No experience but it crossed my mind a few times and I would multiply all the dimensions by 1.5
On the other hand I think the tuning will not work this way.
Only Steve could answer this one.

Bart

Thanks for the responses so far. I am using a TC Sounds TC3000 15" DVC.  Currently its in a 3.6 cubic foot poted enclosure tuned to 35 hertz. It plays quite loud and sounds fantastic on rock. Decent on my son's rap/hip hop. I am just looking for other box designs that will show off this sub.

I will have to pull some specs on that sub, but it seems like a 5+ cu ft enclosure tuned around 30hz worked really well. Big port in a big box.

Haven't tried one of those in a down firing yet. Sounds like a good idea though.

What vehicle?

Take care,
Robert

my jbl 18" is in the back of my corvette !



please excuse my wiring nightmare.  hahahaha.

The Housewrecker IS meant to be used in the house, not the car!

You might want to learn a bit more about speaker building first.
A closed box is best to control the excursion.
With a ported box, the excursion below the tuning frequency is way out of control!
So, you can get a vented box with a really low tuning, but not as efficient.
Or just use a sealed one, that's the best control you get and the simplest to calculate.

If you tune, lets say, at 40Hz in a vented box, you have minimal excursion at 40Hz with a maximum sound output.
If there's a thump at 30Hz, there will be no resistance from the box anymore, it's just an open hole in the box to that frequency. The result could be a lot of damage to the driver if that tune keeps on firing!
Also, that 30Hz won't be very audible as it's canceled out quite a bit.

This all sounds bad but it also depends on the car itself, so even riding with the window opened up an inch or two, can make a huge difference!

►Do some research.
Bart

Thanks guys for the input. Just so you know I did use WinISD to model the current enclosure I am using. And sorry I did not clarify what I meant about excursion regarding sealed vs ported. I do use a subsonic filter (high pass at 31.5@24db/oct) just below my tuned frequency to protect the woofer. I get the loss of control under the tuning frequency. WinISD showed excursion reaching close to the limits. Near 22mm if memory served

Space is at a premium in my car. The trunk is a lot smaller than I guess I planned for. I want to say that my box does in fact sound great.It is well controlled and does in fact have gobs of output. I swear it knocked a kidney stone loose in a buddy of mine. I was just looking for other possible box designs.

Musgofasa, I went a bit higher tuning to get the increase (it had a slight bump in output over the flatter curve tuned to 30hz)in output and the smaller overall box design. Though it's pretty giant as it is. I used a double baffle and a big arse slotted port. Of course the port took up a huge portion of overall box volume. Thanks for the advice

I was incredibly impressed with how it sounds. I know I keep saying it but it is so musical. Dire Straits "so far away" is awe inspiring. The string bass in any of the Holly Cole Trio songs is simply amazing.

It makes me excited to get the rest of my system installed. Continue with the input advice. I really do value it. And I know I didn't mention it but thanks Bart