5 tips for adding a subwoofer to your stereo hi-fi system to boost bass performance

Any desire to add a subwoofer to your stereo hi-fi system will naturally stem from your desire to hear more bass, deeper bass, or both.

After all, typically even the largest floorstanders packed with woofers that are on the larger size won’t be able to produce the deepest bass frequencies to adequate levels – good luck to any trying to deliver those sub-bass notes in Billie Eilish’s bad guy.

And if you own standmount speakers instead, you will inevitably be missing out on even more low-end goodness due to their typically smaller cabinets and drive units.

There are relatively straightforward ways to boost your system’s bass performance, such as by moving your speakers closer to a rear wall or in a corner, giving your room acoustic treatment or toying with your amplifier’s EQ, but these solutions often come with consequences, and none will make the kind of significant impact that adding an external subwoofer to the mix can.

A subwoofer can boost and extend bass, and importantly relieve your speakers’ drive units of those tiring duties, reducing the potential for distortion and allowing them to concentrate on upper bass, midrange and treble.

Sure, subs are more commonly part and parcel of a surround-sound home cinema system (such as a 5.1 set-up) than a stereo one, but they can just as effectively play the same role alongside just two speakers in a traditional hi-fi – if integrated properly.

Indeed, this quest isn’t as simple as buying a subwoofer, placing it somewhere convenient and plugging it in and connecting it to your amplifier. There are crucial factors to consider to implement a subwoofer correctly based on your system equipment and room, and common mistakes to be wary of. Let’s dive into them.

1. Buy sensibly

Firstly, you want to buy a suitable subwoofer for your partnering speakers. Many subs share common features and functions that make them widely suited to all speakers, but common sense applies in that choosing a 16-inch/1600W sub for a pair of compact standmounts, or a high-end Perliston sub for modest Fyne Audio speakers, won’t be the smartest decision.

We would advise asking your speakers’ manufacturer for recommendations for your specific model (many nowadays have at least one subwoofer in their own lineup), or otherwise your local dealer.

2. Get the speaker/sub relationship right

On a sub’s rear panel, you will typically find three adjustments – one each for crossover, phase and volume – and they should be set according to the speakers they’re working with.

Let’s take the crossover first. The crossover level is the point at which your sub will take over from your speakers, delivering all the frequencies below that point and leaving the speakers to handle only the frequencies above it.

This should be set to around 10-15Hz above the lower boundary of your speakers’ frequency range (otherwise known as the ‘low-frequency cut-off’), which can often be found in the supplied paper manual, the technical specifications on the manufacturer’s product page, or within a What Hi-Fi? review!

Have old speakers you can’t find the frequency parameters for? A safe bet would be to set the crossover range at around 100Hz, if they are small, 60Hz for mid-size speakers and around 40Hz for something larger.

These values should be considered the starting point, and you should experiment from there.

This 10-15Hz figure generally ensures you don’t get too much bass or, worse, a hole in the frequency range that neither the speakers nor the sub is delivering.

So if you own, say, a pair of Fyne Audio 501E floorstanders, which have a stated frequency range of between 36Hz and 34kHz, you would set the connected sub’s crossover level to around 50Hz to start with.

Next up: phase. This setting ensures the movement of the speaker’s bass drive and sub’s woofer is ‘in phase’ with one another (when one kicks forward, so does the other). This aligns the timing of the sub’s frequencies with those being delivered by the speakers, and ensures the combined output arrives at your ears at the same time.

If they are out of phase, that means the sub’s woofer is moving backward while the speaker’s driver is moving forward, essentially – and counterproductively – cancelling the speaker’s bass delivery and reducing overall output.

Phase settings are either a dial or a flick-switch that can be simply set to ‘0’ or ‘180’. To find which one represents ‘in phase’, simply listen to a song with a constant, familiar bassline, such as Queen’s Another One Bites The Dust. It’s arguably easier to use dedicated subwoofer test tones, but they’re more accessible from an AV amplifier than a stereo one.

While you listen in your preferred listening position, get someone else to swap between the two settings. The one where the bass sounds louder and fuller is the right one.

If you can’t tell the difference after a handful of dial/switch swaps, it could be that your sub’s volume levels are too high and drowning out your speaker’s bass contribution, so try turning it down before repeating the process.

Lastly, volume, which can be labelled as gain instead. There’s no hard or fast rule (although lots of opinions on!) about whether it should be set at 50 per cent, below that or at maximum – it depends on your room, your sub and speakers and your preference for bass quantity.

In our minds, the easiest way to set volume is to start the dial at the mid-point, slowly turn it up until the bass starts to become too dominant for your liking, and then dial it back a notch.

Again, use music while doing this. Whether or not you’re setting up a sub in a stereo or a surround system, our advice would always be to play a song you like that contains varying bass frequencies – not a movie – to help you set it up, but it especially makes sense for a sub/stereo speaker pairing.

Want a more scientific method to set gain? Then dust off your Sound Pressure Level (SPL) meter and check out our expert how to set up your subwoofer guide.

3. Think about the sub’s location

Based on the assumption that your hi-fi room is smaller than the typical home cinema room in which you would find a fully fledged speaker package, and that your stereo set-up might well be neater and more compact than an AV one, you’re probably pretty determined to place your subwoofer by one of your front speakers.

While bass is less directional than midrange and treble, in a stereo set-up it generally makes sense to put the sub somewhere near and in between the two main speakers, if possible.

Your sub will likely sound better in some areas of your room than others due to its acoustics (determined by size, shape, flooring and furnishings etc), so it’s worth identifying them to see if you can accommodate one of those optimal spots.

To do this, place the sub in your usual listening position and play bassy music through it (but not through the speakers). Crawl around the room (or walk if you have large windows looking out to a pedestrianised street), mark the spots in which the bass sounds best, and put your sub in the most practical one. There, easy!

4. Don’t scrimp on the sub cable

Just as you wouldn’t scrimp on speaker wire or the audio interconnect cables connecting your sources to your amplifier – right? – you shouldn’t disregard the importance of a quality subwoofer cable.

Any RCA cable will do the job, but you want one that’s well constructed, well shielded and, of course, long enough to run between your subwoofer and amplifier. Check out our best audio cables buying guide for our top tried-and-tested recommendations.

5. Should you add two subs?

Just as two heads are better than one for solving a problem, having two subwoofers in your set-up is better than having one for delivering bass. But that’s not to do with getting more bass.

With two subs at play, the volume level on each would be lower than the setting of a sub working in solo, meaning that the overall bass quantity would essentially be the same.

The difference is that each sub would only be working half as hard, and therefore would sound better because of that.

Additionally, using multiple subs pressurises the room they’re in more evenly, providing a more balanced bass performance.

MORE:

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The best speakers you can buy, tried and tested by our review experts

29 of the best tracks for testing bass