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Terminology question

 

New member
Username: Jbam

Post Number: 1
Registered: Dec-11
Hey Guys,
I want to start box building but I have one question I can't seem to find the answer to. In the picture attached to my post, which one is port Area, A or B? Or are they supposed to be the same?
Thanks!
JBam
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Gold Member
Username: Joe1234

Post Number: 1074
Registered: May-09
It's A but only the actual HOLE, if the port turns then it will also be B.

If you give me the external dimensions of the box as you can fit and the model of the driver I can provide a design suggestion.
 

New member
Username: Jbam

Post Number: 2
Registered: Dec-11
So in the above picture, the port turns, meaning I want to make A equal to B?

This particular enclosure (rendered below) is for a friend of a friend who wants to pay me to make it. He wants two 15" Kicker Comp VX's in a ported enclosure. I told him that he doesn't need two 15's but he insists. So here I am. Thanks for the help!
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Gold Member
Username: Joe1234

Post Number: 1076
Registered: May-09
Kicker recommends for the Comp VX15 the following:

Vb = 3 cuft (net internal vouume)
Fb = 35Hz (box tuning)

So here is a design suggestion:

Enclosure Specifications:

Fb = 35 Hz
Vb = 3 ft^3 (per chamber)

Subwoofer Mounting = Front Mounted

External Height = 17 in
External Width = 48,57 in
External Depth = 20 in

Port Width = 2 3/4 in

Cut List:

* All Dimensions in Inches.
* Wood Thickness is 3/4 for all Parts.

External Enclosure Parts:

Front = 41 9/16 x 15 1/2
Back = 48 9/16 x 15 1/2

Left & Right Sides + Center Divider (3 parts):
2 x Side = 20 x 15 1/2
Center = 18 1/2 x 15 1/2

Top & Bottom = 48 9/16 x 20

L Ports Internal Assembly Parts (2 of each) :

Front to Back = 15 3/4 x 15 1/2
Extension = 4 1/2 x 15 1/2


Please note that the cutlist is to generate a box such as this:

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If you want a center port you have to change things a bit.

Maybe I will ask you for a cut
 

Silver Member
Username: Alonzoub

Orlando, Florida

Post Number: 342
Registered: Apr-10
Right, so the port area is denoted by the AREA of A, and should be constant throughout the length of the port, meaning if the port were to extend long enough to require a TURN, then B should be = to A. The problem with the sketch in your first picture is that the "end" of the port is too close to the back wall. Typically you want to stay away from ports the end like that, you either want to leave a space equal to about 1.5 - 2 times the WIDTH of the port. Or you want to extend the port to make an actual turn by putting an L shaped port turn.

Ill draw some pictures later tonight to better illustrate what I mean.

As far as that second picture goes, those ports seem rather thin. I would personally go with a thicker port, but that can work if you don't mind some port noise.
 

New member
Username: Jbam

Post Number: 3
Registered: Dec-11
So, this is what I gather from your response, Alonzoub.
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That makes alot more sense.

And Joe, is there a reason why you chose 3 cubic feet? I know their site says 3-5. Is smaller more responsive? Or will it just save me on the cost of supplies?
 

Gold Member
Username: Joe1234

Post Number: 1078
Registered: May-09
Not at all J-Bam as you see it, now has an external volume of almost 9.6 cubic feet, a monster already, imagine if I choose a Vb of 5 cubic feet per sub!! You would need four people to put it in if it fits at all.

If the dims I used do not fit I can always change them.,
 

New member
Username: Jbam

Post Number: 4
Registered: Dec-11
So the green area in this picture is accounted for in the port volume, not the box volume, correct?
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Silver Member
Username: Alonzoub

Orlando, Florida

Post Number: 344
Registered: Apr-10
I can't really tell from the picture, is it an L-port?
 

Silver Member
Username: Alonzoub

Orlando, Florida

Post Number: 345
Registered: Apr-10
Heres alittle more info:

The length of the port can be apprixmated by measuring the length of the dotted line in the picture below. Notice how if you use the box wall as a port wall, it extend the "length" of your port by about half of the width of the port. You also want to take that into account as part of your port volume.
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So the Yellow volume you see below belongs to the port, everything left inside the cavity will be your box volume (minus bracing and subwoofer displacement).
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New member
Username: Jbam

Post Number: 5
Registered: Dec-11
Ahh, I see. Yea thats my quick rendering of an L port.
That clarifies things (especially the second pic)
Thanks again Alonzoub.
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