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Article ED00015: Electronic Band Amplification for Live Performance with iPads & Other Devices

Summary:

This article presents solutions to the problem of connectivity for live sound performance and amplification with iPad ensembles, or indeed any combination of electronic musicians using computer devices or other electronic hardware as instruments.

Application:

Teachers, general staff, students and anyone else who might be faced with the task of directly connecting multiple purely electronic devices like iPads, smart phones, Android tablets or laptops to a PA system for an electronic ensemble performance.

Details:

The following video provides a narrated visual overview of the concepts discussed in this article, and demonstrates how the setup might look in a typical performance space:



How much control do you need?
 
There are a couple of options, so let’s begin with two questions that might be posed with regard to audio mix control in this scenario:

  • Do you want to be able to mix every iPad/Device performer from the sound-engineer’s perspective at front of house?

  • Or would you be happy with performers themselves controlling the overall mix on stage and you’d only have control of the overall volume from the FOH mixing position?

 
Depending on which answer you choose, it will dictate some of your options.

If you want the first option – ultimate control, you’ll need to get either a summed MONO signal or a stereo signal from each iPad/Device to an individual channel of your PA system.

*Note; You can NOT DO THIS WITH WIRELESS options unless you want to spend a serious amount of money on dedicated pro-performance wireless hardware.  Don’t get the idea that you can wirelessly capture all of the audio streams with some sort of BlueTooth or WIFI option when dealing with multiple devices in a synced performance environment.  Such options for transferring Audio Wirelessly are only intended for single device connectivity and streaming audio and/or video for that device alone. 
They are also not intended to maintain the integrity of the signal’s timing, so you’ll have delay issues with all signals involved, making it impossible for performers to play in time with one another.

So, now we know we have to connect every device with an analogue audio cable.  This can get a bit messy on stage if you have a large number of performers, but if you know you have to deal with it that way, then you can plan for it accordingly.

So what would the logistics of this look like?

Let’s take a relatively large ensemble as an example – 12 performers, each with their own iPad.
 
If you’re planning to connect them to a PA system with at least 12 XLR input sockets you’ll need the following:

  • 12 x 3 meter stereo breakout to twin TRS cables:

    Image result for hosa cmp-159

  • 12 x stereo headphone splitter cables:

    Image result for headphone splitter cable

    These are connected to each iPad so you can send one copy of the stereo signal to the DI box (discussed below) and you can still connect headphones to each iPad.  This allows each performer to have their own direct monitoring of their signal through headphones, and we all know how important personal monitoring is when playing with a large ensemble.

     

  • 12 x sets of DJ style headphones:

    Regarding the use of headphones, they should usually perform in such a situation with one ear on/one ear off, just like a DJ would when setting up ‘the next track’. This means each performer can hear their own signal nice and clear, but will still pay attention to the context of their performance in the overall mix.  Investing in DJ style headphones that allow one ear to be pushed aside easily is wise for this, like these pictured below with ‘swivelling earpieces’:


     

     

  • 12 x XLR cables (length will depend on how far your performers are from the PA mixer inputs).

  • Stage breakout box:

    Note; It’s generally best to deal with shorter cables on stage and connect them to a ‘stage breakout box’ (pictured below), which in turn runs a combined cable ‘snake’ all the way to the mixer inputs, keeping everything neat and tidy with less to trip over:


     

  • 12 x DI boxes that can either provide two separate XLR balanced outputs for the incoming left and right channels, or units that can perform a true ‘Mono Summed’ signal containing both the left and right of the stereo channel.

    Image result for Behringer Ultra DI DI20
     

So, for a convenient summary, the following items are required for a dozen iPad performers:

12 x 3m stereo breakout to twin TRS cables:

12 x stereo headphone splitter cables:

12 x DJ style headphones (swivel ears):

12 x XLR cables:

12 x DI boxes:

1 x Stage breakout box:

Image result for hosa cmp-159

Image result for headphone splitter cable
 

Image result for Behringer Ultra DI DI20


A little word on DI boxes and stereo signals…
 
The ‘DI box’ pictured above is the Behringer ‘Ultra-DI D120’ unit.  This is an affordable unit ($44.00 + GST at the time of writing this in late 2017) that can accept both the left and right channels of a stereo pair and send them out as two separate balanced signals via XLR cables.  However, it can NOT perform true stereo summing to balanced mono output.
 
DI boxes that CAN perform true stereo summing to balanced mono output are VERY EXPENSIVE – around $300 per unit.  They do provide great convenience for dealing with multiple stereo signals though, as they will allow you to send the combined stereo signal from each iPad as a proper summed mono channel down a single XLR cable, so you don’t lose any of the audio info but you only use one channel on your mixer per stereo device.
However, if we wanted to mono-sum the output of each of our hypothetical dozen Mono signals from our 12 iPad performers, we’d need a dozen of these very expensive DI boxes with this capability, leading to a significant cost of around $3600 on DI boxes alone.

While high-quality DI boxes are certainly a very useful devices to have readily available in large numbers for any well used theatre/performance space, many will see this cost as prohibitive, so a solution utilising cheaper units like the Behringer model above is discussed below.


Why should we turn every stereo output into a ‘mono’ signal anyway?
 
In the live performance environment, mono signals are generally much more practical to deal with than stereo, for the following reasons:

  1. You only need half the channel number at the mixer end to receive them.  If we wanted to send all 12 iPads to the mixer in true stereo, we’d need 24 channels instead of 12, which would double the number of connections required.

  2. When managing the mix itself, it’s generally easier to find a place in the mix for each instrument when you’re only dealing with mono signals.  It simplifies the application of EQ and other effects, and you only have half the channels to contemplate too, which makes the mixing board itself less daunting to deal with.

  3. Mono signals allow you total control of panning each signal appropriately, to spread them across the front-of-house stereo field, making best use of your stereo PA system and enhancing the immersive experience for the audience.  The overall effect will be more detailed and interesting as a result.

 
 
How can we get ‘mono’ signals from our stereo iPad’s if we’re not using expensive ‘mono-summing’ DI boxes then?
 
If we’re planning to use the cheaper Behringer DI unit detailed above, by default we’ll only send the left channel of each iPad to the mix.  We’ll still connect both, so you don’t leave the right-side TRS connection from the iPad dangling, but only one XLR cable from the left channel XLR out will be sent to the mix, as detailed in the image below:
 

 
Now, this will be OK for most melodic/harmonic virtual instruments, but if one or more performers is playing a ‘virtual drumkit’ or another virtual instrument that has a lot of specific stereo panning set between the left and right channels, then it may be necessary to do one of the following for those particular performers:

  1. Connect two XLR cables to the DI box and send them both to the mixer, using two channels instead of one.  In this case you’d need to ensure the respective channels used are panned to hard-left and hard-right as appropriate on the mixing board itself, to preserve the original stereo positioning.

  2. Alternatively, if the virtual instrument they’re using has left/right panning controls for its individual drums and/or the main output, they can usually use these to pan the whole output to the left-hand side in the App itself, thus preserving all audio info and simply sending it all to the left mono output channel of the iPad. 
    This is easier to deal with for the person mixing and saves the need for connecting/using two channels in the mixer for the one device, but is less preferable for the overall listening effect, as the drums will no longer have their specific preset stereo positioning in the mix.

 
 
So what would all of this look like when it’s connected and ready to go?:

The image below shows a possible stage set-up modelled for our 12 iPad performers, all connected in ‘left mono’ through the Behringer DI box to a stage breakout box in the centre.  The stage-box outputs through a ‘cable snake’ that you can see running from the centre off the front of the stage and out of view to the mixer it’s connected to.



For maximum clarification, please check out the video below, which is an animated 3D model of the space in the image above.  It provides a narrated and annotated walk-through detailing every step of connectivity.




Are there alternatives to doing it the way described above?

A couple of alternative options that compromise by giving you less control from the front-of-house mixing position can be summarised as follows:

  1. Connect directly to a mixer/PA on the stage itself that is controlled by the performers, or a student/teacher nominated to be the ‘mixing engineer’ for the group.

    This can work OK, but it’s impossible for a band/person on stage to mix in direct consideration of the audience’s experience. 

    It also means more gear on stage, which can look messy and make the stage environment more cumbersome to deal with.

    However, if you’re dealing with a wireless app controlled digital mixer like the Behringer XAir or PreSonus RML series though, then you can effectively control the mix from anywhere in the venue with a laptop or iPad over WIFI, so the mixer being on stage is not usually an issue.  The digital mixers mentioned here essentially look just like ‘stage boxes’ (all the clever mixing electronics is hidden inside the box), so they don’t clutter the stage like an analog mixing board can.

    Below is a picture of PreSonus ‘UC Surface’ App for iPads, Windows, Mac and Android devices which is used to remote control PreSonus rack mixers described above:


     
  2. Connect each performer to their own keyboard amplifier or portable PA on the stage itself, or connect a number of performers to a few keyboard amplifiers/portable PA systems. 

    Keyboard amps and portable PA’s usually have multiple inputs, so if some devices like this are all you have to work with, you could get by with them.  The sound quality will be quite varied in this scenario though, so the experience for the audience and performers alike will be significantly compromised, as there won’t be a ‘unified mix’ coming out of a central PA for everyone to follow.  It therefore might be difficult for certain performers to hear each other in order to play in time/key and the audience may hear some performers much more than others.

 

See also:

27th of July 2018 Update (new related tutorials):

Our YouTube tutorial series on using a Behringer XR mixer with its  XAir Application control software has been uploaded here:

Behringer XR Series Mixer & XAir App Tutorials

A 'digital' mixer like the Behringer XR series can greatly simplify the setup, general use and management process of a live sound environment.  Check out the videos at the link above to see how it works.

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