zvx 18 trunk 4th order bandpass port issues

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Hi everyone, I will build a 4th order bandpass enclosure for my zvx18, it'll be port facing foward sealed from the trunk.

the problem I have is that if I follow the rule of 12-16 sqin per cuft, a 4 cuft net of the ported side, will have a very different port size compared to a 8 cuft net ported side.

so basically, I don't know how to choose the port size.

here's a render of the box, 3,93 cuft net sealed side, 7,52 cuft gross ported.

2:1 ratio 4th order bandpass enclosure, big sealed part to get loud low end and ported I want 45-50 hz tune.

any input will help

Thanks!

[RooTxBeeR]

Hi everyone, I will build a 4th order bandpass enclosure for my zvx18, it'll be port facing foward sealed from the trunk.

the problem I have is that if I follow the rule of 12-16 sqin per cuft, a 4 cuft net of the ported side, will have a very different port size compared to a 8 cuft net ported side.

so basically, I don't know how to choose the port size.

here's a render of the box, 3,93 cuft net sealed side, 7,52 cuft gross ported.

2:1 ratio 4th order bandpass enclosure, big sealed part to get loud low end and ported I want 45-50 hz tune.

any input will help

Thanks!

The bolded part, I don't understand what that is there for. You're going to make the ported section 4ct? I'm confused. Also, tune the port to the Fs of the seaeld section for optimal results.

[[email protected]]

I meant that skar audio recommends for a normal ported enclosure, 4 cuft, but, as I'm using 7,5 cuft, I don't know how much sqin port I need :/

[RooTxBeeR]

I meant that skar audio recommends for a normal ported enclosure, 4 cuft, but, as I'm using 7,5 cuft, I don't know how much sqin port I need :/

That's how 4th order bandpasses are supposed to work. You build the recommended sealed section then use your desired ratio to build the size of the ported section. I'm no guru when it comes to port area though, so hopefully someone can chime in and tell you how much port area one of those subs actually needs.

[[email protected]]

thanks mate, any input is great to me

[[email protected]]

ok, I made a final design which I will build soon. changed my mind about the port direction, so it will now be a 4th order bandpass rear deck blow through

sealed: 2.99 cuft.

ported: 7.63 cuft net (after driver and port displacement)

port: 102 sqin (gives near 14 sqin per cuft)

tune: 41 hz

wish me luck in this quest for my first 4th order bandpass

[jroo]

whats the reponse and rolloff going to be with a tune of 41? I assume this box is only good for 50Hz down or something close to that? I sat in a car with a 4th order similar to your design and it was brutal. Guy was ported through the deck on Kickers but design looked almost like yours except he had a round port.

[timc31610]

Did you account for the extra port length to get through the rear deck?

[Joe X]

Not checked your box but the 41Hz tuning claimed will likely require you to have rather good midbass support from your front stage.

[[email protected]]

yeah, there's no need for port extension because the box is almost the same height as the rear deck, (box is like the one on the mazda with 2 21" subs, just that I wont loose the back seats but will have to cut some metal)

about the tunning I think is ok, considering that I'll get 2 sets of polk audio MM6501 for the front stage in custom pods in my doors.

I really love to design and create stuff, that's what I like of this hobby