Parallel speakers

[Ajaysdisco]

but to be honest I think it's better to give subs a bit of wellie rather than under power them anyway (IMHO)

I would if they weren’t mine but because they are I would like them to last

What model of NJD bass cab is it?

From the NJD manual:

Frequency Response
The NJD models are equipped with a built in passive crossover network, which
ensures a smooth transition between the individual frequency ranges. The
Individual crossovers are tailored to perfectly suit the cabinet and give the best day to day performance.

Pin Arrangement
The NJD cabinets are equiped with 2 Neutrik(C) speakon sockets wired in
parallel.

The pin arrangement is as follows..... blah blah blah

Thanks Tony and everyone else for your help, its made things clearer