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Help with custom 4th order bandpass
Help with custom 4th order bandpass
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Old 29th February 2012, 07:49 PM   #1
LincolnSwe is offline LincolnSwe  Sweden
diyAudio Member
Join Date: Feb 2012
Red face Help with custom 4th order bandpass

Im new here but hope there is some help for me here

I have a Lincoln Continental -64 and to get some descent sound in my car i want to build a 4th order bandpass or something else that works with my 2 Kicker solo-classic 12".

The thing is i want it ported through the rear deck. But its only 25cm under there and its 24 cm to the border before it starts.

Ill post 2 pics and try to get this right in english O.o
ImageBay.us File Viewer
ImageBay.us File Viewer


1080 mm between wheelhouse.
500 mm from the "edge" to the rear deck/back seat.
930 mm between hinge brackets?
240mm between rear deck and the upper floor.
From the bottom floor to upper floor its 450 mm

So in this space i would like to have 2x Kicker Solo-Classic 2x2 Ohm

FS = 26 Hz
Qms = 10,19
Vas = 93,8 Liters
Xmax = 15,49 mm
540, sq.cm
Qes = 0,486
Re = 7,04
Z = 8, ohms
PE = 600 watts

Got a suggestion from vendor on a three chamber bandpass

Chamber 1 and 3 lower frequenzy
Vb = 45,72 liters
Fb = 44,83 Hz
QL = 6.518
F3 = 26,61 Hz
Fill = minimal

Chamber 2 - upper frequency
Vb = 65,63 liters
Fb = 44.83 Hz
QL = 6,717
F3 = 75,24 hz
Fill = minimal

Vents = 1
Shape = Round
Vent Ends = two flared
Dv= 15,24 cm
Lv = 30,52

I have tried to measure different shapes and setups to get the vented box close enough for the 30cm 6" vent to be close enough to get through the rear deck. Another issue is that the flared end that should be in the box is to large so it wont fit in the box since it 250 mm and its only 240 mm under there minus 44mm walls.

So here i am with alot of questions wondering what i should do.

So are there any way to maintain the values and get longer port? Or if i can get a bigger vented box with same values.
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Old 4th March 2012, 03:20 PM   #2
gfiandy is offline gfiandy  United Kingdom
diyAudio Member
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Join Date: Jul 2003
Location: Cambridge UK
You can extend the port and keep the same tuning by making the port diameter larger. The best way to sort out exactly what you want would be to download WinISD from here:-


Enter the characteristics of your driver, to do this follow the help instructions on entering drivers exactly, it doesn't let you enter data that is not theoretically correct and lots of manufacturers data is inconsistent. So follow the sequence they give and it will work, don't enter data they don't request as it calculates this theoretically.

Your data doesn't seem to match your earlier statement 2x2 Ohm, the driver data lists the driver as 8 ohms, its important you use the correct data for your driver or you will get the wrong tuning.

WinISD allows you to adjust the box volumes and see what bass response you will get so you can move away from a classic alignment if you want to. The classic alignments are a butterworth with a Q of 0.707 this has no peak in the frequency response but does in the time domain. Some people like a chebycheve with a peak of a few dB in the bass to create lots of thump. Q is normally around 1.0. But if you want it to play music really well I find a Q of about 0.5 is the best for this as this approximates a Bessel alignment which has no peaking in either the frequency or time domains. However you need a system that can genuinely play really deep for this as there is no emphasis of the bass.

Lots of people on here have used WinISD so if you have any trouble with it they should be able to answer any questions.

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