[Josh[_2_]]

Hi,

I have had a 15" P1 rockford fosgate subwoofer in a sealed enclosure
in my car for about a year.
I liked the sound of it and the bass etc - but i want to switch to
vented to get a little more spl.

I built the box to be sealed, but made it between the sizes the
manufacturer recommended for vented and sealed boxes.

So i took out my hole saw the other day and cut the hole in the box
for the vent.
That sub can really move some air!!!
but anyways - it doesnt sound that great, i know that the response
wont be as good as sealed, but i cant seem to turn up the volume as
much, because it starts "farting" the sound out, if you will.

I haven't put a tube in the hole yet, but i know this will help with
the travel of the sound.

I know that this sub box and sub has potential being vented, so if you
have any suggestions on how i can get it to sound better, (and be able
to get the volume up more) it would help me out a lot. Maybe some tube
designs, shapes (bends) or something with putting a material in the
box, or in the tube, or whatever you know works or might work, without
having to rebuild the box (which i will do someday when i can get some
money) i will try it out.
Thanks in advance.

[D.Kreft]

On Mar 14, 1:41 pm, "Josh" wrote:

So i took out my hole saw the other day and cut the hole in the box
for the vent.
That sub can really move some air!!!
but anyways - it doesnt sound that great, i know that the response
wont be as good as sealed, but i cant seem to turn up the volume as
much, because it starts "farting" the sound out, if you will.

What you have done is to tune your enclosure to a relatively high
frequency--which makes it pretty stinking loud, but offers you "crap"
in terms of low-frequency extension. What you should know about ported
boxes is that below the frequency to which you tune the enclosure, the
subwoofer "unloads" or plays as if mounted in an infinite baffle
enclosure. In other words, the restraining force that the mass of air
in the box places on the subwoofer completely disappears and causes
undue mechanical stress on the driver--farting.

I haven't put a tube in the hole yet, but i know this will help with
the travel of the sound.

It has nothing to do with "travel of the sound" but everything to do
with the frequency to which the enclosure is tuned.

I know that this sub box and sub has potential being vented, so if you
have any suggestions on how i can get it to sound better, (and be able
to get the volume up more) it would help me out a lot. Maybe some tube
designs, shapes (bends) or something with putting a material in the
box, or in the tube, or whatever you know works or might work, without
having to rebuild the box (which i will do someday when i can get some
money) i will try it out.

You first need to contact an RF dealer and tell them the model of your
sub, the volume of your enclosure and ask them how big to make your
port. DO NOT simply try to jam a length of pipe into your hole and
pray it'll work--for sure, whatever you jam in there will be better
than your current situation, but you'd have to be really lucky to
accidentally stumble upon the optimum alignment.

I would also suggest you read the some of the tutorials on JL Audio's
website (http://mobile.jlaudio.com/support_pa...p?page_id=127). The
fact that you're using RF subs is largely irrelevant--there's a lot of
information at the JL site that is universally applicable.

Until you get your port specs, I would strongly recommend you undo
your "fix"--plug that hole and seal the box back up so you don't
destroy the voice coil former on your speaker.

-dan

[Josh[_2_]]

On Mar 14, 4:11 pm, "D.Kreft" wrote:
On Mar 14, 1:41 pm, "Josh" wrote:

So i took out my hole saw the other day and cut the hole in the box
for the vent.
That sub can really move some air!!!
but anyways - it doesnt sound that great, i know that the response
wont be as good as sealed, but i cant seem to turn up the volume as
much, because it starts "farting" the sound out, if you will.

What you have done is to tune your enclosure to a relatively high
frequency--which makes it pretty stinking loud, but offers you "crap"
in terms of low-frequency extension. What you should know about ported
boxes is that below the frequency to which you tune the enclosure, the
subwoofer "unloads" or plays as if mounted in an infinite baffle
enclosure. In other words, the restraining force that the mass of air
in the box places on the subwoofer completely disappears and causes
undue mechanical stress on the driver--farting.

I haven't put a tube in the hole yet, but i know this will help with
the travel of the sound.

It has nothing to do with "travel of the sound" but everything to do
with the frequency to which the enclosure is tuned.

I know that this sub box and sub has potential being vented, so if you
have any suggestions on how i can get it to sound better, (and be able
to get the volume up more) it would help me out a lot. Maybe some tube
designs, shapes (bends) or something with putting a material in the
box, or in the tube, or whatever you know works or might work, without
having to rebuild the box (which i will do someday when i can get some
money) i will try it out.

You first need to contact an RF dealer and tell them the model of your
sub, the volume of your enclosure and ask them how big to make your
port. DO NOT simply try to jam a length of pipe into your hole and
pray it'll work--for sure, whatever you jam in there will be better
than your current situation, but you'd have to be really lucky to
accidentally stumble upon the optimum alignment.

I would also suggest you read the some of the tutorials on JL Audio's
website (http://mobile.jlaudio.com/support_pa...p?page_id=127). The
fact that you're using RF subs is largely irrelevant--there's a lot of
information at the JL site that is universally applicable.

Until you get your port specs, I would strongly recommend you undo
your "fix"--plug that hole and seal the box back up so you don't
destroy the voice coil former on your speaker.

-dan

Thanks for the info!! I do have the port specs at hand - it is 4"
diameter and 9.5" long

so what if i dont have enough room to put a 4" hole? can i split the
numbers up, as long as the end diameter equals 4"? also would i change
how far in the port goes, if i make 2 holes?

If i make a 2.5" hole, and then another hole diagonally from the first
hole on the same face being 1.5" in diameter - would that be ok? and
now that it would have 2 holes, would i change the port length
according to the diameter change, or just leave it at 9.5"?

as far as tuning goes - i just need to change my frequencies and all
of those bass and subwoofer settings on the amp and stereo right?
Because i originally went with what sounded good.
from what i understand - i should up the frequency to stop stressing
the driver - i had it at i believe around 30Hz. or so....

Thanks for your help

[D.Kreft]

On Mar 14, 2:56 pm, "Josh" wrote:

Thanks for the info!! I do have the port specs at hand - it is 4"
diameter and 9.5" long

so what if i dont have enough room to put a 4" hole? can i split the
numbers up, as long as the end diameter equals 4"? also would i change
how far in the port goes, if i make 2 holes?

The JL Audio ports tutorial covers all of this...it's not simply a
matter of achieving an equivalent port diameter.

If i make a 2.5" hole, and then another hole diagonally from the first
hole on the same face being 1.5" in diameter - would that be ok? and
now that it would have 2 holes, would i change the port length
according to the diameter change, or just leave it at 9.5"?

Your ports should all be the same diameter. See the Ports tutorial.

as far as tuning goes - i just need to change my frequencies and all
of those bass and subwoofer settings on the amp and stereo right?

I don't know what you mean by "change my frequencies."

Because i originally went with what sounded good.
from what i understand - i should up the frequency to stop stressing
the driver - i had it at i believe around 30Hz. or so....

Again, I don't understand what you mean by "up the frequency."

-dan

[The Lull]

On Mar 14, 7:42 pm, "D.Kreft" wrote:
On Mar 14, 2:56 pm, "Josh" wrote:

Thanks for the info!! I do have the port specs at hand - it is 4"
diameter and 9.5" long

so what if i dont have enough room to put a 4" hole? can i split the
numbers up, as long as the end diameter equals 4"? also would i change
how far in the port goes, if i make 2 holes?

The JL Audio ports tutorial covers all of this...it's not simply a
matter of achieving an equivalent port diameter.

If i make a 2.5" hole, and then another hole diagonally from the first
hole on the same face being 1.5" in diameter - would that be ok? and
now that it would have 2 holes, would i change the port length
according to the diameter change, or just leave it at 9.5"?

Your ports should all be the same diameter. See the Ports tutorial.

as far as tuning goes - i just need to change my frequencies and all
of those bass and subwoofer settings on the amp and stereo right?

I don't know what you mean by "change my frequencies."

Because i originally went with what sounded good.
from what i understand - i should up the frequency to stop stressing
the driver - i had it at i believe around 30Hz. or so....

Again, I don't understand what you mean by "up the frequency."

-dan

....I think I see what Josh is getting at.

Josh man,

The tuning frequency of the box is determined by the volume of the box
(size inside, minus everything taking up space), and the number of,
size, and length of any and all ports (or lack thereof) - to put it
simply. The frequency that D.Kreft speaks of, has more to do with the
specs of the subwoofer in conjunction with the box - NOT the settings
on your HU or Amp.

Read the suggested tutorials and whatnot - porting a box is not
*usually* just throwing some pipe into an enclosure, there's a whole
bunch of science and measurement behind doing it correctly.

I can also recommend a free computer program "winisd" (google it to
find it) to give you a pretty good starting off point for building a
ported box [I recommend the beta version of the program as it's a
little simpler to work with]...

Hope that helps.

~Mister.Lull