Sound at the 9:30 is generally pretty phenomenal. I don't know if maybe it's just because of where I usually stand or the shows I go to see, but having been to some places with abysmal sound (the Aragon Ballroom in Chicago, Lisner Auditorium at GWU, Nation) I can safely tell you that the 9:30 has improved quite a lot since the days it was WUST Radio Music Hall. A lot has to do with how much money a venue will put into its PA...and of course who is performing, what kind of equipment they bring in, etc. Generally, bands love to play the 9:30 because for the most part they can show up, know that there will be few problems, and just put their focus into doing a good show. The House of Blues generally has good sound (I've been to a few of them in different places.) There are some steep ticket prices, but I still love the 9:30 and aside from some minor complaints I believe it truly is a great concert venue.