How to Set Up a PA System with Free or Cheap iPhone Apps

I have a 3G iPhone now because of the toolkit I could have in my hand when working on AV projects. For live sound gigs, it is very small and convenient to use and I now prefer it over my cumbersome laptop and hand held SPL meters. 

Don't get me wrong, I will always use my probe-mic ANSI IEC Type II SPL meter for paid consultations along with my Radio Shack analog meter for details, but when I set up a sound system, I usually try to identify gross fluctuations rather than fine details, so the iPhone app seems to give me my feedback problems and my 'boxy' frequencies to correct.

Method for ringing out feedback with RTA Lite:

1) With amplifiers turned up and balanced properly (unity gain or thereabouts), turn up the master volume fader of the mixer to unity (or '0dB' or about 75% up, depending on the mixer), turn up the mic channel fader to maximum setting (unity or +5dB, depending on how you handle your gain structure), then increase the mic channel trim pot slowly until mild feedback occurs (a slight ringing only!!).

2) Cup the bulb of the mic carefully to induce more feedback, but don't allow spikes! With the RTA Lite app, see which frequency is reacting the most and cut by about 5dB. 

3) For Low frequency resonance, be sure the high-pass filter for the mic channel is disengaged and say some low-toned words directly into the mic to see what is reacting ans cut those frequencies a bit just enough to stop the 'trail' of resonance. For 'boxy' sounds, say words like 'walk' and 'dog' to identify where to cut and what bandwidth of frequencies.

For estimating maximum SPL and headroom with Studio Six SPL Meter:

1) For live bands - set the meter to 100dB on the dial and sing very loudly (or shout, if you can't sing). A very loud singer should be able to sing just over 100dB, A-weighted. The bass drum (or loudest low frequency transient sound) should be between 106-110dB, C-weighted. Anything louder than that and you're on you're own.

2) For speeches - set the meter to 60dB and speak into the main microphone at a distance of about two feet from the mic, to simulate the worst case scenario. You should be reaching conversational level throughout the room (between 55-65 dB, A-weighted). Anything quieter than that and people will complain (get the speaker to talk closer to the mic).

3) For media soundtrack playback - set the meter to 70dB, A-weighted and set the playback levels to about 60-65dB for dialogue. Switch to C-weighted and adjust low frequency EQ so it runs at about 65-70dB (depending on the soundtrack mix). Business presentation media will be as compressed as a TV commercial (around 5dB of dynamic range) and feature films will be as follows - 60dB for A-weighted dialogue and up 80dB C-weighted or more for the loudest sound effects.

The results you get will be fairly accurate and you should get great results for less than five dollars of iPhone apps.

One last note - do you need pink noise to ring out a sound system? The answer is: maybe, maybe not. Pink noise will help to EQ a system to a 'flatter' response, but flat doesn't always mean it will be good-sounding. In fact, trust a reference song or pre-recorded speech when it comes to tuning for naturalness and clarity.

I'd want to tune a large concert system or a movie theatre with pink noise, but not necessarily a night club or conference room. I mainly aim for four areas of correction in this order: upper middle frequency feedback, boxy vocal sounds, low frequency resonance trails and proper SPL delivery, and the two apps I use help me do just that.

Buck Moore

B4UShowit.com

The USB Key, Woe is Me!!

Oh, the USB key! Both the savior and bane of my AV existence. When I started working with computer presentations, as a part of live events, I would get last minute PowerPoint updates on floppy disks and CD's, with only a small handful of presenters who were savvy enough to carry USB keys. Clearly, those savvy presenters were a sign of what was to follow.  

Once upon a time when data projectors with 800 x 600 native resolution ruled the day, having floppies and CDR's to upload data was somewhat precarious, and hot-swapping PC computers with 15-pin VGA cables was a recipe for disaster. 

As we entered the age of the highly portable USB key, 64 MB beat floppies and 128 MB was a luxury for some. As things progressed, storage increased dramatically, prices plummeted, USB2 picked up speed (punny!) and audio-video files for playback became commonplace. Oh, what a wonderful, digital world! Or, is it?   

Having these fast-loading hot-swappable little memory banks is necessary  for the fast-paced world of live events, but they can also be and excuse for being unprepared! Since presenters can keep making countless updates, it is a very simple matter to hand over a USB key to an AV technician to load onto a host computer, unless the technician gets five at once with no labels, unclear file names (and hierarchy), font changes, .pptx files, missing PowerPoint images, unlinked AV files and the list goes on. 

The technology has gotten smarter and faster, but it can also be a crutch when half a dozen presenters leave everything until the last minute and thus, to chance. The newer technology doesn't matter when the planning has been compromised and results in details falling through the cracks or the wrong presentations appearing on a huge projection screen.

With that all being said, here are some great tips for presenters and meeting planners who are a part of all-day events with multiple presentations:

1) Avoid interrupting anybody who is actively loading and double checking a presentation. Instead, develop a system* for updates and last-minute presentations with an AV control sheet and sticky notes, or little Zip-lock (tm) baggies with presenters names marked on them. Nothing should be left to memory.

2) Ensure all media files on the USB key are linked to the presentation software. The presentation file and the media files should be in the same folder, usually located on the desktop for easier access. If the media files won't play, start the presentation from the USB key directly, plan a workaround so the technician can assist in the playback manually. 

3) Ensure all the files are sensibly named on the USB key and put into a folder that makes sense when someone else is looking for it. 

4) Bring a USB extension cable if your key is wider than average or it won't fit into the USB port with other peripheral devices beside it. 

5) Label the outside of the key or put it in a labeled envelope (or baggie) with first and last name, and name of the file.

6) If the USB key is password protected, make arrangements for someone else to open it when they need to.

Hope these tips help you to experience a smooth conference or other business meeting!

Buck Moore,

B4UShowit.com

* One such system I developed involves numbering preloaded presentations for every presenter. If presenter #1 and #4 have preloaded presentations on a host computer (or master USB key), but #2 and #3 bring theirs on the day of the event, the numbering order should be the following: 

Presenter #1 - 1

presenter #2 - 1a

presenter #3 - 1b

presenter #4 - 2

Both the AV sheet and the computer files should be re-named with the numbering system as the prefix for each. That way, they will show up in numerical order and can be located quickly and tracked as to when they were received. If the first presenter of the day did not have a pre-loaded presentation, but brings on the day of the event, the should be numbered "01", so the order is always right.

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