building my 1st ported box,kicker L7

[scampo77]

i am tryiing to switch from a sealed encloser to a ported one in hopes of getting louder. i asked kicker for specs and this is what they sent me

"Ported do 2.14 cubic feet includes port displacement. 3”X10” slot port at
22.5” in length"

i am building a "truck box" it is shaped like a triangle that has a rectangle behind it. my total volume inside is 2.319 cubic feet and that is including the
.09 cubic feet that the speaker takes up (2.409 without speaker). i built them just to fit in the cab now i realize they are too big.

so my questions are....

- is .18 cubic feet a lot to be out?

- when buildng a ported box do i subtract the entire port size from the total volume of the box?

-when building the port do i build it flush to the surface or can i build a "collar" i thought if i build a collar then i could have interchangable ports till i find one that i like. if i do build a collar then do i measure the total length of the port or just the part that is inside the box?

-the guy from kicker gave me a huge port size and it was very non specific. but the port calculator on BCAE1.com gives me one much smaller bcae is 50" and the reccomendations from kicker is 60". which one do i trust

- how do i know which frequency to build the port to? is 20 htz reserved for crazy compitition set ups? or is 30? or 40?. what number should i be aiming for?

i realize this is a lot of questions but any help would help me out a lot and also teach me a lot. thanks in advance to anyone who helps me out

[Zero D]

Hi,

is .18 cubic feet a lot to be out? Not really it's about 5 Litres which is about 7%

It will though make a difference to the low end, as the response will fall off sooner.

You will need to recalculate the port size to tune it lower. Then it will go lower, but with slightly reduced output.

I think 40-60 Hz tuning would be much better than trying to get anywhere near 20Hz.

If you post a link to the driver i'll plug the TS into WinISD and see what i can come up with for you. In the meantime you could do the same and post your results.

Regards,

Zero D

[novadave]

In car audio its best to tune for 35hz. No need to tune to 20Hz

[Glowbug]

Anything between 30-40Hz would be good to shoot for...tuning higher in the 40-50Hz range might be better if you were building a one-note enclosure for SPL competition, but you'd lose the exaggerated low end for rap that goes down that low.

[scampo77]

this is great but i still need help understanding the port. if i am using 1 inch mdf and i want to build a 7 inch deep tube. do i count the 1" that is the thickness of the box? what i would like to do is build a collar around the port that is also 1" thick so now my port keeps getting shorter.

when i do build this port and i am tryiing to figure out the inside volume of the box. do i calculate the interior volume as if the tube was not hollow? or do i just figure out the volume that is making the structure of the port? i guess what i am asking is the inside of the port is part of the interior volume or not?

[GM]

Yes, duct length is its total path-length.

Yes, the duct has its own air mass 'plug' that resonates at Fb, so subtract all its volume (Vp).

GM

[scampo77]

ok i installed the port into my box today and i must say im a little dissapointed. according to bcae1.com and their calculator this is the figures i got

Gross box volume = 2.409 Ft3
Net box volume = 2.392 Ft3
Port Length = 4.253 Inches
Port Area = 7.069 Inches2
Port Volume = 0.017 Ft3

i can tell where the port stops braking the speaker and i wonder if i have done something wrong. it seems to be louder and deeper with a small sealed box. i have no way to meause the output of the subs so i am just going off of my untrained ear.
my questions are....

-why not just tune the box to 15-20 hertz? it seems that if it can act as a dynamic brake at those low frequencies it should work all the way up, no?

- is a ported box signifigantly louder/deeper then a sealed box? or is it one of those things that adds 2% and its not really noticable until the power numbers in play are completely insane, ie 10,000 watt sub and amp is 8 decibels louder becuase of the relativly small gain.

does a sealed box ever run into the problems of not being able to act as brake to the speaker at low extremes?

these speaker boxes take up a lot of space vs my sealed boxes and i wonder if i should just build some sealed ones

[scampo77]

the port that i made had an inside measurement of 2x3.5 and it is 4.25 deep. and it is flush with the exterior of the box, i didnt build the collar i originally wanted to

[richie00boy]

What size sub is it? The port area seems a bit small.

The reason you don't tune low like 20Hz in this application is because you lose most of the benefit of the port. Ports are most effecting round their tuning frequency.

[scampo77]

it is a 12" kicker L7.

how much range to get from a port? if it is tuned to 35 hrtz like it is now, what would be the upper and lower range?

and what range is bass heavey music? or a movie with explosions?