Please check over my newest box design

[Raven 10+ year member]

Lots of work into this one. If you could, would you tell me how accurate the port tuning is? Just about everything you need to know is in the picture.

Sorry about the small image size, high res people out there.

Click to read more...

 

[bcarpenterfhl 10+ year member]

i cant tell what the port width is? and whats the frequency you're shooting for?

EDIT: just saw what you were shooting for. also, why does the port length go from 31.5 inches to 30 inches? you only subtract 0.75 from the port length when you're trying to calculate the port displacement.

 

[jellyfish420 10+ year member]

i cant tell what the port width is? and whats the frequency you're shooting for?
EDIT: just saw what you were shooting for. also, why does the port length go from 31.5 inches to 30 inches? you only subtract 0.75 from the port length when you're trying to calculate the port displacement.

effective port length...since one wall of the port is one wall of the enclosure the port should be 30" and the driver will see 30+1/2 of the port width....

3" width=30+1.5=31.5 effective port length

 

[bcarpenterfhl 10+ year member]

aslo why wouldnt you just have the port like this?

 

[Raven 10+ year member]

I screwed up royal somewhere. I should try paper & pencil first. =p

 

[bcarpenterfhl 10+ year member]

hmmm...i've been thinking about this one for awhile, and i just cant see how it takes up anymore space. just to see for myself, i'll design a box with your external specs, then do the port the way i was talking about. just to make it a little easier on myself, what was your port displacement?

 

[jellyfish420 10+ year member]

i came up with .97ft^3 for the straight around the box port and .96ft^3 for the zig-zag port.....

 

[bcarpenterfhl 10+ year member]

i got 1.0009 ft. ^3 for the way i mentioned. [3.75(port width + 0.75 for MDF) x 15(port heigth) x (31.5 - 0.75)]/1728

 

[Raven 10+ year member]

Either way, I gotta go through an rethink this one. JMac informs me I'm hideously wrong on the port tuning.

 

[jellyfish420 10+ year member]

straight

3.75*15=56.25

56.25*30=1687.5

1687.5/1728=.9765625

OR

zig-zag

6.75*16.5=111.375

111.975*15=1670.625

1670.625/1728=.966796875

 

[bcarpenterfhl 10+ year member]

straight3.75*15=56.25

56.25*30=1687.5

1687.5/1728=.9765625

i multiplied by 30.75 instead. b/c the port length was 31.5 i thought, and you subtract 0.75 to account for the part of the port that's next to the baffle.

 

[jellyfish420 10+ year member]

i multiplied by 30.75 instead. b/c the port length was 31.5 i thought, and you subtract 0.75 to account for the part of the port that's next to the baffle.

edit: nevermind i see what you did...

the acutal port is 30" the effective port length is 31.5 because of the 1.5" end correction factor.

 

[Raven 10+ year member]

I'm abandoning this design. I'm over here talking to Jmac on AIM, still, and getting the obvious out of the way... more port bends = less accuracy and more cancellation. Should have seen that coming. I'm trying for a roundabout (L shaped) port instead. No clue how this is going to affect it. So much info to learn. Gah.

Going to bed. Classes tomorrow, bright and early. I'll just take a random port length to go with. Let's say 32.25" even. 14.25" from the mouth to the bend, and 18" from there. At about 4 cubes shared and a 45^2 port area, that should get loud and low enough. Hahaha.

 

[bcarpenterfhl 10+ year member]

i dont think the L shape affects the Vb much, if at all...

 

[Raven 10+ year member]

Well, it does logically, I mean, every time a sound wave bounces it loses energy. Since MDF soaks up sound waves, you'd theoretically lose a lot more energy with a lot of curves. Also, since there are more corners, you'd get more cancellation. I'm just lost on one last thing... Getting the sound INTO the port. Meaning if I put the port mouth right in the middle of the box, would I get more sound INTO the port than if I put the internal mouth off to the side?