How To Connect A Subwoofer To An Old Amplifier Or Vintage Receiver

Got a vintage amplifier or receiver? When it comes time to add some great low-end bass you might be scratching your head wondering how – and if – you can add a subwoofer. 

The great news is that there are several ways to connect a subwoofer to an old amplifier or vintage receiver.

Even better, it won’t cost a lot, either! Read on and I’ll share with you 3 ways to connect a subwoofer along with clear subwoofer diagrams anyone can understand.

Home stereo subwoofers explained

Passive vs active home subwoofers diagram

Comparing passive (non-powered) vs active (powered) home stereo subwoofers. Powered subwoofers have an internal amplifier and one or more signal input options: speaker inputs, RCA input(s), and in some cases, digital audio inputs.

There are two kinds of home stereo subwoofers: powered (“active”) and non-powered (“passive”).

  • Powered subwoofers use a low-signal signal which is boosted greatly using the built-in speaker amplifier, power supply, and 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 the bass enclosure which is directly wired to the speaker terminals or a passive bass crossover inside. These types are less common.

How does a subwoofer work?

An amplifier boosts the low-level input signal in order to drive the subwoofer’s voice coil with sufficient power and move the speaker cone, producing sound. As the cone moves the air inside of a specially designed enclosure (speaker box) deep bass, contained in the musical input signal, is produced.

They’re designed for only low-end bass and not voice or other musical instrument frequencies.

A powered subwoofer includes an amplifier already inside the subwoofer enclosure. It also has a built-in low-pass crossover to block higher sound frequencies in order to produce clear and great-sounding bass only.

For non-powered subwoofers the problem comes when you connect one to an amplifier or receiver’s outputs without a crossover – it sounds terrible!

Old amplifiers and vintage receivers vs new receivers

Unlike older amplifiers, more modern home stereos and especially home theater receivers have a subwoofer output jack (or pair of jacks) dedicated to this bass signal a subwoofer uses to create sound. This is usually from stereo music signals or the subwoofer (“.1”) channel sound in multi-channel surround sound material such as Dolby Digital or DTS.

For example, you may see terms like “5.1” or “2.1” speaker systems or surround sound audio listed for movies. In this case, the first number represents the number of main speakers. The “.1” is used to represent a sound channel limited to only bass for subwoofer use.

Older amplifiers and receivers don’t provide a subwoofer output so we’ll need to connect a subwoofer using some other ideas.

Powered subwoofer inputs & controls to know

Powered subwoofer example with inputs and controls labeled

Shown is an example of a powered subwoofer’s rear panel with 2 kinds of inputs: speaker inputs and RCA (low level) input jacks. Note that not all subwoofers offer speaker level inputs, meaning if yours doesn’t have them it’s a bit harder to connect the bass signal input.

Powered subwoofers usually have a few different inputs and controls. It always depends on the particular brand and model you buy.

Here’s what you’ll usually find on most:

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

In most cases, a subwoofer input jack, if you had one on a receiver, is a “mono” (monaural, 2 stereo channels combined into one) signal you connect with a single RCA cable.

Receiver subwoofer output jack example

Shown: What a receiver with a subwoofer output jack looks like as found on many newer receivers. These connect to the RCA input jack on the subwoofer, if present.

Of course, if you’re reading this it’s because you don’t have a receiver with a subwoofer output. 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.

Subwoofers with speaker level inputs are great to have for exactly this reason as you can connect them directly to an older amplifier or vintage receiver’s speaker outputs.

Even if you buy (or already own) a subwoofer without speaker level inputs, it’s ok – there’s another way to basically connect it essentially the same way!

Below you’ll find a diagram showing how to connect an old amplifier or receiver without a subwoofer output easily.

Diagram & examples: Connecting a subwoofer to an old amplifier or vintage receiver

Diagram showing how to connect a subwoofer to an old amplifier or vintage receiver

1. Connecting an old amplifier or receiver to a subwoofer with RCA input jacks

Example of a powered subwoofer RCA jacks & RCA Y adapter cable

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.

If you’ve got a subwoofer with 1 or 2 RCA input jacks and no speaker level inputs, here’s a simple and high-quality way to connect it: by using a line level converter.

What is a line level converter and how do they work?

Line level converters (also called RCA speaker level adapters) are small electronic devices that connect to speaker outputs from an amp or receiver and scale down the higher-voltage signal to a low level (“line level”). The outputs are RCA jacks which can then be connected to any amplifier or subwoofer with RCA jacks.

 While you almost never see them used for home stereo systems, they’re extremely handy in the car stereo world because they make it possible to connect a stereo without RCA outputs to any amplifier or powered subwoofer.

Likewise, they can be used for home stereo amps and receivers, too!

Image showing examples of line level RCA converters

Shown here are two examples of line level/RCA speaker level converters that work well for home receiver/amp to subwoofer use.

How much do line level converters cost?

Line level converters vary in price a bit depending on the quality and features, selling around $15-$25 or so in many retail stores and online stores.

How to use a line level converter

To convert speaker level outputs from your amplifier or receiver to RCA jack subwoofer outputs, you’ll connect the provided speaker wire connections (marked by colors and striped) just like you would regular speakers. You then connect RCA cables (or a single cable, depending on your particular one) to your powered subwoofer.

The internal electronics not only scale down the speaker output voltage from a receiver but also help prevent noise from the audio path, too. Most, but not all, speaker level adapters do not need a power source.

If your subwoofer has 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 a single mono RCA plug.

Subwoofers with 2 (stereo) RCA jack inputs will need a standard stereo male-male RCA cable.

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2. Connecting a subwoofer with speaker level inputs

Example of subwoofer speaker level inputs

A subwoofer with speaker-level inputs is especially easy to connect to your older amplifier or receiver! To do so, just connect to the speaker outputs on the source unit using speaker wire and then to the matching inputs on the subwoofer. You can even power speakers from the amp or receiver at the same time.

If your subwoofer has speaker level inputs built-in you’re in great shape! Just connect them directly to your amplifier or receiver’s speaker outputs, either to unused speaker terminals or at the same time (in parallel) with speakers connected to the receiver.

Just like an off-the-shelf line level RCA converter I mentioned earlier, the subwoofer’s internal electronics will scale down the speaker signals to a much lower line level signal the internal amp can use.

You can still expect very nice sound quality as the signal used is just divided down and isn’t changed. Because speaker level inputs have a very high input impedance (total input resistance), in most cases it won’t hurt to connect them to your receiver or amp at the same speaker wire terminals where speakers are already connected.

To do so, you’ll just connect them in parallel: positive speaker inputs to positive speaker outputs and negative speaker inputs to negative speaker outputs.

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.

Note: Subwoofers with speaker level inputs and outputs provide a way to easily connect both at the same time. The outputs are internally connected to the input connectors, making it easier to add speakers and the subwoofer to a receiver simultaneously.

3. Connecting an amplifier’s speaker outputs to a passive (non-powered) subwoofer

Example of a passive subwoofer low pass crossover

A passive subwoofer low-pass crossover, unlike an electronic crossover, works using capacitors and inductor coils instead of electronic components to filter out the unwanted higher-frequency sound that would otherwise go to the subwoofer. This lets you power the subwoofer with only a lower bass sound similar to how a powered subwoofer works.

Using a passive (non-powered) subwoofer is definitely not as easy as a powered one. The good news is that it can be done, and relatively easily, too. In fact, it you don’t have to worry about going broke, either, although you will need to do a bit of shopping.

To connect your amplifier or receiver to a non-powered subwoofer as is shown in the diagram above, you’ll need to pick up a low pass crossover that you’ll connect between the amp or receiver and the subwoofer.

These will filter out sounds above the crossover frequency and provide only a nice bass sound to it.

How to choose a subwoofer crossover

Speaker crossovers like the one shown are sold both in a single (one speaker) or dual (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, for an 8 ohm subwoofer, you’ll need to use a crossover designed for 8 ohm speakers. Otherwise, the sound filtering is radically different and won’t sound right since the speaker load will change how the crossover filters the sound quite a lot.

Normally you’d choose one with a low-pass frequency of close to 100Hz or close to that. You may need to shop around to do so.

Where to shop for passive subwoofer crossovers

Speaker crossovers are sold where speaker parts & related components are sold as well as marketplaces like Amazon or Parts Express. Other speaker specialty stores where replacement speaker parts are sold may have them, too.

Stereo vs surround sound receiver subwoofer output comparison

Stereo vs surround sound receiver differences diagram

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.

Just as a side note, one thing to be aware of is that when you connect a subwoofer to an old amplifier or receiver you won’t be able to get the separate dedicated bass sound channel (.1 channel) like you can with a surround sound receiver. 

Those are able to extract the dedicated bass sound from a DVD or other media and route it to the subwoofer output jack. On the other hand, it might not even be a problem.

Did you know? The surround sound receiver “LFE” (low-frequency) output is considered optional – hence the “.1” name. 

Surround sound receivers and amplifiers are designed so that you can play nearly all the sound through the main speakers if needed.

In some cases, for example, some movies and music use the bass channel to really draw you into the experience. Using a receiver without that output means you can’t get the same effect, but that’s only for surround sound mode.

The good news is that in stereo mode, both new and old receivers & amps have very similar subwoofer behavior when connected as you’ve seen here. In other words, you probably won’t really miss it if you’re using an older receiver or amp.

That’s just something to be aware of in case you’ve considered upgrading at some point.

More articles with speakers, speaker wiring, and diagrams to help

I’ve got some other great info to help you learn more and get your system going:

Questions, comments, or etc?

Please feel free to leave a comment or question below – I’d love to help, and it’s appreciated. Note: please provide specific information like brand & model numbers, speaker ohms, and so forth so I can best help you.

Need direct help? Feel free to contact me here via my Contact page.

Your comments are welcome!

  1. Hello there. If I where running my sub with a single output into a vintage amp as the diagram explains perfectly BUT my sub had no volume. What would happen? And is there anyway of rectifying this? Thanks for this article!

    • Hi Mike, can you be more specific about how you connected it? I assume by “single output” you mean “input” for a powered subwoofer – is that right?

      I need more details in order to help.

  2. No sir. I have a sub from a 2.1 system. I recently bought an amp and speakers as an upgrade. I was not particularly looking for a sub but after having one so long I kind of miss the sound. I was wondering if I could hook that up somehow. Its a single one RCA leave out from a cable. No ins or outs. My though was to get a female to 2 male splitter then a line out convertor then hooking it to the speaker ports…but then theres no volume control. I will eventually just but a new, proper sub but after this initial lay out it may be a while

    • Hi Mike. I’m sorry, but I’m still not clear on specifically what type of connections you do (and don’t) have available. It’s very important in order to help you the best I can.

      For example:
      • You have a passive (non-powered) subwoofer, correct? Model number? Is it a single voice coil/8 ohm, or dual voice coil (DVC)/etc.?
      • Does your receiver have a low-pass/”LFE” RCA jack? Or only speaker outputs and no RCA output jacks?

      It may be helpful to send me the model numbers of the amp/receiver and the subwoofer so I can see what you’re dealing with. You can also reach me directly by email/send a message via my Contact page here.

      • Hi Marty. Ok so my Passive sub was part of a 2.1 Laptop setup a while back. (Fc360 Microlabs) I have no idea whether its SVC or DVC.
        My receiver is an old Trio KA1500 and only has speaker outputs along with standard tape/phono/aux/tuner ports only and im running them through Monitor Bronze BR1 speakers.
        I know like i said buying an active sub would be best but just a random idea to maybe see if this works until I get the money to buy a sub eventually. THANK you.

        • Hi there, ok if it’s not an active sub then I would test the sub with a test meter or even a 1.5V or 9V battery across the terminals to make sure it’s working.

          If you get no sound from it then it’s some other issue. I’m a bit confused as the pic of the FC360 2.1 set I found shows it using RCA connectors & a powered sub from what I can tell.

  3. Hello, I have a question about the diagram of connecting a powered subwoofer with speaker level inputs. The diagram looks like I would connect the subwoofer into the same outs that I had connected to my main pair of speakers. Is it okay to have wires out that go to two my main floor speakers and the subwoofer? Will that affect how my speakers perform? Thank you so much for this great article.

    • Hi Curtis. No, in nearly all cases it shouldn’t have any effect. That’s because speaker level inputs are typically “high impedance” (very high resistance, basically) which can be used in parallel with speakers. The amp or receiver should still see an 8 ohm load (or whatever ohm rating your speakers are.)

      For sure I wouldn’t have recommended it if that wasn’t a safe thing to do. Thank you for the compliment on my article as I work hard on them. :)

  4. Thank you for some of the best technical writing I have seen in a long time. Your clear, no B.S. explanations are most appreciated. Question- i have a powered, active sub with line in/out connectors and that is working fine with one set of speakers (right speaker). I was given another sub (Fisher SW-9050 tower) “with 2 active Bass drivers” according to the label, which just has +/- speaker inputs only. If I understand your article correctly I can run another pair of wires from my left amp output to this sub? ( as opposed to connecting the Left speaker in parallel to he sub?) The speakers are 4 ohm Thiels. If I pick up a 3 channel power amp, can I devote the 3rd channel to his Fisher sub?
    Thanks in advance!

    • Hi Richard I appreciate your feedback on my writing. I try hard!

      If the SW-9050 is a powered subwoofer, you should be able to connect it to any speaker output terminals either alone or also in parallel with speakers already connected. That’s because the input resistance (“impedance”) of a powered subwoofer is very high and shouldn’t cause an issue.

      If you want to use the signal outputs of a 3 channel power amp you can use any speaker output connection. Not that if the SW-9050 is not self-powered you’ll have to use a dedicated amp channel output. (I could not find pictures or information about the SW-9050 so I’m not 100% clear what you’re dealing with in this case. Most powered subwoofers should have RCA inputs also, for example).

      If necessary you can always send pics etc to my email address which you can find on my contact page. I hope this helps!

  5. Hey Marty, my receiver is built with a passive subwoofer output (has two normal speaker(subwoofer) terminals) and the active subwoofer I want to use only has an RCA input. So would it work if say, I take a normal RCA and cut the other end and then split the neg & pos of the RCA, put it in the receiver and the uncut in the sub?

    • Good morning, Senzo. No, I’m sorry but that won’t work. You’ll need to use a line level adapter as I showed in the article in order to do that.

      It’s not just a matter of the physical connection but also that the signal levels aren’t compatible. Example #1 in the diagram shows that (although you don’t have to have L & R speaker inputs – you can use a single speaker channel)

  6. Dear Marty, I own an older Marantz with no dedicated sub out, but it has a preamp out, to connect a power amplifier. Can is safely connect an active subwoofer via rca? The subwoofer has a rca entrance ( – +) In my opinion, an active subwoofer is a type of amplifier, so it should work, but I prefer some advice :-)
    Greetings, Jan (Netherlands)

    • Hello Jan. Yes, you should be fine connecting it with the RCA output. Also the powered subwoofer should take care of the low-pass filter as it’s normally built into it was well.

      Greetings! :)

  7. Hello, I have a mint condition outboard DBX XB150 Subwoofer Power Amplifier. I also have a powered 12″ subwoofer but the amp inside has died. I want to remove the old amp, keep the 12″ sub cone and box, then connect with wire either the LEFT pos/neg speaker input (or) RIGHT pos/neg speaker input to the outboard sub amp (XB150). The sub amp has L/R Receiver inputs and L/R Speaker outputs. Is This possible? Or safe? Any suggestions would be helpful. Thank you.

    • Hi Mark I don’t see any reason why that wouldn’t work as long as the 12″ subwoofer has the right impedance for the XB150. I would check and make sure.

  8. Hi Marty. Both the 12″ subwoofer AND the XB150 sub amp are 4ohm. Since the sub amp has both L pos/neg and R pos/neg speaker inputs I guess it shouldn’t matter which side I choose. Thank you for your help.

    • Ah ok, got it. Yes, I don’t think should matter which side you use unless there’s something unusual about the design. I think it’ll likely be fine however. :)

  9. First of all you guys are God sent you are right on the point of what i wanted to know and THANK YOU VERY VERY MUCH ,how you explained it could not be any better ,I think you need to show other companies on how to break thing down on explaining a object or a system GOD BLESS AND HAVE A GOOD DAY, AND PLEASE SAY SAFT VICTOR

  10. So happy to see your dedication to help people. I need some technical help that;

    Whether subwoofer out signals are similar to normal audio signals (to be amplified) excluding high or mid range frequencies?

    Whether subwoofer out signals from a Yamaha receiver can be amplified through any amplifier equiped with equilizer and can be listened on speakers attached to the amplifier?

    • Hello Saijid. Subwoofer out signals are normally low-pass filtered, meaning that only bass is sent out – no midrange or highs.

      Yes, you can amplify subwoofer out signals with any amplifier as long as it has line level (RCA) inputs.

  11. Marty – Great article and great writing!

    Getting back in home audio game. Current equipment. New Kliptsch RP-8000 speakers. Sub is a Klipsch R-120SW run by a 1977 Pioneer SX 780, w A +B. Sub has duel RCA’s only.
    1. I’m running all 4 speaker outputs from B speakers to Sub using converter?
    2. Tell me which line level converter you recommend.
    3. Do I lose any sound quality w/RCAs? Compared to Sub with speaker outputs?


    • Hi Joe & thanks for your comment.

      1. You can use speaker outputs A or B with the LOC, doesn’t matter (as long as it’s a full-range speaker output channel; some are not on surround-sound receivers/home theater receivers.)

      2. The SCOSCHE LOC80 or PAC LP3-2 are two good choices (and affordable too).

      3. Not really – even if you do a tiny bit, if everything’s working right it would be next to impossible to tell any difference. If for some reason something isn’t quite working well together there could be an issue, but that shouldn’t be the case. Usually it’s only with full-range sound – and if someone has VERY discerning hearing – that they might be able to tell.

      Have a good day. :)

  12. Hi Marty! Happy New Year! Guess where I’m still a bit confused is how the vintage powered amp without a sub out connection sends an amplified signal to a subwoofer already self powered. Which power source takes control, the amp or the powered sub? I’ve got a mint Marantz 1250 integrated amp pushing SVS Ultra Bookshelves, but I’m adding an SVS 2000 sub to let the SVS bookshelves focus on midrange. Please clarify to this old geezer how i set this up so that the sub operates without conflict between 2 powered sources. Thx brother! John

    • Happy New Year, John. :) A powered subwoofer does all the work, so there’s no power draw needed from your receiver. In the case of a powered subwoofer with speaker level inputs, it doesn’t draw power from the receiever’s speaker outputs as the speaker level inputs are extremely high impedance (resistance).

      In your case, the SVS2000 only has RCA inputs, so you’ll need to follow example #1 in the diagram and use a line-level converter commonly used for car audio. I have some examples shown in the article.

  13. Hello! Can I use rec out (output for recording to a cassette tape) from an amplifier as a line out for subwoofer? It won’t burn it out?

    • Hi, it should work if as long as there’s a signal output. I’m not 100% if it depends on the amp’s controls or not. If the REC outputs are RCA line-level outputs it’s fine and won’t hurt anything.

  14. Hi there Marty,
    Happy new year! I’m really impressed with your generosity and sharing your knowledge here. Thank you!

    I am trying to connect a Klipsch Sub Woofer to my old Sansui amp, that only has one speaker line.
    I had bought the PAC LP7-2 L.O.C, and I noticed it has an additional wire for power. I wonder if it needs external power or will it feed from the high output line running from the amp?



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