Are you trying to connect a subwoofer to your receiver or amplifier, only to realize it doesn’t have a subwoofer output? This is a common problem, and there are at least a couple of quick and extremely easy solutions, as well as several more that are also pretty simple and straightforward.
So, before you go out and buy a new subwoofer or a new amplifier, read on – I will outline these methods as clearly as possible, and help you understand if they will work for you.
Can I Connect a Subwoofer if I Don’t Have a Sub Out?
If you are trying to run a line from your receiver, amplifier, or preamplifier to your subwoofer, but the receiver or amp doesn’t have a special output for subwoofers, it can be frustrating – but there are a few ways to proceed.
But before we get into some of the more involved answers, you may be able to use one of these 2 extremely quick and simple solutions.
- If your receiver has a line-level output – and they all should – you can buy the wonderful little Fosi Audio TP-02 Subwoofer Amplifier, which will do two different things:
- For active powered subs, it will give you a subwoofer output connection!
- For passive subs, it will give you a superb amplifier optimized for bass frequencies and designed to make any subwoofer sound amazing.
Setup for Active Subwoofers or Passive Subwoofers couldn’t be easier – either:
- Run interconnect cables from your receiver’s line outputs to the Fosi and then from the Fosi to your Active Subwoofer. You can get all the cables you need with the cheap and well-made Cable Creations 3 Lead Interconnects – intended for video, but perfect for this use.
- Run Interconnect cables from your receiver’s line output to the Fosi and then run speaker cable from the Fosi to your Passive Subwoofer’s speaker input connectors. For this purpose, I recommend Cable Creations 2 Lead Interconnects, and for subwoofer speaker cable I like a thicker gauge, like the excellent InstallGear 14 Gauge Wire.
That’s all there is to it. Your subwoofer will only get the low frequencies it is designed for and will work perfectly and sound great, and you can even adjust the subwoofer’s sound and volume/level on the Fosi’s front panel.
- If your subwoofer has speaker inputs – whether it is an active powered subwoofer or a passive unpowered subwoofer – and it also has a “low pass filter” or “crossover” built-in, you can simply connect your receiver’s Speaker 2 or Speaker B outputs to the subwoofer (the Speaker 1 or Speaker A outputs are used for your main speakers), and it should work beautifully!
- You can determine if your sub has a low pass filter or crossover by checking the back panel, where it should be clearly marked, or by consulting the owner’s manual. And again, for the subwoofer speaker cable, I do think a thicker gauge sounds better, like the excellent InstallGear 14 Gauge Wire.
- One very important no-no to mention. Despite what other how-to guides say, you should never try to connect your subwoofer and your main speakers to the same outputs – that is, always connect your main speakers to the Speaker 1 or Speaker A connectors and the sub to the Speaker 2 or Speaker B connectors – otherwise you can really overwork and even damage your receiver, and anyway it just won’t sound as good.
But now let’s explore some other ideas and options – in the next two sections, I will explain some solutions for powered active subwoofers and passive subwoofers.
If you have an active subwoofer check out the first section, just below, and if you have a passive subwoofer CLICK HERE and you will be taken to the second section further down.
How To Connect an Active Subwoofer to a Receiver Without Subwoofer Output
If you have a powered subwoofer, also called an active subwoofer, it has an amplifier built-in, so you can run a low-level output from your receiver into it. The active sub will have an RCA input jack on the back panel to facilitate this.
- Now here is a very important point, which most other guides seem to completely miss – this is the only information you can get from lots of experience, or from searching through audio and audio/video forum posts and their often seemingly endless replies, late at night while the rest of the family is peacefully asleep…
You do not want to run a normal signal into a subwoofer! That is, you don’t want to run an audio signal that has both high-frequency and low-frequency information – like an auxiliary output, a tape output, or even a preamplifier output – directly into your sub. The subwoofer output (the very thing you don’t have) sends only bass notes to the sub, which is very important.
Making the sub deal with all of that unwanted and unneeded high-frequency and midrange-frequency signal will result in poor sound. In addition, if you run an auxiliary output or a tape-out output directly into the subwoofer, this output bypasses the receiver’s volume control, and your subwoofer will play dangerously loud – especially if it doesn’t have its own volume control. You can easily and very quickly damage your sub this way – and maybe your hearing as well!
So let’s look at a better, and far better sounding, solution:
Using A Separate Subwoofer Crossover
To make sure that only low-frequency audio signals get to your active subwoofer, you can use a crossover that filters out the mids and highs.
This is a brilliant way to go, and requires only two little plugs which connect to your wires – the FMOD Crossover Pair is the perfect product for this.
So basically all you have to do is run a normal interconnect wire from the preamplifier output of your receiver – like this cheap and excellent AmazonBasics 15 Ft Interconnect – and plug the other end into the FMOD plugs.
Then you plug the FMOD plugs into your subwoofer’s inputs and you are good to go.
The only other issue is that you might have only one RCA input on the back of your subwoofer, which means you should plug the FMOD plugs into what is called a splitter, which will take the two down to one connector – I like the also cheap and excellent AmazonBasics Splitter.
- It’s not recommended to use a normal auxiliary output or a tape output for this, because – unlike the preamplifier output – they bypass the receiver’s volume control and always output full volume. If your sub doesn’t have its own volume/level control – or even if it does and you’re not careful – you will get painfully loud volume and may blow your sub!
What if I Don’t Have a Preamplifier Output?
Excellent question – and indeed, if a receiver doesn’t have a subwoofer output it also might not have a preamplifier output.
Now we have to be a bit more creative, though the answer is still simple enough. We need to run the audio signal from the speaker outputs on your receiver, and then into what is called a line-level convertor – a small box that reduces the high current of speaker outputs to the much lower current needed by a subwoofer input.
- Please note, before we proceed – if your active subwoofer has speaker inputs, and also has a “low pass filter” (the same thing as the crossover we discussed earlier) you can skip all of this, and simply run the Speaker B or Speaker 2 outputs from your receiver into those inputs – case closed!
You can tell if the sub has a low pass filter by looking at the back panel – where it might be labeled as such, or even have a frequency control knob – or by checking the subwoofer’s manual.
But so many powered subs don’t have speaker inputs, only RCA inputs, so we continue on with our creative approach – a solution often used in car stereo setups, but which works just as well for home audio.
Again, all we do is get a line-level converter, like the very basic but effective Bully Performance Audio Convertor, and connect that to the Speaker B or Speaker 2 outputs on the back of the receiver. Then you proceed just like with the above solution – that is:
Connect RCA cables, like the AmazonBasics 15 Ft Interconnect, to the female outputs of the Bully Convertor, connect the FMOD Crossover Pair low pass filters to the other end, and then plug them into the back of your subwoofer – using a two plug to one plug AmazonBasics Splitter if necessary.
How To Connect a Passive (Unpowered) Subwoofer to a Receiver Without Subwoofer Output
Because a passive subwoofer doesn’t have an amplifier built-in, it needs the power from your receiver’s amplifier, so we want to use the receiver’s speaker outputs for connection.
And here’s where so many of us make an assumption that may not be true – that is, that we actually need to have a subwoofer output on the back of our receiver.
In fact, that sub-out is way too weak to power a passive subwoofer, and won’t help us here anyway.
The good news is that the overwhelming majority of passive subwoofers these days have a crossover, or low pass filter, built in. This is important because, as I mentioned earlier, you don’t want to run high frequencies to the subwoofer, and the crossover or low pass filter will filter out all of the highs and mids, and only let the low-frequency bass signal pass through.
So if you have a subwoofer with a built-in low pass filter or crossover, you can simply run the Speaker 2 or Speaker B outputs to it and you are all set!
- You can tell if the sub has a low pass filter by looking at the back panel – where it might be labeled as such, or even have a frequency control knob – or by checking the subwoofer’s manual.
- You should check your subwoofer to see if it has an extra set of speaker wire outputs for the main speakers – if it does, you can connect your stereo speakers to those outputs, instead of directly to the receiver.
This may give you better sound since the speaker outputs from the subwoofer should filter out all of the low frequencies (which are being reproduced by the subwoofer) and pass only mids and highs to the speakers.
But please, experiment! Try both connection methods and see which sounds best to you.
What if my Subwoofer Doesn’t Have a Crossover?
If your subwoofer doesn’t have a crossover you should, in theory at least, be able to connect a simple crossover or low pass filter to your speaker wires, placing it between the receiver’s speaker outputs and the subwoofer’s speaker inputs.
But, somewhat mysteriously, it is nigh-on impossible to find such a beast – at least for home audio setups. They are, however, quite common for automobile installations, and luckily these car audio crossovers will work just great for our purposes.
Again, the basic idea here is that you don’t want to run the full signal from your receiver’s Speaker B output – with all of the midrange and high frequencies – into your subwoofer, mainly because the sound quality will really suffer.
So instead you can get a pair of in-line crossovers, like the excellent DS18 Passive Crossover 2-Pack, and simply connect the receiver’s speaker outputs to the crossover’s inputs, and then the crossover’s woofer outputs to the subwoofer.
You can also connect the crossover’s tweeter outputs to your main speakers, which will work fine, but feel free to experiment – that is, try the main speakers connected to the Speaker 1 or Speaker A outputs of your receiver and the subwoofer/crossover connected to Speaker 2 or Speaker B, and then try both speakers and subwoofer connected to the crossover, and see which sounds better to you.