Great tests,with results to see.I would use as a reference. The 511 shows good performance,maybe the acoustic loading of a 500Hz horn is a possible factor.It would be good to show your test at different levels, also I wonder what effect a loading cap would show with each fram. Another thought: 2 frams,same part # How would the one about 3 yrs.(let's say in cinema,arena,school) show against the other new from stock?