ok so when jacob opens up the pre-sale on these i will be ordering 6, they will be ran off of a saz-3500D at .7ohm. now i used a box calc. off of the *** forum, and got my box all figured out, its just the port thats confusing me, can someone help me out with this as to i cant figure out my actually port cut outs, the box will be in a 99 s10 ext cab, subs forward, port up (drivers side) here are the specs of the box.

6 10" Sundown sa's

box height - 29

depth - 14

Length - 43

Port height - 12.5

width - 7.5

length - 24.5

net air space 6.24ft3. port area 93.75 in2. @32.33

thanks!!

ok so when jacob opens up the pre-sale on these i will be ordering 6, they will be ran off of a saz-3500D at .7ohm. now i used a box calc. off of the *** forum, and got my box all figured out, its just the port thats confusing me, can someone help me out with this as to i cant figure out my actually port cut outs, the box will be in a 99 s10 ext cab, subs forward, port up (drivers side) here are the specs of the box.

6 10" Sundown sa's

box height - 29

depth - 14

Length - 43

Port height - 12.5

width - 7.5

length - 24.5

net air space 6.24ft3. port area 93.75 in2. @32.33

thanks!!

A 7.5" wide port? Are you sure about that?

It'd be nice to get this moved to the fabrication section. More box-builder types would notice it.

And how do you mean you can't figure out the cutouts?

It'd be nice to get this moved to the fabrication section. More box-builder types would notice it.

And how do you mean you can't figure out the cutouts?

ah sorry, i dont use this forum other then the sundown section so i really haven't explored over here. lol sorry, also, when i calculate this to paper to draw it up and get my cut outs, the port doesn't match up, i measure down the middle of the port. and it seems that it just wont work, i dont know what im doing wrong.

i measure down the middle, and subtract out of the total box height the .75 from the bottom sheet, and 7.5" from the port inside, that leaves me with the first cut at 20.75", so i need a total port length of 24.5", so i measure down 3.75" and over 3.75" plus .75" for the piece of wood for the port, and that gives me 29, so that means its longer then the port i need. ( when i say i measure the port i measure the middle of the port (the blue line)

this is a quick picture i drew up in paint, (red is port, blue line is what i measure)

You just figured out that the calculator you are using is off, it doesn't notice when a port has to bend. I'd also question they way it calculates tuning and volume then.

here is your figures-

Using single sided 0.75" MDF all the way around, I get 8.25cuft GROSS.

I estimate and subtract 0.65cuft for all 6 10s and get 7.6cuft GROSS.

I then build port as follows-

12.5" depth-wise

7.5" width-wise

20" Deep Internal(leaving 7.5" of space before hitting floor keeping port width at 7.5")

Physical port length- 20" internal. (this is what you make)

Acoustical port length- 32.75" (this is what the box sees)

tuning - 32hz.

NET Volume - 6cuft even

here is your figures-

Using single sided 0.75" MDF all the way around, I get 8.25cuft GROSS.

I estimate and subtract 0.65cuft for all 6 10s and get 7.6cuft GROSS.

I then build port as follows-

12.5" depth-wise

7.5" width-wise

20" Deep Internal(leaving 7.5" of space before hitting floor keeping port width at 7.5")

Physical port length- 20" internal. (this is what you make)

Acoustical port length- 32.75" (this is what the box sees)

tuning - 32hz.

NET Volume - 6cuft even

How does it see such a long port? I figured a 20" port was a 20" port... Gosh I must be tuned super low...

here is your figures-

Using single sided 0.75" MDF all the way around, I get 8.25cuft GROSS.

I estimate and subtract 0.65cuft for all 6 10s and get 7.6cuft GROSS.

I then build port as follows-

12.5" depth-wise

7.5" width-wise

20" Deep Internal(leaving 7.5" of space before hitting floor keeping port width at 7.5")

Physical port length- 20" internal. (this is what you make)

Acoustical port length- 32.75" (this is what the box sees)

tuning - 32hz.

NET Volume - 6cuft even

How does it see such a long port? I figured a 20" port was a 20" port... Gosh I must be tuned super low...

The bend in the port as it ends in the corner and half port width for end correction.

I see...

Said the blind man to his deaf wife who was listening to the radio.

Thanks for clarifying... Guess I'm sitting at like... 30-31Hz for my box then...

Oh and sorry for getting off topic OP, not trying to thread-jack or anything.

Edited January 30, 201015 yr by Don Ganso

yep, acoustical length is typically at it's highest when the port has a bend in it.

because the internal height is 27.5" high, this is what happens-

build port wall 20" long leaving it 7.5" from hitting the floor.

So we have 20" + thickness of baffle(0.75")

So now we are at 20.75"

At the very end of the port inside, it must bend around the corner.

the bend around the corner's length is equal to the port's width.

So 20.75" + 7.5" = 28.25"

Now you must account for 0.75" more for the thickness of the port wall itself.

Now we are at 29"

Because this port is sharing the walls of the enclosure, it is a slot port. Take half the width of the port and add it to 29"

29" + 3.75" = 32.75"

If your port doesn't share the side wall of the box, then the acoustical length will not be that far off from the physical length.

Let's say the physical port length was only 5" internally.

That would be 5" + .75" for baffle thickness - 5.75"

then you 'd take half the width which is 3.75" so this answer would be-

physical length to cut - 5"

acoustical length seen by box- 9.5"

that's only 4.5" increase vs 12.75" for your current box drawing. That's why bends in a slot port have high acoustical lengths and the wider the port, the longer it is.

yep, acoustical length is typically at it's highest when the port has a bend in it.

because the internal height is 27.5" high, this is what happens-

build port wall 20" long leaving it 7.5" from hitting the floor.

So we have 20" + thickness of baffle(0.75")

So now we are at 20.75"

At the very end of the port inside, it must bend around the corner.

the bend around the corner's length is equal to the port's width.

So 20.75" + 7.5" = 28.25"

Now you must account for 0.75" more for the thickness of the port wall itself.

Now we are at 29"

Because this port is sharing the walls of the enclosure, it is a slot port. Take half the width of the port and add it to 29"

29" + 3.75" = 32.75"

If your port doesn't share the side wall of the box, then the acoustical length will not be that far off from the physical length.

Let's say the physical port length was only 5" internally.

That would be 5" + .75" for baffle thickness - 5.75"

then you 'd take half the width which is 3.75" so this answer would be-

physical length to cut - 5"

acoustical length seen by box- 9.5"

that's only 4.5" increase vs 12.75" for your current box drawing. That's why bends in a slot port have high acoustical lengths and the wider the port, the longer it is.

Ah-ha!

ok sorry, the box calculator i am using, DOES account for bends in the port, here is a screen pic of what i have (using the calculator) (also sub displacement is 0.12 jacob said, witch is 0.72 for all 6) also i dont use the cutouts that the calculator gives me, i figure it out on my own.

Just waiting on new cone sample to start pre-order on the 10s

Just waiting on new cone sample to start pre-order on the 10s

i cant wait jacob!!!