[pulseaudio-discuss] Weak bass in stereo mode – possibility of virtual 2.1 sound profiles

[Karl Ove Hufthammer]

Hi!

I use my NVIDIA graphics card as a combined graphics and sound card, 
connected to my 5.1 home theatre system via an HDMI cable (something 
which works surprisingly well). Using the default audio profiles in 
‘pavucontrol’, I can easily switch between 5.1 sound (e.g. for DVDs) and 
stereo sound, which is great.

The 5.1 profile (‘hdmi-surround-extra1’) also work fine for *some* 
stereo material, mainly music. But for *most* stereo material, the 
upmixing makes everything sound too echoey (this is typically a problem 
for movies with just stereo sound and for vocal-heavy music), so I 
usually just use the stereo profile (‘hdmi-stereo-extra1’) for stereo 
material.

But I have noticed than when playing music or videos using the stereo 
profile, the sound is missing quite some oomph, i.e. the bass is *much* 
weaker (compared to the same material played using the 5.1 profile).

I guess the reason is that PulseAudio outputs a pure stereo sound, and 
my home theatre system doesn’t redirect enough of the low-frequency 
sound to my subwoofer. And unfortunately, my (not too expensive) home 
theatre system doesn’t have any options for increasing this (for HDMI 
audio).

To summarise, when listening to stereo material, I can currently choose 
between echoey 5.1 audio with nice/powerful subwoofer sound or 
non-echoey stereo audio with very weak subwoofer sound.

My question is, is it possible to have my cake and eat it too? A virtual 
2.1 speaker option/profile, where the left/right *rear* speakers are 
silent, and where PulseAudio redirects some LFE audio to the subwoofer, 
just like it does for the 5.1 profile? (Or perhaps even a 3.1 speaker 
option, if that sounds better – front left + centre + front right + 
subwoofer?)

Is this possible using some PulseAudio config magic? Currently, I use 
the following settings in my config file:

   enable-remixing = yes
   enable-lfe-remixing = yes

   default-sample-channels = 6
   default-channel-map = 
front-left,front-right,rear-left,rear-right,front-center,lfe

I don’t have a problem with having to *manually* choose between a 5.1 
and and a 2.1 profile (I use ‘pactl’ aliases to quickly switch between 
profiles). But of course the *best* solution would be that PulseAudio 
automatically sent stereo material as 2.1 audio output (i.e. really 5.1 
data with the rear channels (and centre channel?) silent) and 5.1 
material as normal 5.1 audio output.

Any suggestions?

Thanks in advance,

Karl