Headphone Bluetooth Technology You Must Know About

How do Bluetooth wireless headphones work? Does Bluetooth ruin sound quality? And more facts about wireless headphones.

There are different types of wireless headphone technology.

• Bluetooth
• 2.4GHz proprietary radio-frequency technology – popular for wireless gaming headsets
• KleerNet
• Infrared

And Bluetooth is the most popular by far.

How Bluetooth Works

Bluetooth technology is the most common wireless technology in headphones. It’s an international standard used by thousands of companies.

How does the Bluetooth Communication Protocol Work?

Bluetooth works over the same radio frequencies that are reserved globally for scientific, medical, and industrial purposes also known as ISM bands. It operates at 2.4GHz with a set of standardized rules and specifications, so it doesn’t interfere with WiFi, baby monitors or other radio frequencies (RF).

If you want to get more technical, here’s a more in-depth explanation of the Bluetooth protocol.

How is Bluetooth Transmitted?

Bluetooth sends low-powered signals to avoid interfering with other wireless devices that might be present on the same radio frequency (between 2.402 and 2.480 GHz).

Due to low power, its range is limited, up to 33ft (10m) for Bluetooth 4.0 and below, and over 100ft (30m) for Bluetooth 5.0 (the max range in perfect conditions is longer).

Physical obstacles don’t—or shouldn’t—interrupt the Bluetooth signal. So, if you leave your smartphone in another room and listen to music with your headphones, music shouldn’t be interrupted. Though, it happens more often than you’d want.

It can connect up to 8 Bluetooth devices at the same time. All of the devices have to be in the range of around 33ft (10m) for a stable connection. It uses the frequency hopping spread-spectrum (FHSS) method to avoid multiple devices using the same channel.

This way, it optimizes the use of a limited radio field. It changes the frequency of 1600 times per second from 79 random values. Basically, it makes it almost impossible for 2 Bluetooth devices to interfere.

How Does Bluetooth Pairing Work?

When 2 Bluetooth devices come into range of each other, communication happens automatically. Depending on their status they determine if they have data to share or if one takes control of the other (or if they don’t connect).

In the case of Bluetooth headphones, your smartphone sends music data and takes control of the functions (volume control, song selection, play/pause, etc.).

Once the initial conversation happens, Bluetooth gadgets create a network called PAN (personal-area network), also known as a piconet. It consists of a minimum of 2 devices synchronized to the same frequency channels, common clock, and hopping sequence. This way, they stay connected and communicate even when other piconets are present in the same room.

At every point, there is one active “master” and up to 7 active slave devices. Also, there can be up to 255 inactive—parked—slave devices ready to replace one of the active ones.

How Wireless Headphones Play Audio

How does Bluetooth allow you to play sound from a device wirelessly?

Let’s assume an example. You have a phone with your favorite music, and you want to listen to it with Bluetooth headphones.

In the process, a couple of things happen:

The smartphone sends music to headphones via Bluetooth. Music stored on your smartphone or streaming service is digital. It’s a bit stream of 1s and 0s. Bluetooth sends a digital signal of the music to the headphones.

Headphones can’t “play” digital signals but need an analog input. Electricity is required for the headphone drivers to produce sound.

DAC (digital-to-analog converter) inside the headphones takes the digital signal and changes it. It converts it into analog music and electricity.

DAC sends decoded analog music to the headphone amplifier. Afterward, the analog sound is played through the speakers inside the headphones. And you can hear the music.

What is the Technology in Wireless Headphones that Converts Bluetooth Signal into Sound?

Since Bluetooth can only send digital and not analog music over its connection, transferring analog music into digital is necessary.

You might have a CD player, and if you connect the headphones with 3.5mm wires, then the analog music can travel straight to headphone drivers.

But, if you have a Bluetooth CD player and you connect to wireless headphones, then it has to be converted into digital form before Bluetooth can transfer it.

For this purpose, any audio Bluetooth device that can read analog music has an analog-to-digital converter (ADC). It does the opposite process of a DAC. Once the music is in digital form, it can be sent over wirelessly.

In case the music device is a smartphone on which all music is digital, then the ADC processing is not required for Bluetooth.

And once the digital music signal reaches the headphones, it needs to be transferred back into an analog signal so the drivers can play it.

The tool that does the transformation is a digital-to-analog converter (DAC). It does exactly what the name suggests, converting digital data into analog music that any driver can understand (headphones and speakers).

Not all headphones have a DAC. Read about other types of headphones here.

How do wireless headphones play audio with virtually no delay?

Bluetooth connection has an inherent audio delay, but it should always be under a second. Listening to music and podcasts isn’t problematic, but when you watch a movie or play games, it’s deal-breaking.

For your brain to think the audio is in synchronization with the video, the delay has to be under 40ms.

Unfortunately, only speed-dedicated Bluetooth codecs achieve this limit. You should look for aptX Low Latency (aptX LL) and AAC-Low Delay (AAC-LL). Others still have a slight delay that can take away from the listening experience.

Nonetheless, the standard aptX codec has a lower latency that’s better than SBC—which is the standard codec—but can’t compare to aptX LL (still the fastest).

• aptX LL – up to 40ms delay
• classic aptX – 180ms delay
• SBC – 250ms delay

The audio delay isn’t a problem for music, but if you intend to play action games, you should look for headphones that support one of the faster Bluetooth codecs.

Hopefully, the LC3 Bluetooth codec, which is faster, soon becomes widely supported.

Does Wireless Technology Damage Audio Quality?

Bluetooth headphones have long been known for bad sound quality due to wireless connection limits, but today the difference is almost gone.

Purists and audiophiles still stand with cables, but average consumers are perfectly happy with the audio of Bluetooth headphones.

What is the bottleneck in audio quality when using wireless headphones?

Bluetooth was not initially made for audio transmission.

It has a limited bandwidth that requires compression of files into smaller sizes.

Uncompressed FLAC or WAV music files take up a lot of space. And if you want to send this data over Bluetooth with a narrow bandwidth, you need to compress it (make it smaller).

The music compression process usually takes away from the audio quality.

Lossy compression is supposed to remove parts of the music that are hard to hear and don’t take away from experience. Nonetheless, some loss in quality occurs.

Lossless compression doesn’t change the audio quality but also can’t be compressed that much (results in bigger files).

But not all compression is equal. How much data and how compressed is the music depends on the codecs you use. A codec is an encoder and decoder of the digital music files and dramatically impacts the sound quality you end up with.

All Bluetooth audio devices come with an SBC codec as standard, which does a decent job. If you’re not an audiophile, you’ll be more than happy with its sound quality.

But if you want the best the technology allows, you should maximize the use of the bandwidth that is available. Look for the support of efficient Bluetooth codecs like aptX, LDAC, AAC, and other Advanced Audio Distribution Profile (A2DP) codecs.

Make sure both your headphones and music device support the codec you want. Otherwise, it won’t work.

Are there any wireless headphones with sound quality as good as professional studio headphones?

No. Studio headphones are made for monitoring jobs where every detail needs to be heard as naturally as possible.

Keeping the music uncompressed and in its original state is of paramount importance. A musician needs to hear their music as it actually sounds without distortion.

For this reason, wired headphones that don’t require encoding and decoding are the best for the job.

On the other hand, wireless Bluetooth headphones are made for convenience before sound quality. Bluetooth requires encoding, which takes away from audio quality.

But this information is only relevant for professionals, average people probably can’t hear the difference.

Does the audio quality of wireless headphones degrade over time?

If the technology in the headphones works as intended, then the audio quality should stay the same. Bluetooth or other wireless technologies don’t impact degradation over time.

But the thing that does degrade over time is battery life. Lithium-ion battery loses capacity over time, which means any Bluetooth headphones become useless eventually. It’s the limitation of the technology which hopefully improves in the future.

Where to Find the Best Wireless Headphones?

See our buying guides on all types of headphones.

Some of the popular:

• Want to listen to music wirelessly, but you’re afraid of water damage? Worry no more with waterproof Bluetooth headphones.
• Do you have a limited budget? These are the best affordable options for Bluetooth earbuds.

Matija Ferjan

Matija Ferjan is a seasoned audio enthusiast reviewing headphones since 2015. He has personally tested hundreds of headphones and earbuds. He’s an active member of the Headphone Audio community and a true nitpicker, always looking for the “best-value-for-money” headphones.