In the ticket business, you start to see a trend when it comes to live music. Outdoor venues, amphitheaters in particular, do much better in terms of sales than colosiums or indoor theaters. You might think it's simply because of the fact that people would rather be outdoors, but according to Nathan Mattise in WIRED magazine's May 2012 print issue, "No, it's not the drugs. Music really does sound better outdoors."
Apparently you'd need a sound engineer to really understand every detail of why this is fact, but the basic principle is fairly simple; there's nothing for sound to bounce off of in an open-air amphitheater. That means sound engineers don't have to compensate for sound waves bouncing off of every wall in the venue. "The PA won't ever sound better than it does outside." proclaims Mark Carlson, CEO of Carlson Audio Systems.
I suppose this summer I'm going to a few more amphitheater concerts to listen to the difference. I haven't been to Red Rocks Amphitheater since Depeche Mode came a few years back, so my memory of the sound quality is a little murky.
Great read Nathan Mattise! If anyone has a link to the online article, please post it in the comments so others can give it a quick read.