I fired the cab up in the rehearsal studio tonight and have some observations:
1 - It's very loud; when compared to my usual cab (Eden 2x15, no tweeter) using the same amp settings it gives noticeably more volume.
2 - Frequency response (or perceived frequency response) is very good; it maintains sweetness in the high end and it doesn't get overly clacky, even with the bass's tone control fully up.
3 - It's chuffing heavy; I've not weighed it, but it's somewhere between monolithic and made of the hearts of collapsed stars.
4 - It's very responsive; even with my Cali76 Bass compressor in use the dynamics are pretty open, and when digging in it moves air around without hesitation, but when playing normally it stays pretty sweet.
5 - The bottom end is big and full but not woolly.
6 - It pairs well with my amp.
All in all I'm very happy with how the project has turned out.
Cheers,
JRK