ludu wrote:Many thanks Martin for this message and this hope for the future.
Meanwhile, I am interested to learn if other organists have tried what I described above: the front speakers with the original acoustic and the whole organ sounding in the rear speaker with an additional processor (particular equalisation, additional reverb or another process).
I have tried what you describe using a few different approaches, both with an external reverberation unit and through something like Reaper as an example where you can add reverb, delay, etc., only to the rear channels / speakers. In fact, in theory you could truncate the entire set for the front speakers and add reverb back to the rear signals with either an external unit like a Lexicon or again using a program like Reaper.
Since I've been a big fan and user of rear speakers for a long time regardless if it's a surround set or not, I have two separate instances of HW set up, one for actual surround sets where the rear ranks are sent to the rear speakers, and another instance where the rear speakers are on 'mix-down' of the entire organ as Martin suggests. The trick with either is careful balancing of volume between the front and rear speakers, and in either surround or non-surround the rear speakers do not need to be anything special, a good pair of bookshelf speakers for the rear is all you need, they are there just for the rear reflection and are not meant to be the main sound producers, that's what the front speakers are for. Honestly in my comparisons with proper front to rear speaker volume balancing there's not a whole lot of a difference between a surround and non-surround set, and you are able to get very satisfactory results with a non-surround set using the 'mix-down' scheme and no additional reverb, delaly, etc.
Marc