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Needing a 4th order design


Ferguson621
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You start using sealed chamber size as specified by the manufacturer the ported chamber double that, tuning is set 40-50Hz, the rest of bandwidth will be handled by your front stage so choose wisely, port area better be generous, below 20 m/s. Your modeling software should take it from there. Drivers for 4th bandpass boxes should at least work fine in sealed boxes as well, these are just very general guidelines, loud and good sounding 4th bandpass boxes need some experimentation and system wide tuning to get right, if you are not familiar with car audio better leave the job to someone who is.

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  • 1 month later...

Alright so I built a box, I came up with 35 tall x 40 wide x 40 deep. The sealed side is 7 cubes. Ported is 16 cubes. Port is 30 wide x 11 tall x 5 deep for a tuning of 42 hz. 330 sq inches of port area. 

 

To the designers. Would you care to verify for me? 

I still need to cut a small section of the hole for the blow through, and the box is sitting about 3 inches from the bed at the moment. But as it sits with it not being sealed off it's doing 147 with a 50hz tone, and 146 on music. I have an spl labs meter for verification, and it's on the windshield right below the mirror. 

 

This is my first 4th, so any help would be greatly appreciated lol. I'm hoping once I get it sealed off properly it'll do 150.

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Two fi btl4 18's

Taramps [email protected] ohms

Ad244 alternator, plan on adding a second one 

Two group 31's and a redtop under the hood 

Four runs of 2/0 welding wire

Two runs of 4/0 for power to the amp

2000 extended cab s-10

The box is double layered all the way around including the baffle for the subs

 

So this is where I'm at so far.....

Ill take a few more once the sun comes out 

 

 

 

IMG_20220218_130035.jpg

IMG_20220219_141031.jpg

Edited by Ferguson621
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Your box by modeling specs would look good, where I see differences is in the layout, since the baffle is at about the middle of the box, it looks much more like a 1:1, about 11-12 cubes per chamber instead of the 7:16 is supposed to be.

 

The port area as in the model would be great but it would need to be fully external not to take internal volume from the front chamber. Also longer port due to a shorter front chamber net volume.

 

Lastly you don't specify if your port has any common walls or not, this changes tuning calculations quite a bit.

 

 

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Yes the port is external, and the sealed side is 31x40x18, I wish I was better at math. Unfortunately it's my weakest point.

 

 

How long should the port be? Currently it's 5 inches, and what would you recommend I tune to? Ive always tuned around 35-38hz.

 

I was doing some searching and people have said 30-32hz for the btl's. What's your opinion?

 

And the port has 1 common wall. Thank you for taking the time to help me figure this out. I have zero help or guidance. So much appreciated.

 

Edited by Ferguson621
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Can you provide a sketch of the enclosure finished as you envision it and the measured internal dimensions of each chamber (H,W,D)? I will answer your other questions later, I have to readjust the model to your actual dimensions.

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