how to connect subwoofer to amp without sub out

Asking how to connect subwoofer to Amp without Sub Out? We’ve got you covered!

Especially when bothering with old subwoofer technologies, not having the correct ports to work with could make it really challenging to make use of the device.

In this guide, we’ll get you familiar with all of the possible ways of hooking up your passive/active sub to an amp!

To connect a subwoofer to the amplifier, you could either use a “Y” RCA cable and the “Preamp” Output or connect the subwoofer to a “Line In” port as a speaker.

Let’s learn all about the following methods in our detailed guide!

How to Connect Passive Subwoofer to Amp Without Sub Out?

connect passive subwoofer to amp

To understand all the different possible ways of connecting a passive (or active) subwoofer to an amplifier, we’ve provided you with 3 separate methods for performing the connection.

If something doesn’t work out for you, you’ll find the solution in the next, upcoming method!

Important: While connecting your sub, make sure it is powered on at all times for testing purposes. 

This is the only way to figure out whether the device has connected.

Let’s start with the first method!

Method #1 Use “Y” RCA Cable & Preamp Output

use y rca cable and preamp output

The most standard way to connect a subwoofer (passive or not) to an amplifier, without a “Sub Out” port is present, is to take advantage of the Preamp Output

Using a piece of “Yshaped RCA Cables, you could efficiently connect the subwoofer to any amplifier.

That is, of course, if a subwoofer cable is not present, used for connecting your passive device to an amplifier or video/audio device.


In order to use the Preamp Output with a “Y” shaped RCA cable, the amplifier must also support a Preamp input.

Otherwise, you’ll not be able to take advantage of the port and connect your subwoofer to the speaker system.

Here are the instructions for setting up your sub using the “Preamp” output in two methods:

setting up sub using preamp output

Using the Subwoofer’s Original Cable:

  1. Make sure that your subwoofer is connected to power and turned on.
  2. Connect the single end of the cable to the “Pre-Out” on your amplifier.
  3. Plug the male end of the subwoofer’s original cable into the red port on the sub.
  4. Test the audio…

Using a Splitted “Y” RCA Cable:

  1. Hook up the RCA cable to the “Amplifier Out” port.
  2. Choose “Right” or “Left” on your sub.
  3. Connect the male side of the RCA cable to the “Preamp” output on the sub.
  4. Plug in one of the female sides of the RCA into the main-in on the amp.
  5. Test…

We know it’s complicated, bothering with such a large amount of cables, and in fact, you’ll even sometimes need RCA cable extensions, if you’re using such wires.

If you’ve connected the subwoofer to the amplifier correctly, there should be audio now.

Method #2 Treat the Subwoofer as a Speaker

treat the subwoofer as a speaker

Another way how to connect subwoofer to Amp without Sub Out is to treat the subwoofer as a speaker.

All you have to do is connect the subwoofer to a “Line In” port, and the device will start behaving as a speaker.

This is not as bad as it sounds, since the function of the subwoofer will remain the same, although it’ll use a different wire to connect with the amp, that’s all.

In fact, you’ll still get good sound quality when connecting the sub to a “Line In” port, using a speaker wire.

Can I Connect my Subwoofer to an Amp Using “Line In”?

Before we try to get this done, you should first inspect your amplifier and make sure there is enough free “Line In” ports.

Since those are the connectors that speakers get plugged into, you may have used up all of the free ports or not have as much as needed, to connect the sub.

  • Take a look at the back of the amp and check if the “Line In” ports are free!
Note: On most amplifiers, there is about 5-6 Line In Ports, all in different colors. 

What Cable is Used for Connect a Sub to “Line In”

cable used to connect a sub to line in

A regular speaker cable. That’s right. You could use a 3,5 mm AUX cable to connect your sub to the amp, as long as it is in a “Line In” port, where speakers usually connect at.

The speaker cable used for the purpose has one end on each of the sides and one is usually delivered with your subwoofer.

How to Connect My Subwoofer to the “Line In” Port?

After examining your setup and making sure that such a connection is possible, it’s time to connect your subwoofer as a speaker, to the amplifier.

Follow these instructions to connect your sub hooked up to the amp as a speaker:

  1. Get the 3,5 mm AUX cable that you’ll connect the subwoofer with.
  2. Plug the first end of the cable into one of the “Line In” ports on the amplifier.
  3. Connect the other end of the cable, to your subwoofer’s “Audio Out” ports.
  4. Make sure that the connection is stable and reliable.
  5. Test the subwoofer…

Once the subwoofer has been connected, play music from the amplifier and determine if the sound quality is acceptable.

Many users have said that their subwoofer has maintained the quality of sound, even when it was connected to a “Line In” port on the amp.

Note: Your amplifier will not perceive the subwoofer as a “Speaker” in the settings!

Method #3 Configure the “LFE+MAIN” Feature!

configure the lfe+main feature

When your subwoofer does not have a “Sub Out” port and none of the methods above worked for you, enabling the “LFE+MAIN” feature is another solution. 

The LFE+MAIN setting is a crossover regime of the functionality of your sub that we would normally find in any sound system, which is producing deeper frequency sounds.

These deep, low-frequency sounds that go lower than the crossover point to both the subwoofer and speakers, could be optimized by enabling the “LFE+MAIN” feature and allowing the connection.

Note: On top of that, the feature is also configurable!

How Does the LFE+MAIN Feature Works?

The thing is that setting your subwoofer to the LFE+MAIN Mode will allow the device to make any port that transfers output sound, suitable for connection.

This means that even if your subwoofer does not have a “Sub Out” port, you could still use one of the available ports.

If your subwoofer has an interface on its own or there’s an “LFE+MAIN” button on the back, determine how to get the setting enabled.

Based on how you’ve established the setting, connect the subwoofer to the amplifier respectively, and basically, make use of what you have!

Subwoofer Not Working With Amplifier – Fixed!

subwoofer not working with amplifier

Even if you’ve connected the subwoofer to your amplifier, but the device is still refusing to work, there are a couple of things to attempt.

Let’s review the most-powerful solutions:

Power Cycle your Audio System

Unplug both your subwoofer and amplifier for an estimated 5 minutes. Once the time has elapsed, re-attach the device’s power cords.

Try a Different Port

If you’ve managed to successfully connect the subwoofer to the amplifier, make sure that the port is not faulty. Connect the sub elsewhere on the amp.

Check the amp’s mode

Make sure that your amplifier is set to “Stereo” and that there is another mode messing up with the audio output.

If you’ve tried all of the following instructions, but couldn’t get the subwoofer to work with your amp, this is likely to be a hardware malfunction.

Deliver your audio system to a technician and have them take a look at the setup, which hopefully will provide you with some answers!

Good luck!

Quick Recap:

The answer to “how to connect subwoofer to Amp without Sub Out”, is either to use the “Preamp” output or connect the subwoofer using a “Line In” port and use it as a speaker.

The last available option is enabling the “LFE+MAIN” feature on the sub and using any available ports on the subwoofer.

We hope that this guide was interesting and helpful so follow us for more!

Nicole B