Large PA requiring a simple Autopilot mode

[RoyS]

Hi All,

 

I work part-time as sound & LX tech for school that has the following hall FOH:

4x passive 2”+15” flown tops, plus 4x 18” subs powered by 4 stereo amps (1ch per box). The amps are fed from a Behringer DCX2496 crossover.

The main mixing desk is a LS9-32 which I also use as a system graphic across the main L+R outputs.

I have now had a request for an autopilot mode for safe use by non techs when I’m not around. This has to extremely simple & robust....

 

Unfortunately there is not a secure location where I can leave the LS9 setup for use with just a few XLR tails accessible on the stage to plug in an SM58 and a laptop. If I could, I could use the LS9’s graphic & setup some EQ, compressors & limiters on the inputs and outputs.

 

I am now considering a separate mixer/compressor/graphic arrangement that be simply patched in when I leave. Perhaps a dip box on the stage for user to patch a few mics and a laptop. The levels being preset on the alternative kit in my secure tech room on the stage.

For this alternative kit I am looking at a small 3U rack mount mixer like a Behringer Eurorack Pro RX1202FX and a Behringer compressor/limiter and 31band graphic.

 

A couple of issues for consideration:

1. The amp rack has 4x amps and a crossover which have to switched on one at a time or to avoid the mains tripping. The new autopilot kit, along with the amp rack will have to be switched on and off in the correct order to avoid nasty thumps from damaging drivers. I guess I therefore need to give extremely clear instruction regarding the power up/down sequence.

 

2. As the user will have access to the room where the autopilot kit will be housed I guess I can let them adjust the mixer levels as they feel appropriate but having the house graphic and comp/lim accessible worries me..

 

Sorry this is a bit of a ramble, but can anybody suggest alternatives to the above methodology?

 

Many thanks

[GreatBigHippy]

Initial thoughts.

1. Power up/down. I have seen custom set-ups where a bank of switchs have been wired in one line and connected to the various bits of kit. That way anyone can come in and all they have to do it make sure that they hit each switch in sequence. If you needed to be doubly sure then a smart sparky could sort out a time delay system of some description.

 

2. If your LS9 is too expensive to leave out and you are worried about people messing then why not get a small cheap desk and send the stereo outs into the locked up LS9 somewhere. It can be set to load a default set-up on power on and as such you can set maximum levels/limiter/eq without anyone even seeing it. The Mac method - simplicity through obfuscation. <edit - just re-read the bit where you suggest the separate mixer! Everything else still stands though>

 

3. With that you can have your cd player and a radio mic or two left accessible and lock everything else away in an enclosure. Leave very clear step by step instructions (including pictures) and the simple stuff they want to do should be fine. It won't be top quality but what do you want from an idiot proof setup?

[Simon Lewis]

An EMO power switcher allows keycode access to the system, and powers up and down in the correct sequence.

 

A device such as the Allen & Heath analogue installation mixer (GR2) or DSP boxes (iDR) or a BSS Soundweb can allow the front end to be replaced by a reasonably complex controller with a very simple interface.

 

The iDR series have small wall plates that can select presets, or give local level control without compromising other parameters.

 

None of this is cheap, or necessarily easy to install and programme, but it is possible to have simple push button or touch screen control so that the system effectively runs itself.

 

Simon

[RoyS]

Thanks for the replys so far.

 

I am aware of the EMO switcher which I think is useful if overpriced. Soundwebs are also great but don't fullfill the entire remit. They are also not cheap.. Sorry I should have said that I'm trying to do the project for under 1K£

 

Provided that I put the graphic and comp/lim behind some security panels I guess It will be fairly safe, system tuning & protection wise) The rack mount mixer (from any vendor) will leave the most room for audio problems. This and the power up/down cycling will have to be addressed with clear and simple training. A step-by-step user guide will also help.

 

In the coming months I am going to train up some pupil helpers to operate some of the kit described. ...I worry about enterprising little Jimmy patching his iPod directly into the I/P of the crossover....

[TomHoward]

Just as a thought with regard to the power-up - if it's a trip problem and you could avoid the power-on thump problem, do you need to use all four tops and subs for the simple system?

 

We have a similar setup, and when I'm not around we swap out the LS9 for a Behringer Xenyx 802 patched via a limiter into just the top cabs. Services well enough for laptops & DVDs, and it's not as daunting as trying to patch in an LS9. You could also run the limiter and graphic on the LS9, but that might mean leaving it on continually, so it may be as well to use a cheaper hardware alternative.

 

It's also only £50's worth of mixer so wouldn't be too much of a risk to leave out if they wanted to adjust levels.

[GreatBigHippy]

In my experience the trained students are not often an issue. Assuming you train them properly they are often keen and attentive and quick to learn. It is the older "trainees" that will need very clear instructions, and possibly the odd update.

[RoyS]

TomH - Good point. They can live without the subs. I've tried plugging in the rack with two amps switched on and it still trips. I guess they'd probably be happy with one amp driving one pair of tops..

 

GBH - Yes I know what you mean regarding the grown-ups...

 

I'm of to a gig now so won't be replying for a while. Cheers to all....

[aidso]

if it is in a school you could have your contracted sparks put in a time delay unit(something similar to the emo power switcher just not as pretty). Your idea of having a single 1u mixer is ok, but it will still be possible to over drive the system if they turn it past clip. Nothing is ever idiot proof.