But where's the damping on a material like that? Nice for a midrange enclosure but less good for heavy duty bass.

The resonances in 18mm MDF shift and change in amplitude depending on the panel size, bracing and thickness.

18mm on its own:

With bracing:

As you can see, with bracing it shifts the resonances well out of the subs operating range.

I'm using pretty extensive bracing as well as the subdivided panel technique I used with the Perceives which raises the resonances compared to a single large MDF sheet. The wall thickness adds mass extra damping and further stiffens the enclosure to raise resonances further.

It worked very well on the bass cabinet for the Perceives, so we'll see how it copes in a more heavy duty capacity.

Its not going to break any depth or SPL records but I'm really looking for something that can match the dynamics of the mains in the same effortless way. Hopefully its 4th time lucky for this sub attempt.

I think I'm getting to the stage now where I could spray an entire car in a day, blindfolded. I've had plenty of practice over the last year. Time is running out too! The weather will start to turn in a month or two so I better get my finger out on this one.