Show Redundancy

  • Posted by Simon Byrne
  • On July 5, 2017

Technical difficulties: you’d expect them at a five-bands-for-five-bucks bash at your local, but when they happen at prominent or world class events, it is a serious problem.

A few recent high profile event failures have highlighted the need for better redundancy in show systems. Particularly as systems are increasingly more complex, and now highly reliant on data networking and computerisation. With the advent of social media, a failure is big news.

Radiohead’s PA System failure at Coachella this year is a case in point. It brought worldwide coverage but remarkably it seemed that there was no readily accessible backup system when the AVB link on the Avid E6L processing engine failed between Front of House and the stage. Ugly.

Avid’s Senior Market Specialist Robert Scovill, is also Tom Petty’s FOH Engineer. He is mixing the current tour on an Avid S6L. His FOH setup includes a second backup E6L processing engine. He cannot do a seamless switch over so another S3L desk is standing by with mix stems already setup from the foldback department. Yes, the guy from Avid tours with 2 backups at FOH.

Lighting guys have done this for years. Until recent times, lighting desks have been routinely flakey so the there has always been spare standing by, ready to go.

However production systems are rarely fully redundant in the true sense and in all but the biggest of events, the budget does not permit fully redundant systems. Risk assessments need to be done.

When planning for what can go wrong on events, an assessment needs to be done of what you or the client are likely to put up with in terms of failures. Do you need to guarantee a perfect seamless gig every time? That gets expensive because more equipment and labour is needed. Or can you get through with say a 10 minute downtime? The budget for a small community gig combined with the rarity of a audio desk failure may mean the cost of carrying (or renting) a couple of $20,000 consoles may not be financially viable.

A great solution in these cases is to have an emergency mix setup in the foldback desk. That way when FOH fails for whatever reason, just plug the foldback desk into the FOH speakers and away you go. The system might be off for a few minutes but in the context of the event that might be okay, if undesirable. A an old analog desk can sit in the truck for the same reason.

The key is to have properly thought through and tested options for when there is a failure. Because there will be a failure…one day.

There are some simple redundancy/risk management solutions that should be on every show:

Calculate and spread the total power load and ensure that you have not just enough, but plenty to spare. Running close to capacity means you run the risk of losing a circuit, but also voltage drop which can lead to problems with equipment being underpowered. Also, inductive loads (transformers, motors etc) will initially draw substantial inrush current, up to 10 – 15 times their rated draw for a couple of cycles (about 40 milliseconds). In the event of power failure, your power supply system needs to be able to cope with that initial massive draw of your whole rig without tripping the supply breakers.

I always use a 3 phase distribution board even if I know my total load is under 10 amps. It means I have a 40 amp supply and circuit breakers are immediately accessible to me. Talking of breakers, find out where the house breakers are, inspect their rating to ensure they are adequate, and get the number of the person with the key to the electrical cupboard in case of them being tripped.

This leads to basic power management and distribution. Don’t leave yourself exposed to something being overloaded or something being able to be kicked out. On my shows, the distribution board is always up on a case ensuring that plugs cannot be kicked out. Investing in good power cabling and distribution is worthwhile.

In Australia, I’ve had more problems with uninterruptible power supplies (UPS) than I have had with the actual power supply. Power supplies in equipment are really good nowadays so it could be argued that with the complexity and more connections of the UPS, it has added risk so there needs to be a real reason to use them.

Therefore, I only use them on devices that need to boot up and don’t have their own battery. Laptops have their own batteries so I won’t unnecessarily load up the UPS with them. However, a digital mixing desk which takes 20+ seconds to boot up, absolutely is on a UPS. It means a 1 second power dropout recovers straight away because the desk does not need to reboot. In Asia and South Pacific the power is variable and a UPS is critical.

RJ45 connectors are an inherently rubbish connector from both a mechanical and electrical tolerance point of view for what we do. As is Cat 5e/6 cable. Through clever design, the designers have managed to stuff a massive amount of data through it cheaply, but it is fragile.

Yet it is the standard which we are often forced to rely on in our high abuse environment. It is prudent to use shielded cable for it’s mechanical protection. You don’t really need the shield for electromagnetic noise rejection in this instance (it can actually reduce the data performance of the cable) but it is really useful for mechanical protection. Ethercon shells should always be used to limit the damage to the RJ45’s.

For mission critical applications, run two cables. Cabling is a big, if not the biggest point of failure. Even if your equipment won’t permit redundant connections, it is very worthwhile to run 2 anyway so that should your primary line gets damaged, you can quickly changeover.

Never, EVER update software or firmware on show days. There are countless examples of this not going well. Your day is stressful enough and you don’t want to find incompatibilities mid show.

Two microphones on the money sources – It is always great to have 2 microphones on a lectern or 2 wireless lapels on a presenter. If one goes noisy, simply switch over.

There is no point in having redundant systems if they are not tested properly. This is absolutely critical as there will be some surprises and it better experience them when it doesn’t matter. It is amazing the amount of supposedly failsafe system, fail badly.

I often see overly complex rigs which in my view, the complexity does not add much to the final result. That being the case, costs and the risk of failure has been increased for little or no benefit. Are the added features worth the increased risk of failure? If not, don’t do it.

It’s not a matter of if, but when you have a big ugly, embarrassing failure. Are you ready that day? Yes, Radiohead now tour with 2 desks…

I am a contributing writer to CX Magazine . CX Network is the voice of technicians in entertainment and audio visual across Australasia.

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I am a contributing writer to CX Magazine . CX Network is the voice of technicians in entertainment and audio visual across Australasia.

Lot’s of great stuff!

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