In this case , the unique line array consists of :
I) The upper and lower 6 pcs of the 3” FR units , that are the “shaded” ( i.e. frequency contoured ) part of the line array , to control vertical beaming and diffraction loss.
II) The central 6 pcs 3” FR units ( 3 under and 3 above the ribbon tweeter ) that constitute a 7th order Bessel Array.
III) The ribbon tweeter in the centre of the line array , at the Zero of the 7th order Bessel Array.
The Efficiency depends on the realised beam characteristic, the calculation have shown around 90dB, but that is not finalised yet.