For the sub I am currently building I am using 1" mdf with 2" in front. The reason why I chose to do this had nothing to do with the old discussion of BB vs mdf but all about just building a good solid box. Since mine is going to be plain black it didn't make any difference in looks.
BB is very much stronger than mdf in every way I can think of. Good construction methods can offset that strength advantage a lot.
I have read often that some speaker builders like 1/4" plywood laminated to 3/4' or 1/2" mdf, giving the outside a wood grain finish and some additional strength without messing around with veneering. Thats an idea laminate the two materials. BB and mdf are not the same, pro's and cons exist for both, there are advocates for both materials. I always thought that construction methods made more difference to sound than small differences in the material.
I read so many times on the forums about so many folks being woodworking novices so at the risk of sounding like lecturing here is some safety info ...
If you are working around mdf dust. Use the right dust mask. For that matter look below under masks about regular wood dust as well.
"MDF, or medium density fiberboard, is a composite material made from wood fibers glued together and contains formaldehyde, which has been shown to cause cancer in animals and is a probable human carcinogen. It also irritates the eyes, skin and mucous membranes. Even brief exposure to low concentrations can trigger asthma attacks in sensitive people. Cutting, drilling and machining MDF generates large amounts of fibrous dust, and breathing this has been linked to asthma and cancer. The possible risks have been widely publicized and DIYers are advised to take precautions, such as wearing face masks and opening doors and windows."
Dust mask types ...
P1: for harmless, non-binding dust
In other words: simple jobs around the house, sweeping the garden, etc.
P2 : for harmful dust
You need this as a MINIMAL protection when you drill, sand, grind, cut, saw etc. the following materials:
All ferro-metals, such as carbon steel, etc.
All polyester and aramide fibers, such as micarta, all plastics, but also MDF, etc.
All soft woods, such as pine, spruce, etc.
Dust from wheat, flour, crops, etc.
Dust from cement, concrete, etc.
And more.
P3 : for toxic dust
For enzymes, spores, bacteria, viruses.
Quartz, silcum/silicate materials (for instance sand lime bricks)
All hardwoods: oak, beech, but also tropical species such as meranti, bankirai, and the well known species like cocobolo etc etc.
All non-ferro metals like stainless steel, aluminium, copper, brass (tubing!), lead, gold, silver, etc.
Fumes from welding
And more.