• Chris

Wifi for Sound



Every mixing desk these days comes with an iPad app - some more useful than others! Whilst most shows can be operated without an iPad, they can often be a timesaver and offer a level of system setup/mix tweaking that would be impossible from behind a desk.


But all of this relies upon your wifi working. And so below I'll reveal what I've learnt through practical testing and some reading up!


PROBLEM: Your wifi works in an empty room but not at showtime


You've filled up the nice empty venue with a load of bags full of water and meat ("the audience"). Your fragile wifi signal is getting disrupted/soaked up by all of them. You sort of need them there to have a show. So you need to find ways to negate their presence...


1) Use 5GHz Wifi


Speaking to wifi site networking engineers at a festival, they explained that 2.4GHz is "dead in the water" for a good connection. All of those audience members have turned up with phones and a greater percentage of those phones are 2.4GHz wifi. They're all looking for a network and whilst not connecting to your wifi network, they are congesting the airwaves.


2.4Ghz is like being at a busy party. There's a lot of background chatter! And you can't shout any louder than everyone else.


5GHz is like moving to a quieter room. There's less chatter so you can hold a conversation better. You've found some clearer airwaves!


2) But doesn't 2.4GHz travel further because it's a lower wavelength?


In theory, yes. But the background chatter at 2.4GHz from other devices can negate any benefit.


I mixed a corporate show at Liverpool Arena. 2.4GHz & 5GHz wifi worked fine in rehearsal. I could operate the FOH desk from side of stage. Then 2000 people turned up, and 2.4GHz broke down 10m from the desk. 5GHz still worked at side of stage.5GHz is supposedly less robust, but real world scenarios can give different results.


3) Line of sight


Sticking a router in the back of a dog box will work in the warehouse and at soundcheck, but you will be prone to dropouts when that pesky audience arrives.


So raise your antenna up! And I mean high. Stick it on a mic stand above people's heads if you can. Whilst you can have the most over engineered wifi transmitter that annihilates any network in the vicinity, you still need to get a return signal from your feeble iPad back to your Crystal-Palace-inspired wifi antenna.

World BMX Supercross Championships - mixing MSC Big Band from the stand

I use an access point that uses Power-over-Ethernet (PoE). Thus you can stick the antenna anywhere you like and run a cat 5 back to the PSU down on the floor.

I use a Mikrotik GrooveA 52 ac. It is designed to be used as part of a point to point system, using a directional antenna to beam wifi to another unit up to several km away. However with an omnidirectional antenna it also works very nicely as a general Access Point. And it's IP rated (i.e. good for outdoors)

Nb. The Groove can do 2.4 or 5GHz, but not both simultaneously.


There are lots of other manufacturers available - Ubiquiti Bullet & nanostation, and any number of domestic routers.


4) Bandwidth

Some Wifi Access Points (AP's) will allow you to choose a 20MHz or 40MHz bandwidth.


Your AP has a certain amount of transmission power and receiving sensitivity. It's up to you to decide how you want those resources to be used.


You're not streaming video over this AP, so you don't need lots of space for data. So use a narrow bandwidth (20MHz). Your TX power is now being concentrated into a smaller bandwidth, so you'll get more range. Wider bandwidth = more space for data = less range.


Equally if you know you only want wifi TX/RX in one direction you could get a directional antenna. You have to decide how you want your limited TX/RX power to be used to best effect.


Same total TX power for each (area under each graph) - but narrow band has much higher peak power

5) Fixed IP

It just saves a whole load of negotiation between your iPad and a router if your ip is fixed. Every time you go out of range and reconnect, your iPad doesn't have to ask for an ip address to be dished out.


You could set ip's to be reserved for a set amount of time once they have been used once, but when you're trying to make something just work every time and 10s extra connection time feels like an age, this can help. Your network in most cases is pretty simple and hopefully your own dedicated space, so managing 2 or 3 devices shouldn't be too difficult.


If you're using an access point in bridge mode, it won't hand out a DHCP ip address anyway!


6) IP address, Router address & Router mode

I setup my access point in bridge mode - that way it is just a repeater. Whatever desk or ip you connect it to, it just spits it out as wifi. It saves a whole lot of time logging in and tweaking router ip's and subnets for a new desk every day.


Put your iPad ip address close to the ip of the desk, and use the subnet mask to reduce the number of addresses that the desk and iPad are looking to respond to. 255.255.255.0 should limit you to 256 addresses, which is much easier to deal with than searching through a subnet of 255.255.0.0 addresses: 65536 addresses!


I find my iPad gets upset if I don't specify a "router address", and doesn't show a wifi signal strength indicator. So pop in the address of the desk and it seems to be happier.


7) Wifi Scanner

On rare occasions, if your signal is really struggling you could try to look for a clear wifi channel. Some Venues may have site-wide Wifi that obliterates anything in its path. So get a wifi scanning app on your phone or iPad and know how to change the channel on your Access Point. I find this a pretty rare problem in 5GHz but in 2.4GHz it's more common.



8) Fing

Fing is a free app for your iPad that tells you all the devices that are connected to your network. Before even opening your desk app, scan the network and check if you can "see" the desk on the network. Otherwise there's no chance the app will!

I often hunt down problems like loose cat5 cables, the iPad has locked onto a different wifi network, wrong sub addresses, or the desk needs a new ip confirming / restarting.


9) Don't hide your network

I've not really found a visible network to be a problem in 5GHz. Even when hidden, there are still ways of seeing that a network is out there, and you've got a strong password on your network anyway, right?

If anything, keeping a network visible helps in the troubleshooting and setup process: you can check your network strength on any device as you walk around, and you don't have to read the name out letter by letter if you are getting someone else to connect their device.



Conclusions

This list isn't exhaustive, but hopefully will allow you to have more robust wifi. I still like to be in a situation where having an iPad makes a gig easier rather than being a show stopper if it stops working.

But the above tips are things I've found out the hard way - and the more you test things out, the more you get a feel for guesstimating if your wifi is going to work or not.


Let me know if you have any more tips and I'll add them.

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