CPU: Intel Core i7-2630QM @ 2.00GHz

Mainboard: Intel HM65 Express

RAM: 6/8GB DDR3

Display: 15,6" HD LED (1920x1080)

Graphics adapter: Intel Core Processor Integrated Graphics Controller, NVIDIA GeForce GT 555M

Soundcard: Integrated Intel HDA, Bang & Olufsen speakers with external subwoofer

Network: Atheros Gigabit Ethernet Controller, Intel Centrino Wireless-N 1030

Hard disk: Seagate Momentus 750GB 5400rpm SATA

Webcam: IMC Networks

Touchpad: Synaptics

There is a BIOS update (v207) on ASUS support website (go to the English one if you do not find) that fix the numpad bug.

Follow the official documentation: ALSA or/and PulseAudio.

We need PulseAudio profile which will use surround21 ALSA device:

/usr/share/pulseaudio/alsa-mixer/profile-sets/default.conf

...
[Mapping analog-surround-21]
device-strings = surround21:%f
channel-map = front-left,front-right,lfe
paths-output = analog-output analog-output-lineout analog-output-speaker analog-output-desktop-speaker
priority = 10
direction = output
...

Lfe remixing must be enabled for remixing third channel:

~/.config/pulse/daemon.conf

enable-lfe-remixing = yes

To prevent volume changing of PCM set volume to ignore in:

/usr/share/pulseaudio/alsa-mixer/paths/analog-output.conf.common

[Element PCM]
switch = on
volume = ignore
override-map.1 = all
override-map.2 = all-left,all-right

Install blop, cmt and ladspa and append these lines to your default.pa if you want to configure subwoofer on every PulseAudio daemon start:

~/.config/pulse/default.pa

load-module module-ladspa-sink sink_name=ladspa_low_pass master=alsa_output.pci-0000_00_1b.0.analog-stereo-21 plugin=lp4pole_1671 label=lp4pole_fcrcia_oa control=200,0
load-module module-remap-sink sink_name=remapLFE master=ladspa_low_pass remix=no channels=1 master_channel_map=lfe channel_map=lfe
load-module module-remap-sink sink_name=remap20 master=alsa_output.pci-0000_00_1b.0.analog-stereo-21 remix=no channels=2 master_channel_map=front-left,front-right channel_map=front-left,front-right
load-module module-combine-sink sink_name=combine slaves=remap20,remapLFE channels=3 channel_map=front-left,front-right,lfe
set-default-sink combine

Commands to control volume:

pactl set-sink-volume 0 +10%
pactl set-sink-volume 0 -- -10%
pactl set-sink-mute 0 toggle

External subwoofer + low pass filter configuration. Configuration uses blop, cmt and ladspa.

/etc/asound.conf

# upmix 2channels to 3, one for LFE
pcm.upmix2021 {
 type plug
 slave.pcm lowpass2121
 slave.channels 3
 ttable {
 0.0 1
 1.1 1
 0.2 1
 1.2 1
 }
}

# low pass filter for LFE channel
pcm.lowpass2121 {
 type ladspa
 slave.pcm upmix2121
 path "/usr/lib/ladspa"
 channels 3
 plugins { 
 0 {
 id 1672 # 4 Pole Low-Pass Filter with Resonance (FCRCIA) (1672/lp4pole_fcrcia_oa)
 policy none
 input.bindings.2 "Input";
 output.bindings.2 "Output";
 input { controls [ 200 0 ] }
 }
 1 {
 id 1098
 policy duplicate
 input.bindings.0 "Input";
 output.bindings.0 "Output"; 
 } 
 }
}

pcm.upmix2121 {
 type plug
 slave.pcm surround21
 slave.channels 3
 ttable {
 0.0 1
 1.1 1
 2.2 1
 }
}

pcm.!default upmix2021