Adding a subwoofer to your sound system is one sure way to improve the audio output. This is a great option if you enjoy listening to loud music with augmented bass quality. However, connecting a powered subwoofer to a mixer is not a straightforward process. In this article, we will shoe you how you can easily connect a powered subwoofer to a mixer in a PA system.
Let’s get to it.
What Is A Powered Subwoofer?
Subwoofer systems are known as passive or powered (active) subwoofers depending on whether or not they have built in amplifiers.
Powered or active subwoofers are those that come with both an amplifier and woofer driver in the subwoofer box. In other words, they include integrated power amplifiers.
Besides, powered subwoofers are considered more efficient as they produce more substantive bass.
Also, powered subwoofers may sometimes include active crossover circuits that allow you to have a direct connection to the speaker system to the stereo mix and send the rest of the signal (mids and highs to the rest of the sound system)
Why Connect Subwoofer To Mixer?
Subwoofers are designed to handle low-frequency audio. Although adding great impact to low frequencies is not the only good reason to have a subwoofer, it helps you get to another level of sound clarity. As a result, perceived loudness is achieved without particularly upping the SPL.
Are There Different Ways To Connect Powered Subwoofers To A Mixer ?
Yes. Generally, this kind of connection can be achieved in three different ways. These are:
- Crossover method
- Leveraging the active crossover that comes in a powered subwoofer
- Setting up a sub-mix through the mixing console
Let us look at each of these methods in more detail.
1. The External Crossover Method
This is the simplest and most common type of connection used among many PA system operators. However, crossovers come in different formats and complexity.
Why Use External Outboard Crossover Network?
Some PA speakers and powered subwoofers are built with internal active crossovers. However, these crossovers tend to be simple with very simple crossover points around 100Hz.
Using an outboard crossover gives you the freedom to set up gains and cutoff frequency for each band.
This is why outboard crossovers are preferred, even with powered subwoofer systems. When using an outboard crossover, ensure that you use the bypass switch to bypass the active crossover in the sub.
In this method, the output of the mixer is run through a crossover network. The signal is then split into several frequency bands, each of which is sent to a separate speakers and of course the bass frequencies are sent to the sub.
Of course, you can achieve this frequency separation with 3 or 4 way crossovers, while simple 2 way crossovers won’t be as efficient.
Although the method is common with passive subwoofers, it is also very convenient and reliable with powered subwoofer systems.
How To Connect The Crossover
Crossover connections offer you two different connection options to try. You can either choose to use an external connection that gives you more control over the system, or the internal active one that comes with the powered subwoofer. We will talk about the internal active one in the next section.
The main advantage of using external crossover networks is that you can set-and-forget this connection and not worry about the subwoofer after.
To connect the external crossover network, begin by connecting the external crossover system to the mixer. Now wire the powered subwoofer unit into the crossover system. Also wire the main speakers to the crossover. Then, feed the full frequency signal into the crossover. Here’s an illustration:
However, its a good idea to use high-pass filters on channels that don’t need extended bass. Otherwise, low-frequency noise projected from the subwoofer might muddy your audio output.
2. Leveraging The Active Crossover Built In The Powered Subwoofer
As we already mentioned, powered subwoofers are made with an inbuilt crossover. You can therefore utilize the included crossover to seamlessly add a sub to your mixer.
The greet benefit is that this will not cost you anything extra as the crossover is already included in the sub.
When you leverage the active crossover built in the subwoofer system, you will be able to connect the full-range signal from the main outputs of the mixer console directly into the subwoofer system. In other words, you will get the low, mid and high frequencies sent to the sub.
The inbuilt crossover then separates the full range signal into different frequencies that are fed into the inbuilt amplifier before they are sent out into individual speakers and the subwoofer.
In this case, you would connect the speakers directly to the subwoofer using the professional speaker level outputs on the subwoofer. Check out this guide on how to connect speakers to subwoofer line level outputs.
Here is an illustration:
3. Setting Up A Sub-Mix With The Mix Console Using AUX
Having more control over low frequencies gives you more powerful bass. This is because you can easily choose specific signals you want to send to the sub. The submix often only includes low frequency channels such as bass and kick drum. As such, only these frequencies will receive added bass boost, preventing low-frequency muddiness in the mix.
This is only possible if you set up a sub-mix with the mix console, and this is one reason why many music lovers chose this method of connection.
The other reason why you may prefer this method is the concern with sound muddiness that comes up when using outboard crossovers without any frequency filters.
Moreover, if the mix or sound filter process experiences a problem, too much low-frequency signal may pump through without adequate adjustment.
The sound will therefore deliver a smeared time response with very weak harmonics. As a result, the sound may not be clear. Setting up a sub-mix with the mix console solves this problem.
How To Set Up A Sub-Mix With The Mix Console Using AUX
With this method, the sound is fed into the subwoofer through the “Aux Send.” The method is ideal with a larger mixer, and several mics engaged.
With a typical analog mixer, connect a cable from the “Aux send Output Connectors” to the input of the subwoofer. Once you have the connection, you can easily adjust the frequency levels using the Aux knob available on each channel. You can therefore adjust every channel depending on the frequency you intend to send to the sub.
Here is an illustration:
Also, the channels have “Aux Send Master Volume Control” knobs that help to decrease or increase sound volume for every selected channel.
This mix console, therefore, gives you much more control over what is sent into the subwoofer. It, therefore, helps you to avoid sound muddiness while giving you a much cleaner mix.
However, keep in mind that this method is mix-specific and so it’s generally used for touring systems that are used repeatedly by the same audio technicians for the same band.
4. Use An Unbalanced to Balanced Bi-Directional Converter
If you want to connect your main speakers directly to the mixer, you may not have any additional connection points for your sub.
Now consider the fact that many active subwoofer have unbalanced inputs, or consumer line level inputs/outputs inputs and not professional line level inputs/outputs.
In this case, here is what you will need to do:
Take the mix-output from both main speakers to feed the subwoofer.
Convert the speaker output from balanced (professional line level) to unbalanced (consumer line level).
Here is an illustration:
The boxes in the illustration above represent Unbalanced to Balanced Bi-Directional Converters.
The Sonifex Redbox RB-BL2 is an example of such a converter. With this converter, you would use input 1 and output 1 as well as input 2 and output 2 to complete the connection.
Please however keep in mind that Unbalanced to Balanced Bi-Directional Converters are expensive and hard to source and so if you don’t already have one, its better to get another sub that has professional line level inputs/outputs.
Before attempting to connect a powered subwoofer to the mixer, understand the type of subwoofer and mixer you have and whether the subwoofer has an active internal crossover or not. Without an in-built crossover, you will have to put this in your budget or check your audio store for an external crossover to add to your connection. Whichever connection method you choose, enjoy the deep sound of bass!