Open Standards/ChoirWire distributed audio mixing/Application Examples

Example of a mixing console

fig. 23: Example of a mixing console

This example shows a possible mixing console with the possibilities in a certain situation: On the left side there are 24 (of possible 256) input selectors/displays. On each there is the input number and a “solo” button / lamp on which the channel (here 10) has more volume (Solo add). Then the level indicator chain of the input and – the most important thing- a selection button in several colours: If it is off, then the input is not connected in the physical ring. If it is green, the input is present and OK, but is not selected. If it is red, the input has encountered a problem – for example, a bad wire. If it is yellow, the input is selected. Pushing the input button selects this input, pushing a “Group” button selects the group – and all the inputs assigned to this group are yellow. In this example, group 2 was selected. The inputs 20, 21, 22 and 23 (for example 4 sopranos) are assigned to that group and are yellow. Now the selection buttons (selection volume, selection pitch/balance, selection bass / mid / treble, Monitor 1,2,3,4) will adjust the sound levels of the whole soprano group. If only one input is selected, the selection buttons adjust the sound of this input. The master volume left and right can be adjusted in every setting.

Here an example for calculating the volume of one channel: Input 12: Volume left = Volume(12) + balanceL(12)+[solo(12) if active]+Volume(group2)+ balanceL(group2)+MasterVolumeL So, the input12 gets the information with which level he should add his signal to the main channel left. The calculation adds only the setting levels in db, not the signal level. So the problem of “headroom” as in analogue mixing consoles does not exist. The adjust buttons are position coders. The actual setting of a channel is displayed via LED chain. Of course, if the selected input changes, the present “selection volume” for example changes. The LED chain will display the virtual “position” of the button. It is not possible to use potentiometers, because it may be necessary to turn this button round and round. Analogue faders can be used for master volume setting.

Set addressing of the distributed input

The mixing console sends out a “addressing request” bit to one input channel. (For example, after pushing “select” and “solo” button on the mixing console.) The distributed inputs have an addressing mode (after pushing a button). In addressing mode, the input waits for the “addressing request” bit and accepts the address as his new address for future. It shall be stored in non volatile memory, too. Then this input answers with his address normally – and the mixing console knows, the slave is addressed now and resets the “addressing request”. Example: pushing “address” button on an input, then pushing “select” and “solo” button on the mixing console – and the input is connected or reconnected.

Examples of distributed inputs

Fig. 25: Example of a distributed input with monitor output

This example shows an implementation of a distributed input. In the middle (red) the adjust button for addressing. On the left (or bottom side, if turned) the connectors for the input (microphone, e-guitar, keyboard,…), the monitor output (for example in-ear monitor or headphone) and – the ChoirWire input. A ChoirWire output is foreseen to make chains of musicians possible. With the yellow “solo” button the solo offset of this input can be switched on and off. So no intervening from the mixing console is necessary. With the “mute” button the input can be switched off short time – for example while coughing. The right three buttons are a small mixer for the monitor out. It mixes the own input, and two other channels from main channel, monitor 1, monitor 2, monitor 3 or monitor 4. So for example a singer can individually mix his monitoring from himself, the piano on monitor 2 and the complete set from main. Of course other implementations are possible, for example a pure input without monitoring and a pure distributed output without addressing.

Also possible is a locally controlled distributed input without remote control. This device will send his data directly to main and a monitor channels, volume and sound are locally adjusted. Addressing and remote mixing console are not necessary; the musician controls directly the speaker output and there is no “master control” for all inputs. So this is suitable for small bands only. The number of monitor channels is given by the mixing console (if present) and recognized by this input; if there is no mixing console in use, the number of monitor channels is set to two, with 24 bits.

Fig. 26: Example of a distributed input which local control and without addressing

Example of a Data Collector

Fig. 27: Example of a Data Collector

The data collector is the power supply for all distributed inputs and “collects” the music data from the right and left side of the physical data ring. It can be put in a 19’’ rack, for example, and mounted together with the power amplifier. It contains only connections: for power, for the remote mixing console (or laptop), then the sound outputs main and monitor channels and, of course, the connector for the ChoirWire distributed inputs. Of course, it is possible to build the mixing console and the data collector in one housing. (Then the main outputs are at the FOH – this is kind of taste.)

Application example: Church or town hall

With ChoirWire, present installed wiring for microphones (XLR connector system) can be used for connecting a remote mixing console. So it is easy to use more microphones on the stage than before.

Fig. 28: Example for old configuration with 1-2 mic’s - Fig.29 ChoirWire configuration: 1-256 mic’s