Two of my speakers are missing!

This applies to Kubuntu 16.04 and possibly other Ubuntu 16.04 derivatives.

After getting Kubuntu 16.04 installed on to RAID, I noticed that the centre speaker and LFE (Low Frequency Emitter – i.e. subwoofer) of my 7.1 surround system were both silent. Irksome. Calling-up the KDE volume controls showed no obvious way to control the individual speakers. I’m pretty sure that this used to be possible under KDE4, even if it was volume rather than delay as well. In KDE Plasma 5 – not a hint.  You can test the individual speakers (System Setting/Multimedia/Audio and Video/Audio Hardware Setup) but not set volume for them.

Testing showed that yes, they were indeed silent and it’s not just me ears. Cue much grubbing around the floor checking the cables. Nope, not the cables. Cue much ponderings.

I installed “pavucontrol” which gave me proper control of the volumes, but that didn’t seem to fix anything (nice to have the proper sliders though). We must delve deeper!

Firing up the old faithful of “alsamixer” and selecting the correct card (“F6“) showed me that yes, “Centre/LFE” had indeed been muted for some reason. Selected that, slapped “M” and presto – all speakers are now working.

So if you are having any speaker grief, start from alsa and work your way UP to the graphical niceties.

If anyone knows of a sensible way to manage speaker delay via alsa or Pulseaudio, I’d love to heard about it.

I’d also like to know how to stop what appears to be volume-levelling; it seems to cause sudden surges during streams.

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