How To Connect Passive Subwoofers To 2 Channel Stereo Amplifiers

Norvan Martin
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If you are looking to connect passive subwoofers to your existing home theater setup, then we have all the detailed instructions for you. As most audiophiles will tell you, passive subwoofers do not contain amplifiers and so must be connected to an external amplifier to get the proper performance by your subwoofer.

To connect a passive subwoofer to your amplifier, you can use RCA cables to connect the amplifier’s output to the sub’s input. We explain more below:

  1. Make sure that the amplifier is switched off.
  2. Look for a jack on the amplifier labeled Low-Frequency Effects, LFE or maybe Subwoofer output.
  3. Plug the RCA cables into this socket.
  4. Plug the other end of the RCA cable into the subwoofer input jack on the subwoofer
  5. That’s it, the connection is complete!

For a more detailed procedure, we will discuss the instructions in detail below. But first, let’s understand what a passive subwoofer is.

What’s a Passive Subwoofer?

Passive subwoofers are subs that need to pair with an external amplifier like traditional loudspeakers. A powered subwoofer on the other has a self-contained amplifier.What is a Passive Subwoofer

As you might have guessed, powered subs come with an inbuilt amplifier as opposed to passive ones.

As such, the actual integration of the two subwoofers with your home audio system is quite different depending on the type of subwoofer that you’ve chosen.


What’s a 2-Channel Stereo?

A surround sound system is what you need to enjoy the best audio performance when watching a movie.

A 2-channel system is the simplest stereo system that doesn’t offer surround sound but attempts to provide a better experience than a single speaker.

What is a 2-Channel Stereo

That’s because a two-channel system delivers the sound in multiple directions, attempting to replicate the way a stereo sound operates.

In a 2-channel system, the main components include two speakers (right and left), an amplifier, and the audio source (this could be a receiver).

That makes it ideal for connecting with a passive subwoofer as your receiver comes with an inbuilt amp (although some setups may have an additional amplifier). Here are some pointers to help you choose your gear for setting up your home audio system:

  • Speakers – You’ll want speakers with a high power handling capability, low distortion, and a balanced sound. It’s advisable to use wide-dispersion speakers to easily move them around without changes in audio quality or volume.
  • Amplifier/ Receiver – When choosing a receiver/amp, you’ll want one with dedicated stereo settings and a high power rating. The right receiver will allow you to play your music without any distortion at high volumes, especially on the high notes.
  • Cables – In a 2-channel stereo system, every component, including the speaker cables, have to be of the highest quality. That ensures the signals reaching your subwoofer and speakers are as clean as possible.


How to Connect Your Passive Subwoofer To Your 2-Channel Stereo: Step By Step

As mentioned earlier, passive subwoofers must be hooked up to an external amplifier as they don’t feature any internal amps.

Here are the steps to follow when connecting your subwoofer with a 2 channel stereo amplifier.

1. Ensure Everything Is Off

Before connecting your system components, ensure the sub and the amp are both disconnected from the power and turned off.

2. Properly Connect the Subwoofer to an External Amplifier

Before starting the set-up process, you need to decide where your subwoofer will stand. Fortunately, the sub doesn’t require a lot of directional pushing, though proper subwoofer positioning is paramount to get the best audio performance from your system.

Connect the Subwoofer to an External Amplifier

To start the actual hook-up, connect the subwoofer to your external amplifier using RCA cables. However, you’ll need to use two sets of cables if you want to get a stereo set-up. Good thing most RCA cables come in pairs like the Monoprice 1.5ft Premium 2 RCA Plug. Essentially, the set-up process involves connecting your amplifier’s output to your subwoofer’s input. On your amplifier, the jack might be labeled “subwoofer output.” If your receiver doesn’t have a sub out, note that there are many other ways to connect your subwoofer to an amplifier that doesn’t have sub out.

3. Check your subwoofer

If you have any issues, you need to check the sub. This step requires some understanding of your subwoofer.

The subwoofer may be using a single voice coil system, which means it will have a negative and positive terminal.

Alternatively, it might be using a dual voice coil subwoofer, meaning it will come with two negative and two positive terminals and has two separate drivers inside with isolated coils.

Dual voice coil subwoofers are highly flexible compared to single voice coil subs, as they have multiple wiring options. However, you may need to check your subwoofer manual for more specifics if you’re not sure.

3. Connect your Amplifier and Stereo Receiver

Given that modern receivers are essentially tuners with inbuilt amps, the functions of a receiver and an external amplifier might overlap.

However, an audio-visual receiver functions as an audio distribution center, allowing you to match the sound from your TV with the output from your home audio system.

To connect your amplifier with the stereo receiver, you’ll need to connect cables from your receiver to the amplifier to synchronize the sound from your entire system.

In this step, you’ll need to connect a cable from the receiver’s pre-out socket and link the other end with the input jack of your external amplifier.

4. Connect the Speakers To The Receiver or Amp

Connecting your two-way receiver with your speakers should be your last step to enjoy an audiophile-quality audio performance.

Connect the Speakers to the receiver or amp

Fortunately, that’s pretty easy to do, as your receiver will have output ports labeled either front or main. That’s where the speaker wires go.

When connecting the speakers, ensure that the right and left speakers are connected appropriately.

Additionally, you must ensure the positive terminal from your receiver goes to the positive terminal of your subwoofer to avoid polarity issues. For more detailed instructions, here is how you can connect up to four speakers to a two channel amp.

Hooking up your speakers should complete the connectivity. After that, you can fine-tune the performance of your using the controls on your receiver. You can then switch on your receiver’s power supply and start enjoying your audio performance.


Passive Subwoofer and Amplifier Power

The critical thing to remember when pairing a passive subwoofer with your stereo receiver or amplifier is that it needs to output enough power to sustain its bass effects.

As such, you’ll need to ensure that your subwoofer’s bass won’t drain the receiver’s power supply when connected.

The amount of power required to run such a system depends on your media room’s size and the requirements of your subwoofer.

However, connecting your passive subwoofer to your 2-channel stereo amp isn’t a complicated process, similar to connecting a traditional loudspeaker to an amplifier. Nonetheless, you must understand that pairing a passive subwoofer to your amp is quite different from pairing a powered sub.


Are There Better Options?

Many people opt to connect their subwoofer to a monoblock amplifier instead. A monoblock amplifier is a single channel amplifier that is specially designed for subwoofers because they only amplify low-frequency sounds.

This way, you will have better frequency separation and a better overall frequency response from your audio system. You can find out more about what is a monoblock amplifier is this sounds interesting to you. 


What If My Subwoofer Doesn’t Have LFE or Subwoofer Output?

Many stereo amps have a “subwoofer out” which is usually just a preamp output. This means it’s just a normal line-level signal that uses the crossover in the sub to decide what frequency range to filter.  

However, not all amps have this subwoofer out and in fact, it is not the best way to connect a sub for best performance. The better method will work even if the amp doesn’t have a subwoofer out connection, but you do need a subwoofer that can accept a “high level” (also called “speaker level”) input.

With this method, all you need to do is to connect the subwoofer to the back of the amplifier where you would normally plug in your speakers. However, you need to be careful because since you are using a passive subwoofer, it will pull power from the amp. With an active subwoofer, you wouldn’t have this problem.

One easy fix for this is to set up your amp like a monoblock amplifier using a mono switch. This way, you would double the power output to the sub. This is similar to how you would wire two channels to one speaker

However, you still need to be careful and ensure that the amp is feeding the sub with enough power. You can calculate this by checking the power output of the amp and then checking how much current the sub will pull based on its impedance. 

How Do You Connect A Passive Subwoofer To An Older Amplifier?

A sub with speaker-level inputs is much easier to connect to an older amplifier or receiver. To do this, connect to the speaker outputs on the source unit using speaker wire and the matching inputs on the subwoofer. Besides, you can even power the speakers from the amp or receiver at the same time. 

How To Connect Subwoofer To Receiver Without Subwoofer Output

There are two methods most commonly used with powered subwoofers. 

Method #1

Receivers that come without subwoofer outputs will majorly have preamp outputs on the back. You can use the preamp outputs to connect the subwoofer to the receiver. In addition, all receivers have RCA inputs. You can use them instead to join the sub. If your receiver comes with one RCA only, use a “Y-Adapter” to perform the connection.

Method #2

You can use this method if your receiver does not have preamp outputs. In this case, you will treat the subwoofer as a speaker and connect it with the amplifier. 

Connect the front and right terminals on the receiver to the left and right terminals of the subwoofer. 

However, if you have passive subwoofers, you will need an external amplifier to connect to the receiver to deliver the required power. In this case, you will wire the receiver to the amplifier and then the amplifier to the subwoofer. 

Bottom Line

When it comes to getting the best audio performance from your home audio system, pairing a passive subwoofer with your amplifier is easy and simple. All you need to do is to connect with an RCA cable and then connect the rest of the devices.

However, many audiophiles will tell you that a little experimentation is necessary when setting up your system, to ensure that the subwoofer positioning allows you to get the best audio performance. Finally, check out our guide on how to connect passive speakers to amplifiers

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Norvan Martin is the founder of He is a professional Electronics Engineer and is passionate about home theater systems and AV electronics. BoomSpeaker was created as an online hub to share his knowledge and experiences as it relates to home theaters and home audio electronics. My email: [email protected]  Connect on Pinterest and Linkedin