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SuperSaeYoung
05-03-2012, 05:43 AM
What are your thoughts on this design? How would I calculate tuning fhz? I want to have a better understanding of the science behind enclosure building before I have someone design one for me. Yes I'm designing a box so someone else can design a better one for me. Both of these boxes are 24x15x15.

These are the design I'm going for.
http://i.imgur.com/fuNAF.png
and
http://i.imgur.com/eumh1.png

subzero
05-03-2012, 07:54 AM
hard to tell without measurements. but I guess it would be in the low 30s

---------- Post added at 04:54 AM ---------- Previous post was at 04:53 AM ----------

RE AUDIO - Box Calculator (http://reaudio.com/box.php)

SuperSaeYoung
05-03-2012, 08:24 AM
hard to tell without measurements. but I guess it would be in the low 30s

---------- Post added at 04:54 AM ---------- Previous post was at 04:53 AM ----------

RE AUDIO - Box Calculator (http://reaudio.com/box.php)

I wanted to calculate it myself. I think it's 24x15x15, port length being 12, height 5, and slot is 1. That box is not actually going to be build. It's going to be about 32hz with port on the side. I'm looking for thoughts on the port being the way it is in the picture.

SuperSaeYoung
05-04-2012, 12:56 AM
Bump, did another design.

ssteele18
05-04-2012, 01:05 AM
Usually people design their ports in that way if they want more Sqin of port. Hard to say without numbers. Looks like alotta port.

SuperSaeYoung
05-04-2012, 01:13 AM
Usually people design their ports in that way if they want more Sqin of port. Hard to say without numbers. Looks like alotta port.

That's where you come in for the final design.

I forgot about the first, but the box slot is 24.5x1. L1 is 12.5, L2 is 8.5 that should be 32hz says the 12volt box calculator, but I want to know how it was calculated.

Having more sqin of port is a good thing right, less port noises so I read?

ssteele18
05-04-2012, 01:20 AM
Lol. No easy answer. Too thin of a port, also not great. Long story short, we'll work it all out. lol

SuperSaeYoung
05-04-2012, 01:32 AM
Lol. No easy answer. Too thin of a port, also not great. Long story short, we'll work it all out. lol

Well I still need to figure out how much trunk space I'm going to use, and how much I actually got.

ssteele18
05-04-2012, 02:33 AM
Well figure out what subs you're using. Once you got that, find how much volume you need per sub. Then Give me your maximum usable space in your car, and I'll design something.

SuperSaeYoung
05-04-2012, 04:57 AM
Well figure out what subs you're using. Once you got that, find how much volume you need per sub. Then Give me your maximum usable space in your car, and I'll design something.
I will do when I get a measuring device.

So if the dimension is 30x15x15 and I subtract 1.5 from 30x15x15 I get 28.5x13.5x13.5 that equals to 3.00585937 cubic ft, each sub will have about 1.5 cuft without port displacement. I can't figure out the port displacement and how to calculate tuning hz without a box calculator.

SuperSaeYoung
05-04-2012, 09:02 PM
Having the port like this would be a bad idea huh?

http://i.imgur.com/X0S31.png

snyderd758
05-05-2012, 01:33 AM
google "torres box calculator" you plug in all your numbers and it tells you the tuning of the box. The last design you post looks like the port goes from larger to smaller that wont work. To calculate the volume of your port its LxWXD/1728.

SuperSaeYoung
05-05-2012, 01:40 AM
google "torres box calculator" you plug in all your numbers and it tells you the tuning of the box. The last design you post looks like the port goes from larger to smaller that wont work. To calculate the volume of your port its LxWXD/1728.

I understand that there's a box tuning calculator, I just want to be able to figure it out MYSELF without the CALCULATOR.

hispls
05-05-2012, 01:56 AM
I understand that there's a box tuning calculator, I just want to be able to figure it out MYSELF without the CALCULATOR.

You can search the formulas but they're pretty ugly. If you're really the math type, you can find spreadsheets that do it and actually see the formulas used in the cells. Using a program is best.

I don't like a port that narrow if I can help it myself.

SuperSaeYoung
05-05-2012, 02:03 AM
You can search the formulas but they're pretty ugly. If you're really the math type, you can find spreadsheets that do it and actually see the formulas used in the cells. Using a program is best.

I don't like a port that narrow if I can help it myself.

Thanks, I found a thread on caco, but his way of finding net volume was way off for me. That was my last design before I went to sleep, I redid it and it looks better now. I did a few slots on the side, and I already know I like them, I just want to see other options.

These are not final design, I'm just trying to see what I like best and what you guys think of them.

http://www.caraudioclassifieds.org/forum/tutorials-quick-references/7717-designing-enclosures-tutorial.html

http://i.imgur.com/XGGDT.png

hispls
05-05-2012, 02:23 AM
Thanks, I found a thread on caco, but his way of finding net volume was way off for me. That was my last design before I went to sleep, I redid it and it looks better now. I did a few slots on the side, and I already know I like them, I just want to see other options.

These are not final design, I'm just trying to see what I like best and what you guys think of them.

Designing Enclosures: Tutorial - Car Audio Classifieds (http://www.caraudioclassifieds.org/forum/tutorials-quick-references/7717-designing-enclosures-tutorial.html)

http://i.imgur.com/XGGDT.png

That is a lot of work to build, but helps with having a port too narrow.

SuperSaeYoung
05-05-2012, 02:30 AM
That is a lot of work to build, but helps with having a port too narrow.

These are just ideas.
I don't think 13.5x2 is narrow. I'll start looking into aero ports later tonight.

SuperSaeYoung
05-05-2012, 03:22 AM
Looks like an aero port would save a lot of space.
http://i.imgur.com/E7N65.png

hispls
05-05-2012, 10:21 AM
These are just ideas.
I don't think 13.5x2 is narrow. I'll start looking into aero ports later tonight.
I meant your first port was too narrow.

3" aero might not cut it either.

SuperSaeYoung
05-06-2012, 06:37 AM
I meant your first port was too narrow.

3" aero might not cut it either.

Yeah I just said **** it with those ports. Going towards side ports now/aero ports now.

Also, is there any special way to put the box together? Can I just have the box with the top and bottom the same size, left and right same size, back and front same size, cut a slot for port and sub on the front, and attach port lengths to the front, or is there suppose to be a 'right' way of doing it?

hispls
05-06-2012, 12:40 PM
Yeah I just said **** it with those ports. Going towards side ports now/aero ports now.

Also, is there any special way to put the box together? Can I just have the box with the top and bottom the same size, left and right same size, back and front same size, cut a slot for port and sub on the front, and attach port lengths to the front, or is there suppose to be a 'right' way of doing it?

So long as it's airtight and no flexing panels, really the only other thing that will hurt badly would be to have port opening too close to internal walls.

SuperSaeYoung
05-06-2012, 08:18 PM
So long as it's airtight and no flexing panels, really the only other thing that will hurt badly would be to have port opening too close to internal walls.

Where should the port be placed then?
http://i.imgur.com/5erZu.png

I also did a spreadsheet, the tuning is not the same as reaudio but it works.

hispls
05-06-2012, 11:21 PM
Where should the port be placed then?
http://i.imgur.com/5erZu.png

I also did a spreadsheet, the tuning is not the same as reaudio but it works.

That is a more typical arrangement. If your tuning is off by 2-4hz you'll never notice the difference unless you're chasing 10ths on the meter IMO>

SuperSaeYoung
05-07-2012, 12:53 AM
That is a more typical arrangement. If your tuning is off by 2-4hz you'll never notice the difference unless you're chasing 10ths on the meter IMO>
I've been on sketch for 3 days and I'm really enjoying it. I just need to find a port size I like, then move onto aero port tuning. Do you know where I can find the calculation for aero port tuning?

Yeah, I'm starting to like the port on the side more now, I just did flushed and indent, my girl likes it better with sub on top, and she wants to add another 2 subs that I don't have...

http://i.imgur.com/SQpCN.png
http://i.imgur.com/Kjzc3.png
http://i.imgur.com/7Em3B.png

ssteele18
05-07-2012, 01:02 AM
[QUOTE=SuperSaeYoung;8020322]Yeah, I'm starting to like the port on the side more now, I just did flushed and indent, my girl likes it better with sub on top, and she wants to add another 2 subs that I don't have...

Typical woman... Thinks money grows on trees and then you can simply "shove another one in"... haha

hispls
05-07-2012, 01:05 AM
Bass Box Pro has options to calculate flared ports. If you were unscrupulous you could pirate it, otherwise buy it.

SuperSaeYoung
05-07-2012, 01:15 AM
Yeah, I'm starting to like the port on the side more now, I just did flushed and indent, my girl likes it better with sub on top, and she wants to add another 2 subs that I don't have...

Typical woman... Thinks money grows on trees and then you can simply "shove another one in"... haha
Don't lie, you know you got a money tree in your closet... I mean I wouldn't mind if she gets me 4 new subs.

Bass Box Pro has options to calculate flared ports. If you were unscrupulous you could pirate it, otherwise buy it.
Well of course I'm going to torrent...

hispls
05-07-2012, 01:18 AM
Don't lie, you know you got a money tree in your closet... I mean I wouldn't mind if she gets me 4 new subs.

Well of course I'm going to torrent...

For the record, I don't advocate pirating software. That would be immoral and make baby Jesus cry..... just saying what someone who was a bad person would do.

ssteele18
05-07-2012, 01:18 AM
Don't lie, you know you got a money tree in your closet... I mean I wouldn't mind if she gets me 4 new subs.

Ha! Yea.. Don't tell anyone, but once a year I trim it up and spoil myself with some new tools for enclosures.. ;)

SuperSaeYoung
05-07-2012, 01:25 AM
For the record, I don't advocate pirating software. That would be immoral and make baby Jesus cry..... just saying what someone who was a bad person would do.
We'll call it a trial, thanks for the input so far, I really appreciate it.

Ha! Yea.. Don't tell anyone, but once a year I trim it up and spoil myself with some new tools for enclosures.. ;)
It would be nice to just have some tools...

ssteele18
05-07-2012, 01:26 AM
We'll call it a trial, thanks for the input so far, I really appreciate it.

It would be nice to just have some tools...

lol. One step at a time bro..

SuperSaeYoung
05-07-2012, 03:46 AM
lol. One step at a time bro..
I like to take giant steps!

Is there such thing as too long of a port?
http://i.imgur.com/MRkS3.png

Ronny
05-07-2012, 04:04 AM
Yes and no, the longer the port, the less efficient it is. However, if you are only able to obtain desired tuning with having a ridiculously long port, where you cannot utilize volume and port area to obtain desired tuning instead, sometimes you just have to stick with a long "less efficient" port.

SuperSaeYoung
05-07-2012, 06:52 AM
Yes and no, the longer the port, the less efficient it is. However, if you are only able to obtain desired tuning with having a ridiculously long port, where you cannot utilize volume and port area to obtain desired tuning instead, sometimes you just have to stick with a long "less efficient" port.

Thanks.

My to do list now is figure out aero ports, whats t/s parameter and how they're going to apply to enclosures. I'll start researching more about t-line when I figure out everything else.

How do you guys do round edges? This is my attempt.
http://i.imgur.com/JYFJy.png

ssteele18
05-07-2012, 11:34 AM
Thanks.

My to do list now is figure out aero ports, whats t/s parameter and how they're going to apply to enclosures. I'll start researching more about t-line when I figure out everything else.

How do you guys do round edges? This is my attempt.
http://i.imgur.com/JYFJy.png

That looks like a rounded corner to me. If you're talking about KERFT port, that's different.
But it looks good man! Keep playin with it.

SuperSaeYoung
05-07-2012, 11:38 AM
That looks like a rounded corner to me. If you're talking about KERFT port, that's different.
But it looks good man! Keep playin with it.

Yeah, I''ll need to actually build a couple enclosure to even think about kerfing.
What I did to get the round edges was build a .75x.75 block and draw a circle, delete what wasn't needed, how do you do it?

ssteele18
05-07-2012, 11:41 AM
Yeah, I''ll need to actually build a couple enclosure to even think about kerfing.
What I did to get the round edges was build a .75x.75 block and draw a circle, delete what wasn't needed, how do you do it?

That works too but there's an actual "arc" tool as well. It may be easier, or harder for you. That's how I do most of mine though.

SuperSaeYoung
05-08-2012, 01:58 AM
That works too but there's an actual "arc" tool as well. It may be easier, or harder for you. That's how I do most of mine though.

Alright thanks, I'll try the arc, and how do you determine space needed with t/s?

SuperSaeYoung
05-08-2012, 04:12 AM
I saw one of Buck design and it was a design that I was trying to do, I'm trying to replicate it for my needs, I know that the ports need to be bigger, I'll figure it out tomorrow

http://i.imgur.com/yMqma.png

SuperSaeYoung
05-08-2012, 06:13 AM
Need to find another way to brace it.

http://i50.tinypic.com/2ztggph.png
http://i47.tinypic.com/25tau0j.png

Buck
05-08-2012, 09:09 AM
I would avoid that port style if you can.

SuperSaeYoung
05-08-2012, 04:14 PM
I would avoid that port style if you can.

But, but, but why? It's the one I've been waiting for! It's dual exhaust man it's always better.

I can make the back port into an L port.

As long as the port length and port area is the same the tuning should around where it should be right? I also need with with t/s specs and why and how to 45's kerf, and are 45 just 45's or is there 'special' 45's because I see some 45's with a long width.

SuperSaeYoung
05-09-2012, 04:15 AM
I think this will be ******. Walled off trunk.

Subs and Amp
http://i.imgur.com/zaW2o.png
Port through armrest.
http://i.imgur.com/5CfTG.png
Top view.
http://i.imgur.com/uFRfW.png

Moble Enclosurs
05-09-2012, 11:44 AM
Yes and no, the longer the port, the less efficient it is. However, if you are only able to obtain desired tuning with having a ridiculously long port, where you cannot utilize volume and port area to obtain desired tuning instead, sometimes you just have to stick with a long "less efficient" port.

Not necessarily. The length of the port is not directly related to efficiency. It is indirectly related to coupling, that is directly related to efficiency. The length is a determination of how to couple the compression area with the port "volume", but the area is a direct relation to cutoff frequencies, and not in terms of smaller=lower tuning. But where larger=higher efficiency(to a point). SO, that is where the efficiency is directly related to port characteristics.

The length, again, is related more to coupling and even phase response. SO, having a port that is considered longer than normal is a way to increase efficiency in the lower frequency region, not the other way around. You have to consider it a separate space, just like any other physical space that conforms to a given pressure with a point of lowest resistance (the opening). The idea is to have the pressure and the intensity to balance from the beginning of the port to the end and match with the drivers direct radiation(if any) in terms of phase and coupling for increased efficiency. SO, the length is a relative way to control that. There is no direct longer=less/more, shorter=less/more when it comes to the calculations. :D
Just wanted to clarify that is all. So, it is possible to have too long of a port, but you have to understand or know what is too long and why, just as it can be possible to have too short of a port. The relationship of length and area are not to determine tuning..that is a by-standing factor in the acoustics of what actually occurs. The point is to couple. That is pretty much the most important factor.
This is the reason why prefabs are not great to use for every application regardless of it having the tuning you are looking for.

Ronny
05-09-2012, 04:18 PM
Lovely! Thanks for the post. I really enjoy the good reads a few of the users like yourself on this forum write every so often.

What are you referring to when stating intensity? Is that a function of the pressure inside the loading chamber? Would direct radiation be referring to the effective internal Sd of a certain driver?

Moble Enclosurs
05-09-2012, 04:48 PM
Well, intensity and compression can be explained easily. If you are to take a driver and play a 50Hz tone through it (example) and put your hand in front of the cone, you will feel and hear what is being played at the same time, correct? Well, what you hear is the intensity. What you feel on your hand is the compression. The intensity is an acoustical effect and the compression is a physical effect. BUT, the reason why these are so alike is that they both contribute to each other and the form of output. Intensity can be increased without the parallel increase in compression, and compression can be increased without much added intensity.

The direct radiation is what controls the intensity. And distance creates the losses from that effect, not dimensional limitations. The dimensions, or creating a boundary for the driver (such as a box) only increases the resonances from the original source to increase intensity, or in a sealed design, separates the phasing issues between both direct radiating sources of the driver. Direct radiation is important when you are looking for output. And yes, it refers to the cone area of the driver, effectively.

Take this for example: blow air out of your mouth like you are blowing out a candle. The compression increases in your mouth to get the air to push out at a certain velocity. BUT, no sound is present, so no acoustical intensity exists. Now hum and blow out. These two can work together to create output or SPL, but are two different effects. When you hum, you create a compression also, but the compression is accompanied by expansion as well. This is the major difference in compression and intensity when dealing with port velocity and sound "loudness" or SPL numbers or output in general. The direct relationship is the physical parts of the driver that in order to create a compression, it needs to play a frequency so the separation of direct compression and intensity from the use of a driver is not possible as the driver operates by means of frequency changes.

This is why horns can get loud without having blown so much air out, or why they can "seem" louder when they do not produce the numbers as an SPL design does. The acoustical resistance changes when it enters the environment and therefore compression decreases, but the intensity can remain if there are less resistive obstructions between the drivers radiated area and the listener.
Ever wonder why walls became so popular? It is because in order to maintain the ratio of compression and intensity equal, you need to increase compression in the vehicle by decreasing the size of the vehicle to keep up with the intensity of the drivers direct output, which can be lost in a ported design with too many bends, lol. Then resonances are more reliable for output. This is also why less bends are usually a better concept, as we all know. And why those bends are more efficient with a less acute angle.

It all works together, and when you find the right amount of each part of the design to use, and when, then you can get a pretty nice output from even something less than what we would normally consider capable.

Moble Enclosurs
05-09-2012, 04:50 PM
So, take a vehicle, use half for a box and make the cones face the driver as close as possible to the driver, and create a port that couples at 0 phase with the drivers front radiation, and give it max power and seal the vehicle the best possible, and you have yourself one hell of an SPL machine that can have ALSO (and very importantly) a smooth as hell response. That is the idea lol.

SuperSaeYoung
05-10-2012, 12:32 AM
My long *** post that I'm going to make you read 5 times.
Thanks, it gives be a better understanding of how the driver and enclosure react to one another.

Lovely! Thanks for the post. I really enjoy the good reads a few of the users like yourself on this forum write every so often.

What are you referring to when stating intensity? Is that a function of the pressure inside the loading chamber? Would direct radiation be referring to the effective internal Sd of a certain driver?
I enjoyed it too!

Moble Enclosurs
05-11-2012, 03:01 PM
"Originally Posted by Moble Enclosurs
My long *** post that I'm going to make you read 5 times."

I actually did not say that part.....I think someone may have hacked me lol. Think its time to change my pw.....

SuperSaeYoung
05-12-2012, 02:33 AM
"Originally Posted by Moble Enclosurs
My long *** post that I'm going to make you read 5 times."

I actually did not say that part.....I think someone may have hacked me lol. Think its time to change my pw.....
I don't know if you're serious or playing, I edited the quote.

I'm looking into t-lines and horn enclosure now, but can't find much information about them, do you know where I can start?
I also want to know about T/S specs and how they work with enclosures. Only thing I can really find is that ebp.

I also am having trouble planning out cut sheets. What would be the optimal less cuts/less space cuts using the length on the bottom.

I would like to thank you for all who helped me understand enclosure better.

14.25 x 30 – 2x - Baffle & Bottom
13.5 x 30 - Back
13.5 x 28.5 - Baffle
12.75 x 13.5 – 2x - Sides
30 x 15 - Front
12.75 x 11 - Port 1
12.75 x 5 - Port 2

Moble Enclosurs
05-12-2012, 11:28 AM
I don't know if you're serious or playing, I edited the quote.

I'm looking into t-lines and horn enclosure now, but can't find much information about them, do you know where I can start?
I also want to know about T/S specs and how they work with enclosures. Only thing I can really find is that ebp.

I also am having trouble planning out cut sheets. What would be the optimal less cuts/less space cuts using the length on the bottom.

I would like to thank you for all who helped me understand enclosure better.

14.25 x 30 – 2x - Baffle & Bottom
13.5 x 30 - Back
13.5 x 28.5 - Baffle
12.75 x 13.5 – 2x - Sides
30 x 15 - Front
12.75 x 11 - Port 1
12.75 x 5 - Port 2

Nah, Im playin lol. But, yea as far as horns and tline go, they are designed (or are supposed to be) much different than any other enclosure design, so it can take a lot to learn what you need to get it going right.

There are a few actual programs out there, not sure if they are paid or not, that can help with that a bit, but I use my spreadsheet for nearly everything so I have a different approach than most, I believe.

But, the best thing to do is understand acoustics and physcoacoustics and physics before enclosure design itself because that is what it is all about.

If you can find explanations for:
Propagation
Time delay
Mirror effect
Transient response linearity
rarefaction
reflection
dampening (by material and percentage)
compression
expansion
coupling
absorption
speed of sound
sine waves
hz (full explanation will help a lot)
crossover effects
basic electronics(like transistors, diodes, jumpers, relays, transformers, inductors, capacitors, etc)
etc
etc

Much more to note. Then learn not just what each are, BUT MORE IMPORTANTLY how they work together within given physical limitations and changes, then you will begin to understand the concepts and work of each design.
BUT.....it must be expressed, that the most important thing to do in learning these common terms, is to experiment with them as well.
Get some cheap wood and some cheap drivers, derive their specs and build something common, like a BR. Then try changing the volume, port length, port area, etc.....tapering, etc and log the acoustical changes in a program that measures the information you need in real time, like REW5. And note what happens when you do "this" or "that". Then you can get more of an understanding of why it works, not just that it does.
And over time, you can figure certain things out that a lot of others know about conventional designs, and then work into horns and tlines and measure them in direct comparison with the conventional designs and log efficiency (which can be calculated based on voltage and output for each frequency, etc), and phasing, which can be a little more tough to log if you do not know the process, which i wish I had time for right now, cause you got me going lol. But, yea, log as much as possible and do a lot of diy projects, take the information into account for different environmental changes, and note those changes as well, so you can find constants in the design, because most of us do not have an anechoic field to work in lol.
And just go from there. Sounds complicated, because it can be. But most of what I have learned was from military training and college and DIY projects of my own over the course of 10+ years so far.....since Jan 2001. ANd I have been nonstop ever since, improving my techniques, calculations, formulae, pricings, and every aspect of the work I do to make sure what you get is as accurate as I can make it.
Horns and tlines are not an easy task for certain major reasons that I will not go into right now that I found to be the key to their output success, but let me tell you.....it took me nearly 4 years to figure certain things out about them and the discovery of the tapped idea was not a fluke Ill tell you what. I had that idea back in 2008 when I started building everything for the business based on the quasi 6th BP design, which I found works very well for overall output in a vehicle. Then I figured that the layout and acoustics of the tapped idea works much like what I would call a quasi 4th, though some would say that does not exist. But in the limited space requirements for a vehicle, it does exist.
So, it takes work and experimentation and a LOT of trial and error on your own part before you can believe these online logs of others findings to be correct or incorrect. Dont rely on what anyone else comes up with because a lot of the readings you will find will be their own trial and error and they are mostly based on general ideas of acoustics and not to details, thoguht they may look detailed based on the formulas and information put into them.

Moble Enclosurs
05-12-2012, 11:31 AM
As far as the cutsheet, best thing to do is find the common dimension that exists for most cuts, such as the height of the ports, and cut those first. then part them by length. The top(s) and bottom(s) may take up to a 3rd of the sheet so those should be done first, then the common dimension. If you cut the common dimension all together, you will not have any pieces that are higher than the other. ;D.

SuperSaeYoung
05-20-2012, 05:50 AM
As far as the cutsheet, best thing to do is find the common dimension that exists for most cuts, such as the height of the ports, and cut those first. then part them by length. The top(s) and bottom(s) may take up to a 3rd of the sheet so those should be done first, then the common dimension. If you cut the common dimension all together, you will not have any pieces that are higher than the other. ;D.

I haven't been playing around with box designing and tuning for awhile, been busy with finals but I tried doing the common and it works out great. It should be around 35 hz.

http://i.imgur.com/zqmAc.png
http://i.imgur.com/6BaXb.png

Top & Bottom Pieces: 30x15 – 2X
Back Piece: 30x13.5
Front Piece: 26x13.5
Side Pieces: 14.25x13.5 - 2X
Port Pieces: 11x13.5 – 2X
Corner Braces, 2x13.5 - 5X

SuperSaeYoung
05-27-2012, 06:58 AM
How does having 2 port work? Will the 2 port add up to one port? The box is 30x15x15

2 2" port equals to 4 inch, I got 39hz is this correct?
http://i.imgur.com/Ll1fe.png

Moble Enclosurs
05-27-2012, 03:32 PM
It is the layout that is deceiving in this concept. 2 ports are not much different, especially if they are mirrored in the box (symmetrical), than having a larger port equal to the area of the 2 ports total. If the second port is located right next to the other, it is like having a wall in the middle of a single large port, and if that wall is taken away, its like moving the port over the same thickness as the wall to make it one port. The distance is only of concern when the port area of a single port equals the port area of a dual port. Then this would be a reduction in the port area, which to keep a similar tuning, would require a shorter port.

That is where it can get confusing. As far as resonance is concerned, the tuning is an effect of both the enclosure and the subs mechanical parameters, so exact tuning cannot be figured by just the box alone in a more accurate calculation. Also, the thickness of the wood as well as sub displacement would change the tuning, so not enough information is here to verify the correct tuning yet......at least in this pic. I don't recall, if it were mentioned, what subs you are using and what wood you are using. :D