>>At what number of WL do we reach diminishing returns on any added length?
Again it depends the freq.

Attached is a link to Jim Griffin's white paper on the subject, a vary good paper with lots of info, it's what I used when I designed up my arrays. Plug in some numbers and it'll give you some idea.

HTH
Bill W.

• Near field line arrays

You don't state what your basic concern might be in extending the length of a line. The pat answer is that you should have a line length that places your listening position well within a near field. A floor to ceiling line length would place the entire room in the near field. At low frequencies you should assume coupling to the floor and ceiling surfaces as the line will image from this planes at their lower frequency limit (see my white paper for discussion and a diagram). In theory you would have a lower freqeuncy limit but a floor to celing line array would work as a line source down to the bass limitations of the individual driver. That means don't expect 20-30 Hz bass coverage from a driver that cuts off around 100 Hz even though you have an array that has 100's of these drivers.

Bottom line: You should read my white paper as it covers the line length issue in detail.

Jim

• Near Field Line Array White Paper