port design help for dual sundown sa 8 v3s

[Jspawn80]

Hi i wanted to see if someone could help me design the port for my subwoofer box for under the seat of my nissan titan, i bought some pvc pipe with an internal diameter of 2 and an outside diameter of 2.375 or 2 3/8 based off of a design i found on the sketch up library but im not sure if that even the best diameter for my box as mine is bit bigger than the one in the rendering but with the same shape

The total volume of the box is 2.371 ft^3, i have some subwoofer supports that when added together are .01 ft^3, and on there website sundown stated each sa8 has 0.08 ft^3 of displacement so 0.16 ft^3 of displacement i guess. I was thinking of using two ports one on each side, the maximum length each port could be would be 16 since that the clearance i have on either side of the box. on there website sundown says there recommended ported box is 0.5-0.75 ft^3 @ 35h. im not sure what to tune at, i want something that will play almost everything as this is going in my daily driver and i listen to all kinds of music from rap to country to jazz.

could someone please help me figure out what size my ports would be if i tuned at 35h or if they recommend and different running frequency. i also attached a picture of the google sketch up i designed my box off of

Click to read more...

 

[germanyt 10+ year member]

You need 10-12ish sq inches of port per cubic foot. I imagine you have 1-1.5 net cubes. And you cannot port on both sides. Itll create cancellation.

 

[germanyt 10+ year member]

Also, you need to make absolutely certain the SA8 motor wont hit the top of the box. The motor on the SA8v3 stands 7 inches off the cutout bottom.

 

[Jspawn80]

You need 10-12ish sq inches of port per cubic foot. I imagine you have 1-1.5 net cubes. And you cannot port on both sides. Itll create cancellation.

What is net cubes? Also the box it already mostly assembled and the subs test fitted and they fit perfectly they just clear the top with about half an inch also should i port towards the front of the box in between the subs or would i be fine on one sideof the side? Would it make a difference since the port would be closer to one subwoofer if i ported to the side?

 

[Jspawn80]

Also you said 10 to 12 inches of port, what tunning would that be?

 

[germanyt 10+ year member]

What is net cubes? Also the box it already mostly assembled and the subs test fitted and they fit perfectly they just clear the top with about half an inch also should i port towards the front of the box in between the subs or would i be fine on one sideof the side? Would it make a difference since the port would be closer to one subwoofer if i ported to the side?

Net volumeis the air space inside the box minus the sub port and bracing volume. I max out then dimensions under a crew cab silverado with a 3/4 seat lift and get 1.6 cubes net for 2 8s. Port is 29 inches long for about 32 hz tuning with a little over 19 sq inches of port area. Id ditch the 2 inch tubes and put in a 4 inch if you can fit it.

 

[germanyt 10+ year member]

Also you said 10 to 12 inches of port, what tunning would that be?

Thats square inches of area. A 4 inch diameter tube has 12.6 square inches of port area.

Go to where it says round port calculator.

Subwoofer Enclosure Calculators, Parallel, Series, Port Length and Volume

You need to know exactly what air space is inside the box to figure this out. Remember that changing the length of the port to alter the tuning frequency also changes the net volume of the enclosure so that must be considered.

Example, lets say you figure out that a 4 inch port in 1.5 cubes needs to be 25 inches long for 35 hz but you want to be 32 hz. You can't just lengthen the port to 29 inches because thebextra port takes up more space in the box. Perhaps dropping you from 1.5 to 1.4 cubes net. Now your new port length is off becuase its in 1.4 instead of 1.5.

 

[The_Dealer]

I'd shoot for 1.6cuft@33.5hz net with 2 4" aeros

Sent from my SM-G920T using Tapatalk

 

[Jspawn80]

I made a small mistake in calculating the Gross volume of the box and instead of it being 2.371 its actually 2.231 ft^3, I fixed it in my first post. Everything else in my first post is correct and i calculated that when i subtracted the subwoofer displacement and subwoofer supports my net volume come out to be 2.061 ft^3. I put all my values into the calculator germanyt suggested and im not sure if what it gave me is correct i attached picture of one screen shot with a 4" port diameter and another with a 2" diameter.

 

[Jspawn80]

also what do i do about the volume that the port takes up

 

[germanyt 10+ year member]

Youre throwing me off when you talk about gross volume. I cant tell if you mean net and are saying gross or arent sure the difference. Gross volume is the total volume the outer dimensions of the box. Net is inner dimensions minus subs and port displacement. The space inside the port does not count as air space inside the box. Id be surprised if youre getting 2 cubes under the seat in anything. Especially a truck with a crossmember hump in the floor the size of a titans. A silverado has a 3/4 inch hump in the floor and I can barely squeeze 1.6 cubes net in there with a 48 inch wide box.

 

[Jspawn80]

Youre throwing me off when you talk about gross volume. I cant tell if you mean net and are saying gross or arent sure the difference. Gross volume is the total volume the outer dimensions of the box. Net is inner dimensions minus subs and port displacement. The space inside the port does not count as air space inside the box. Id be surprised if youre getting 2 cubes under the seat in anything. Especially a truck with a crossmember hump in the floor the size of a titans. A silverado has a 3/4 inch hump in the floor and I can barely squeeze 1.6 cubes net in there with a 48 inch wide box.

My subwoofer box is 54 wide by 11 deep and the front of the box is about 10.5 and the back is 8, with the transmission of 3 i think and i did a 1.5 seat lift to fit it

The interior volume of the box is 2.231 ft^3, the woofer supports take up .01 ft^3 and the subwoofer displacement for both subs is 0.16ft^3 leaving me with 2.061ft^3 of net volume since u subtract the supports and subwoofer displacemnt from the total interior volume, now what i dont understand is how to calculate the port since the port itself takes up volume inside the box

 

[germanyt 10+ year member]

Ok so you really need to take up .5 cubes or so of volume to have the best air space for those subs.

Not sure what youre options are on port but I recommend a 5 inch diameter pvc about 26 or 27 inches long. Or a number of ports that gets you to 19 sq inches of port area. That will reduce net volume to about 1.7 and give you a 32hz tuning give or take a couple hz.

 

[Jspawn80]

Ok so you really need to take up .5 cubes or so of volume to have the best air space for those subs.

Not sure what youre options are on port but I recommend a 5 inch diameter pvc about 26 or 27 inches long. Or a number of ports that gets you to 19 sq inches of port area. That will reduce net volume to about 1.7 and give you a 32hz tuning give or take a couple hz.

Behind one of the subs the biggest i can go is a 4 inch port. I read that its best to port towards the doors of the truck instead of the front so i kind of didnt wanna port towards the front. So im not so sure what i can do now to take up space i made the box bigger cuz if not the subs wouldnt fit. And you said i cant port both sides of the box but what if i split the box into 2 chambers, im just throwing ideas out

 

[germanyt 10+ year member]

Def don't port to both sides. If a 4 inch is all you can fit due to the configuration of the box then go with a 4 inch. port to either the driver or passenger side. You likely won't hear a difference either way. A 4 inch port in 1.8 ish net cubic feet at 15 inches long is 32 hz. 10 inches long will leave you with about 1.8/1.9 cubic feet and a high 30s tuning. Up to you. I start by cutting a hole out that will allow the 4 inch port to fit and leave it like 20 inches long or even longer. Play it and listen to it for a bit. If you think the tuning is too low or it doesn't sound right then pull out the port and cut 5 inches off of it. Repeat down to 8 or 10 inches if necessary.