Quick question for enclosure wizs

[Dr. Slam 10+ year member]

When building a ported box where does port volume stop? If the port side stops before turning what do I account for the area from the end of the port to the back of the enclosure? If the port bends is the entire back of the enclosure now considered port volume past where the port stops?

I ask because this would alter my tuning calculations if I don't adjust for this.

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[THATpurpleKUSH 5,000+ posts]

I have always understood the volume is up to where the port stops, then you add an end correction factor of one half the width of the port to the physical length down the middle of the port to get the effective length.

 

[Dr. Slam 10+ year member]

So if my port length is 27.5", width 6.25", height 16" and my box is 34 inches deep. I have to add 325^2 inches back to my net box volume which would alter tuning?

 

[Dr. Slam 10+ year member]

On second thought that would create an essentially never ending cycle. So what's the deal here box guys. I'm building my second enclosure and I want it to be as accurate as possible

 

[THATpurpleKUSH 5,000+ posts]

Your port disp will be 7(6.25 + .75 port wall thickness) x 16 x 27.5 / 1728 = 1.7824 cu/ft port disp, now subtract that with the sub displacement and you will have the final volume that the woofer will see.

The effective tuning length of the port will be 27.5 + 6.25/2 = 30.625in

 

[05trailblazer 10+ year member]

ive been told the height of your port determines how deep it has to be like you already have it. but definetly an enclosure expert should chime in. n it looks like ram is only available

 

[Dr. Slam 10+ year member]

Your port disp will be 7(6.25 + .75 port wall thickness) x 16 x 27.5 / 1728 = 1.7824 cu/ft port disp, now subtract that with the sub displacement and you will have the final volume that the woofer will see.

The effective tuning length of the port will be 27.5 + 6.25/2 = 30.625in

I appreciate your help bro. I'm still a little confused as to what to do with this though

 

[Dr. Slam 10+ year member]

ive been told the height of your port determines how deep it has to be like you already have it. but definetly an enclosure expert should chime in. n it looks like ram is only available

I've been reading online days and days. There's so much information out there that it's hard to weed though and get exactly what your looking for

 

[05trailblazer 10+ year member]

yea i know what you mean it just gets confusing after a while of people saying diff things but that the way they showed me. but looks like what hes saying make a lot of sense as well

I've been reading online days and days. There's so much information out there that it's hard to weed though and get exactly what your looking for

 

[THATpurpleKUSH 5,000+ posts]

I appreciate your help bro. I'm still a little confused as to what to do with this though

Port length determines the tune frequency of the port. Goto the 12volt and punch in the box volume after port and sub displacements are subtracted, then put in the size of the port opening and the desired tune frequency and it will tell you the length you need to get the desired tune.

 

[813thumper 10+ year member]

eww dont use 12 volt.

use this: Torres' Box Tuning Calculator - SMD Forum

 

[Dr. Slam 10+ year member]

Port length determines the tune frequency of the port. Goto the 12volt and punch in the box volume after port and sub displacements are subtracted, then put in the size of the port opening and the desired tune frequency and it will tell you the length you need to get the desired tune.

It must be something I'm missing here. If I do that I'm back to square one because my port length has changed. Maybe because I'm tired idk but ima look over everything in the morning cuz it still isn't making sense to me.

*it gives me a new port length so I have to do the displacent equation again. So the first port displacement equation is rendered irrelevant.

 

[Dr. Slam 10+ year member]

eww dont use 12 volt.
use this: Torres' Box Tuning Calculator - SMD Forum

Ima try in the morning and see what I come out with

 

[Dr. Slam 10+ year member]

No one knows the answer to this?

 

[hispls 5,000+ posts]

If the port bends you must measure down the CENTER of the port.

Easiest is to make a spreadsheet that subtracts port displacement from the volume based on the size of the port...juggle it around a bit til you have the correct tuning...though IMO if you're off by a couple inches generally you'd never notice the difference unless you're chasing 10ths.

Also worth mentioning is if it's a slot port that runs along a wall of the box you must add 1/2 the port width to length because the wall that continues after the port acts to extend the port. SO where the port ends internally, picture it forming a right triangle extending out a port width.