Latency is the time it takes for a signal sent from a source to reach its destination. For headphones, this means the delay between the moment the audio is played and when you actually hear it.
Wireless headphones provide freedom of movement that regular wired models don’t. With wireless headphones, you don’t need to have your smartphone directly on you to enjoy your favorite tracks, and there are no wires to trip over or tangle in your pockets. All great things have drawbacks, though, and most wireless connections create a significant amount of latency. This can result in a perceptible delay between what you see and what you hear while gaming or watching a movie on your TV.
Many gaming and home theatre headsets use dedicated radio frequency (RF) transmitters to ensure a lower-latency connection; however, this often comes at the expense of portability, since these headsets need to be in range of their transmitters to work. Bluetooth headphones are more versatile, but tend to have worse latency performance. To combat this issue, various Bluetooth audio codecs exist that improve latency performance.
Our latency test measures the base RF or SBC Bluetooth latency, as well as the time delay of additional codecs like aptX and aptX Low Latency (LL).
Latency may not be a major concern for you if you only listen to music or podcasts, but it can be frustrating when what you hear doesn’t match what you see while gaming or watching a video. To give you a better understanding of how latency can affect your videos, we prepared a few samples delayed by 0, 50, 100, 150, and 200 ms.
This means that wireless headphones with high latency (>200 ms) generally aren’t suitable for watching movies or gaming since the audio they reproduce may be out of sync with the images on your screen.
However, certain mobile Bluetooth devices and applications seem to provide some form of latency compensation, which means you may not notice as much audio lag with certain setups as you would with others. For example, Bluetooth smart TVs tend to have worse latency than smartphones and dedicated streaming apps. Depending on the platform and operating system, there may also be less visible latency when streaming video content on specific apps that support lower latency. Although we don't yet have a dedicated test that measures how latency interacts with different apps and devices, keep in mind that you may experience less latency than what we measure depending on the Bluetooth source and apps you use.
We measure the base latency of RF and Bluetooth headphones as well as any additional codecs aptX and aptX (low Latency) that may improve their latency performance.
We measure base latency using different Bluetooth dongles depending on the codec tested or with the headphones’ dedicated RF transmitter. The dongle/transmitter is then connected to a sound card, which supports ASIO (to limit sync issues) and transmits a click-track generated by a digital audio workstation (DAW). The signal produced by the headphones is recorded through a mic that is fed back into the sound card, creating a loop that shows when the audio signal was sent and when it was received in the DAW software. This is done three times and then averaged to give the final latency number.
Base latency refers to the default sub-band coding that most wireless headphones use when connecting via Bluetooth. This typically occurs if the headphones do not have any additional codecs like aptX or AAC. It also happens when the codec is not supported by both Bluetooth devices. We also test the base latency of RF headphones with the same setup, but with the RF transmitter in place of the Bluetooth dongle.
We measure base latency using a Bluetooth 4.0 dongle that doesn’t have aptX or with the headphones’ dedicated RF transmitter. We connect the dongle/transmitter to our test sound card and record the test signal through the headphones, measuring the feedback delay. This is done three times and then averaged to give the final SBC latency number. Typical SBC latency ranges between 150 and 250 ms and RF between 20 and 75 ms.
AptX is a proprietary codec by Qualcomm (previously CSR) that improves audio quality and bit rate efficiency. This means headphones with aptX sound a bit better and less compressed when playing audio wirelessly. They also have a bit less latency than SBC although not as much as with the dedicated aptX (Low Latency) codec.
We measure aptX with a similar set up as that of the SBC sub-band coding latency. However, in this case, we use a Bluetooth 4.0 dongle with aptX support to measure the feedback delay. This test is also done three times and average to get the final aptX latency number. Typical aptX latency ranges between 50 to 150 ms.
AptX Low Latency (LL) is the fastest of the aptX codecs designed to reduce sync issues when watching videos or gaming. This codec usually performs much better than the standard aptX codec in terms of latency but does not improve sound quality.
Like the SBC and aptX latency test, a click track/input signal is sent to the headphones wirelessly, which is then recorded to determine the delay. For this test, we use a Bluetooth 4.1 dongle with aptX and aptX(LL) support. Again, we measure the latency with the DAW software three times to get the final aptX (LL) latency number. Typical aptX(LL) latency ranges between 30 and 50 ms.
There are a couple of elements that we don't test for explicitly. These elements include:
If you feel there is an item missing that should be included, please let us know in the Discussions below.
Our latency test measures the delay caused by transmitting data over a wireless connection. For headphones, it's the time it takes for audio to play through the drivers, which can be out of sync with video content. We measure the base latency for RF and Bluetooth headphones as well any latency improving codecs such as aptX or aptX (LL). The higher the latency, the more delay there will be between the images you see and what you hear. Depending on your choice of headphones and listening habits, it may not be as big of an issue for you; however, bad latency can significantly worsen your movie-watching or gaming experience. That said, certain devices and applications seem to provide some form of compensation, so you may not notice it as much with certain setups as you would with others.