Introduction

In small spaces such as bathrooms, en-suites, or dressing rooms, it may not be desirable or possible to install a typical stereo pair of speakers. Installing a single speaker in a multiroom audio system using products like the Sonos Amp is possible, but here we'll discuss why stereo sound is desirable, the right way to cable for a single speaker, the wrong way to cable for a single speaker, common mistakes, and possible solutions to poor wiring.

The importance of stereo and how to wire for single speakers

First, a little history lesson... Proper audio for music (so not your portable Bluetooth speaker!) has been produced in stereo since around the late 1950s. Having separate left and right channels mixed and recorded for stereo creates a soundstage which is much more immersive than single channel mono audio.

Two speakers will always be better than one, and stereo sound will always sound more involving than mono, so when installing a music system it is always recommended to install stereo pairs, or single stereo speakers. A single stereo speaker is a special kind of speaker which typically has a single bass/mid driver, two tweeters, and separate left/right inputs. This allows a single speaker to produce an element of stereo sound.

The proper way to install a single speaker on the majority of systems is to use a single stereo speaker and wire it to the amplifier with left and right feeds just like a stereo pair. Indeed most amplifiers since the 1960s have been stereo, and should always be used with a pair of speakers, or a single speaker specifically designed to emulate that. This is no different today, so always think in stereo when designing or wiring a system.

Common wiring mistakes & why single mono speakers are bad

Stereo amplifiers do not typically like to be run with an uneven load, ie. only one speaker connected to one channel (or indeed two speakers on one channel and one on the other). Depending on the type of amplifier design, this could actually cause permanent damage to the circuitry. Modern digital amplifiers like those found in the Sonos Amp are a little more forgiving, but despite this, even channel loads are always the right thing to do to avoid any long term damage to the system.

Assuming that speakers are like downlights where you can just put one wherever you want is one of the most common mistakes when designing and wiring for multiroom audio systems. We are contacted by people on a daily basis who have wired systems in this way, and it can be a big problem that is often costly or difficult to rectify. Proper planning and a clear understanding of how to wire for multiroom audio will prevent a lot of headaches later on.

So... and I can't stress this enough... if you want a single speaker in a bathroom or other space, use a single stereo model and wire it with either 2x regular 2-core speaker cables, or a special 4-core cable. Wiring for single mono speakers, or just putting a 2-core speaker cable wherever you think you need a speaker, is very bad practice and will inevitably create problems when trying to connect amplifiers to drive them.

Aside from amplifier connection issues, individual mono speakers cause problems with other equipment too. For example, speaker switches are also designed to operate in stereo (this isn't the 1940s after all!), and some switches, like the Audioflow smart switches, will actually refuse to operate and protect themselves if you try to connect a single speaker to the outputs.

If you are in any doubt regarding the wiring specifications for a single speaker or an entire house, please get in touch with us for advice. Incorrect wiring is incredibly common, even when carried out by professionals who may give you the impression that they know what they're doing! Do yourself a favour and speak to the experts.

Help... I've wired a single speaker with only one 2-core cable

This is not a good situation to be in, but there are a couple of things you can do to rectify the situation. Here we are going to be specifically discussing Sonos, but many other systems like Denon HEOS, and Marantz HEOS can be treated in the same way.

1. Run new cables and/or relocate the amplifier

This is arguably the best solution to the problem, and may not be as difficult as it sounds. If you can't get a second cable to the same location as the original one, then maybe consider relocating the Sonos Amp. It may well be easier to run two new cables a short distance to a suitable local location for the amplifier. Access to the amplifier is recommended, but as a last resort it could be installed in the ceiling if the ceiling speaker cut-out is large enough to get the amp through and mains power can be provided in the ceiling (via a fused spur).

2. Use Dual Mono mode to run a single mono speaker

This is not something we strictly recommend, and is definitely a last resort, but it is possible to run a single speaker on a Sonos Amp if there is no other option. The Sonos Amp features a Dual Mono mode which sums the left and right channels so both outputs are mono. This, along with some other settings, can help configure the amp for a single mono speaker.

1. Connect the speaker to either the left or right channel on the Sonos Amp.
2. Activate Dual Mono mode from the Sound menu - see here.
3. Use the Balance control in the Sound/EQ menu to shift the balance fully to the side that you connected the speaker - see here.
4. Set a volume limit in the Sound menu - see here. The Sonos Amp is a powerful amplifier, so it is highly recommended to set volume limits for single speakers (and often pairs too). This will help prevent overdriving the speakers, either intentionally or unintentionally. Any amplifier and speaker combination is at risk of damage if driven into distortion at high volumes. Set the volume limit to something sensible like 60%, but adjust it according to the level requirements of the space. If you only ever use the amp to a maximum of 40% then set it around there. Better safe than sorry!
   
   Please note that the Now Playing screen will still show a full volume slider but will adjust to the limit you set. If you set the amp's max volume to 50%, sliding the volume bar all the way to the right will output a volume of 50% instead of 100%.

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