> > > My laptop has built-in front left, front right, rear left, rear right
and
> > > subwoofer and something is strange.
> > > When I set channel output to 5.1 or 4.1 and external speakers are
> > > disconnected, then front left and front right work as expected but
> >
> > built-in
> >
> > > subwoofer is heard only if I test rear left channel (wrong channel
> >
> > mapping?)
> >
> >
https://git.kernel.org/cgit/linux/kernel/git/tiwai/sound.git/commit/sound/pc
> > i/hda/hda_codec.c?id=cd4035e814b04c009ece9939396d06370c53ed44
> >
> > Seem only two pairs of stereo speakers and internal subwoofer at left
> > channel before this patch
> >
> > ALSA: hda - Enable surround speakers (when line out is also present)
>
> On my laptop case "Virtual SurroundSound" is written . When I test front
left
> and rear left, I hear distinct sound, so it would mean it's from two
different
> sources of sound.

The driver use more than two channels only after David 's patch

But all internal speakers of the notebook are at front of  the user, The 3D
sound effect is quite different from your external 5.1 speakers

Do you mean your 5930g need champ {FL FR RL RR LFE }?

This can be easily implemented by using "swap center/lfe" switch for those
codec support R/L swap

http://git.alsa-project.org/?p=alsa-lib.git;a=blob_plain;f=test/chmap.c;hb=HEAD

http://git.alsa-project.org/?p=alsa-lib.git;a=tree;f=src/conf/pcm;hb=HEAD

If codec does not support R/L swap, your 4.1 swap chmap need 5.0 routing

Do you expect pulseaudio show 4.1 swap(5.0) profile for internal speakers
and 4.1 and 5.1 profiles for external speakers ?