Committed after system build
diff --git a/system/configuration.nix b/system/configuration.nix
index 7c279ce..d17dc00 100644
--- a/system/configuration.nix
+++ b/system/configuration.nix
@@ -112,7 +112,16 @@
       support32Bit = true;
     };
     pulse.enable = true;
+    config.pipewire = {
+      "context.exec" = [
+        {
+          path = "/usr/bin/pipewire";
+          args = "-c /etc/pipewire/7.1-surround-sound.conf";
+        }
+      ];
+    };
   };
+  environment.etc."pipewire/7.1-surround-sound.conf".source = ./pipewire/7.1-surround-sound.conf;
 
   # Enable touchpad support (enabled default in most desktopManager).
   services.xserver.libinput.enable = true;
diff --git a/system/pipewire/7.1-surround-sound.conf b/system/pipewire/7.1-surround-sound.conf
new file mode 100644
index 0000000..aa23099
--- /dev/null
+++ b/system/pipewire/7.1-surround-sound.conf
@@ -0,0 +1,120 @@
+# Convolver sink
+#
+# start with pipewire -c filter-chain/sink-virtual-surround-7.1-hesuvi.conf
+#
+context.properties = {
+    log.level = 0
+}
+
+context.spa-libs = {
+    audio.convert.* = audioconvert/libspa-audioconvert
+    support.*       = support/libspa-support
+}
+
+context.modules = [
+    { name = libpipewire-module-rt
+        args = {
+            #rt.prio      = 88
+            #rt.time.soft = -1
+            #rt.time.hard = -1
+        }
+        flags = [ ifexists nofail ]
+    }
+    { name = libpipewire-module-protocol-native }
+    { name = libpipewire-module-client-node }
+    { name = libpipewire-module-adapter }
+
+    { name = libpipewire-module-filter-chain
+        args = {
+            node.name        = "effect_output.virtual-surround-7.1-hesuvi"
+            node.description = "Virtual Surround Sink"
+            media.name       = "Virtual Surround Sink"
+            filter.graph = {
+                nodes = [
+                    # duplicate inputs
+                    { type = builtin label = copy name = copyFL  }
+                    { type = builtin label = copy name = copyFR  }
+                    { type = builtin label = copy name = copyFC  }
+                    { type = builtin label = copy name = copyRL  }
+                    { type = builtin label = copy name = copyRR  }
+                    { type = builtin label = copy name = copySL  }
+                    { type = builtin label = copy name = copySR  }
+                    { type = builtin label = copy name = copyLFE }
+
+                    # apply hrir - HeSuVi 14-channel WAV (not the *-.wav variants) (note: */44/* in HeSuVi are the same, but resampled to 44100)
+                    { type = builtin label = convolver name = convFL_L config = { filename = "hrir_hesuvi/hrir.wav" channel =  0 } }
+                    { type = builtin label = convolver name = convFL_R config = { filename = "hrir_hesuvi/hrir.wav" channel =  1 } }
+                    { type = builtin label = convolver name = convSL_L config = { filename = "hrir_hesuvi/hrir.wav" channel =  2 } }
+                    { type = builtin label = convolver name = convSL_R config = { filename = "hrir_hesuvi/hrir.wav" channel =  3 } }
+                    { type = builtin label = convolver name = convRL_L config = { filename = "hrir_hesuvi/hrir.wav" channel =  4 } }
+                    { type = builtin label = convolver name = convRL_R config = { filename = "hrir_hesuvi/hrir.wav" channel =  5 } }
+                    { type = builtin label = convolver name = convFC_L config = { filename = "hrir_hesuvi/hrir.wav" channel =  6 } }
+                    { type = builtin label = convolver name = convFR_R config = { filename = "hrir_hesuvi/hrir.wav" channel =  7 } }
+                    { type = builtin label = convolver name = convFR_L config = { filename = "hrir_hesuvi/hrir.wav" channel =  8 } }
+                    { type = builtin label = convolver name = convSR_R config = { filename = "hrir_hesuvi/hrir.wav" channel =  9 } }
+                    { type = builtin label = convolver name = convSR_L config = { filename = "hrir_hesuvi/hrir.wav" channel = 10 } }
+                    { type = builtin label = convolver name = convRR_R config = { filename = "hrir_hesuvi/hrir.wav" channel = 11 } }
+                    { type = builtin label = convolver name = convRR_L config = { filename = "hrir_hesuvi/hrir.wav" channel = 12 } }
+                    { type = builtin label = convolver name = convFC_R config = { filename = "hrir_hesuvi/hrir.wav" channel = 13 } }
+
+                    # treat LFE as FC
+                    { type = builtin label = convolver name = convLFE_L config = { filename = "hrir_hesuvi/hrir.wav" channel =  6 } }
+                    { type = builtin label = convolver name = convLFE_R config = { filename = "hrir_hesuvi/hrir.wav" channel = 13 } }
+
+                    # stereo output
+                    { type = builtin label = mixer name = mixL }
+                    { type = builtin label = mixer name = mixR }
+                ]
+                links = [
+                    # input
+                    { output = "copyFL:Out"  input="convFL_L:In"  }
+                    { output = "copyFL:Out"  input="convFL_R:In"  }
+                    { output = "copySL:Out"  input="convSL_L:In"  }
+                    { output = "copySL:Out"  input="convSL_R:In"  }
+                    { output = "copyRL:Out"  input="convRL_L:In"  }
+                    { output = "copyRL:Out"  input="convRL_R:In"  }
+                    { output = "copyFC:Out"  input="convFC_L:In"  }
+                    { output = "copyFR:Out"  input="convFR_R:In"  }
+                    { output = "copyFR:Out"  input="convFR_L:In"  }
+                    { output = "copySR:Out"  input="convSR_R:In"  }
+                    { output = "copySR:Out"  input="convSR_L:In"  }
+                    { output = "copyRR:Out"  input="convRR_R:In"  }
+                    { output = "copyRR:Out"  input="convRR_L:In"  }
+                    { output = "copyFC:Out"  input="convFC_R:In"  }
+                    { output = "copyLFE:Out" input="convLFE_L:In" }
+                    { output = "copyLFE:Out" input="convLFE_R:In" }
+
+                    # output
+                    { output = "convFL_L:Out"  input="mixL:In 1" }
+                    { output = "convFL_R:Out"  input="mixR:In 1" }
+                    { output = "convSL_L:Out"  input="mixL:In 2" }
+                    { output = "convSL_R:Out"  input="mixR:In 2" }
+                    { output = "convRL_L:Out"  input="mixL:In 3" }
+                    { output = "convRL_R:Out"  input="mixR:In 3" }
+                    { output = "convFC_L:Out"  input="mixL:In 4" }
+                    { output = "convFC_R:Out"  input="mixR:In 4" }
+                    { output = "convFR_R:Out"  input="mixR:In 5" }
+                    { output = "convFR_L:Out"  input="mixL:In 5" }
+                    { output = "convSR_R:Out"  input="mixR:In 6" }
+                    { output = "convSR_L:Out"  input="mixL:In 6" }
+                    { output = "convRR_R:Out"  input="mixR:In 7" }
+                    { output = "convRR_L:Out"  input="mixL:In 7" }
+                    { output = "convLFE_R:Out" input="mixR:In 8" }
+                    { output = "convLFE_L:Out" input="mixL:In 8" }
+                ]
+                inputs  = [ "copyFL:In" "copyFR:In" "copyFC:In" "copyLFE:In" "copyRL:In" "copyRR:In", "copySL:In", "copySR:In" ]
+                outputs = [ "mixL:Out" "mixR:Out" ]
+            }
+            capture.props = {
+                media.class    = Audio/Sink
+                audio.channels = 8
+                audio.position = [ FL FR FC LFE RL RR SL SR ]
+            }
+            playback.props = {
+                node.passive   = true
+                audio.channels = 2
+                audio.position = [ FL FR ]
+            }
+        }
+    }
+]