I moved a part of this question from the Electrical Engineering forum here, since I was suggested that it is more appropriate here.
I ordered a pair of Bluetooth headphones which apparently work on Bluetooth 4.0 but my computer only supports Bluetooth 2.1 + EDR.
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Would upgrading my computer's Bluetooth improve the audio quality if I use the headphones over a Bluetooth 4.0 adapter or do I get the same result?
Bluetooth 4.0 should improve audio quality, provided you have devices that support aptX or A2DP:
aptX, an audio codec designed for CD-quality audio transfer over Bluetooth.
A2DP, or Advanced Audio Distribution Profile, which is designed for sending stereo audio over Bluetooth to speakers, car stereos, and headphones.
The problem with Bluetooth audio has always been digital compression: in order to send your audio to your headphones, you were forced to sacrifice quality. Traditionally, especially on older devices and with older Bluetooth versions, this meant the sound was so badly compressed that the result sounded robotic, buzzy, noisy, and all around awful.
Listening to podcasts and spoken word through them wasn't a big deal, but when it came to music, they were just the worst. You got none of the richness or warmth of sound that a pair of wired headphones offers.
In addition to compression just ruining the audio quality, there are other factors at play. For one, Bluetooth rides the same 2.4Ghz wireless frequency that so many other things in your home, like wireless mice or keyboards, Wi-Fi signals, or even microwaves.
Those things won't have a huge impact on sound quality, but they can—and often do—cause audio drops and other quirks. Of course, all of those are reasons why Bluetooth audio was never—and still isn't—a match for traditional wired audio. That doesn't mean it's without its merits.
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Bluetooth has improved, and the audio compression isn't nearly as bad as it was even five years ago. Bluetooth standards have improved significantly since the days of Bluetooth 1.1 and 2.0 (which is when Bluetooth headsets and headphones really hit the market), and today's Bluetooth 3.0 and 4.0 devices are built with more attention to stereo audio in mind.
If you want the best possible audio quality from a Bluetooth device, look for headphones and speakers that support aptX, an audio codec designed for CD-quality audio transfer over Bluetooth. Alternatively, look for support for A2DP, or Advanced Audio Distribution Profile, which also requires compatible devices, but is designed for sending stereo audio over Bluetooth to speakers, car stereos, and headphones. In either case, even if you don't have supported devices, you may be able to find adapters to help bridge the gap.
That said, it's still not as good as wired audio, and some people say it's still unacceptable overall. Still, there are situations where it's good enough for what you want.
