[jimbo_limited]

I seriously need help on building my own ported box... I had built a Dual Twelve box with the port right down the middle. For this box i want to have Three Seperate ports on Top of the woofer. All i want to know is how to tune a port.

The box im building is 43 Inches wide, 17 inches Tall and 17 Inches deep. The ports will be 3 Inches wide in a rectangular shape and about 13.5 inches wide. Keep in mind there is Three Separated ports. How Long should i make the port? I was thinking 13 inches long but i want some opinions and the most amount of help i can get.

I can increase the depth of the box up to 20 inches max.

:::Edit:::
The wood i will be using is 1/2 Inch MDF wood


Here is a blueprint of the box:




if that doesnt work the link is http://i6.photobucket.com/albums/y23...imited/box.jpg

[GregS]

In article , jimbo_limited wrote:

I seriously need help on building my own ported box... I had built a
Dual Twelve box with the port right down the middle. For this box i
want to have Three Seperate ports on Top of the woofer. All i want to
know is how to tune a port.

The box im building is 43 Inches wide, 17 inches Tall and 17 Inches
deep. The ports will be 3 Inches wide in a rectangular shape and about
13.5 inches wide. Keep in mind there is Three Separated ports. How
Long should i make the port? I was thinking 13 inches long but i want
some opinions and the most amount of help i can get.

I can increase the depth of the box up to 20 inches max.

:::Edit:::
The wood i will be using is 1/2 Inch MDF wood


Here is a blueprint of the box:

[image: http://i6.photobucket.com/albums/y23...mited/box.jpg]

You plug the parameters of the drivers into a program, and the box size
and port size will be determined depending on what type of alignment
you want. To tune a box, you usually measure the impedance peak
and adjust the port so there is a double peak withing the
bottom end range. You can roughly tune a port by adjusting
it so the drivers are traveling at their minimum near the bottom end.
A signal generator or CD frequency disk and a meter are minimum requirments
of electrically tunning a box.

greg

[D.Kreft]

On Dec 18, 4:37 pm, jimbo_limited
wrote:

I seriously need help on building my own ported box... I had built a
Dual Twelve box with the port right down the middle. For this box i
want to have Three Seperate ports on Top of the woofer. All i want to
know is how to tune a port.

You really need to know what the manufacturer recommends--you shouldn't
just be arbitrarily picking port dimensions and hoping it'll serve you
well.

Then you can use the information in the JL Audio Ports tutorial to
build 'em:

http://mobile.jlaudio.com/support_pages.php?page_id=165

-dan

[jimbo_limited]

Originally Posted by D.Kreft

On Dec 18, 4:37 pm, jimbo_limited
wrote:

I seriously need help on building my own ported box... I had built a
Dual Twelve box with the port right down the middle. For this box i
want to have Three Seperate ports on Top of the woofer. All i want to
know is how to tune a port.

You really need to know what the manufacturer recommends--you shouldn't
just be arbitrarily picking port dimensions and hoping it'll serve you
well.

Then you can use the information in the JL Audio Ports tutorial to
build 'em:

http://mobile.jlaudio.com/support_pages.php?page_id=165

-dan

The recommended specs are as following:

Description Value
Size 12"
Impedance 4-Ohm x 2
Power Handling 500 RMS
1000 Peak
Sensitivity 87 dB
Motor Size 102 oz. double stacked
Voice Coil Diameter 2.5" aluminum
Speaker Connector Dual 8 AWG compression
Mounting Depth 6.375"
Rec. Sealed Enclosure 0.75 cu. ft.
21.24 liters
Rec. Vented Enclosure 1.75 cu. ft.
49.56 liters
Tuning Frequency (vented) 37 Hz
Shipping Weight 25.2 Lbs.
(11.4 Kg.)

[KU40]

go to www.linearteam.org and download winISD. you plug in the box size
(after all displacements), tune you want, and port area, and it'll tell
you how long to make each port.


--
KU40

[Erik]

jimbo_limited wrote:
I seriously need help on building my own ported box... I had built a
Dual Twelve box with the port right down the middle. For this box i
want to have Three Seperate ports on Top of the woofer. All i want to
know is how to tune a port.

The box im building is 43 Inches wide, 17 inches Tall and 17 Inches
deep. The ports will be 3 Inches wide in a rectangular shape and about
13.5 inches wide. Keep in mind there is Three Separated ports. How
Long should i make the port? I was thinking 13 inches long but i want
some opinions and the most amount of help i can get.

I can increase the depth of the box up to 20 inches max.

:::Edit:::
The wood i will be using is 1/2 Inch MDF wood


Here is a blueprint of the box:

[image: http://i6.photobucket.com/albums/y23...mited/box.jpg]


if that doesnt work the link is
http://i6.photobucket.com/albums/y23...imited/box.jpg




--
jimbo_limited

If you were running a single 12" sub, I could understand going with a
slot vent, but running three in separate sealed chambers will make
construction much more difficult. It would be easier to put them in a
shared chamber and run three 4" flared ports. But that's just a small
issue with the design you've got so far...

The dimensions you've given won't get you anywhere near the 1.75cu ft
per sub @37hz that the manufacturer suggests, with the additional
internal volume taken up by separate chambers. As it stands, you're
looking at around 1.1cu ft per chamber. If you extend the depth to 20"
you'll be getting about 1.5cu ft per chamber (just a rough estimate
since you didn't include the displacement of the drivers themselves).
Keep in mind that slot port volume is not included in the overall
volume of the internal chamber. You're just not going to get the
volume you need for the subs with the dimensions you've laid out.

Your biggest problem at this point isn't the length of the slot ports,
but the overall dimensions of the box itself.

There's no downside in running 3 subs in a ported shared chamber.

Can you provide the t/s parameters for the drivers? Or better yet,
provide the make/model of the subs?

Good luck...

[D.Kreft]

On Dec 25, 6:45 pm, "Erik" wrote:

There's no downside in running 3 subs in a ported shared chamber.

I don't think this is entirely true. Using three discrete chambers...

1) makes it much simpler to create a very rigid enclosure. The
alternative is use smaller pieces of wood to brace the heck out of the
walls of the enclosure. Bracing should be used regardless, but having a
solid wall in between each pair of drivers not only makes the box
really strong, but it also multi-functional.

2) makes the subwoofer system more fault tolerant. If you have a single
common chamber of volume V for N subwoofers and one sub fails, the
effective enclosure volume per driver will be V / (N-1). In real
numbers, if you have 3 12" subs in a box with a volume of 4 cubic feet,
if one driver fails the remaining two drivers will each "see" 2 cubic
feet...and will be seriously mistuned at that. With three discrete
chambers, however, even a failure of all but one driver won't affect
remaining good speaker.

3) will minimize the amount of interaction between the subwoofers. No
two drivers are perfectly identical in all respects (even drivers
coming from the assembly line in the same batch), so each is going to
respond to incoming signals in slightly different manner. If the
drivers share a common volume in the enclosure, they'll tend to
modulate one another, which is not ideal. Now, in all actuality, this
is probably too fine a point to stress as the differences are
(hopefully) so small as to be unperceptible by the human ear, but I
mention it for completeness' sake.

For more on box design and bracing, see:

http://mobile.jlaudio.com/support_pages.php?page_id=164
http://mobile.jlaudio.com/support_pages.php?page_id=166

Of course, on the flip side, using a big common chamber can make it
much easier to use large-diameter ports of shorter length to achieve
the same tuning, but that's not to say that there is no downside at all
to using a large, common chamber. Like anything field of engineering,
there are always tradeoffs to be made--you cannot get something for
nothing.

-dan

[almond]

well think of it this way. sya 3 subs in a 3 cube foot bx. they are all
sharing 3 cubes see each one sees 1 cube foot. now when a sub stops
working it will now see 1.5 cubes. that doesn't seem like much of a
difference but when you have 3 subs in 12 cubes and one goes out you
now go from 4 cubes each sub to 6 cubes.


--
almond

[D.Kreft]

On Dec 26, 10:43 am, I. Care wrote:

SNIPDan, I don't understand the math on this in a logical manner.

Do you see where my difficulty lies in understanding your logic?

Yeah, a bad analogy. The problem with your analogy is that your people
are *in* the room, and the subwoofers act *on* a room from the outside.

One of my favorite activities, even to this day, is to go to fairs and
get in the bounce houses with the kids. If you spend enough time in
these things, you'll quickly note that if everyone jumps up and down at
the exact same time, you'll get a lot higher because there really isn't
much of a place for the displaced air to go, so it compresses--which
takes quite a bit of energy to do. If everyone jumps at the same time
and with the same force, your pushing down will push up someone else
who is pushing down (and visa versa) and so the floor seems fairly
stiff.

Now, if half of the people stop jump altogether and just kinda go along
for the ride, you'll notice that the floor of the bounce house is a
*lot* spongier...when you attempt to jump, your feet sink further into
the cushion until the internal pressure balances or exceeds that of
your upward thrust. If you're really big like me (7'0", 270lbs), and if
you try hard enough, you can even hit the ground under the bounce house
if you're the only one making any attempt to jump--and that's painful.
Unlike a loudspeaker, I don't have a surround and a spider to
mechanically limit my travel, so I'm at the mercy of the springy air
mass below me.

The bounce house analogy also exaplains why you don't ever put two
drivers of a different size in an enclosure. Let's say there's me, at
270 lbs., and my 3-year-old boy who weighs about 60 lbs. or so and
we're both in the bounce house. Caleb can jump up and down all he wants
and as hard as he wants for as long he wants and it's barely going to
affect me--I'll just stand there, relatively close to the hard ground
beneath me and just bob up and down a tiny bit. Then if, while he
continues to jump, I start making large, slow movements, I'll start
"modulating" his jumps...and if he is at the bottom while I'm hitting
the cushion, I'm going to send him through the roof (and then he'll run
out of the bounce house crying and seeking hugs from his mommy :-).

Get it now?

-dan

[D.Kreft]

On Dec 26, 11:28 am, almond
wrote:

well think of it this way. sya 3 subs in a 3 cube foot bx. they are all
sharing 3 cubes see each one sees 1 cube foot. now when a sub stops
working it will now see 1.5 cubes. that doesn't seem like much of a
difference but when you have 3 subs in 12 cubes and one goes out you
now go from 4 cubes each sub to 6 cubes.

And to further complicate matters, the lame driver will act as a
passive radiator (assuming that the driver hasn't locked-up due to a
torched voice coil that's slid off the former and cooled into an
amorphose blob at the bottom of the magnetic gap), which will do really
icky things to the tuning of the enclosure.

In my business (software engineering and distributed systems design),
we talk about the "fault tolerance" of a system. If we have one part of
a system go down, we want to be somewhat assured that one piece being
down won't destroy everything around it. Having all your subs in one
common chamber is decidedly *not* fault tolerant, because if one or
more drivers fail, you immediately put your other, working subs at
great risk of mechanical damage.

-dan

[Erik]

On Dec 26, 9:40 am, "D.Kreft" wrote:
On Dec 25, 6:45 pm, "Erik" wrote:

There's no downside in running 3 subs in a ported shared chamber.I don't think this is entirely true. Using three discrete chambers...

1) makes it much simpler to create a very rigid enclosure. The
alternative is use smaller pieces of wood to brace the heck out of the
walls of the enclosure. Bracing should be used regardless, but having a
solid wall in between each pair of drivers not only makes the box
really strong, but it also multi-functional.

A well constructed box won't flex. You can make it 10" thick and the
only thing it will gain you over a properly constructed 3/4" mdf box
is a bunch of weight and a bigger box.

2) makes the subwoofer system more fault tolerant. If you have a single
common chamber of volume V for N subwoofers and one sub fails, the
effective enclosure volume per driver will be V / (N-1). In real
numbers, if you have 3 12" subs in a box with a volume of 4 cubic feet,
if one driver fails the remaining two drivers will each "see" 2 cubic
feet...and will be seriously mistuned at that. With three discrete
chambers, however, even a failure of all but one driver won't affect
remaining good speaker.

At least you'll know that one of the subs is blown I had a buddy
running around with four separate ported enclosures (fiberglassed into
the interior) and he didn't realize one of them was blown! There's
more danger with a sub blowing in a shared *sealed* chamber though.
One blown sub can actually cause damage in the other good subs. In a
vented box, it's possible but much less likely.

3) will minimize the amount of interaction between the subwoofers. No
two drivers are perfectly identical in all respects (even drivers
coming from the assembly line in the same batch), so each is going to
respond to incoming signals in slightly different manner. If the
drivers share a common volume in the enclosure, they'll tend to
modulate one another, which is not ideal. Now, in all actuality, this
is probably too fine a point to stress as the differences are
(hopefully) so small as to be unperceptible by the human ear, but I
mention it for completeness' sake.

Uhhh... yeah. I'll bet a million dollars you could do double blind
tests for the rest of your life and not be able to tell a difference.

For more on box design and bracing, see:

http://mobile.jlaudio.com/support_pages.php?page_id=164
http://mobile.jlaudio.com/support_pages.php?page_id=166

Of course, on the flip side, using a big common chamber can make it
much easier to use large-diameter ports of shorter length to achieve
the same tuning, but that's not to say that there is no downside at all
to using a large, common chamber. Like anything field of engineering,
there are always tradeoffs to be made--you cannot get something for
nothing.

-dan

Your points are valid but the end result is negligible. But
realistically, how often do you see a box with 3 separate chambers
using *slotted* vents. Ported vents, yes... slotted? I have to admit
I've never seen one before and I've seen a lot of boxes.

You get more port turbulence with slotted vents if they aren't done
right. I hate a chuffing box

[Erik]

On Dec 26, 7:16 pm, "Erik" wrote:
using *slotted* vents. Ported vents, yes... slotted? I have to admit
I've never seen one before and I've seen a lot of boxes.

You get more port turbulence with slotted vents if they aren't done
right. I hate a chuffing box

*EDIT*

I mean to say "Round vents" not "Ported vents".

But back to the issue at hand. The original poster's dimensions won't
work for application he's trying to use. Sounds like he has limited
space to work with. Using round ports vs. slotted vents makes more
sense.

E

[D.Kreft]

On Dec 26, 6:16 pm, "Erik" wrote:

A well constructed box won't flex.

I'm sorry..did I somehow suggest it would? My point was that it's
easier to *make* that well-constructed box well constructed when it's
broken up into discrete chambers.

You can make it 10" thick and the
only thing it will gain you over a properly constructed 3/4" mdf box
is a bunch of weight and a bigger box.

I'd be willing to bet that the 10" box would be less lossy than your
3/4" MDF box. Unless, of course, you're talking about a spherical
subwoofer enclosure...in which case the thickness of the wall isn't as
important as the tensile and compressive strength of the material used
to create the enclosure. :-)

At least you'll know that one of the subs is blown I had a buddy
running around with four separate ported enclosures (fiberglassed into
the interior) and he didn't realize one of them was blown!

I'd rather run around for a month and not realize I had a blown driver
than to have one fail and wind up *having* to purchase two. As your
emoticon suggests, this is a pretty silly argument.

Uhhh... yeah. I'll bet a million dollars you could do double blind
tests for the rest of your life and not be able to tell a difference.

As I said...I was just being thorough. USENET is a great forum for
getting shredded for omitting obscure edge cases.

Your points are valid but the end result is negligible. But
realistically, how often do you see a box with 3 separate chambers
using *slotted* vents. Ported vents, yes... slotted? I have to admit
I've never seen one before and I've seen a lot of boxes.

I've seen 'em with two drivers
(http://mobile.jlaudio.com/products_e...=8&page_id=25).
It's been a *long* time, but if memory serves, I think I actually
designed one for three JL Audio W6 drivers that used three slotted
ports.

You get more port turbulence with slotted vents if they aren't done
right. I hate a chuffing box

You get lots of problems with anything if it's not done right. I get
chafing on my inner thigh if I don't put my underwear on right, but
that doesn't mean I get up in the morning and decide to "give us us
free."

-dan

[jimbo_limited]

The subs I'm going to install are TWO Punch Stage 2 and ONE Punch Stage 3. Obiously they are all Twelves.

To make building alot easier and less frustration:::


Are sealed box good? I never used a sealed box before and honestly never heard 12's in a sealed box (Only 10's). All other 12's i only heard in Ports and Bandpass.

Will Sealed still give me a High SPL? I read that it gives a better SQ and gives a cleaner BUMP. What other benefits will i get when i go Sealed?

Mike