I've done a search and couldn't see anything on this topic, but if this has been answered before, please feel free to point me at the relevant thread.
I was wondering if anyone had developed/discovered a simple spreadsheet or website that can tell you, for given inputs of speaker size and configuration, sensitivity, resistance, etc. what the effect on volume would be of combining different speaker cabinets. I appreciate that if you have two identical cabinets then this is relatively simple, but as this may not occur often it would be useful to be able to have a ready reckoner/rule of thumb guide for doing this which would help determine whether it's worth doing. This may only be hypothetical as there are many real-world factors that could influence the results, but it would be good to have a starting point. If I understood the science I'd be happy to look into this, but this would be a far easier task for someone with more experience than me.