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Help with building circle port calculation

 

Gold Member
Username: Delsole

Post Number: 1546
Registered: Feb-05
Ok guys i have been trying to figure this out by myself but there's a few things that are really confusing me.

When i calculate port size on car stereo.com i type in all the information that applies. I decided to use the 4in ports since the 6in are on back order at parts express. Any way I figured i would use 2 or 4 4in ports. Now the more ports i use the longer it tells me to make them.

If i did everything right my box is 9.26 cubic feet. I could really use a hand figuring out how many 4in ports to use and what length they need to be. I also have no idea what i want the box to be tuned to. I was thinking 35Hz but i have no idea what would sound best. It will be a daily driver but i also want it to be as loud as possible while still sounding decent.

Any help is appreciated.Upload
 

Gold Member
Username: Dustin3

Box Designer & Builder...Dustin

Post Number: 5590
Registered: Oct-05
Use, http://www.psp-inc.com/tools.html for your aero calculation.
 

Platinum Member
Username: Glasswolf

Post Number: 13651
Registered: Dec-03
or the basic enclosure calculator page on www.bcae1.com
 

Gold Member
Username: Delsole

Post Number: 1547
Registered: Feb-05
What do you guys think i should tune the box to?

How many 4in ports should i use?

Do you think the box design will do ok?
 

Platinum Member
Username: Glasswolf

Post Number: 13654
Registered: Dec-03
for 15" subs I wouldn't use less than 6" ID ports, myself.
 

Gold Member
Username: Delsole

Post Number: 1549
Registered: Feb-05
Any ideas on making them or anywhere else to buy them? Parts express has them on back order.
 

Gold Member
Username: Delsole

Post Number: 1550
Registered: Feb-05
Also mounting depth on the subs are 8.8 inches and my box will only be 15 inches deep. Would the 6 inch ports be to close to the woofers?
 

Gold Member
Username: Delsole

Post Number: 1554
Registered: Feb-05
bump for a good answer.
 

Gold Member
Username: Kyle_lowe

Post Number: 1096
Registered: Apr-06
try this calculator maybe

http://www.carstereo.com/help/Articles.cfm?id=31

or get ahold of that guy that makes the 8" ports. i cant remember if he is on caco or ca.com though
 

Gold Member
Username: Delsole

Post Number: 1555
Registered: Feb-05
i only have about 7 inches from the sub to put a port in.
 

Gold Member
Username: Kyle_lowe

Post Number: 1098
Registered: Apr-06
i thought i had your box design figured out but i have been staring at it for so long trying to figure something out that it is playing tricks on my eyes and i cant tell what the shape is suppose to be.

its going to be a trapezoid with the wider end up?

i dont know if the 15" is the max height that you can go, but if you could increase it by a couple of inches you could make it work with four of the 4" precision ports from parts express. doing it this way would mean that the subs would be moved either to the very front or the very back of the box and installing the ports either facing front or back, depending on where you mounted the subs.

another option could be to install the ports firing up, the same direction as the subs are firing. if i am understanding your drawings correctly, you shouldn't have a problem with getting them to fit that way.

also, is the 9.26 cubic feet before or after sub and port displacement? it should work regardless, but at the max length the ports would need to be 10.6" each. shorter than this if the 9.26 is before all displacements.

EDIT: those port lengths are if you wanted it tuned to 35 hz. the length would be longer if you were to tune it lower and shorter if you were to tune it higher
 

Gold Member
Username: Delsole

Post Number: 1556
Registered: Feb-05
I was gonna mount the subs facing up towards the roof and with the ports firing towards the trunk. The wider end of the box will be on the top. The 30 inches will be the bottom.

9.26 is before all displacement.

I think i can get away with the 4 4in ports.

With that said what do you think i should tune this to for a loud daily?

Also do you think i should do the ports firing up with the subs or leave it the way im already thinking?
 

Platinum Member
Username: Glasswolf

Post Number: 13686
Registered: Dec-03
you need room for the port.
if you don;'t have room for the port, then your sub is too large for the vehicle application or your box needs to be redesigned.
 

Gold Member
Username: Kyle_lowe

Post Number: 1101
Registered: Apr-06
yeah, to do it the way you are thinking you would need to add a couple of inches to the height of the box.
 

Gold Member
Username: Delsole

Post Number: 1558
Registered: Feb-05
I believe i have plenty of room for the 4inch ports. I cant go up and higher because it hitting my rear hatch.

Now should i put the subs over the ports or towards the front of the car?

I already have the subs so i have to make them fit, and as for a redesign i have no idea. I have been boggling my mind the past week over making this thing.
 

Gold Member
Username: Delsole

Post Number: 1559
Registered: Feb-05
Also what do you guys think would be a good tuning frequency?
 

Gold Member
Username: Kyle_lowe

Post Number: 1102
Registered: Apr-06
maybe i missed it but what are the subs that you are using?

what you are wanting to do is put all of the ports in a single line?
with the way i am seeing it, it will not work because with roughly 30" to work with you will not have enough room. with just over 7" needed for each port they are going to need 29" of space at the very least. that does not leave any room because i am assuming you are building with at least 3/4 mdf which would then put your total width to need to be at least 30.5" which is wider than what you have. this is if you put the ports at the bottom of the enclosure.

what you could do is move the subs to the rear of the box (towards the front of the car) and move the ports up higher on the box and you should have room. this would be your best option because it seems like it would work fine with your current design.

the displacement of the ports is going to be around .32 cubic feet and your subs might take up .16 cubic feet each totaling somewhere around .65 cubic feet of total displacement.
that is just a guess on the displacement of your subs. at any rate this would make the volume of the box to be about 8.61 cubic feet. to tune to 35 hz the ports would need to be 10.9" each in length

by the way, this is all assuming that the volume you listed was the internal volume, i would need to recalculate if that is not the case.
 

Gold Member
Username: Delsole

Post Number: 1561
Registered: Feb-05
I'm going to be using Audioque HDC3 15's.

I used the12volt.com to get the enclosure volume and they asked me for the wood thickness.

So the 4in flared ports are around 7in wide on the flare?

This is going to be my daily driver but i want it to be as loud as possible. They will have almost 2k watts apiece. This is my first major box so i really don't know what i want it to be tuned to.
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