I am doing a 4th order in my GF's 1998 Mustang GT convertible. The box will be where the back seat should be since the trunk is sealed off.

She has 2 db Drive K9 12"s and a db Drive A7 1,500. I want to do a 4th order bandpass with a woofers behind either seat facing into the ported wide which wiill port into thr middle. =

I am thinking 1 cube each sealed with 2 each in the ported side. So 2 sealed 4 ported with 80-100^2 port tuned to 48Hz.

Any thoughts?

How did you pick those volumes and why?

You need to run the T/S parameters through a box calculator, just randomly picked volumes makes no sense, like ^^^ said......

Run your T/S numbers and input them here

It was about the same specs we used on a 8 12" bandpass in my friend's F-150 that worked exceedingly well.

This is what I came up with.

what kind of BS boxcalculator is that ?and even that you're not using it right , read the upper 2 sentences again .

sure..............a passband from 26 to 70 hz but how linear is it ?

Why an F3 of 26 hz ?

I'm not a huge fan of band pass boxes but what do you think of the results you got with the calc?

4th Bandpass can have as good, if not better performance than a standard 4th vented.

The trick is, you need to find a driver suitable, and many times this is not easy with most "car audio" subs on the market. The biggest problem is that most of the newer subs are so uncompliant that they have a super low Vas and must must be put into small enlcosures to avoid excess ripple. In a bandpass this is a problem do to the fact that 100% of the output is coming from the vent, and it is often very unpractical to get the size vent you need into the proper box. if you are using a 10" or 12" driver with a Vas less than 2ft3 or so, good luck... Especially if you are using a single driver.

When you find a driver that suits the bandpass criteria better (I listed a few and modeled them on a thread last month to help a guy out, turned out to be a waste of time) model it on any of the availible programs. Look for a decent response with less than a few db of ripple and don't get all crazy with the gain. A few db is a good target to start with.. If you start getting gain happy, you'll either end up with a very narrow passband or a very narrow passband and an unacceptable amount of ripple. 60-70Hz of bandwidth is well more than enough. I wouldn't try to extend the lowend F3 below 30 Hz for in car use if it sacrifices efficiency or increases ripple....

Good luck...

what kind of BS boxcalculator is that ?and even that you're not using it right , read the upper 2 sentences again .

sure..............a passband from 26 to 70 hz but how linear is it ?

Why an F3 of 26 hz ?

Dude I've never fucking seen that before, some one just linked me to it and I posted results so you need to calm your ass down.

Idk what I'm looking at on there, is the reason I made a thread for some help.

I've always just taken the recommended sealed, shrunk it a little and then doubled it for the ported side, as per Scott Owens advice, and it's worked great so far.

didnt mean to be rude or bash the whole idea .........but if you're gonna do it , do it right !

This is all the information I have on the woofers

This is their "recommendation" for a normal box.

Ported Enclosure

Box Volume 1.90cu ft.

Box Tuning 38Hz

Port Diameter 2 x 4in

Port Length 24in

T/S specs

K9 12D4

FS...........27.52Hz

Qts...........0.45

Qms..........4.38

VAS.........37.73L

XMAX........0.98in

Re............6.43Ω

Pe........1000/2000

QES...........0.50

SENS.......83.85dB

37 Liter Vas is more than likely going to be the deal breaker....

Since your not trying to get into a cab from a trunk, going wiht a normal 4th order vented, or even sealed might be your best option.

37 Liter Vas is more than likely going to be the deal breaker....

Since your not trying to get into a cab from a trunk, going wiht a normal 4th order vented, or even sealed might be your best option.

I was thinking of just doing a normal 4th. But sealed will never be built by my hands if I can help it. lol

I gave a bunch of info/possible drivers here-

my wasted time helping with bandpasses thread

I gave a bunch of info/possible drivers here-

my wasted time helping with bandpasses thread

I will read through for info, but she already has the woofers.

And I'm 100% sure db Specs are right. They have their slightly lower series 12" with a higher VAS but a smaller recommended enclosure.

As promissed , I've run the numbers and came to the conclusion that 95Honda is absolutely right , these woofers are far better of in a vented or sealed enclosure .

3,5cuft tuned to 33hz would be fine , just make sure you don't make a trunk rattler ..so sealed it of from the trunk and directly play into the cabin