Bluetooth continues to evolve as one of the most prominent wireless technologies used in practice every day. Look around, chances are your smart devices make use of Bluetooth technology. From your car radio, smartphone, laptop, and wireless speakers, Bluetooth is at the heart of the majority of wireless devices used by consumers.
Upon the debut of the official Bluetooth 1.0 spec in 1999, there have been many great strides in the technology with respects to range, data throughput and connection stability. Audio more specifically, has made major tangible advances that can be heard sonically through your wireless audio device of choice. Although audio coloration of what “sounds good” may be subjective, there is no denying that through the years of Bluetooth’s evolution, gains in data throughput and efficiency have increased audio fidelity exponentially.
• Bluetooth 1.0 – Theoretical Speed @ 1mbps
• Bluetooth 2.0 – Theoretical Speed @ 3mbps
• Bluetooth 3.0 – Theoretical Speed @ 3mbps (Classic), High Speed (Leveraging WiFi chipset) @ 24mbps
• Bluetooth 4.0 – Theoretical Speed @ 3mbps (Classic), BLE @ 1mbps
• Bluetooth 5 – Theoretical Speed @ 3mbps (Classic), BLE @ 2mbps
When Bluetooth 1.0 was first released, data transfer speeds were capped at 1mbps. Version 2.0 offered over double the theoretical speed of up to 3mbps which is still widely in use today. When version 3.0 was released, it offered a mode called HS (High Speed), which allowed the Bluetooth radio to leverage a neighboring WiFi chipset to gain speeds of up to a whopping 24mbps! Bluetooth 4.0 and the upcoming 5 spec focus on BLE (Bluetooth Low Energy), created for IoT (Internet of Things) devices requiring extended range in extremely low power applications whilst deployed in the field. Bluetooth 5 offers twice the speed of 4.0 for BLE capped at 2mbps. However, these are all theoretical speeds as variations in hardware, codecs, and connection stability are major factors that play a role in data integrity and audio quality.
What is a codec?
A codec in its simplest terms encodes and decodes digital audio data coming from your source device (For example: your smartphone) into a digital audio signal audible through your Bluetooth headphones or speakers.
Bluetooth Compression Codecs and Data Rates
AAC – Max speed @ 250kbps
SBC – Max speed @ 320kbps
aptX – Max speed @ 354kbps
aptX HD – Max speed @ 576kbps
LDAC- Max speed @ 990kbps
Although the theoretical speeds of Bluetooth are more than capable of handling these codec transfer rates, large data transfer can introduce latency and additional data processing, which degrade the listening experience for users, especially if used in less than ideal connection conditions.
SBC is a standardized codec which is mandatory for AD2P (Advanced Audio Distribution Profile or Bluetooth Audio Streaming) devices. YouTube and Apple prefer the AAC codec for their media platforms. Manufacturers such as Qualcomm and Sony create proprietary codecs which increase data transfer rates to effectively increase the audio fidelity of devices using their codec.
As a comparison, here are common data rates associated with media:
Compressed “Lossy” Format – Normal Spotify Streaming/Average Mp3 @ 160Kbps
Compressed “Lossy” Format – High Quality Spotify Streaming/High Quality Mp3 @ 320kbps
Lossless – CD Quality (16bit, 44.1khz) @ 1411.2kbps
Uncompressed – Raw Master Recordings (up to 24bit, 192KHz) @ 9216kbps
Audio data compression is the downsizing of the master audio file to reduce its size and digital foot print. This is to take into account transferring files to other users, or mitigating the variances in user connection speed for streaming services like Pandora and Spotify. Instead of sharing a massive 900MB uncompressed audio file with another user, compression can bring it down to a more manageable 10MB MP3 (A Type of Compressed Audio File). This will of course sacrifice audio quality, but for most use cases, the average user will not notice the difference.
Bluetooth audio streaming has had great audio quality improvements in recent years, but compared to traditional wired audio systems, there is simply no comparison audio fidelity. Wired systems simply sound better than their wireless counterparts due to bottlenecks in wireless bandwidth. As the wireless benefits of Bluetooth outweigh the need for the full uncompressed audio signal, many users will sacrifice audio quality for wireless convenience.
Bluetooth technology has come a long way, and with the specification continuing to develop, so will the advancement of codecs. As data transmission efficiency and bandwidth increase with updated Bluetooth specifications, audio fidelity will follow suit. While the technology is not quite there yet to stream true lossless media due to limitations with battery life and bandwidth, significant progress is still being made, and the silver lining is that Bluetooth will continue to evolve as the prime consumer audio wireless technology.