New Project - Underbed Sub Mk IV

[Surtsey]

Apparently, I rocked someone's world in the wrong way. I was made an offer I couldn't refuse for my MK III under-bed sub.
A MK IV design is afoot.
I'm going for a ported design.
Maximum driver size is 6.5"
Cabinet volume is 46 litres.
I err on the side of efficiency.
Where should I start looking? 4 x 5" or 2 x 6.5"?

 

[maxolini]

what is your target SPL ?

 

[Surtsey]

what is your target SPL ?

That's a tough question. The classic definition (1w/1m) doesn't really apply. The main listening position is on the other side 150mm of mattress & 50mm of pillow, The sub needs to excel between 35 & 60Hz - the mains can take care of the rest.