PCM audio vs CarPlay

[Fedex77]

Am I hallucinating or does the audio from Apple Music sound much better played directly via the PCM app compared to CarPlay? Is this even possible?

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[OhRichman]

I don't have any hard data to point to, but I too think the PCM paying Apple Music sounds better than when I use wireless Apple Car Play. I assume it has something to do with the bandwidth limitations of wireless Apple Car Play transmitting the audio.

 

[dtich]

My memory says that the spec on CarPlay is that wired will pass full LPCM bitrates up to whatever the cars system will handle, but that a wireless connection is limited to 48kHz/16bit, or CD quality, files with added audio compression on top*. So, yes, much better quality with a wired connection is possible.

In the wireless case my understanding is there should be an adhoc WiFi connection that facilitates wireless CarPlay audio, and that BT is only used to establish the connection, not for audio transport.

*Edit: I may be wrong about 'added audio compression on top' in the wireless connection as in some places Apple's CarPlay spec says it *will* serve lossless over wireless, albeit at 48/16, and in other places it plainly says a *wired connection is required* for lossless.

However, if you are used to listening to hi-res files, as I am, eg. 192/24, even lossless 48/16 will sound quite a bit worse. Most of the change will be in the high end, so room depth, space, reverb, reality, ring outs... and certainly the bass will be thuddy and lack nuance. Once you go hi-res it's hard to go back. YMMV.

 

[Raphie]

Carplay audio quality is shit, always use the native apps where possible. Same for Spotify
https://discussions.apple.com/thread/252115033?page=2

 

[f1eng]

In order to do a valid listening test comparison the volume level needs to be set the same to within 0.1 dB.
It is one of the ways HiFi demos are made to sound better, just a little bit but not obviously louder always sounds clearer and more dynamic.

Dealers know how to sell expensive kit that is actually no better using this trick.

If there is a volume mismatch - and there probably is - the quieter will always sound worse in direct comparison.

The Blutooth data transmission spec is not lossless but in a car I'd be shocked if the difference is audible rather than placebo.

 

[Fedex77]

I did a “side to side” comparison of the same song played via PCM Apple Music and CarPlay Apple Music. Definitely sounds richer coming from PCM, possibly due to the Bose effects? Can’t explain it any other way unless CarPlay is using low bitrate

 

[Raphie]

It‘s the phone DA car usb AD, there are 2 additional conversions over USB compared to PCM

 

[Genau]

It‘s the phone DA car usb AD, there are 2 additional conversions over USB compared to PCM

Huh? I thought audio travels digitally over USB, same as it does over WiFi for wireless CarPlay. Why would there be any analog <> digital conversions for audio going over USB?

 

[Raphie]

USB supports analog channels as well. Depends on implementation.

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