You can build an N23 as two panels with a packer between....
Data for One Dimensional QRD (Quadratic Residue) Diffuser
Standard N23 panel: Shifted left 12 wells
Design frequency 994 hz
Number of wells: 23
Deepest well in mm 135
Fin width in mm: 2.5
Width of wells in mm: 40
Ratios 6 8 12 18 3 13 2 16 9 4 1 0 1 4 9 16 2 13 3 18 12 8 6
Well depths in mm 45 60 90 135 22 97 15 120 67 30 7 0 7 30 67 120 15 97 22 135 90 60 45
Phase shift in degrees 93 125 187 281 46 203 31 250 140 62 15 0 15 62 140 250 31 203 46 281 187 125 93
LF cutoff frequency 497 hz HF cutoff 4300 hz
Panel width 977.5 mm
Minimum distance to seating position 2076mm (3 times wavelength of LF cutoff frequency)
Here are the N23 and the N11 - re-arrange to get what you are looking for...
Since you have used up the zero-depth well of the N23 to split the panel, there's no need to left-shift the N11's.
The N11 is thus:
Data for One Dimensional QRD (Quadratic Residue) Diffuser
Custom N11 panel: Shifted down 2 depth units
Design frequency 811 hz
Number of wells: 11
Deepest well in mm 135
Fin width in mm: 2.5
Width of wells in mm: 40
Ratios 2 3 6 0 7 5 5 7 0 6 3
Well depths in mm 38 57 115 0 134 96 96 134 0 115 57
Phase shift in degrees 65 98 196 0 229 163 163 229 0 196 98
LF cutoff frequency 405 hz HF cutoff 4300 hz
Panel width 467.5 mm
Minimum distance to seating position 2544mm (3 times wavelength of LF cutoff frequency)
Arrange the panels with the Barker Code:
I guess two lots of the pattern for 3 panels gives you
N11 N11 N23 N11 N11 N23
This would build up like:
Dressing up each end of the completed array of panels with an extra zero-depth well shouldn't hurt anything