15 in full range drivers

From what I'm hearing (from my sealed box TangBand W8-1808 single drivers with dual SVS SB1000 pro subs), full range single drivers have opened my eyes/ears to a more liquid sound stage and depth i haven't heard before. Truly unbelievable for just one driver, but to only 70 db. More volume than that and, ya, they start braking up. I don't want louder than that anymore so, happy camper here.

Any full ranger will have limitations and all are subject to cone break up.  The problem is when you generalize and assume all drivers sound the same when pushed to their limits. They don't. Cone break up is easily measured and looks quite different from driver to driver. I would be willing to bet that if the OP swapped out his AN driver for a 15 inch Lil driver his "suffering" would be largely mitigated.  

Every example limps as the saying goes. But anyway, below is Paul Miller's measurements of the Lowther Almira which uses an eight inch DX3 driver supplemented by a supertweeter. I've never hear a "full range" driver which uses a whizzer cone to extend frequency response that didn't sound ragged. A 15in driver is going to be very compromised in the midrange - more than the Lowther driver.

The best sounding efficient loudspeaker I've personally heard is the Devore Fidelity 096. Expensive, but properly engineered to perform with low powered amplifiers.

I'm curious about the cabinet design... did you buy plans?

Bass reflect single port 43 in tall by 20 wide and 18 deep. 1-1/2 in thick walls.  Solid and heavy..