Slotted Port Help

[ladi3sman55 0]

hey guys i need some help figuring this out..

i have a box with a slotted port.. the port will be 15.5 tall and 4.5 wide the question i have is how deep does it need to be?

i want the box tuned to 38 hz

the dimensions are 17x30x25.5 (HxWxD) for a total of 5 cu ft

im waiting for this i have all of the box cut and ready to be put together other than the port..

btw this is for a mach 5 spl-15 i'll get pics of everything when im done too

[BKOLFO4 29]

17" long should work pretty good.

38 Hz is pretty high for daily. If you are going for SPL, you can start with a port length of 20", sweep and measure SPL, cut 1" off the port, sweep and measure SPL, cut 1" off the port. . .repeat until the port is around 10" long. You can also measure the true tuning frequency of each port length just for reference to see how it compares to your peak output frequency.

If this is for daily, I would make the port wall 20" long for a tuning around 34 Hz.

Brian

[shizzzon 461]

if you are using 0.75" of the length as the thickness of the wood when air travels out of the port, then for 38hz it need to be exactly 16" long.

Of course if you cut the box to where the port length runs all the way out of the box, then it will need to be 16.75" long.

For 34hz, it needs to be 22.5" long if using the outside wall of the box as 0.75" of the port length.

[BKOLFO4 29]

17" is close enough to 16.75". . .

And it can't be 22.5" long on a box that is 25.5" deep. Assuming 3/4" wood, you only have a 2.25" opening left at the back on a 4.5" port.

[dave_Edwards 1]

I guess you can't bend a port???

[shizzzon 461]

yea, i was on my way to bed, didnt remember the actual depth of the box...

But still, 22.5" long is required.

[BKOLFO4 29]

I guess you can't bend a port???

Of course you can. . .20" deep takes into account the bend making the port 25.5". I find when the port ends without a piece actually extended the port along the back wall, you don't get the full effective length of the corner, you get about half making the effective of the port in this case about 22-23" inches.

Brian

[ladi3sman55 0]

thanks guys this is for a loud daily if i dont like it i plan on just extending the port a bit i'll probably move down to roughly 35hz if i dont..