Does Bluetooth ruin a session?

The usual worry about Bluetooth is latency, and for this use it is the wrong worry. Two other things matter more, and one of them is rarely mentioned at all.

Latency does not matter, and here is why

Bluetooth adds somewhere between about 30 and 300 milliseconds of delay depending on codec and device. That is a serious problem for video, where it desynchronises lips from speech, and for gaming and music production, where it desynchronises action from sound.

A generated session has nothing to synchronise against. There is no picture and no keypress. The audio arriving 200 ms late is audio arriving 200 ms late in a thirty-minute continuous field, which is to say it is indistinguishable from audio arriving on time.

Ignore latency entirely for this purpose.

Channel separation does matter, for one mode

Binaural delivery depends on each ear receiving a different frequency and the auditory system constructing the beat from the difference. Anything that mixes the channels degrades it.

Standard stereo Bluetooth keeps the channels separate, so this is usually fine. The failure cases are specific:

• Mono fallback. Some devices drop to a mono profile during a call, or when one earbud is out of the case, or in certain accessibility modes. A binaural session in mono is two tones summed into one signal, which is a different sound with no beat.
• "Spatial audio" or head-tracking processing. Anything that reprocesses the stereo field is manipulating exactly the cue the beat depends on. Turn it off for binaural sessions.
• Upmixing and enhancement modes. Same reasoning.

None of this affects isochronic or monaural sessions, which carry the rhythm in the signal itself and survive mono, a single earbud and a phone speaker. The comparison of the three methods sets out why that robustness is the reason we default to amplitude modulation rather than binaural.

The one that nobody mentions: dynamic range and processing

Modern wireless headphones do a lot of digital signal processing. Bass enhancement, adaptive EQ, compression, sometimes loudness normalisation.

At the level a generated session wants to be played, this matters more than it does for music. These sessions are quiet, sparse and consist largely of steady tones and a noise bed. Compression that is inaudible on a dense mix becomes audible on a sustained pure tone, and adaptive EQ that flatters a drum kit can put a slow wobble into a noise bed.

If a session sounds unstable or oddly alive on wireless and clean on wired, this is why. Turn off enhancement modes before you blame the session.

Codec: mostly a distraction

SBC, AAC, aptX, LDAC. The differences are real and small, and they are smallest on exactly this kind of material: low-bandwidth, low-level, mostly steady content is the easiest thing a codec ever has to encode.

There is one edge case. Very low-frequency content and long steady tones can occasionally expose codec artefacts as a faint warble. If you hear that, it is more likely the enhancement processing above than the codec.

Do not buy a headphone for its codec for this purpose.

Practical settings

Turn off spatial audio and head tracking for binaural sessions.

Turn off enhancement, adaptive EQ and bass boost for everything.

Check both earbuds are connected before a binaural session, or use a mode that does not care.

Use a wired connection for sleep if you use headphones at all — though a speaker is better. Delta Sleep Gateway on a quiet speaker beats any headphone for a session you intend to fall asleep after.

Otherwise, wireless is fine. Vipassana Sensory Gating or Sensorimotor Calm Focus on ordinary earbuds at a low level will do what they are meant to.