Stories From the Road

By Allen Rowand

December 12, 2008

11: Minneapolis, or You Better Carry That Weight(ing)

One of the first things I like to do when I start to look at a venue is to see what is happening in the room acoustically.

This is not what I like to see in the room with no signal being played! Taking a look at the spectragraph showed what was going on:

Tons of air handler noise which was echoing around the room. Just for laughs I played pink noise to see what was going to happen:

These are the 3 mics in the orchestra level; the green trace shows a drop in high frequency since the underbalcs aren't on. Upstairs looked like:

Here, there's high freq rise in the magenta trace since the mic was about 45' away from the clusters. Average all the mics and you get:

A little bright, a little low end rise. But that hump below 50Hz? Ridiculous! The house not only had a loud HVAC system, but the architecture was amplifying it. The amount of sub-bass energy was making my spl readings completely inaccurate. Since SpectraFoo doesn't natively offer weighting, I relied on the MIO Console to do the job.

This effectively removed the low end resonance I was getting in SpectraFoo, and gave me a more usable and realistic measurement. Here's a shot of the house with the weighting in place and after a bit of EQ:

Having the MIO's dsp environment is great in letting me tailor my inputs to SpectraFoo, and in more ways than simple weighting. If I see a frequency spike due to interference from other devices (like gear spitting at 16KHz) I can notch it. I catch this a lot from switching PSUs at the console, or video monitors in the booth behind the mix position.

Until next time,
Allen