About 25 years ago I was a car audio installer and subs were the deal.
I set out to make a sub that was very fierce but cost effective at the time.
I really did not have design tools and software just a box program that would help with tuning.
I was using a driver called an MTX Blue Thunder (first iteration).
I was designing for pickup truck install because these where typically hard to get sub bass in as most where single cab trucks and of course that's what I had, a 78 f150.
What I eventually had was a bed mounted box similar in design to what peteb's link showed but instead I had 4 individual chambers for the 4 10" drivers into a mouth as wide as the box that housed the drivers with increasing dimension into the cab of the truck. I think they were in the area of 2.3 cu ft per chamber.
The "boot" kind of like a camper boot got it from the bed to the cab without water leakage.
The individual cabs where then ported into the mouth at an angle on the baffle at the rear or smallest part of the mouth. If I remember correctly they where tuned to about 28 hz.
This design worked very well and I ended up putting in about 30 of these over the next few years. The outside of the box was covered in fiberglass for weather/water protection.
As said earlier I did not have any measurement tools so I really do not know how they looked in simulation but this box was driven with 50 watts per driver and playing some content at and below 30 hz would really shine. If you rolled down the windows you could tune it even better.
Here is a crude drawing.
:beer:
