You may have noticed that most subwoofers have two line inputs and wondered what it is about the speaker. That warrants two line inputs. . I did the same when I was looking to buy a speaker. It’s not a unique feature to subwoofer. When you buy a home theatre subwoofer, one of the first things to check is if it has two Line In sockets or not. If it does, that’s great because you can immediately use it with any audio source.
If it doesn’t, you might feel a little stuck because most modern AV receivers no longer have a dedicated subwoofer output. And almost all of them only have one Line In socket for connecting speakers or sound bars.
How do you then connect your subwoofer? There are two ways to accomplish this. Either by utilizing a speaker-level signal-accepting external amplifier (ideally from an output on your AV receiver). or by purchasing subwoofers with integrated amplifiers and then using a Y-adapter cable to combine the two inputs into one.
What is a stereo line input?
A stereo line input is a unique input on an audio device. That accepts both audio and a signal ground signal at the same time. It is used in professional audio equipment and home theater subwoofers. And it allows you to connect these devices to any signal source without worrying about their output interruptions, signal strength or voltage levels.
Because most audio devices have their Line In sockets configured to accept both a balanced and unbalanced signal simultaneously, meaning they can take even a single-ended signal while blocking out its polarity and impedance. This is why you don’t need an adapter to connect a subwoofer to a receiver regarding Line In sockets.
You only need access to the audio and signal grounds of the jack. You are connecting to them because they shouldn’t be separated. Although it’s ideal, you shouldn’t always connect the signal ground to the device’s base when you plug in a subwoofer.
How to connect a subwoofer with a built-in amplifier
If you want to connect a subwoofer to an AV receiver with a built-in amplifier, it should have one or two speaker output terminals with which you can connect your subwoofer. Most AV receivers have a speaker output that receives single-ended and balanced signals. So you only need to connect the subwoofer to one of these terminals, as shown in the picture above.
However, there are two ways to adjust the volume. The subwoofer uses a volume knob (which it should be) or connects an output of the receiver to the subwoofer’s volume control. The downside is if you use the volume knob on your subwoofer and connect it to the receiver’s volume control. Then you cannot control the volume on both devices simultaneously.
So if you are watching a movie or listening to music and want to change the volume, you must do it on both devices. It changes its volume using the receiver’s remote control. And then changing the subwoofer’s volume can be done using your remote.
How to connect a subwoofer with an external amplifier
If you’re connecting a subwoofer with an external amplifier, you have two options, as shown in the picture above. The first is to connect it to the single speaker output of your AV receiver. And then connect the subwoofer and amplifier to the same volume knob of the receiver.
Another option is to connect an adapter cable with two RCA connectors (to connect a subwoofer and an amplifier) and then connect the two RCA connectors to the receiver’s single RCA jack.
The main benefit of this setup is that you can use the volume knob on the receiver while still being able to control the volume independently on all devices.
Why does a subwoofer have two Line Inputs?
Most home theater subwoofers have two line-in terminals. Because the same device has to be used as an audio source and a subwoofer, this means you can plug any audio device into one of your subwoofer’s line jacks. And can use it as an input for subwoofers.
When you turn on the volume knob in the subwoofer, you will hear audio from the connected source. When you change the volume on the connected device, the subwoofer will be louder or quieter. This is a nice feature because it allows you to plug in a sound bar or a TV connected to your AV receiver in the subwoofer and control the volume separately on both devices.
Wrapping up
Subwoofers are used to add deeper bass sounds to your audio. As a rule of thumb, you should have a subwoofer if you want to feel a song more than hear it. The problem is that most AV receivers don’t have a dedicated subwoofer output anymore. And the ones that do have it have a feeble production that is unsuitable for powering a subwoofer.
That’s why home theatre subwoofers have two Line In ports – one for receiving audio signals and another for receiving a power signal so you can connect them to an AV receiver.
The good news is that you can use almost any audio source with a subwoofer. Such as an AV receiver with a music player, a TV, or a single output. You must connect the audio source to the subwoofer’s line-in, setting the maximum volume of your references. Then turn the volume knob of your subwoofer down until you hear the base sound.
