[LAU] On the fly bass downmixing to mono (mpd or alsa)?

[Shani Hadiyanto Pribadi]

On 10 February 2014 06:51, Matt Garman <matthew.garman at gmail.com> wrote:

> Sure, no problem.  What I have is:
>     (1) Linux server with a media collection in a basement network closet
>     (2) A powered subwoofer on the main floor, with only a single coax
> run between the sub and network closet in the basement
>     (3) In-ceiling speakers on the main floor, all wires terminating
> in same network closet

Are the in-ceiling speakers connected in pairs?
If they are then you need 3 channels, L,R,M. where M = L+R.
If you have a soundcard with at least 3 channels and insist on using
alsa output then you can use
http://alsa.opensrc.org/Low-pass_filter_for_subwoofer_channel_%28HOWTO%29
to upmix from 2 channels to 3 channels in ALSA. (you can ignore the
part about low pass).

Or you could instead use the jack mpd output plugins and just connect
the channels
like
MPD_out_L -> HW_L
          -> HW_M
MPD_out_R -> HW_R
          -> HW_M

There is also jackminimix for a OSC controlled mixer.
I think ecasound can also be used for that purpose.

> Note that in this solution, I'm sending the full-range signal to both
> the in-ceiling speakers and the sub.  The sub has a builtin crossover,
> and the speakers can handle the full signal.
>
> As a side note, if you read the AudioCircle thread above, you'll see I
> already have an AVR that can send a bass signal over coax... my goal
> is to get rid of the AVR though, as I have more speakers than it has
> outputs (would rather not use the AVR and speaker selector), plus I
> want to move control off the AVR and onto the Linux server (mpd).

Now this is where I lost you, how many speakers do you have exactly,
and how many amps for them? Doesn't it mean that you need as many amps
for each speakers you have if you ditch the speaker selector?

If indeed you want to control it like that then you also need a soundcard
with as many output channels as the number of power amps channels for
the speakers.