terrible mistake on box for 2 x12s

[James8371]

I recently got another x12 and wanted to build a good looking box. I researched my port design to find out how to measure the port length right but I must have misread. Originally, the box was suppose to be tuned to 31hz but after playing it I found its around 37. I calculated the port length using both sides plus the main piece but after I installed it I realized that I needed to calculate only using the length of one side. Is this the correct way to calculate the port length of this shape?

box is 44x21x17 od, 4.8 cubes with subs in, port is 5.5x15.5, 85in^2

if the box looks bowed in its because my camera has a fish bowl, the box is perfectly square.

[DiBo]

Looks like your port is too big along the back wall. Needs to be half of the sz of the port opening. If you opening is 5" make it 2.5" along the back. 

FYI... You're going to need double front baffles and 45° pieces in the corners as well as some type of Port bracing along the back wall for flex. X12's are the real deal lol

[06RTCharger]

1 hour ago, DiBo said:

Looks like your port is too big along the back wall. Needs to be half of the sz of the port opening. If you opening is 5" make it 2.5" along the back. 

FYI... You're going to need double front baffles and 45° pieces in the corners as well as some type of Port bracing along the back wall for flex. X12's are the real deal lol

Would port length be measured down the opening and then just ONE side of the ports "T"? 

[Triticum Agricolam]

1 hour ago, 06RTCharger said:

Would port length be measured down the opening and then just ONE side of the ports "T"? 

Yes, measure down the centerline of just one side. 

[James8371]

Was making sure. I am going to attempt to remove 2 pieces and make a L port. So far the box has held up, but is only powered by a bc2k at .5 so there is much more to come when I can afford a bc5k. Heard vinegar, a heat gun, and some patience can remove wood glue so I will try and reconstruct the box. Do not know if anyone has heard of a way to remove glued wood without destroying it.

Ive always heard you want the port to be the same distance from the back wall as it is wide, otherwise tuning will change

[Markous]

17 minutes ago, James8371 said:

Ive always heard you want the port to be the same distance from the back wall as it is wide, otherwise tuning will change

You'll want halve it when separating to each chamber after the junction of the 1 splitting into 2.

I look at it as building two boxes but delete the wall that would separate them

[Joe X]

4 hours ago, James8371 said:

I recently got another x12 and wanted to build a good looking box. I researched my port design to find out how to measure the port length right but I must have misread. Originally, the box was suppose to be tuned to 31hz but after playing it I found its around 37. I calculated the port length using both sides plus the main piece but after I installed it I realized that I needed to calculate only using the length of one side. Is this the correct way to calculate the port length of this shape?

box is 44x21x17 od, 4.8 cubes with subs in, port is 5.5x15.5, 85in^2

if the box looks bowed in its because my camera has a fish bowl, the box is perfectly square.

 

Like this:

 

L1 + L2 = center line length  of the port, in Torres that is labeled as "port Length".  

Starting from the turn you need to half the width of the port to each side an that is because in a standard ported box, port area needs to be preserved (same either side) to tune as expected, that is why you are getting a higher tuning.

 

[Markous]

Physical length in Torres is the red line and i threw some text in to describe the port length, this is correct isn't it Joe X?

 

 

 

[Joe X]

15 minutes ago, Markous said:

Physical length in Torres is the red line and i threw some text in to describe the port length, this is correct isn't it Joe X?

 

 

Torres Physical port length is like this:

 

Two problems with that,  the label "physical port length"  is normally understood as the center line length of the port end to end to differentiate form the   "effective port length" which includes the end correction for slot ports, so that is an unfortunate name he picked, the other problem is when you are using more than one layer baffle, the easiest and more reliable method is going by the center line length as explained  in my previous post. 

 

 

 

[Jessica]

maybe i do it wrong but i draw a 45° line at the start of  of my port  across he width, into the chamber for the subs. then  i measure from the port exit to that line down the center to find effective port length and find my actual volume. It works for me when i test in the car. May not be the exact right way.