Bluetooth has become the most common way to connect devices wirelessly, and while its dominance is unlikely to last forever, it remains a core feature of many modern electronics. The main reasons for its success are its affordability, ease of use, and quick pairing. Additionally, Bluetooth has broad support, with all modern smartphones having Bluetooth integration. But behind its apparent simplicity is a sophisticated technology that is constantly evolving. This guide will help you understand more about how Bluetooth works and its likely future.
The History of Bluetooth
In the early 1990s, the mobile phone industry was booming with innovation, and the Swedish manufacturer Ericsson was working hard to move ahead of competing brands in developing new technology for their devices. They hired a Dutch electrical engineer named Dr. Jaap Haartsen to assist in this innovation. Dr. Haartsen was a graduate of the Royal Institute of Technology, where he attained his master’s degree.
At Ericsson, he was tasked with creating a short-range wireless technology that would allow the company to pair their phones with headphones, computers, and other mobile phones. This project led to the innovation of Bluetooth, though at the time, no one anticipated the broad adoption that the technology would receive in the coming decades.
It wasn’t until about a decade later that the first Bluetooth speakers were released, which, compared to today’s standards, suffered from high latency and limited range. As the technology evolved, it began to be adopted by other electronics, including various types of speakers. Amplifiers and receivers started to include Bluetooth in their design, allowing for the integration of Bluetooth into home audio products.
How Bluetooth Got Its Name
Given its colorful name, people often wonder about its origins. The name Bluetooth is a reference to a Danish King from the 10th century, who united Denmark and Norway. Like King Harald Bluetooth, the technology united different electronic components, allowing them to work together.
How Does Bluetooth Work?
Bluetooth works by using a special Bluetooth receiver and transmitter that sends radio waves between the two devices at a frequency band of 2.4 GHz. Some devices have the receiver and transmitter built into them, while others may require a Bluetooth adapter.
These radio waves can transmit various forms of data from the transmitting device to the receiving device. However, the size and type of the file influence the feasibility. Bluetooth audio codecs are among the most advanced, allowing for effective compression and subsequent low-latency transfer. In contrast, video files can be transferred between devices, but attempting to stream video can be challenging.
Simply put, Bluetooth connects two devices in a short-range connection. This connection can be asynchronous or synchronous, depending on whether both devices have receivers and transmitters, or if they operate with the sole purpose of sending or receiving data.
The exact process differs between products, but when discussing audio, the transmission pipeline is fairly simple:
- The source device compresses the audio using one of several available compression methods.
- The compressed data is sent wirelessly from the transmitting device (such as your phone) to the receiving device (e.g., headphones, earbuds, Bluetooth speakers).
- The receiving device then decompresses the audio and processes it through the DSP (Digital Signal Processor), where it’s converted into an analog format so that the speaker can play it.
- The audio is then passed onto the speaker driver, where it delivers sound to the listener.
Bluetooth vs. Radio Frequency
Bluetooth uses radio frequencies to facilitate communication between devices. However, while it is a form of RF (Radio Frequency), it separates itself from traditional RF in a few ways.
Unlike traditional RF, Bluetooth can hop between frequencies to reduce interference. It can jump between 79 different channels within its 2.4 GHz frequency band, something not afforded by traditional RF technology, which retains a static channel. Newer versions of Bluetooth also support AFH (Advanced Frequency Hopping) for improved results.
Bluetooth is also more energy-efficient than traditional RF connections, allowing for broader use among more devices and improved battery performance.
Traditional RF focuses on a fast data rate, which is great for creating a low-latency connection but requires more power to operate. Bluetooth seeks to find a balance between low latency and efficiency. Recent Bluetooth versions have managed to lower the latency while still requiring less power.
Understanding Bluetooth Codecs
Bluetooth codecs are methods of compression that, in the case of audio, take a sound file and compress it to become smaller and easier to stream between the two devices. The type of codec being used differs between products and Bluetooth versions, with newer Bluetooth versions typically supporting more efficient codecs. These are the most common codecs for audio transfer:
- SBC (Subband Coding) – The default codec for Bluetooth audio. It provides a balance between sound quality and compression but tends to have higher latency.
- AAC (Advanced Audio Codec) – Offers improved audio quality over SBC. It’s commonly used in Apple devices.
- aptX – Developed for increased latency performance over AAC and SBC, supporting higher-quality audio.
- aptX HD – Enhances aptX with support for 24-bit high-definition audio, providing listeners with better sound quality.
- aptX Adaptive – Adapts audio quality and latency dynamically based on the connection quality, balancing performance and reliability.
- LDAC (Low Latency Audio Codec) – Developed by Sony, LDAC supports high-resolution audio streaming and offers three different bit rates for varying audio quality.
- LC3 (Low Complexity Communication Codec) – LC3 is the new standard codec in Bluetooth 5.2 and is designed to provide high audio quality with lower power consumption and improved efficiency.
The Bluetooth Pairing Process Across Devices
One of Bluetooth’s many strengths is its ease of use, and pairing Bluetooth devices together is often as simple as the touch of a button. When connecting your phone to a Bluetooth speaker or pair of Bluetooth headphones, you’ll need to set the device into pairing mode (this is sometimes automatically active when turning the device on). Most devices will have a pairing button that you press to activate the process.
Once active, the receiving device will look for nearby Bluetooth devices that are ready to establish connections. Once selected, the pairing process will be complete within a few seconds, and you’ll be ready to listen to your favorite tracks.
Whether you’re pairing a phone to your wireless earbuds or your home stereo setup, the general process is the same. This is one of Bluetooth’s biggest strengths, as it is universal with a very forgiving learning curve.
Historically, Bluetooth was limited to a single connection at a time, meaning you couldn’t use one phone to connect to several speakers at the same time. However, Auracast has changed that. Auracast is a new Bluetooth technology where one source device (such as a phone) can connect to multiple speakers (assuming they all support Auracast) to play the same audio across multiple speakers simultaneously.
Benefits and Drawbacks of Bluetooth
There’s no such thing as the perfect wireless protocol, but Bluetooth comes close. Still, any technology has inherent benefits and drawbacks, and understanding the limitations of Bluetooth is important.
Strengths of Bluetooth:
- Ease of use
- Affordability
- Broad support
- Relatively good latency (in newer versions)
- Highly efficient and lower power usage
Weaknesses of Bluetooth:
- Not a viable option for multi-room audio
- Limited range
- Only supports one connection at a time (unless supported by Auracast)
Using Bluetooth for Multi-Speaker Pairing
Manufacturers have found unique and innovative ways to incorporate Bluetooth into their designs and push the boundaries of what’s possible with the technology. One such method is implementing a master and slave relationship between multiple speakers, allowing for TWS (True Wireless Stereo) and general multi-speaker pairing.
Speakers that support multi-speaker pairing have a built-in transmitter to connect to another speaker’s receiver and pass along the audio. This relationship sees the main connected speaker as the ‘master’ while the second speaker receiving data from the master is considered the ‘slave’.
In a TWS connection, each speaker is assigned its channel (left and right), where one speaker will only play the left channel audio and the other the right channel audio. The result of a TWS connection is an improved soundstage.
The other type of multi-speaker pairing is a traditional mono connection between multiple speakers. This works similarly to TWS, but audio isn’t split into separate channels. You’ll usually be able to connect multiple speakers together in this format, sometimes up to 100 speakers.
Using Bluetooth for multi-speaker pairing can be largely beneficial, but it still has its limitations. Most notable is the limited compatibility. Usually, TWS is only supported by speakers of the same model, and while multi-speaker pairing support tends to be broader, it is also frequently limited to similar speakers from the same brand.
The latest addition to multi-speaker is Auracast, which can establish a synchronous connection to multiple Bluetooth speakers at the same time, with a direct connection, instead of relying on a master and slave relationship between the speakers.
Bluetooth vs. Wi-Fi
Bluetooth and Wi-Fi are both options for wireless audio, but the two technologies have distinct differences. Wi-Fi support is an emerging technology, while Bluetooth is already broadly adopted, the increased popularity of full home integration has seen Wi-Fi become a popular choice in recent years, catapulted by Sonos and their approach to wireless ecosystems. Smart speakers also rely heavily on Wi-Fi connectivity, and the increase in their popularity has continued to make Wi-Fi an appealing option for homeowners.
In addition to portable devices, Wi-Fi has become increasingly popular for home audio installations like ceiling speakers and in-wall speakers. The reason why people are opting for Wi-Fi over Bluetooth for these types of speakers is that Wi-Fi is faster than Bluetooth, negating the need for heavy compression and allowing the streaming of lossless audio. Additionally, these speeds result in less latency, which is essential when using speakers together with video.
Wi-Fi is faster and supports a wider network of speakers across a household, but it’s not as easy as Bluetooth to set up and is not as well suited to casual music listeners. Instead, it’s a better choice for those seeking the highest-quality home audio.
The Future of Bluetooth
Bluetooth is constantly evolving, with new versions being released every year or two. The changes between versions are not always remarkable and may consist of minor improvements. However, in recent years, particularly since the introduction of LE Audio. LE Audio (Low-Energy Audio) is the next generation of Bluetooth and focuses on improving audio quality through more efficient compression methods and lower power consumption.
LE Audio is the technology that Auracast pairing is built on, and we’ll likely see further refinements to this technology as we move forward. At this point, the technology is available, it’s just a matter of adoption from manufacturers. We expect the majority of Bluetooth speakers to support Auracast over the next three years, with a strong focus on multi-stream and broadcast capabilities.