calculating aero port?

[marcin93 10+ year member]

Im trying to build myself a box for 4 SA 8's and so far i have a 4 cu.ft. box before any displacements. I wanted to add two 4" ports so that it it is tuned to about 33 hz. Anybody know how to calculate the length I need and if this plan sounds good? they be fed by a soundstream 2500D.

Click to read more...

 

[THATpurpleKUSH 5,000+ posts]

aeroport calculator

 

[Imtjnotu 5,000+ posts]

take the volume of the box after sub displacement for the correct aero port length

 

[marcin93 10+ year member]

how do I calculate the sub displacement?? also, does that page consider that the aero ports are in the box or outside???

 

[CHEMMINS 10+ year member]

Ports in the box.....and what subs ya have?

 

[marcin93 10+ year member]

I have 4 sundown audio SA-8's. Im trying to get about .6cuft each, so after all the displacements Im pretty sure ill be in that ballpark.

 

[OmegaBunny 10+ year member]

Box seems too big. (2) 4" ports for a 4cu ft box would be 13.6 inch each. The volume for both would be about .2 cu ft. Then each woofer displaces .1 so another .4 is .6 cu ft of total displacement.

You are aiming for .6 each so total volume of 2.4Ft ^ 3.

4ft^3 - 0.6^ft = 3.4ft^3. You need to loose another ft.

Assuming my math is correct.

 

[marcin93 10+ year member]

Ok so here is a pic of how my box design looks right now. I was wondering if I put 45's in the corners, would that take away enough Ft^3 to make it into about 3.3 Ft^3. Then after the .4 for the subs and .2 for ports It would be about .675 per sub.

 

[Imtjnotu 5,000+ posts]

First off how much power are you running to each

 

[OmegaBunny 10+ year member]

45's won't take much but will reduce the volume some. You may save another .2-.4 but that would take it down to about .8-.6 for each which would be fine.

 

[marcin93 10+ year member]

They will be getting 625 watts each which is why im tryin to keep the Ft^3 down at around .6 each.

 

[Imtjnotu 5,000+ posts]

Why not just shrink the whole box in general to 3.5 cubes and go from there.... You only need 2.4 and after disp and port I think you will be right around there

 

[marcin93 10+ year member]

yes but im working off an old box I wave and I dont really want to cut it into pieces. This box is only temporary too, I just want to be on the safe side.

 

[hispls 5,000+ posts]

Dunno why you'd worry about the box being a little too big. with such low tuning the port sould control cone pretty well as low as you need.

 

[marcin93 10+ year member]

SA-8 Power vs. Box Size - SMD Forum

^here is why