can someone check this over for me?

[KiKaZz74]

Getting a new vehicle in a month or so and this is the rough box im going to be building for the Fi BL 18 that im buying back from the guy i sold it too. going in the back of a durango most likely. sub inverted. sub and ports up. i need to know what the tuning of this thing will be as i am unsure with the 2 ports. let me know if you need for info.

will be made of baltic birch and stained or mdf and carpeted. glued, all corners siliconed, and screwed with 1 5/8" coarse thread screws. final will also have a plexi window probably right in the center.

let me know what you guys think and give me any tips you can.

[Triticum Agricolam]

So looks like you have about 6.5 cubes net airspace. Two ports with 50.625 sq in of port area, roughly 19" long. Should tune you to about 35 Hz.

Its a nice looking design. You might find a way to brace that bottom panel though.

[Nightshade]

I would condense the two ports into one port. Your woofer will end up louder that way. I have personally tested slot ported boxes like that and unless you are running two woofers with a divider in the middle of the box it is going to be quieter than if you go with one port.

[KiKaZz74]

going with two ports as a recommendation from a friend for non meter reasons. not going for the meter here. was going to kerf the inside but decided not to. to get lower tuning extend the bottom of the port? looking for a low 30 high 20s tune. im wanting low end bass on this build. as for bracing ill do 2 vertical braces also and 45s in the corners where the two port pieces meet.

[Triticum Agricolam]

You are going to have a tough time getting below 30 hz w/o a more significant box re-design. If you extended the ports 12" internally that should get you closer to 32 hz. It will also eat up almost a whole cubic foot of internal airspace.

[KiKaZz74]

Wider ports? That's one thing I dont understand is tuning. If I can get it lower or bend it back up if needed then let me know.

[Triticum Agricolam]

To get it below 30 Hz you are going to have to put another bend in those ports to get them long enough. At that point you are probably going to want to make the box taller/wider/deeper to get back some of your internal volume too. Box tuning is determined by three things: net internal volume, port length, & port area. Assuming you leave two of those alone and change the third this is what will happen:

- Longer port = lower tuning

- Shorter port = higher tuning

- Larger internal volume = lower tuning

- Smaller internal volume = higher tuning

- Smaller port area = lower tuning

- Larger port area = higher tuning

[KiKaZz74]

I'll see what I can come up with for sure when I get the final vehicle. This was just going off what I could find. But thanks so far guys. Bend will be most likely

[Joe X]

A few tips, you will need some more port area if going with twin ports than a single, also, port length is not the same as if it was for a single port for a given tuning, hope this guy have a good reason to recommend the twin ports, lastly firing everything up is likely not the best for the vehicle type only if you are behind the third row without a chance to do any rear firing then go everything up.

[KiKaZz74]

It was due to testing by others with port noise, air turbulence and loading. Large inner kerf with a slight round over on the outer Yielded best results. It's some huge paper and design project I think is where it's from. And not much room to go back since I still want room back there. But as far as tuning, area, volume etc how does that all check out? Like others have said?