Bluetooth Speakers: what they are & how they work

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Bluetooth speakers or wireless speakers as they are often called, are now very common and they provide a very convenient way or listening to music almost anywhere.

Increasingly music is being stored on or streamed via devices like mobile phones, tablets, laptops, etc. that are Bluetooth enabled.

Using a Bluetooth loudspeaker it is possible to listen to music from these small portable devices without the need for connecting wires, and this makes them very flexible and easy to use.

As most Bluetooth speakers or wireless loudspeakers are battery powered using internal lithium ion batteries, they can be used almost anywhere, often outside as wel as inside the home.

Bluetooth speakers or wireless speakers should not be confused with smart speakers that are very different - wireless speakers are only able to receive music or other audio over a Bluetooth link, whereas smart speakers are able to take spoken commands and stream music over a Wi-Fi link without the need for a device like a phone, tablet, etc.

How do Bluetooth speakers work

As the name implies, Bluetooth speakers use Bluetooth connectivity to provide the link between the music source and the Bluetooth speaker.

The Bluetooth speaker contains the Bluetooth connectivity, an amplifier, and the speakers. A battery is also generally included making the speaker self contained and portable.

Often an auxiliary input may also be provided enabling wired connectivity if required.

The controls on the Bluetooth speaker generally consist of the On / Off switch, volume controls, a pairing button and indicator, and in some instances NFC may be available to make pairing easier.

In terms of the circuitry required for a Bluetooth speaker, there are a number of blocks as can be seen in the block diagram below.

The main elements of the speaker include the following elements

• Bluetooth receiver:   This is probably the most fundamental element oft he Bluetooth speaker. It receives the incoming Bluetooth signals and returns status data, etc. It also provides the pairing capability and looks after the various other elements of the system associated with the Bluetooth link.

• Digital to analogue converter, DAC:   The data emanating from the Bluetooth module will be in the form of digital data packets. These need to be converted to an analogue format to be amplified in the following stage.

• Amplifier:   The amplifier is an important block within the overall Bluetooth loudspeaker. It takes the output from the digital to analogue converter and amplifies this to the required level.

  The design o this stage present some challenges. Being the most current hungry, it must be optimised to use the least energy possible so that the battery life is preserved. A decision needs to be made about whether a Class A, Class B (push pull) or Class D amplifier is used. It is a balance between a number of parameters.

  Also, with the overall frequency response being a critical issue, especially in terms of providing sufficient bass response, this must also be accommodated during the design.

• Loudspeaker:   The loudspeaker is a key area of the Bluetooth speaker. The overall frequency response must be good, and in particular the bass response must extend far enough down. As the size of most Bluetooth speakers is small,, this naturally means that the loudspeaker itself must be small. Having a good bass response means that the latest technologies must be incorporated to ensure that the overall unit sounds good enough.

  Also in some systems, it is possible to have a second loudspeaker for stereo.

  The power levels are also a consideration. These small units are often expected to fill large rooms, or be used outside where volume levels need to be high not to be lost as a result of the area needing to e covered and to overcome the local noise. Power levels of several watts are not uncommon.

• Battery:   The batteries that are almost invariably used these days are lithium ion types. These provide the best performance for this type of electronic equipment.

• Battery management:   As with most other items using rechargeable batteries such as the lithium ion types, a battery management system is used. This will control the charging and regulate the power being supplied to the various circuit elements.

How to pair a Bluetooth speaker

The Bluetooth pairing process is exceptionally easy, and once paired, the devices normally connect when they are turned on.

To pair the wireless speaker, simply turn it on, and then go into the settings for the source device: a mobile phone, tablet or laptop, etc and navigate to the Bluetooth settings.

Make sure the two devices are in range - normally this might be done with both devices only a metre or so apart.

The ID or identification for the Bluetooth speaker should appear - tap the notification in the source device, and they should pair. Very simple.

When the devices are used another time, they may well automatically connect, or if not this simple process can be repeated.

Difference between a wireless Bluetooth speaker & a smart speaker

It may be possible to confuse wireless or Bluetooth speakers and smart speakers under some circumstances.

Wireless or Bluetooth speakers and smart speakers are very different items, although both operate remotely and can play music.

Essentially a Bluetooth speaker will connect to a device like a smartphone, tablet or laptop, etc using Bluetooth and play music or other material from the device.

The music may be stored on the device, or it may be streamed from one of the many music streaming services, etc, but all of this is routed via the smartphone, tablet or laptop, etc.

With a Bluetooth or wireless speaker, it effectively acts as a remote speaker that is linked via a wireless link (Bluetooth) to the source device which is generally a smartphone, etc.

A smart speaker is rather different. It does not require a smartphone, etc to provide the source material.

Instead the smart speaker will connect directly to a Wi-Fi router or hub and link back to a control centre. Voice commands can be issues, typically preceded by words to alert it to an instruction.

Words like "Alexa" or "Hey Siri" might be used. The voice information will be linked back to a central processing centre where the instructions will be decoded.

Answers to questions can be provided, smart devices can be controlled, and music can be streamed from a streaming service. This is far more advanced than a wireless speaker that acts as a remote speaker for a device.

How to pick the best Bluetooth speaker

The first stage in picking the best Bluetooth speaker to buy is to decide exactly what you want to use it for. Some speakers may be for use on the home - others may be for outside, listing when you are barbecuing outside, etc., others may be a portable speaker for when you are travelling.

Before you can decide on the best speaker for you, its necessary to determine what it is wanted for. The best buy Bluetooth speaker for the home, may not be the best for travelling, as the requirements will be totally different.

There are several points to consider when buying a Bluetooth speaker:

• Battery life:   Battery life is a key parameter to consider. You don’t want to be recharging the speaker every hour. It should be able to last as long as you expect to need it. The small speakers tend to have smaller batteries and don’t last as long, but some of the larger ones can expect to last for 24 hours! More typical lengths of operation may be four to ten hours, and it will be specified as average battery life. The reason for this is that the louder you play the speaker, the more current it will use and the battery won’t last as long before it needs recharging. However when buying he Bluetooth loudspeaker, make sure the battery life is long enough for what you need. Also remember that the Li-ion batteries used do not like being completely discharged, so charge them up before you use the speaker, and don’t leave it discharged. Also as the batteries get older, so the amount of charge they can store falls.
• Audio quality:   Obviously it is nice to have a Bluetooth speaker that sounds goo. Often they give specifications for total harmonic distortion and below 1% is a good aim. The lower the better. Some speakers will not give a specification for this, so you may want to listen to it. Also the frequency response is very important. Some speakers sound better than others and this is often as a result of a much better frequency response. Figures include the top and bottom frequencies that are heard before the response rolls away. Figures like 100 Hz to 20 kHz might be seen. The 100 Hz point is the low frequency and 20 kHz the top frequency. As most of us cannot hear up to 20 kHz, especially as we get older, the top frequency is not quite as important. The low frequency point indicates the level of bass we may expect - the lower it goes the better.
• Style:   There are very many different styles which are available for Bluetooth speakers. This means that it is possible to choose the style which most suits what you want.

• Size:   Bluetooth speakers come in a variety of sizes. There are the small conical or cylindrical types aimed at very portable operation and for packing into luggage, and larger ones that tend to provide better quality audio. These may be rectangular or even again cylindrical. Generally the larger they are the better the audio quality, and the larger ones can have a larger battery for longer use.
• Audio power:   Not all Bluetooth speakers have this parameter specified. When it is stated, it is given in watts. Ten watts is loud, although the efficiency of the speakers in such a small case means they will not be very efficient. Be aware that more power is needed for large rooms and for use outside.
• Waterproof :   As Bluetooth speakers are convenient, often because of the fact that they are portable, means that they will be placed in many area, even near water. Water and electronics don’t mix, so it is often very useful to have a speaker that has been made waterproof . Some speakers are even submersible but it is more common to have ones that are water resistant. Water resistant speakers are especially useful when being used at a poolside or on the beach.

• Bluetooth version:   Often there will be a specification for the Bluetooth version. Bluetooth v.1 was the first version that came out many years ago, and it is quite a rarity to find any equipment that uses this now. Version 2.1 is seen a lot but there are also many products that uses later versions like Bluetooth 4.0 and even Bluetooth 5.

  The big question is what the Bluetooth version number means when your buying a speaker. The main advance for audio came with Bluetooth 2.1 which had a profile called EDR, or Enhanced Data Rate. This gave a leap in the audio quality attainable by allowing the wireless link to carry more data that in turn enabled it to provide more faithful representation of the sound. So provided the speaker has Bluetooth 2.1 or higher it will be fine - the higher versions essentially provide additional capabilities for things like data collection from things like fitness trackers or other sensors. So unless your speaker is going to have all sorts of extra functions (unlikely) it does not matter, although it is by no means a disadvantage.

• Connecting multiple speakers:   Some speakers have the ability to connect to an second speaker for stereo sound. If stereo sound is important, then this is a feature that is worth investigating and putting on the “wants” list as there are now quite a few speakers that do it.
• NFC:   Connecting a music source like a phone or iPod to Bluetooth speakers is normally very easy. However it is possible to use NFC, near field communications on NFC enabled speakers to bypass the settings and just start playing music. NFC allows compatible devices to connect to a speaker via Bluetooth simply by tapping the two together. The downside is that even though iPhones have an NFC capability, it is used for Apple Pay, and as a result NFC has been devoted to only this for security reasons. This means that this capability is only useful with Android phones. But, hey, it is very simple to connect with Bluetooth these days.
• Wired inputs:   Many older devices like the iPod classic do not have Bluetooth. Either you can buy a small Bluetooth transmitter, or you could even consider a good old wired audio cable! Virtually all speakers have a 3.5mm jack input so it is still possible to connected wire-only devices via a suitable cable. Before assuming any particular speak has a jack input, it is always best to check.
• Speakerphone capability:   It may be that using a phone as the music source, you may need to take calls. This can be done using speakers that have a microphone incorporated along with speakerphone functionality. This can be useful if the speaker is to be used by a desk - probably quite annoying for others if it is used by the side of a swimming pool, as everyone will hear the conversation.

There is a huge variety of Bluetooth speakers which are available to buy from many outlets. Some are very cheap, whilst others can be quite costly. Dependent upon what you want, go for the best you can as the quality and performance will be better - go for a really cheap one if it is for something like travelling and you will leave it behind and not worry about it.

  Written by Ian Poole .
  Experienced electronics engineer and author.

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