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3 x boxes at 40 degrees worked quite well but because I only built 4 boxes I did not do any settings for 3 boxes, just 2 per side, and yes you will get good output to about 150 - 160 degrees as a guess.The reason I put the 12" drivers in the centre of the box and not directly under the horn was so that they remained the same distance from the 12's in the adjacent box no matter which way they were stacked. i.e. the centre to centre distance remains at 360mm ... what you need for the two to combine OK is less than 1/2 wave length spacing centre to centre (1/4 wavelength is optimum.) This will get you up to about 475Hz, so its OK but not perfect ... but way better than most; and more to the point it works in practice ... this is why it uses a low crossover frequency crossover point around 700Hz, preferably less but the HF horn is a bit small to go much below 700Hz.I have done a SIM on the 12NDL88 ... they look great in this box, just add an 80hz 12dB Butterworth HP crossover and the acoustic response will be very close to a 24dB LR.
3 x boxes at 40 degrees worked quite well but because I only built 4 boxes I did not do any settings for 3 boxes, just 2 per side, and yes you will get good output to about 150 - 160 degrees as a guess.
The reason I put the 12" drivers in the centre of the box and not directly under the horn was so that they remained the same distance from the 12's in the adjacent box no matter which way they were stacked. i.e. the centre to centre distance remains at 360mm ... what you need for the two to combine OK is less than 1/2 wave length spacing centre to centre (1/4 wavelength is optimum.) This will get you up to about 475Hz, so its OK but not perfect ... but way better than most; and more to the point it works in practice ... this is why it uses a low crossover frequency crossover point around 700Hz, preferably less but the HF horn is a bit small to go much below 700Hz.
I have done a SIM on the 12NDL88 ... they look great in this box, just add an 80hz 12dB Butterworth HP crossover and the acoustic response will be very close to a 24dB LR.
