Littera Nova

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A brief post-mortem of technical issues at Solstice - Part 2, General A/V

Word count: 1681 (~10 minutes), Last modified: Tue, 14 Dec 2021 18:30:59 GMT


This year's setup involved 11 inputs and 5 outputs, not including the submaster mix for the livestream. Inputs consisted of two main choir mics, two auxiliary choir mics, two main vocalist mics, a seated vocalist mic, an instrumental mic, a line input for the piano, one floating general-purpose wireless mic, and one wireless headset mic. The outputs were a stereo output to the planetarium speakers, two separate monitor mixes, and a headphone pre-fader listening output. They were connected as per the diagram below.

Second round of notes for setting up the stage. Above is the overall wiring, below is power. The final setup involved mic stands in front of the choir risers rather than behind it because the available mic stands were not tall enough, and inputs 14 and 15 were not present as separate point sources as a result. Instead, they were mounted on the same stands as 13 and 16 which were moved to angle slightly above the heads of the second row of singers, and positioned roughly 6ft equidistant from the center of the risers, angled inwards.

The mixer and control surface were separate this year with the mixer acting as something of a stage box, with all inputs connected directly. This is a change from 2019 where inputs went into an analog snake that was then run back to a desk at the back of the room. The advantage of this was lower noise levels introduced to the signal - long cables tend to pick up hum because they act like a long antenna. It required a different set of controls, however, with the control surface (the bit with the sliders) connected via Ethernet to the remote port on the mixer. The control surface in use does not provide an real-time analyzer, which is used for determining a source's audio frequency composition (e.g. treble versus bass components) by eye. To allow for RTA functions, an additional device was necessary, so an Ethernet switch was used to connect all three devices, with the mixer in DHCP server mode to control the overall network. The secondary device was an iPad running X-Air Edit connected via a USB-C Ethernet adapter, since it was recommended by the manufacturer for this sort of use case. The mixer PFL output was run via a longer 1/4" cable to headphones that I used for monitoring.

The childcare room traditionally has a copy of the performance streamed to it. This year, as in previous years, it was done via the YouTube Live stream. The setup consisted of a Macbook connected to a projector via a USB-C - HDMI adapter.


The auxiliary choir mics were necessary due to a firmware glitch day-of that seemingly failed to route audio from the input channels for the primary microphone pair to the master mix despite going to monitors and visible meters. Rebooting the mixer solved this issue, but this was not discovered day of, and instead the microphones were moved to other ports. To avoid a mid-show mic failure causing a complete loss of signal, additional microphones were mounted in the same positions and the gain, pan and EQ was adjusted to have similar audio qualities. The auxiliary pair were not utilized during the show.

All microphones were on boom-arm stands. This wasn't necessary, and it confused some of the performers who had trouble adjusting them. The intention was that it would be easier to adjust height on the mic stand this way, as performers were of diverse heights, but given learnings from this year I will likely not use boom arms except for instrumentalists who are sitting. For micing the choir, I was generously provided with PRO45 hanging microphones close to day-of by Elena. While this year we were unable to mount these hanging microphones properly due to stands being insufficiently tall for the top of the risers, but they will be used in future to give more flexibility in balancing the four separate sections of the choir. As it stands, the stereo pair used was good but not ideal, as the breadth of the pickup pattern was insufficient for properly covering all three rows of singers, biasing towards the top two.

Many participants did not stand the correct distance and positioning from microphones. Much of this was due to insufficient training for the participants, and there was little way to communicate to participants that they should fix their positioning while the show was ongoing, especially during the darkness. Additionally, since multiple speakers and vocalists did not memorize their parts, they ended up either looking back at the screen or looking down at notes held in front of them. Both of these cases had failure modes for the audio, with the former leading to cut-outs as they sang away from the microphone, and the latter leading to changes in the quality of the sound as they moved further away from it. As a side note, the distance from the microphone is important because as you get further from it, less bass is picked up compared with treble and mids (bass roll-off). If the distance is varied, the audio engineer has to do significantly more work attempting to compensate for the change in equalization. This is especially evident in some singers who have more robust bass voices and also move their heads while singing, in part due to the aforementioned failure mode when memorizing.

The need for quality adapters and cabling cannot be overstated here. During this performance, two separate adapters failed - a USB-C A adapter and a USB-C Ethernet adapter. The first led to failure to record pre-mix signals from all channels for mastering, and the second led to loss of the RTA for the show due to the iPad being unable to communicate with the mixer.

There were no pop screens on the vocal microphones - this was intentional, as they attenuate the signal somewhat and do not work well with multiple speakers and equalization. This may be reconsidered next year if sufficient training to get participants to speak an appropriate distance from the microphones is not achievable.

There were several instances of distortion in sound at different points in the show. This was due to insufficient headroom on two signals, the line input from the piano and the headset wireless microphone. I hypothesize that the former is due to adjustment of the signal on stage, but the latter is due to poor planning on my part in adjusting the gain of the belt pack properly. Pre-show there was an issue where both the wireless stick mic and the headset were on the same channel - this was fixed but bears noting.

Guitars were troublesome to mic this year - in planning, I anticipated that the guitars would have built-in pickups with line outputs that could be run to the board. This was not the case, as I discovered too late in the process to devise a solution that would involve more microphones. Instead, guitarists were expected to adjust a nearby SM58 microphone (either the wireless or one of the center vocal mics) to point at the sound hole. This was a subpar solution in multiple respects, firstly because the SM58 is not really an instrument microphone and has trouble with dynamic range, secondly because guitars move during performance requiring gain adjustment from the audio engineer, and thirdly because it required instrumentalists to adjust microphones that would subsequently be used for vocals into positions that required significant adjustment for vocalists, and many vocalists as previously mentioned did not adjust them back.

The positioning of the mixer control surface was not ideal, as room mixing was mostly done via headphone monitoring of the overall mix. While I have a lot of experience with doing this sort of thing, if an issue had occurred mid-show with speakers that did not show up in headphone cueing, I may have not compensated for it.

A limitation of the X-Touch mixer control surface is that it only has eight channels visible at a time. This is not a huge issue if planned for, as usually no more than eight sources are present in the mix at a given time. However, the choir microphones were set to channels outside of the main 1-8 of the other sources, and so mixing the choir and instrumental sources was an exercise in frustration and flipping between layers of sources on the console. This could have been mitigated by utilizing channel groups, but since setup had unexpected issues, there was not time to adjust and group the choir into a channel group to display on the same layer.

Plans/recommendations for next year

Previous post in this series: Part 1, Livestream