Neat's own product description says:
there must be at least two 6.5" drivers inside the cabinet plus the visible one mounted on the front baffle, for three total. I'm figuring it might be similar to this.
You're probably right to go with a 12", because your towers go so low to start with. You might even consider the Fathom F113 for a deeper and fuller reach.
The visible main drive unit handles bass and midrange and is isobarically loaded by similar drive units located inside the cabinet.So if there are isobarically loaded drive units (plural) inside the cabinet, I figure
there must be at least two 6.5" drivers inside the cabinet plus the visible one mounted on the front baffle, for three total. I'm figuring it might be similar to this.
You're probably right to go with a 12", because your towers go so low to start with. You might even consider the Fathom F113 for a deeper and fuller reach.