Bandpass Help for 2 18"s in a wall

[savagebee]

I just got done building a 7.5 cu ft after displacpement sealed box for 2 18"s
I realized that I could easily make a 4th order bandpass out of this due to my cars internal configuration

so, what size and tuning of a second chamber would I need?

Im wanting a low roll off, with good SPL
First and foremost I want it to sound good, but I also want to be able to get loud as hell on command

This would end up being a wall behind my second row of seating


Thanks in advance

[savagebee]

bump

[galacticmonkey]

Sealed chamber is a little too big. Might want to shrink it so each sub is in around 3-3.5 cubes each.

Somewhere around 15-18 cubes for the ported chamber.

Go for anywhere from 325-400in^ of port, depending on the size of the ported chamber. Tune to around 45hz.

That should be a good start, you should be able to figure it out from there.

[savagebee]

well, unfortunately thats bigger than I can manage
the 7.5 cube box is going to stay, but I can place some wood, fill, whatever to shrink it down

I was playing with win ISD last night, and the plot of my 7.5 sealed into a 5 cube vented to 50 looked nice and flat with a good peak at about 65 I think, which is my cutoff

this seems small to me, with too high of a tuning so looking for some input on this setup

[savagebee]

also, this is a wall behind second row of seating, it gives me cargo space in the back, and I can still keep my babyseat in the back

this is why my space is limited even though its a wall

[savagebee]

bump