https://www.ocregister.com/2018/02/01/the-audio-expert-behind-the-super-bowl-halftime-show-reveals-secrets-about-the-years-most-watched-musical-performance/
Sound engineer Patrick Baltzell designed the audio for the Super Bowl halftime show for the first time in 1998, and in that year and the five that followed it all went great. Fans in the stadium could clearly hear performers such as Smokey Robinson and Stevie Wonder or Phil Collins and U2, and the millions and millions of viewers watching on television never missed a note.
But in 2004, when Super Bowl XXXVIII was headed to Houston, Baltzell realized he had a problem. Reliant Stadium’s shape and P.A. system produced a notoriously muffled sound, and the Texans’ owner and the NFL refused to let any fan’s view of the stadium video screens be even partly blocked by the kind of powerful temporary speakers Baltzell normally employed.