Right click on the Speaker icon in your notification area and go to
the Hardware tab. You should be able to select some Analog Surround
[...] Profile that matches your laptop's sound card. On the output tab
you should now have controls for Balance, Fade and Subwoofer. Try
turning down the subwoofer.

If this doesn't work, there is a way you can tell PulseAudio not to
control the LFE control; i.e. make it not be dependent on the Master
volume. Go to /usr/share/pulseaudio/alsa-mixer/paths/ and edit
analog-output.conf. Find the section for [Element LFE] and make the
following change:

[Element LFE]
switch = mute
volume = ignore
override-map.1 = lfe
override-map.2 = lfe,lfe

Logout and log back in to restart PulseAudio.

This will allow you to change the volume level in alsamixer without
PulseAudio resetting it when you change the Master volume.

Hope this works.

Regards,
Adam

On Mon, Nov 2, 2009 at 12:58 AM, Richard Carter < rwcarter@ncsu.[redacted] > wrote:

> So I've never understood the differences between OSS and ALSA, but now
> 9.10 throws another one into the mix, PulseAudio (which apparently
> sits on top of ALSA?).
>
> My laptop has a small "subwoofer" in it - it makes a very noticeable
> difference in sound quality, and I quite like it. In past versions of
> Ubuntu, the mixer had Master, PCM, and LFE (low-frequency emitter);
> the latter being the subwoofer. Master controls my two normal
> speakers' volumes, LFE controls the subwoofer, and PCM acts as a sort
> of master between the two. So, I would turn Master and LFM to 100%,
> and then hook my volume buttons to the PCM, and everything would be
> great.
>
> Now I can only control Master, and my LFE is always set to loud. This
> means that only one notch above muted, my main speakers are inaudible
> but my LFE speaker is blaring. There's nothing in the volume control
> other than left/right balance.
>
> When I run alsamixer -c 0 in terminal, I can see the PCM and the LFE,
> but I have no idea how to configure it like I used to, so that volume
> up/down buttons control the PCM.
>
> So anyway, with all this said, does anyone know how to allow the new
> audio system to see and control my LFE as well as my speakers?
>
>
> Thanks,
> Ricket
>