Mainly 4 T30's vs 2 T39's
Here's the rub on that.
Go to the SPL charts section, down to the T30 charts.
First thing you notice is a T39 beats output in a T30 from 38Hz and up.
Second thing you notice is, in a driver vs cab comparison, output has a differential of around -3dB in the T30 compared to the T39.
Build 4 x T30's and you make that deficit up, plus some.
You have to build 4 x T30's to allow a 30Hz HP anyway.
With a 24dB brick wall slope you will still get fundamental E string at 28Hz too.
Do you want to utilise your current drivers?
The 3012lf or lab 12 is going to be +6dB in maximum output compared to a BP102 or a Delta12LFA.
You might need to think 6 x (premium loaded) T30's to be better output wise than 4 x T39's...
2 x DR 250 (melded array) with March 2012 plans.
4 x 20" BP102 T39's, 2 x 28" 3012lf loaded underway.
3 x WH8 with melded array.Bunter's Audio and Lighting
"like"s would be most appreciated...