How to Connect A Subwoofer to Amp Without Sub Out

Norvan Martin
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Subwoofers are designed to reproduce low-frequency bass, and, for that matter, improve your listening experience. If you want to introduce a subwoofer to your home theater setup, you will likely be connecting it to your amp.

Typically, connecting subwoofers to amplifiers is simple and does not require much effort or expertise.

All you need to do is plug the sub into the amplifier’s subwoofer output. However, not all amplifiers have a dedicated subwoofer out. Can you connect a sub to an amp without sub out? Yes, you can. But the method you can use varies depending on the model of your subwoofer and its features. Let’s learn about these solutions.

1. Use Preamp Output and a “Y” Splitter Cable.

If your amplifier does not have the sub out, check behind the amp to find out whether it has ‘pre-out,’ also commonly known as the preamp output.

If the amplifier has this feature, confirm whether the subwoofer’s ‘Line In’ can use RCA cables.

Now use the RCA cables to connect the amp to the subwoofer if the ‘Line In’ and ‘pre-out’ ports are functional.

Some amps don’t have pre-out but only line out which may not help you much. Find out more about pre out vs line out.Use Preamp Output and a Y Splitter Cable

If the RCA cable is split in such a way that you have a “Y” connector, “Y” splitter, or y-cable on each side of the channels, you should simply plug in the L and R ports.

Check if the amp also has both right and left RCA plugs. If it does, ensure you plug in the both as well.

In a nutshell, you can connect your subwoofer to the amp using RCA connectors by doing the following:

  1. Connect a subwoofer cable or RCA cable to the amplifier out
  2. Select either Right or Left port on the sub
  3. If you have split y-cable for the Right or Left port of the subwoofer, plug in both. Ensure the male side comes out of the “pre-out”.
  4. Finally, connect one of the female sides of the “Y” connector back into the “main-in”. Also, connect the other side of the “Y” to the subwoofer. Sometimes you will need RCA cable extensions.

Here, we also explain how you can use a Y splitter to connect your sub to a receiver.


2. Speaker-Level Line Outputs

Some amps do not have the preamp output. If yours does not have this useful connection type, you can still use a speaker wire to connect the sub and get good sound quality.

This method will work for you if your subwoofer has spring clips or other speaker wire connectors.

In this case, hook it up using the amp’s speaker line output. Again, you can find out more about pre out vs line out.Speaker-Level Line Outputs

How do you do this? The process is easy. If you have ever connected a basic stereo speaker, you will find this method quite simple since the steps are the same.

Here is the procedure:

Step 1: Run the wires from the amplifier’s line out to the subwoofer. All you will need to do is to connect the cable that was included with the subwoofer to the amplifier’s terminal line out. If you don’t have a subwoofer cable, you can connect a regular RCA cable that can be purchased at any electronics store. Go to the following link to find out more about rca cables.

Step 2: Connect the cables to the amp’s right and left speaker terminals

Step 3: Connect the cable to the subwoofer’s line-in.

Note: If your subwoofer comes with spring clips for both ‘speaker out’ and ‘speaker in,’ you should be mindful that other speakers may also connect to the sub. Consequently, the subwoofer connects to the amplifier.

That is not the case if your subwoofer only comes with a single set of spring clips. For your sound system to produce quality music, your sub has to share the amp connections with the speakers. To accomplish this without any difficulty, you should use banana clips that can effectively plug into each other’s backs. Find out more about banana clips and other speaker connector types.

How to Prevent Subwoofer “Out of Phase”

As a reminder, we are connecting the sub here as the speaker because that is how line out works.

It would be best to connect the speaker-positive terminals (red) on the amp to the positive terminal (red) on your speakers.connect amplifier to subno sub out

Use the same principle when connecting the negative terminals. Even though the color of the wires does not matter, provided all your terminals match up, you should follow the indicators to avoid confusion.

There is no better way to make your speaker or sub “in phase” than follow this basic principle and connect the amp and the speakers correctly.

If your speakers are “out of phase, which means the connections are reversed, you could experience severe sound quality problems and probably blame it on the choice of the speaker-level outputs sub-and-amp connection solution.

The good news is the reversed connections often do not damage any components of sound systems.

Read on for the most common indicators that your sub is “out of phase,” and you need to recheck the connections:

  • A general lack of satisfaction with the quality of the sound
  • Very thin-sounding bass
  • Poor Subwoofer performance

Of course, a few other issues can cause similar problems. But if you are connecting your subwoofer to an amp using the speaker-level outputs method for the first time, you might find it useful to check whether you have done everything right quickly.

3. Set ‘LFE+MAIN’ on the Sub

Another solution when you want to connect the sub to the amp is to set ‘LFE+MAIN” on the subwoofer. Check out the amp to find the subwoofer settings.

LFE+Main is a crossover mode that we normally find in any sound system that produces deep low frequency sounds lower than the crossover point to both the subwoofer and speakers.

The good thing about this setting is that it’s configurable. However, you need to be careful with this setting because it can cause issues with your sound system.

If you are fearful about changing this setting, you can always leave it at the default. Otherwise, read on.

lfe main

If you find the ‘bass out’ feature on the amp, this will tell you how and when you can operate the subwoofer with or without the sub out.

Once you are done, set the ‘LFE+MAIN’ to allow your subwoofer to play when the right and left main speakers are arranged.

If your amp has a two-channel bass management facility, you can use its features such as the independent slow up/down levels and crossover settings.

Also, you can opt to activate the sub for two-channel audio sources.

How To Connect A Subwoofer To An Old Amplifier

A sub with speaker-level inputs is easy to wire to an older amp. Connect to the speaker outputs on the source unit with the speaker wire and then to the matching inputs on the subwoofer.

How To Add A Subwoofer If You Don’t Have A Preamp/Subwoofer Out

As we already mentioned, if your receiver doesn’t have a preamp output, you can treat the sub like another speaker and use speaker wire to connect it to the speaker terminals of your receiver that are designated for the front right and left speakers.

Final Thoughts

Subwoofers are designed to modify low-note sound that speakers cannot handle. So, in case you would like to improve your sound system’s audio bass quality, find the right subwoofer.

Of course, the connection also determines whether you will have a fantastic sound experience.Connect Subwoofer to Amp Without Sub Out

Connecting your subwoofer to an amp without sub out should not be a headache.

As we have seen in detail here, you can connect to an amp with a sub out using the pre-out port, speaker-level line outputs with RCA connectors, or ‘LFE+MAIN.’ With any of these three main methods, you can start enjoying the bass of your favorite tracks whenever you want.

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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