straightforward process, so it’s a good option for beginners.
But, there are not only benefits of having two subs wired to one amp.
The main disadvantage of using one amplifier is that for the most powerful subwoofers, you may not be able to produce as much power as you would with two amplifiers.
Therefore, if I were installing the new system, and the SPL (Sound Pressure Level) would be the only priority to get as much bass as possible, I would consider using one amplifier for each subwoofer.
In other cases where I do not want to make my car a driving boom box, I would use a single amplifier and most likely choose a stereo amp.
How to Wire Two Subwoofers to One Amplifier?
Now that we’ve gone over the basics of wiring two subwoofers to one amplifier let’s look at the different ways you can wire them up.
The main difference between all connection types is the number of voice coils of your subwoofers.
#1. If you have two single voice coil (SVC) subwoofers, you can wire them up in parallel or series.
#2. If you have two dual voice coil (DVC) subwoofers, you can wire them up in parallel-parallel, series-parallel, or series-series.
#1. Wiring Two SVC (Single Voice Coil) Subwoofers
Wiring two SVC subs is the easiest when you decide to run them from the stereo amplifier because of the direct connection of each sub to a separate channel. Simple right?
Well, yes, if you have SVC subwoofers with the same impedance as the amplifier.
In this case, the only thing you have to worry about is the amp’s RMS output per channel which should be at least the same as the wattage of each sub.
In other words, if you have two 300W RMS subs, the amplifier should have at least 300W RMS per channel.
Things look a little different if you have SVC subwoofers but different from the amp impedance, for example, 2 ohm subs for 4 ohms amplifier or vice versa, 4 ohm subs and 2 ohm amp.
For the first scenario, with the low (2ohm) impedance subwoofers and standard 4 ohm amplifier, I am connecting both subs in series, which will increase their total impedance to 4ohm. This combination works when you have a 4-ohm mono amplifier.
If you have a multichannel amp (either a stereo or 4 channel), instead of connecting subwoofers to the individual channels, the better way is to bridge two channels together to reduce the amp’s impedance, and connect the subs in series.
I would avoid connecting them in parallel because that will further reduce their total impedance from 2 ohms to 1 ohm, which may be too much load for the 4-channel amplifier, even if it is bridged down to 2 ohms.
Connecting two SVC subs in series will increase their impedance, reducing at the same time load of the amps bridged channel.
The second option, with 4 ohm subs and 2 ohm amp, is easier. If the 2-ohm amp is monoblock, you should connect subwoofers of a higher impedance parallel to the single channel output.
A parallel connection will reduce the total impedance load to 2 ohms matching the amplifier’s output.
For the multichannel amplifier, the principle is the same, meaning you should bridge two channels together, reduce the impedance, and connect both subwoofers in parallel.
Reduced to 1-ohm amplifier’s load will increase the wattage supplied to the subwoofer, providing enough safety for a loud bass.
To make the connection between two subwoofers and the amplifier more efficient, I recommend using either SVC or DVC subwoofers with a multichannel amplifier, especially if you cannot bridge it.
#2. Wiring Two DVC (Dual Voice Coil) Subwoofers.
Having two DVC subs in the system is the moment when your connection fun starts.
Depending on the subs and amps impedance, you can wire them up in several ways, always resulting in different loads to the amplifier.
Having two DVC subwoofers means that from the connection perspective, you do not have two subs in the system but actually four (two subs with two voice coils each), and the possibilities for wiring them to go up four times.
This is why I recommend always having two single voice coil subs when you start from the ground with your car audio system, but if you decide to go a more advanced way, let’s go through them one by one.
Connecting Two Subs in Parallel-Parallel
Parallel-parallel connection is used when you wire two subs to the single amplifier channel and want to lower the total impedance load.
If your subwoofers are 4 ohms, the parallel-parallel connection will reduce the total impedance to 1 ohm.
For 2-ohm subwoofers, it will be 0.5 ohms, so before deciding about this connection type, make sure the amplifier can work with such low loads.
Connecting Two Subs in Series-Parallel
Series-parallel connection (also called parallel-series) means that you wire both voice coils for each subwoofer in series and then connect the subs in parallel to the amplifier.
This wire configuration is used when your subs and amplifier have the same impedance, and you want to maintain it, whether it is 2 ohms or 4 ohms.
Connecting Two Subs in Series-Series
Series-series connection is precisely what it means, and you connect both subwoofers in series between positive and negative outputs of the amplifier.
This wire configuration is used when you want to increase the total impedance load of your system.
For example, if your subs are 2 ohms each and you wire them in series, the total impedance will be 8 ohms, and for 4 ohm subs, it will become 16 ohms.
The series-series connection is rarely used in car audio systems because of too high impedance for the standard car amplifiers.
All of the above connection combinations are common when you have both subwoofers connected to either a monoblock or a bridged stereo amplifier.
If you have a stereo (2 channel) amplifier, you can connect each DVC sub to a separate channel, but remember about the impedance at the amplifier’s terminals.
The situation is even easier with the 4-channel amp used for two DVC subwoofers, and in this scenario, you can simply connect each voice coil to a separate channel.
Is It Better to Wire Subs in Series or Parallel?
In general, you should connect subs in parallel to reduce their total impedance or in series if you want to increase the impedance load.
Each scenario is specific to the amplifier type you have and its capabilities.
To wire your subs correctly, the most important thing is to have the same impedance on both subwoofers. Otherwise, one of them will be working harder than the other one.
The same for the number of voice coils. Although the number of combinations is endless, I prefer having either two SVC or two DVC subwoofers within the same circuit.
Can I Bridge Two Subs Together?
You can bridge two subwoofers by connecting positive wires with the positive amp’s terminal and negative wires with the negative amplifier’s terminal.
Bridging subs is nothing else than their parallel connection, which means they will have reduced the total impedance. Therefore, I recommend bridging two SVC with either a 2 or 4-ohm load.
To bridge two subs together, you can use either a monoblock or a stereo amplifier with bridged mode, but remember to check if your amplifier can support the lowered impedance, especially if you have 2-ohm subs.
How to Match Subwoofers’ Impedance With the Amplifier?
As I already explained, the impedance depends on the connection type, and it is best when it is matched to the amplifier.
In most cases, you will wire two SVC subs in parallel or series-parallel because those are the most common impedance values for home and car audio systems.
For example, if your subs are 4 ohms each and you wire them in parallel, the total impedance will be 2 ohms which is the most common value for car amplifiers.
The same for two 2 ohm subs wired in series, the total impedance will be 4 ohms, and it is again a good choice for many amplifiers.
How to Match the Power of Two Subwoofers to One Amplifier?
If you already know about the impedance, the next step is ensuring the amplifier is strong enough to support both subwoofers.
To do this, you need to know the RMS power rating of both subs and add them together. For example, if your subwoofers are rated for 1000 Watts each, their total power will be 2000 Watts.
Now you need to find an amplifier that can handle this amount of power continuously, and for that wattage, you should use an amp between 2,000 and 3,000 W RMS.
It is recommended to have an amplifier (especially for the subwoofers) with more power because if it is too weak, you may experience distortion or worse clipping, which I am sure you do not want to experience.
And the last thing. Always look at the RMS wattage and not the peak wattage. Otherwise, the system will be messed up.
How Do I Run Wires for Two Subwoofers in Car?
There are a few ways to wire two subwoofers in your car, but I will explain the most common and the easiest way.
All you need is an amplifier with enough power to drive both subs and some speaker wire.
For the series connection, you first need to connect the positive wire from the amplifier to the positive terminal on the first subwoofer.
Then connect the negative wire from the amplifier to the negative terminal on the second subwoofer. Now all you need to do is to run the wire from the first subwoofer’s positive terminal to the second subwoofer’s negative terminal.
For the parallel connection, the positive wire from the amplifier goes to the positive terminal on the first subwoofer and then to the positive terminal on the second subwoofer.
The negative wire from the amplifier goes to the negative terminal on the first subwoofer and then to the negative terminal on the second subwoofer.
And that’s it. Now you know how to wire two subwoofers in your car, so make sure you have a proper gauge of the speaker wire.
Additional Equipment Needed to Connect Two Subwoofers With One Amplifier
For connecting the subwoofers with the amplifier, you do not need anything else than the good speakers’ wire, pair of wire cutters and strippers, and some terminals if you do not want to place in the terminals bare wire ends.
From the wires, I recommend KnuKonceptz (link to Amazon) with the gauge between 12AWG to 10AWG, depending on how strong the subwoofers are.
Copper wires (OFC) guarantee the best sound quality and power transfer.
And for the terminals, I recommend using the banana plugs or pin terminals depending on the installed terminals (link to Amazon) because they are straightforward to work with, and you do not need any special tools. Just a regular screwdriver is enough.
Should Two Subwoofers Be In One Enclosure or Two Separate Boxes?
For two subwoofers, you can use either one big enclosure or two separate smaller enclosures depending on the preference, subwoofers’ type, space in the car, and of course, budget.
If you want the best possible sound quality, two separate enclosures are the way to go because each subwoofer will have its place and will not interfere with each other. In addition, you will have flexibility in positioning them in the car.
The only downside is that it costs more money, takes up more space in the car, and requires more wires to be used.
If you decide to use ready-made enclosures, I recommend you check out a large selection of SKAR (link to Amazon) and their either loaded or empty boxes.
How to Place Two Subwoofers in the Car
Positioning subwoofers in the trunk can be tricky because you have to consider a few things, like the space available, the type of subwoofers, and the type of car.
If you have two separate enclosures, I recommend you place them as far away from each other as possible so they don’t interfere.
For example, both boxes can be placed on both sides of the trunk with cones facing each other. If you have one big box, it’s best to put it in the middle of the trunk with the cones facing either top or rear of the car.
It’s also important to consider the type of subwoofers you have because if they are ported, they need to be placed away from any walls so the port doesn’t get blocked and the airflow is unrestricted.
If you have sealed subwoofers, they can be placed closer to the car’s interior, or cones can face the backseat.
Placing the subs closer may be necessary, especially in sedans with separated trunk space, and the bass must be forced through the seat to enter the cabin.
If that’s the case, then make sure you have enough power to drive the subwoofers because if not, the bass may be too soft.
For more information, check out the article about positioning subwoofers in the trunk.
Now you know how to wire two subwoofers in your car, what additional equipment you need, and how to place the subwoofers in the trunk.
Critical information you need to remember is the impedance that can be affected by different connection types.
If you connect the subwoofers in series, the impedance will go up, and if you wire them in parallel, it will go down.