I’m open to suggestions on that. My understanding was an active external X over using DSP can take a speaker to another level. I do like the idea per OP of full actives, but bottom line is the quality of the audio. Everything else is secondary. If the designer (you?) feels a passive X over build with X parts will deliver the best audio for the project, that’s what we do, then figure where/how it fits budget wise.
Personally, I’m a DSP guy and will swear by it to my dying day. I was just using the example to show even a passive crossover normally put into a box can be moved to external to the box.
As to the design of the shape, when doing leaning boxes, although they are visually stimulating, they come with trade offs. For starters, the lean means if you mount them straight in the baffle, they are directing the sound up, not necessarily at the user. That means you will have to position the speakers such that your ears and head are on axis, meaning a near-field scenario. Even if doing it a bit at a distance, you would want to optimize the directionality for your seated position, which then puts them lower than people would think you would want them.
That is something people don’t think of. Now, doing an angle also works well for high hung surround drivers.
Now, something they also tried to do with the slant is to time align the tweeter to the woofer for where the motors are positioned. For a passive speaker, that is more of an issue because time alignment on passive components is difficult. But for a DSP driven active crossover, you can simply set the delay for the tweeter to help match it’s arrival to the ear at the same time as the woofers. Meanwhile, if you have the tweeter on the plane of your ear, due to the arc downward of the woofer, it also has all that extra distance to travel in addition to just the offset of motors of the drivers. This is why slants or offset positioning like that was considered before DSP simplified the process to get things to arrive together in the listening position.
As such, I usually design straight on instead of an angle unless doing presence speakers/surrounds meant to be hung higher in the room where the angle makes sense to target the seated position.
But these are me just discussing the tradeoffs in the design. Doing an angle design isn’t too difficult. Personally I like rounded over baffles, others like or prefer chamfered baffles (cut into sweeping back angles). Now, unless you have a roundover that is very large, chamfers often have better performance with baffle diffraction from the studies I’ve seen. But then comes the question of how thick a baffle is being used, how much insulation is being used (you don’t want the insulation touching the driver, so if you put an inch or two of insulation on each side, that is an extra 2-4 inches that you are pushing it out from the driver’s left/right edges, plus the thickness of the MDF used, so another 1.5″ (0.75″ each side) resulting in a decent amount of distance the driver is positioned compared to the edge of the baffle, which can allow for more area in which the frequency can diffract off the baffle. So using 1.5″ (since you want to use a wood, using an 8/4 s4s is about 1.5″ thick, so you will likely either chamfer or use a 1.5″ roundover bit which costs between $125-175 just for the bit. The chamfer is easy, as you can just cut the angle on the table saw. The woodworker would not need specialized tools to do that.
If you can get 2″ thick baffle, that would be best, or if the woodworker has a planer (or jointer and planer, but just a planer can do it), then they can try to minimize the amount removed from the rough 8/4 wood. Or they could look for 10 or 12/4 piece of wood, but the cost obviously goes up at that point.
Now, if using 2″ rockwool, that should give full damping down to around 250Hz (well 84% at that level and fully damp internal reflections above that frequency within the enclosure, which means less energy to cause the enclosure to ring or resonate).
With the addition to bracing inside the enclosure, it should not be an issue on having internal reflections or resonances. And with it being sealed, you also would not have a port resonance to be aware of, etc.
And adding 2″ to the depth, these will be shallow speakers of 4.75″ or so plus the thickness of the baffle, so like 6.25-6.75″ in overall thickness. If doing 2″ insulation for the sides, that is 12.5″ wide, approximately. Then I estimate around 12″ tall as you have around a 7″ driver plus 4″ for the average tweeter diameter, resulting in roughly 11″ while pushed close together, then an extra inch. In fact, you may want insulation at the bottom, so there goes an extra 2″, and for the top, I would instead (because that is behind the tweeter which doesn’t really take up box volume) make the box slightly deeper so I would not have to add extra height. So height would likely go to 14″ and add just a little extra on depth, while the width would stay roughly the same (I’d make sure the internal dimensions are not a pure square shape on the front and backside, but I’m roughing out the shape in my mind, with one vertical brace and two horizontal braces that can interlock and that being inside the box; but whether to do dadoes in the back and sides, I think I’ll pass on doing that for this design, just a lot more fine woodworking and the benefits are minimal).
That means we could do a large round-over or a sweeping chamfer from about the edge of the driver to where the front baffle meets the sides. Also do that at angles around the top where the tweeter is located which is more important as the difference from zero plane matters for the higher frequencies which have more diffraction off the baffle.
I hope some of that makes sense to you.
As to DSP, I can help talk you through generally what is needed to do time alignment and get it setup while using REW, a nice free software everyone can access.