Does FIRmaker optimization with only one FIR channel per cabinet work in practice?
It certainly does! — Field tests (some of which have already been published by AFMG) indicate that substantial performance improvements can already be achieved when using only one FIR channel per cabinet. The explanation is simply that the sound waves in the mid-frequency range have wave lengths of the order of the cabinet spacing in typical line arrays. It is not necessary to have a much higher resolution than that.
However, when it comes to the high frequencies (e.g. 4 kHz and up) improvements using more DSP channels may be possible depending on the arrangement of the transducers and their directionality. It should be noted that any pattern-shaping abilities reach physical limits where environmental influences, as well as mechanical and modeling inaccuracies, are of the order of the wavelength, e.g. in the range of 10 kHz and above.
The positive results that can be attained with only one FIR filter per cabinet allow to use FIRmaker in combination with nearly every conventional line array system. External DSPs are readily available and can be implemented even into existing setups. DSPs can be stand-alone units, integrated into external amplifyers or even built directly active cabinets.