How to Connect a Subwoofer to An Old Amplifier?

Any true audiophile will tell you that there cannot be a complete sound system without a subwoofer. You can get by without having one if you only listen to some specific genres or types of music, like classical music played by a symphonic orchestra. However, the experience of listening to drum and base, for example, with and without a separate subwoofer, is an entirely different story. There is a frequency range your speakers can’t produce. But that is not all. Adding a subwoofer into the mix relieves the rest of the system from even trying to produce that frequency range, giving you much better sound quality in the rest of the frequency spectre.

What is a subwoofer?

For those who may not know this, humans can hear the sound carried by air vibrations in the frequency range of 20 Hz-20.000 Hz (or 20 kHz).

This frequency range is generally divided into subsections:

  • 20Hz – 100 Hz range is called Low frequencies or sub-base.
  • 100 Hz -1 kHz – Low mid-range
  • 1 KHz – 10 KHz – High mid-range
  • 10 kHz – 20 kHz High frequencies

For every subsection, there are different types of speakers, specially designed and best suited to produce them.

Subwoofers are in charge of producing the lowest frequencies of the range. Depending on the intended use and quality, they will cover 20 Hz t- 200 Hz. The better ones will usually take over anything from 120 Hz and below.


Higher frequencies are produced, depending on the setup, by the woofers or midrange drivers (120 Hz-10 kHz). The high frequencies are reserved for the most miniature speakers, called the tweeters.

Now that we got this out of the way, it is clear why you can’t get full sound without the sub-woofer. You can especially notice this when you are watching a movie or show with many effects like explosions. Those won’t sound right if there is no subwoofer in your system.

Newer sound systems, regardless of whether you are buying them as a set or not, usually have a separate port for the subwoofer, making it easy to connect. But what if you have an older amplifier that doesn’t have a special jack for the sub? Well, in that case, everything will depend on what kind of subwoofer you got and what kind of ports you have available on your amp because “There is more than one way to skin a cat”, as they used to say.

What kind of subwoofers can you have?

Subwoofers can be active or passive.

Active subwoofers have their own power source, independent from the amplifier. All they need to play correctly is a proper signal input from the amp.

A passive subwoofer needs power from the amplifier to operate, and it will be as good and loud as the amp you connect it to.

Subwoofers can be active or passive

If you’re using a stereo system, this signal coming from the amp to the subwoofer should contain channels, left and right. If it only contains information for one channel, you won’t hear the bass if it is being played on the other.

How to hook up active subwoofer to an old amplifier

Depending on what type and age of amplifier you got, you might have a mono output on it. If you do, you should find a matching port on the subwoofer and use that as a signal source from the amp to the sub.

active subwoofer


If it’s an older amplifier, it doesn’t have dedicated RCA subwoofer output nor mono output.  Therefore you’ll have to improvise a bit. To make this work, you’ll need a few things:

Your amplifier needs to have two speaker outputs. For sets A and B, and it has to be able to play them simultaneously.

The active subwoofer needs to have a high-level input option and not only regular RCA.

If you checked both of these boxes, set A on your amplifier to connect the regular stereo speakers. Use set B to connect the subwoofer through the high-level input, and you should be fine. Just play both sets at the same time when you want to hear that extra bass. You can even turn it off just by turning off B on your amp.

How to hook up a passive subwoofer to an old amplifier

passive subwoofer

This option is much easier. If you have a passive subwoofer, you will have pass-through connectors on it. This option means you will be able to connect the subwoofers BEFORE the speakers. Your regular speaker cables for both channels will go from the receiver to the subwoofer, allowing it to receive both channels. Then you will be able to connect another set of cables from the subwoofer to both stereo speakers and have the best quality signal and sound for the entire system.


Any true audiophile will tell you that you can’t have a proper hi-fi system without the subwoofer. Yes, many speakers can go very low in frequencies and yes, you might get the ones that go almost as low as the sub. Still, if you add that specialized unit in charge of bass, you will not only get the better low frequencies, but the rest of the spectrum will also sound much better. This improvement happens because your regular speakers won’t have to struggle with the low frequencies anymore. You will be much more satisfied with your sound system as a result.

So, you’ve got a new subwoofer, and you need to hook it up on your old amp that doesn’t have specialized RCA connectors for the sub. What to do? There are two main types of subwoofers, and each is connected differently.

Option number 1 – Active subwoofer

An active or powered subwoofer is the one that has its power and needs a separate power supply to work.

For this to work, your amplifier needs to be able to power two sets of speakers simultaneously. Those are usually named A and B or FRONT and REAR or on some amps MAIN and REMOTE.

The other thing you need to check is that the subwoofer has high-level input on the back.

If all this is the case, then hook up regular speakers on the A and active subwoofer on the B using high-power input, and you’ll be fine.

Option number 2 – Passive subwoofer

The passive subwoofer doesn’t have its power but relies on the amplifier to give it “juice.”

Things would go much easier if you got a passive sub. If that is the case, all you need to do is put it between your stereo speakers and the amp.

In other words, get another set of speaker wires.

One set of wires will go from the amp’s output to the subwoofer, and the other will go from the subwoofer to the stereo speakers.

It’s as simple as that. Enjoy!

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