AES Governor James (JJ) Johnston, a longtime friend of Ed's, introduced the meeting. Ed explained that he got the job because the contractor asked for a design and install from one entity, who would agree to be responsible for the results. He bid, and got the job. He was invited because he had previously retuned Seahawk stadium.

He talked quite a bit (in far too great a detail for a summary) about using various measures of articulation and speech understanding, and how they were applied to the design in the stadium. Ed emphasized that outdoor, or mostly outdoor, stadiums do not obey the usual kinds of acoustic rules predicted by the usual concert hall design principles, and then talked about methods of coverage, how to avoid cross-field echo, and launched into quite some detail about the various clusters, how they were designed, built, hung (in an earthquake area no less) and powered.

The results seem to be quite clear - the sound system has been described with words from "more than adequate" to "<bleep> loud," and provides quite satisfactory articulation. He explained how both time alignment and frequency response, with substantial overlap between patterns, are required in a stadium that experiences 40 mph winds through it (which do indeed move the pattern aim points quite a bit). Some comments on the design of the new bleachers, which resonate phenomenally well at about 125Hz were introduced, and showed that there are many non-electrical and non-speaker issues chosen by architects doing stadium design that may very seriously affect the quality of sound reinforcement in the stadium by providing substantial storage of energy at inconvenient frequencies.

After the break, Ed mentioned the amplifier systems, the extensive use of DSP built into the amplifiers, grounding, isolation, signal paths, wire sizes, and the like. Ed also talked about some other work of his, testing of various solder, resistor, wire, and capacitors via careful electrical measurements using long-term averaging some 100dB below 20 millivolts. His observation: Yes, cables are directional, but at -165dB relative to the input signal. Noise, hum, and the like are a much more real problem. An observation he made along the way is that it's not low-order harmonics that are usually the problem, it's the wide spectral splatter that creates problems for a lot of digital equipment, usually due to the use of inexpensive power supplies, and common supplies for both digital and analog.

More information about Ed and his company