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DOOM_NX
11-05-2008, 11:52 AM
I want to design an L-port in a box with a Slanted REAR side... like the one below

http://i33.tinypic.com/dmed6x.png

How am I gonna make the calculations? Both WinISD and Bass Box 6 Pro do not have an option for L-shaped port... If anyone could help, desired Vb is 2.48 cu.ft. and Fb 38Hz.

mcsoul
11-05-2008, 12:01 PM
I think you are going to have to go by port area and actual port volume.
So you calculate the the volume of a standard 90 degree port with your
given port area.

The trick is to to calculate your actual port volume on the angled box.

Port area and port volume are what you need to know.

uh....I think.

mcsoul
11-05-2008, 12:05 PM
You could probably calculate the p1 port volume using the angled box
calculator on bce. The p2 volume looks standard rectangle.

DOOM_NX
11-05-2008, 12:44 PM
I don't think it's just 2 volumes that I have to match... Watch the green volume that appears...

http://i35.tinypic.com/jb653p.jpg

THUMPPER
11-05-2008, 12:46 PM
you would be better off having the port horizontally across the bottom and have it
go up the rear wall of the enclosure...

or use aero / abs ports

Rashaddd
11-05-2008, 12:51 PM
you would be better off having the port horizontally across the bottom and have it
go up the rear wall of the enclosure...

or use aero / abs ports

or since you clearly dont have room for this, how about from the back of the top, curving down? As in the top of the blue section would be part of the opening

DOOM_NX
11-05-2008, 01:07 PM
THUMPPER, I need to use as little height as possible... Aero tubes would be fine, but in the other thread they told me that the diameter is too small... Anything bigger would require to corner that tube...

Rashaddd, now, that's an excellent idea :) But can u show me how? :S

DOOM_NX
11-05-2008, 02:08 PM
Would you use this page to create your box?

http://www.reaudio.com/speaker_box/LPort_Box_Calc.html

Bass Box 6 Pro and this page results do not match...

mcsoul
11-05-2008, 04:14 PM
Would you use this page to create your box?

http://www.reaudio.com/speaker_box/LPort_Box_Calc.html

Bass Box 6 Pro and this page results do not match...

I would use is only after you figure out how far off your square 90 degree box
calculations is it in terms of tuning frequency and net displacement.

Then create your slanted box to match the RE calc's version of the numbers
you are looking for.

ie:

your 90 degree box has 2.4 cubes net after woofer and port wood displacement
at 38hz

RE calc shows that box is 2.6 cubes net at 36hz.

Well screw RE, your calculations are correct. Now create a slanted box with the
appropriate port width that gives you 2.6 net at 36hz from the RE numbers.
Because you know when RE says 2.6 at 36hz; it really means 2.4 at 38hz.

Do you understand?

DOOM_NX
11-05-2008, 07:00 PM
I see I see... The same way when I entered MTX's suggested ported enclosure measurements, RE calc showed 2.534 cu.ft. and 31.3 tuning freq. I altered the dimensions trying to keep the same vb and fb and came up with this front slanted box.

http://i38.tinypic.com/adhta1.png

I need a rear slanted box so I moved port pieces in this way:

http://i38.tinypic.com/1zn6b7a.png

Is it the same?

IDSkoT
11-05-2008, 07:04 PM
I see I see... The same way when I entered MTX's suggested ported enclosure measurements, RE calc showed 2.534 cu.ft. and 31.3 tuning freq. I altered the dimensions trying to keep the same vb and fb and came up with this front slanted box.

http://i36.tinypic.com/4htxz8.png

I need a rear slanted box so I moved port pieces in this way:

http://i38.tinypic.com/35jgkt2.png

Is it the same?

Yes.
Same "Green" area, and same port area.

Do the math, though. Stop being lazy. Section it off into 3 sections, 2 rectangular prisms, and one pyramid prism.

EDIT:: actually, the second one, the back part will be a rhombus prism.

PSturmer
11-05-2008, 07:08 PM
How am I gonna make the calculations?

before all of these silly programs people designed boxes using a piece of paper and pencil.

bland
11-05-2008, 07:09 PM
Thinking about this, if you made the end of the port (inside the box) at the same angle as the slant it would even out the port length. I'm not good with diagrams so someone else would have to sketch it up if they understand what I mean

bland
11-05-2008, 07:13 PM
Here's some of my mad mspaint skillz.

http://i99.photobucket.com/albums/l297/bland1/untitled1.jpg

DOOM_NX
11-05-2008, 08:55 PM
OK sorry for getting on everyones nerves but all I do the last 3 days is sketching boxes in Sketchup and messing around with BB6 and similar programs.

Now, I finally ended up in the box below. Given that the one RE calc suggests and this one are the same, I think this is the box to go.

http://i38.tinypic.com/vxjjgw.png

If everything is right I'm going to get the cutout plans and start building it... Thanks for your answers and patience again.

DonH
11-05-2008, 09:09 PM
where do you get this program? how much it cost?

406er
11-05-2008, 09:26 PM
where do you get this program? how much it cost?

the name is google sketchup, and its free

as some one already stated, i need to go off port area. i used BBP to modle my sub. that is it. i use this site to determin my port size(http://www.carstereo.com/help/Articles.cfm?id=31). take said port size and turn that into internal volume of the port.(LxWxH) long as your slanted port has the same volume. your fine.

also i used sketch up to determin my gross box volume. then sub track port volume(externail dimentiosn factoring in the MDF sides)

406er
11-05-2008, 09:28 PM
OK sorry for getting on everyones nerves but all I do the last 3 days is sketching boxes in Sketchup and messing around with BB6 and similar programs.

Now, I finally ended up in the box below. Given that the one RE calc suggests and this one are the same, I think this is the box to go.

http://i38.tinypic.com/vxjjgw.png

If everything is right I'm going to get the cutout plans and start building it... Thanks for your answers and patience again.

also dude, get ride of all this 5/16 and ****. work with incraments of 1/8, but i usualy do 1/4. makes it way easyer. and this **** dosnt need to be spot on perfect!

DOOM_NX
11-05-2008, 10:14 PM
Actually, I work with millimeters. I just used inches because you americans are more familiar with... :P

And I failed at increments xD

DOOM_NX
11-06-2008, 12:18 PM
So, if there are no objections, I'm building the box. Thank you everyone for your contribution.

Rashaddd
11-06-2008, 02:38 PM
So, if there are no objections, I'm building the box. Thank you everyone for your contribution.

If you want to wait I can whip up a design the way I was talking about later today.

DOOM_NX
11-06-2008, 08:04 PM
Sure, I'm in no hurry. I'd appreciate a correct design. Just watch maximum height, should be at 402mm. Thanks a lot.

IDSkoT
11-06-2008, 08:07 PM
I use MM when I build anything. It's a lot more linear and easier to comprehend... The Imperial system, you have to do all sorts of math in your head. For the Metric system, it's just like "I need to go up an increment, from 2cm to 21mm. DONE!"

DOOM_NX
11-06-2008, 08:22 PM
Nvm wrong answer lol.

DOOM_NX
11-07-2008, 10:14 AM
Rashaddd, any progress?