Other hardware
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Bluetooth (A2DP)
Advanced Audio Distribution Profile (A2DP)
Standard baseline codecs:
- Sub Band Codec (SBC) – not great
- LC3 – the new baseline of Bleutooth 5.1. About Opus level, allegedly
Standard optional codecs:
- MPEG-1,2 Audio: = MP3, almost never used
- AAC: relatively good support, transparency possible at bluetooth bitrates, but latency can be an issue
- ATRAC: never used
Vendor extension codecs:
- AptX, LDAC, LLDC: in general lower complexity but higher bitrate (still within BT limits) than AAC, transparency possible; AptX and LDAC has wide support
Bitrate is limited by bluetooth link
Sub Band Codec
- Sampling Frequency - 16000, 32000, 44100, 48000 (some are optional, see references)
- Channel Mode - mono, dual channel, stereo, joint stereo
The bitrate used for CD-quality () audio is 229 kbps and 328 kbps for middle and high quality, respectively.
Reference: BLUETOOTH Advanced Audio Distribution Profile 1.0
Headphones
Some Styles (smallest to largest)
- In the ear - outputs directly into the ear canal
- Earbuds - sits in the outer ear
- Supra-aural - sits on the ear
- circumaural - completely cover the ear
Terminology used for comparing headphones
- Noise Cancelling
- active
- passive
- Frequency response - The range of frequencies the headphones can reproduce
- Impedance - Doesn't mean much by itself, but in general, impedence should be matched across a system.
- SPL@1kHz, 1V rms - Sound Pressure Level. How efficient the unit converts electrical energy to sound energy.
- Neodymium - The magnet of choice for high end headphones.
Popular Headphones
- Sub $30
- Sub $100
- $100 - $300
- $300+