This James Boyk article explains how to create a good acoustic situation, and the Red Rocks Amphitheater matches many of the conditions you mentioned.

I’m no expert but I expect it’s because the rocks are surrounding the seating and stage, and their shape is such that they have formed a natural effect on the sounds produced in the amphitheater which concert halls try and achieve with patterns of bricks in the walls, curtains etc.

For anyone wondering what the Red Rocks Amphitheater is: http://www.redrocksonline.com

I am not sure if there is a website but let me take my best educated guess at what is happening. First I assume that you have only seen amplified music at the Red Rocks Amphitheater.

For most amplified rock concerts you want something totally different than you want for a philharmonic or chamber orchestra which is different that what you that what you want for an opera house. (If you are interested in concert and opera houses check out Leo Beranek’s book on the subject)

For an amplified performance you want to have to listener only hear the sound from the speakers and not have it “colored” by the venue. Normally this is done by adding a shitload – note the SI unit ;) – of acoustical absorption or fuzzy stuff. Since there is not roof to the venue, most of the sound goes up and never comes back.

Since the venue is racked, you have a very good line of sight to the stage and hence the speakers.

So basically the venue sound good because they have really god speakers.

Many factors enter the question of what constitutes great sound. One of the most overlooked is the quality of the air surrounding the source. You would be hard pressed to find cleaner air which provides very little to muffle or muddy the music. mvgolden is also correct in stating the raised seating is a tremendous plus. A direct line of sight and sound is preferable. Remember that the Hollywood Bowl also artificially created this effect many years ago. Kinda hard to get that clean air there now.

Well, audio ph iles… am ph itheater… Any resemblance?

@makemo: ...the answer is ph! I knew it all along. :)

(Seriously for a moment, yes there probably is some sort of language connection.)

Planet Hollywood??????.....wonders…..... :)

Type in “Hellenistic Amphitheater of Epidaurus” into your search engine. You will learn a lot about sound waves, how they travel and the architectural marvel in Greece that paved the way for almost every theater space in the world today. The red rocks themselves are similar to the underlying rock structure in the Epidaurus Amphitheater in Greece. Architects have been striving for centuries to recreate the famous Greek amphitheater that is pure mathematical and architectural genius.