I was overwhelmed with the urge to rip into these Mackie's today, so here you have it.
First, is the HD1531:
Mackie did a good job packing a lot into a little space.
I pulled the 15 out, and was surprised to see the amp in a completely different chamber than the drivers. Cool design feature. Lots of bracing inside. The mid range driver was in a sealed chamber, separate from the rest of the drivers. All of the drivers were neo. I didn't want to rip into the MF/HF section, as it just seemed like too much work for today. Maybe next time!
The 15" was a nice lightweight neo driver. No idea who makes it though.
And, the HD1801:
The 18" was not a neo driver though. It was a heavy sucker, probably half the weight of the cab! Again, a nice build with plenty of bracing inside. Much smaller port then I was expecting though.
Evan