their opinions or compare the system’s high frequency sound quality with a
pair of high quality mix position monitors delayed back to the PA. The PA
should sound warmer and more punchy but should never sound brighter than
good monitors unless the man with the cheque book wants it that way.
5) Always get trusted sound crew members to walk the field during the show.
Their reports will be telling you more about climate changes than your system
setup so don't be surprised if they ask for subsection level changes and eq
adjustments. Major changes can occur when:
i. the audience floods in (temperature gradients get disturbed and
humidity can rise)
ii. around sunset (temperature and local wind changes)
2a.2 Wind effects
Side winds
Gusting side winds can dramatically effect mid and high frequency sound by
changing the propagation direction (and, therefore, the way adjacent radiators
interact) as follows:
Single sound source
For example a 50km per hour (31 mph) side gust = approx 13.9m/s.
The temporary change in direction during the gust = arctan 13.9/340
= approx arctan 0.041 = approx 2.3º
This may seem trivial until you realise that this sudden 2.3º change will shift a poorly
arrayed system's polar pattern undulations about 2m to right at a typical outdoor mix
position. Easily enough to swap high-mid and high frequency peaks and troughs
several times in just a few seconds - an effect that went out of fashion in the 60s!
Variable combing (phasing) caused by wind effects should be minimised by avoiding
widely spaced, parallel high frequency sections carrying the same signals.
All material © 2007. Martin Audio Ltd. Subject to change without notice.
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