How To Connect A Subwoofer To A Receiver Without A Subwoofer Output

Got a subwoofer with no sub output handy? Don’t worry – there are several simple ways to connect a subwoofer to a receiver without a subwoofer output.

Read on and I’ll show you several options along with easy and clear diagrams to help.

This article is part of the AV receiver main page.

Home stereo subwoofers explained

Comparison of non-powered (passive) vs powered (active) home stereo subwoofer enclosures.

Home stereo subwoofers are available in two different types: powered (“active”) and non-powered (“passive”).

• Powered subwoofers use a low-signal signal that is boosted using a built-in amplifier, power supply, and output only bass using a crossover. These types are one of the most common and in many cases use an RCA type input jack to connect to the receiver for sound.
• Passive (non-powered) subwoofers are simply a subwoofer speaker inside a bass enclosure.  It’s wired directly the speaker terminals or through passive bass crossover inside in some cases. These types are less common.

How a subwoofer produces bass

The subwoofer works by resting inside of a speaker enclosure where bass frequencies are captured as the woofer cone movies, producing deep bass sound. 

In order to produce clean-sounding bass without vocals or other sounds a subwoofer can’t properly produce, a low-pass crossover is used. The problem comes when you try to connect a subwoofer to a signal without a crossover – it sounds terrible!

The subwoofer output jack on a receiver is normally limited to passing bass only, either from stereo music production or from the “.1” subwoofer channel (dedicated subwoofer music content) of a surround sound system.

For example, when you hear references to “5.1” or “2.1” speaker systems or surround sound audio for movies, the first number represents the number of main speakers. The “.1” is used to represent a sound channel limited to optional subwoofer use.

Powered subwoofer inputs & controls you may (or may not) have

Example of a powered subwoofer with 2 types of signal inputs (speaker level and RCA jacks) along with sound controls. Note: Not all subwoofers have speaker level inputs, which makes it a problem connecting them to a receiver without a subwoofer output.

Powered subwoofers usually have several inputs and controls but it always depends on the brand and model. Here’s an example of what you’ll usually find:

• Power input (AC outlet power)
• On/off switch
• RCA input jack or a pair of jacks
• Subwoofer crossover frequency adjustment
• Subwoofer level adjustment know (the amplifier’s gain [boost] level)

The subwoofer input jack usually connects to a single mono output jack on the receiver, although some models provide stereo RCA inputs but can usually work with just a single mono connection. Mono (monaural) subwoofer output jacks combine both stereo channels into one so that no sounds are lost like can happen with only using the left or right side signal.

Example of the mono RCA subwoofer output jack found on many home receivers. These connect with a single male to male RCA cable to a powered subwoofer.

Some models also include speaker level inputs meaning they can be used with any modern or old home stereo receiver without a subwoofer output.

While that’s nice, if yours doesn’t have that feature, ordinarily you’d need to buy a different subwoofer and waste money.

In fact, some of the information you’ll find right now on the internet says that you have to buy another subwoofer if you don’t have a receiver with an output jack. That’s simply not true.

As I mentioned at the beginning of my article there are several ways to work around this problem.

DIAGRAM & EXAMPLES: Connecting a subwoofer to a receiver without a subwoofer output

1. Connecting a receiver to a subwoofer with RCA input jacks

Left: Example of a powered subwoofer with 2, instead of the typical 1, RCA input jacks. Right: An RCA Y adapter that can be used with a line level converter to connect to a subwoofer with a single RCA input jack.

For subwoofers with only 1 or more RCA input jacks (no speaker level inputs), a simple way to connect them to a receiver with no subwoofer output is by using a line level converter.

What is a line level converter, and how do they help?

Line level converters, also called speaker level converters or “hi-lo converters”, are small adapters that accept speaker wire connections and scale down the speaker level signal to a low level signal (RCA jack) type output used by amplifiers. They’re extremely handy in the car stereo world because they make it possible to connect a stereo without RCA outputs to any amplifier.

They’re not commonly used for home stereos but are still really useful there, too.

Shown here are two examples of line level/RCA speaker level converters that work well for home receiver/amp to subwoofer use. A line level converter takes the higher voltage speaker signal from an amplifier or home receiver and scales it down significantly so it’s safe to use with RCA inputs.

How much do line level converters cost?

Quality line level converters have a price range of about $15-$25 each. They’re connected to the speaker outputs of a radio, receiver, or amplifier. RCA cables are then connected to the jacks provided. The internal electronics not only scale down the speaker output voltage from a receiver but also help prevent noise from the audio path, too.

If you’re using a subwoofer with a single RCA subwoofer input jack, you may want to pick up a “Y” RCA adapter to combine both receiver channels on the output side into one.

Subwoofers with 2 (stereo) RCA jack inputs, however, are fine using standard male-male RCA cable pair.

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2. Subwoofers with speaker level inputs

If you own a subwoofer with speaker level inputs you’re in luck! You can connect these directly to your receiver’s speaker outputs, either by themselves (on unused speaker terminals) or at the same time with speakers connected to the receiver.

Subwoofers with this feature contain internal electronics that scale down the speaker signal from the receiver before it reaches the internal amp that powers the sub. It’s just a line level RCA converter already provided, essentially.

Additionally, there’s a low-pass crossover built in as well to produce great-sounding bass and no unpleasant parts of the music – just pure, low-end bass.

Connect these directly to the receiver just like you would another pair of speakers, either on unused speaker outputs. Generally speaking, you can connect these to receiver speaker outputs already in use as they will not bring down the total Ohms load the receiver or amp sees.

Most speaker to line level adapters have a relatively high input impedance (resistance), which will only have a marginal effect on the total speaker Ohms load seen by an amp or receiver. However, a few do have lower input resistance that can potentially cause an issue so they’re best avoided.

3. Using a mini amplifier for passive subwoofers

When wanting to add a single voice coil (SVC) passive subwoofer, several issues come up. Hands-down, the simplest solution is using a mini amplifier with a mono low pass subwoofer speaker output.

For this setup, you’ll do the following:

• Use a line-level RCA converter to get an RCA signal to the amplifier.
• Connect the passive sub to the subwoofer output.
• Use the AC-DC power supply to power it.

That’s pretty much it! Having a built-in sub crossover means the sound will be nice, clear bass without vocals much like a self-powered subwoofer provides.

Today’s small amplifiers are typically very compact in size as many use an efficient class D amplifier design. They’re sometimes called a 2.1 amplifier as they usually have both stereo speaker outputs and a dedicated subwoofer channel.

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Cost and other notes

They cost around $35 to $50 or so depending on the model. The downside is that if you want a ton of power, they’re not the best choice as many offer about 35W to 68W sub power. If that’s not enough you’re better off getting a more expensive amplifier.

4. Connecting receiver speaker outputs to a passive sub

Example of a passive subwoofer low-pass crossover. Passive crossovers, unlike electronic crossovers, work using capacitors and inductor coils instead of electronic components.

If you’re wanting to use a non-powered (passive) type of subwoofer, there’s still hope, although it can be a bit harder to find the right parts and set up vs using a powered subwoofer.

To use a non-powered subwoofer, as shown in my diagram above, you’ll use a low-pass subwoofer speaker crossover which is connected between the receiver and the subwoofer enclosure. These filter out higher frequency sounds before they reach the sub to help provide clear & nice-sounding bass only.

How to choose a subwoofer crossover and where to find them

Speaker crossovers like this are sold single channel (one speaker) or dual channel (2-speaker) models, depending on the brand & supplier. They also have to be matched correctly to the impedance (Ohms rating) of the sub.

For example, subwoofer crossovers designed for 8 ohm speakers must be used only with those. Otherwise, the sound filtering is radically different and won’t sound as expected since the crossover filter is based on the expected speaker impedance.

For example, you can’t correctly use an 8 ohm sub with a 4 ohm crossover.

Normally you’d choose one with a low-pass frequency of close to 100Hz or in that range. Speaker crossovers are sold where speaker parts & related components are sold as well as marketplaces like Amazon or Parts Express.

Stereo vs surround sound receiver subwoofer output differences

Unlike older or standard stereo receivers, surround sound receivers have a unique output that comes from the surround sound movie or music source. However, in regular stereo listening mode, they act the same as regular receivers.

One thing to bear in mind is that when connecting a subwoofer to a receiver without a subwoofer output, you can’t get a convenient “.1” bass channel like can with surround sound receivers.

On the other hand, it may not even be an issue. In fact, the surround sound receiver “LFE” (low-frequency) output is considered optional – hence the “.1” name. There is a drawback, though: for some movies, especially action or other types, movies and music in surround sound can sound even better.

While using a regular receiver to connect to a subwoofer means you can’t get quite the same effect, the good news is that in stereo mode, both new and old receivers have very similar subwoofer behavior when connected as you’ve seen here.

Also, listening to a surround sound movie through a stereo connection to your standard receiver is still good. For stereo, surround sound tracks are downmixed, meaning all the sound information is mixed into the two channels.

You’ll still get the same bass signal available that you can use to supply your subwoofer.