Looking to port my box (I think)

[NexDeus 10+ year member]

Evening all!

I have a Rockford P2D4-15 sub (the older 250w rms ones) in a sealed 3.5 cu ft box. When I built the box I (obviously) got a bit zealous with the size, and its about 2 cu/ft too big to run sealed. Manufacturer specs are 1.58 sealed and 2.66 ported so I'm not sure if I could even port it being its almost a cu/ft larger than their ported size but Im thinking the only way to save it the box is to port it. How many ports would you suggest doing? Where on the box? I'm in a CRV, so would I want sub up port back or another way? Thoughts on port length/diameter @ 37hrtz? Thanks!

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[CheЯRyMan]

Is there room on the baffle or any side to add another sub. That would but you about right for a sealed box. you can also close off part of the enclosure with a wall to get the volume down. I currently building a sealed/ported combo box. It has a removable sleeve in the port that closes off the enclosure from 6 cubes ported to 5.25 sealed. The subs call for 5 cubes sealed and 6 cubes ported. I made the sleeve look like a port but the opening is really a hand hold for pulling it out.

 

[Jeffdachef 5,000+ posts]

Evening all!
I have a Rockford P2D4-15 sub (the older 250w rms ones) in a sealed 3.5 cu ft box. When I built the box I (obviously) got a bit zealous with the size, and its about 2 cu/ft too big to run sealed. Manufacturer specs are 1.58 sealed and 2.66 ported so I'm not sure if I could even port it being its almost a cu/ft larger than their ported size but Im thinking the only way to save it the box is to port it. How many ports would you suggest doing? Where on the box? I'm in a CRV, so would I want sub up port back or another way? Thoughts on port length/diameter @ 37hrtz? Thanks!

That might be gross cubic feet numbers, not NET usable cubic feet. Measure the box in Depth X width X height and we can tell you what you can do with it.

 

[NexDeus 10+ year member]

Yeah those are my net measurements minus width of material. H15.5" W29.5" D16" with like ~5/8th inch board. (My measuring tape ***** at small measurements) I used http://www.bcae1.com/spboxnew2.htm and recalculated as I thought it was half inch board, so I show 3.436 Ft³. Just doing the math 7316÷1728=4.233 Ft³ but that's outside measurement. I guess I could always cut the box down some, but I wanted it ported anyways as I hear its MUCH better in a SUV.

 

[Jeffdachef 5,000+ posts]

Yeah those are my net measurements minus width of material. H15.5" W29.5" D16" with like ~5/8th inch board. (My measuring tape ***** at small measurements) I used http://www.bcae1.com/spboxnew2.htm and recalculated as I thought it was half inch board, so I show 3.436 Ft³. Just doing the math 7316÷1728=4.233 Ft³ but that's outside measurement. I guess I could always cut the box down some, but I wanted it ported anyways as I hear its MUCH better in a SUV.

I would not cut the box down at all, you just barely have enough. The specs rockford lists are the absolute minimum since they care more about space saving then actual bass reproduction. I would add another baffle layer and add in some bracing to the enclosure to make it stronger because 5/8 is very weak, you might have some output loss through box flex.

you can use a 6 inch aeroport at 14/15 inches long. Flare the ends and you should be fine. I would not go lower than 3 cubic feet for a 15 man. That is just pigeonholing a lot of bass response.

 

[NexDeus 10+ year member]

That's a ****** program there. You're right, it does look like I'm right on the cusp of too small. I'll go with the 6" @ 14" long. I still have the issue of where to put the port. Tips? //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif And thanks for the info Jeff, you're a huge help!

 

[Jeffdachef 5,000+ posts]

That's a ****** program there. You're right, it does look like I'm right on the cusp of too small. I'll go with the 6" @ 14" long. I still have the issue of where to put the port. Tips? //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif And thanks for the info Jeff, you're a huge help!

if you can, fire to the rear with both sub and port facing the same direction, if that doesnt work then sub up, port to the rear.

 

[NexDeus 10+ year member]

Thanks jeff!

 

[hispls 5,000+ posts]

I've often done well porting to the side. Just be sure wherever the box is going to sit you have AT LEAST 6" between the port and any walls. (either inside the box or outside where it's firing)

 

[NexDeus 10+ year member]

Just wanted to update I did the porting today. I ended up having to go with two 3" ports rather than the 6", because there would have been absolutly no way to put the 6" on the baffle and I couldnt find any 6" pvc that wasnt that cellulose core crap locally. Did em at 5.56" long which is what the calculator I used told me and have them 4" (I know someone said 6" but I just couldnt make it fit) from each wall of the box. Have them top and bottom left side. It sounds pretty freakin nice. I need to go in and seal everything up tight, but other than that it's fantastic. Thanks for the help everyone!

 

[CheЯRyMan]

Glad to hear you rescued your box. Just to point out to anybody that might read this two 3" ports do not equal a 6". The area of a 3" port is 7sq" x 2 = 14sq" A 6" port has a area of 28sq". You would need 4-3" ports to equal one 6"

 

[CheЯRyMan]

Im building a box for another member now and he called me Friday with a concern of a 1.5" protrusion in the rear firewall that would partially block the port. The configuration of the enclosure could not be changed but if I take advantage of the area in the wedge I can move the port over another .75 plus the rear wall thickness of .75" Im now even with the protrusion. All you need is a side view drawing

and draw rectangles and match the area. The first drawing shows you the original design easy to build a 4.75" x 5.5" port = 26sq"

The second drawing shows the port moved over .75" and double back wall thats even with protrusion so first draw a rectangle and calculate the volume 4.3 x 5.68=24.4sq" Draw another rectangle in the wedge its 1.3" x 4.3 = 5.59 but divide this number in half to find the volume of a wedge is 2.8" add 2.8 +24.4= 27sq" the new irregular port and original square port are now matched close enough and the port is unobstructed.View attachment 26552010 Josh's original box builder made the mistake of calculating a 6inch port in a calculator but used two 3 inch ports to substitute and Josh was experiencing huffing port noises. After talking with him I modeled his box and confirmed the noises were from the port. On a smaller amp the vent velocity would have gone unnoticed.

 

[NexDeus 10+ year member]

Glad to hear you rescued your box. Just to point out to anybody that might read this two 3" ports do not equal a 6". The area of a 3" port is 7sq" x 2 = 14sq" A 6" port has a area of 28sq". You would need 4-3" ports to equal one 6"

That being said, do you think I should put two more ports @ 5.56 on the right side of the baffle also? I still have enough PVC to make the ports.

 

[CheЯRyMan]

If it sounds good now with the power your putting on it leave it.

 

[NexDeus 10+ year member]

It's a tad farty, but yeah it's a vast improvement from sealed!