My Marantz speakers are poorly, the boxes look awful and have been used as stands for flower pots (don’t even ask 👿 ). I fancy getting them done up, where would you start looking for boxes? I’ve time, plenty of it at times, can spend a few weeks doing them up.
Or should I just measure them, make copies of whatever is best and do it that way?

I’ve made a few subs a few years back (before you could pick them up cheaply from Richer Sounds etc).

I’d suggest copying the existing boxes if this is your first attempt as the sizing/design is critical to how well your existing drivers will perform.

This is the site I used for reference for building my subs, plenty of info on there.
http://www.diysubwoofers.org/

I’ve had good results going to a wood supplier and getting mdf cut into the right sizes then gluing together and painting/veneering.

Could easily add solid wood and that’s what I plan for a design I have in mind.

I’ve also had a mate-joiner make some up.

You can change the shape of the boxes but they should have been designed for the driver units. If you are interested it is possible to measure the drivers’ patrameters with a multimeter and frequency generator, and make sure the box you make is perfectly tuned to them (that’s what I’ll be doing as I’m making a slightly unusual design from scratch).

The originals have/had a great sound, rich and warm, Pink Floyd to Opeth, Bach to Tchaikovsky.
How thick mdf would you use? Why not plywood? Solid wood seems silly expensive here so probably not this time.

I made my own infinite baffle subwoofers and they are incredible, though not the most practical things in the world, each one nearly as big as a washing machine. Anyway, building a solid enclosure is easy, so I’d say go for it if you can find a good design.

edit… my enclosures are 3/4″ ply laminated to 3/4″ mdf, and are *extremely* strong!