Last Updated on November 29, 2022 by Norvan Martin
There are multiple ways of connecting subwoofers and speakers in your home cinema system. The most common way is to connect your subwoofer using the subwoofer output on the receiver.
Another common way is to connect the subwoofer to the AV receiver or amplifier using the L/R speaker channels and then use the dedicated speaker line-level output on the subwoofer to connect to the main speakers.
This is a common way to connect your subwoofer to your receiver without a subwoofer output.
The subwoofer’s speaker line-level output will then pass a high-level amplified signal out to the main speakers.
What Are Speaker Level Outputs On My Subwoofer?
In this case, the subwoofer is connected to the receiver or stereo amplifier and the signal passes to the sub and the sub then passes the signal to the main speakers.
It also provides a quick and easy way to connect a powered subwoofer to a mixer if you want to take advantage of the active subwoofer’s internal active crossover.
In other words, speaker level outputs on your subwoofer are “thru” connections.
How To Connect A Subwoofer To Speaker Level Outputs
For subwoofers equipped with a speaker-level input and a speaker-level output, all you need to do is to connect the receiver speaker outputs to the speaker-level input on the subwoofer and then connect the speaker-level output on the subwoofer to your main speakers.
Here is the typical setup:
- Your receiver or amplifier will have a line-level subwoofer output
- Run a pair of speaker cables or subwoofer cables from the receiver or amp output to the subwoofer
- Run another pair of speaker cables from the sub speaker level outs to your main L/R speakers.
Here is another illustration of the connection.
To recap, subs with speaker outputs will have speaker level inputs as well. Rather than plugging it into a dedicated subwoofer output on the surround sound receiver, you’ll route your normal speaker cables first into the sub, and then onwards to the speakers.
What Do Speaker Line Level Inputs and Outputs Look Like?
In most cases, speaker line inputs and outputs will be labeled clearly on the subwoofer. As an example, we will give you a preview of the KEF KUBE Subwoofer back panel.
The picture below shows a KEF KUBE Subwoofer back panel with the speaker level inputs (Box 1), the volume and crossover controls (Box 2 & 3), and the phase control (Box 5).
The picture below shows the output for the mains on the CVHD-12S sub. As you can see, there are connections for the left and right channels.
What If Your Subwoofer Doesn’t Have Speaker Level Inputs
The purpose of speaker level inputs and outputs is to simplify your setup. This means that there is no need for a dedicated subwoofer output on your amplifier or receiver. It’s an easier and cleaner connection process because the subwoofer just goes in line with your existing components.
So what if your subwoofer does have speaker level outputs or if your receiver or amplifier doesn’t have a subwoofer output?
There’s actually a quick and simple option if your receiver doesn’t have a sub out. Most receivers that don’t have sub-output actually have what is called a Tape Monitor option.
You can actually connect the Tape Monitor output from your receiver as a line-level input to your subwoofer.
So, no need to throw away your vintage receiver just yet! On the other hand, if your subwoofer doesn’t have speaker-level inputs, then you will just have to connect the main speakers to the receiver or amplifier.
How To Control Speaker Level Output Volume
That may not be an easy thing to do. It comes down to sound balance really because the components of the system will work in tandem.
This means that as you vary the volume control on your amp or receiver, the subsystem will go up and down in balance with the main speakers.
In some cases, your subsystem may have a level control that you normally set once to get a good balance between the sub and main speakers.
How Do Speaker Level Outputs Work?
You may be wondering how this setup works internally. How is it that you can connect your speakers to your subwoofer? How do the main speaker signals pass through unaffected? How is it that the frequencies don’t overlap and distort?
Here’s how it works:
Subwoofers with speaker line inputs have a high-impedance electrical circuit inside the unit. This circuit picks up the signal, in most cases using a high pass filter.
This high-pass filter will pass all signals with a frequency above a certain minimum or cutoff frequency (the crossover frequency) and attenuate or block signals with frequencies lower than the cutoff or crossover frequency. This way, only high-end signals above the crossover frequency are sent to the speakers. This is why it is important to properly set your subwoofer crossover.
Of course, these subs also have low-pass filters that pass the low-frequency signals to the sub.
This filter then feeds the sub’s amp or amps which then drive the connected speakers through the subwoofer speaker line out.
How Are The Signals Separated?
So we already mentioned that some subs will have a high pass filter that will pass the higher frequencies above the crossover point to the main speakers and a low pass filter that will pass the frequencies for the sub.
However, some subwoofers have passive crossover networks inside. These networks separate the speaker-level signal from the amp into low and high bands. This part of the subwoofer is called the crossover network. The low-level signals then drive the subwoofer and the higher-band signals then drive the main speakers.
So, in either case, these methods separate the lowest frequencies for the subwoofer from the high frequencies for the main speakers.
Doing so reduces the acoustic interaction that can occur if mains and subs are trying to play the same frequencies. Sending such mixed and out-of-phase sound waves into the listening space will not be pleasant.
While either method is workable, many subs utilize passive networks because they are more efficient. Often, this adds some amount of expense to manufacturing such devices which does drive up the cost.
To recap, separating the low and high frequencies is very important when connecting your main speakers to your subwoofer using the speaker line out port.
This is normally done by a part of your subwoofer called the crossover. The responsibility of the crossover passive networks is to extract the really low bass frequencies that you want the sub to handle and pass the higher frequencies out to the main speakers.
Best Setting For Receiver and Subwoofer Crossover
You might be wondering what you should set the receiver or subwoofer crossover to since you are using one connection for the subwoofer and speakers.
Well, you have two options. Since the crossover in the subwoofer will act as the system crossover for the sub and speakers in this configuration, you can either set the receiver’s crossover to 20Hz or ‘off’.
The best option is to set the receiver’s crossover to off so that it passes all the low frequencies to the subwoofer and then set the subwoofer’s crossover to say 80Hz or so. You can also set the sub’s crossover to whatever the roll-off frequency is for your main speakers. Check the speaker’s specs to find that out.
Where Can I Find A subwoofer With Speaker Level Inputs and Outputs?
There are many subwoofers with speaker level inputs and outputs on the market. Most of the top brands produce the subs including Polk, Bowers & Wilkins, Klipsch, and so on.
Examples include the Polk Audio PSW111, Bowers & Wilkins ASW610, MartinLogan Dynamo 600X, Klipsch C Series C-310ASWi, and many others.
Connecting A Subwoofer To Rear Speakers
Some powered subwoofers come with high level inputs that make it easier to tap into the rear speaker wires. However, if your car has a factory subwoofer, you can use its speaker wires to make the connection much easier. If it does not have the high level inputs, use a basic line out converter that ties into the speaker wires and turns them into RCA output.
Connecting your main speakers to your subwoofer is quite a simple process. All you really need to do is to connect your subwoofer to the receiver or the amplifier using speaker/subwoofer cables (connect to the subwoofer line-in) and then connect the subwoofer to the main speakers using the subwoofer line out.
This is one of the easiest ways to connect your subwoofer to your receiver without subwoofer output.
This means that there is no need for a dedicated subwoofer output on your amplifier or receiver.
To learn about other ways to do this, check our article on how to connect a subwoofer to a receiver without subwoofer output.
Norvan Martin is the founder of BoomSpeaker.com. 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.