For 8″, this RS225 in series would sit at about 34 Hz in a 3 CuFt box and the response chart is fairly flat out to about 1800 Hz. Probably not a bad choice to start designing with. Though I’m still not sure how to deal with telling WinISD how to connect the drivers – I think multiples are, by default, connected in parallel. That would affect how SPL and excursion are calculated, AFAIK. @123toid , do you have any input on that aspect?