first box

[Bosaliniee 10+ year member]

ok this is the first time i have ever built a box, i was planning on making a sealed box for my 15 eclipse that i just got sw8152, my questions are: do i need to spray anything in the box to coat the inside after im done or not; someone told me i should put dynamat on all the walls inside the box, is that a good idea?; is there any dimesions or math that i should use besides figureing out the cubic feet? such as the width should be 1.5 times the height or something of that nature.

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[baseballer1100 5,000+ posts]

No you dont need to do anything like that.. Except for maybe polyfill? th only other thing on the inside is putting some silicone around to prevent any leaks.

 

[saywhat? 5,000+ posts]

u COULD resinthe corners, but thats not needed. just gauruntees a seal

 

[PowerNaudio 10+ year member]

i believe pioneer or mtx also recommended putting sound deadening material inside the enclosure, to absorb the sound wave that's inside the enclosure to keep it from coming right back on to the sub. what audible difference it makes i haven't done any tests my self or research it further.

you want to stay away from making a square enclosure. make them rectangular shaped if possible. use bracing on surfaces larger then 12" x 12" that's just me.

and take in to account any displacement of bracing, sub and if you add internal angles on the edges or corners. use 3/4" mdf board on again enclosures bigger then 1 cu ft. if your cuts are not straight ether use clear 100% silicone to seal the edges or polyester resin.

use glue on all seems. and screws every 2" to 3" what ever you prefer. some people prefer not to use screws if you don't make sure you held the pieces being glued with a clamp and wait till is fully dried before declamping.

 

[mulisharider10 10+ year member]

i use a brad nailer to assemble my boxes and i have never had a problem with them blowing apart. screws are a little overkill for most peoples applications. if u make sure ur glueing surfaces are clean glue will be good. Glue is a lot stronger than the holding strength of a screw if done corectly. And if all your cuts are strait and u apply a good ammount of glue on every seem, there is no need for silicone bc the glue has already sealed it.

 

[Bosaliniee 10+ year member]

http://www.caraudio.com/forum/attachment.php?attachmentid=4915&stc=1&d=1143847580

box.JPG

sub is too tall to fit in the back of the trunk in a box that is more than 17 tall or 17 wide because of the 6x9s in the rear deck. so i made a drawing of what my trunk kinda looks like(top) and 2 box ideas, will either of them be something that shouldnt be done or do they both look like they will be ok(i.e. someone said not to make a perfect square)

 

[Bosaliniee 10+ year member]

just realized i didnt count the .75 all the way around, so i will have to come up with some new measurements, but based on shape will they be ok?

 

[PV Audio 5,000+ posts]

i believe pioneer or mtx also recommended putting sound deadening material inside the enclosure, to absorb the sound wave that's inside the enclosure to keep it from coming right back on to the sub. what audible difference it makes i haven't done any tests my self or research it further.you want to stay away from making a square enclosure. make them rectangular shaped if possible. use bracing on surfaces larger then 12" x 12" that's just me.

and take in to account any displacement of bracing, sub and if you add internal angles on the edges or corners. use 3/4" mdf board on again enclosures bigger then 1 cu ft. if your cuts are not straight ether use clear 100% silicone to seal the edges or polyester resin.

use glue on all seems. and screws every 2" to 3" what ever you prefer. some people prefer not to use screws if you don't make sure you held the pieces being glued with a clamp and wait till is fully dried before declamping.

Unfortunately, that's not true. A cube shape has less internal resonance than nearly all other shapes besides a sphere.

 

[Bosaliniee 10+ year member]

so do you think that both of those boxes i came up with in my thumbnail above will work out very well or maybe just the first one?

 

[PV Audio 5,000+ posts]

I"d do the retangle/cube shape. Many angles = not ideal.

 

[Bosaliniee 10+ year member]

sorry about all the questions, just got the sub and didnt realize my trunk wasnt tall enough for the box, so here goes, what if i make the box 17 deep 11 tall 26 wide and have the sub pointing strait up, after considering the mdf i think that give me about 2.4-2.5 cubic feet. so would the sub sound better pointing to the back of the trunk or strait up or not matter at all?

 

[PowerNaudio 10+ year member]

Unfortunately, that's not true. A cube shape has less internal resonance than nearly all other shapes besides a sphere.

Golden Ratio
Once you have determined the proper volume for your enclosure, the “Golden Ratio” is a simple way to calculate enclosure dimensions that minimize panel resonances.

Begin by finding the volume of the enclosure in cubic inches. If your volume is in cubic feet, simply multiply that number by 1728. Next, find the cube root of this number (you will need a scientific calculator for this). This is your first panel dimension. Then take the first dimension divided by 1.62, This is your second dimension. For the third dimension, multiply the first panel dimension by 1.62.

Example

Volume = 1.75 Ft^3

1.75 X 1728 = 3024 in^3

cube root of 3024 = 14.46” (1st Dimension)

14.46 / 1.62 = 8.93” (2nd Dimension)

14.46 X 1.62 = 23.43” (3rd Dimension)

Remember that these are internal dimensions, so you will need to add for the thickness of the wood. Assuming 3/4” wood, this enclosure would be 15.96 X 10.43 X 24.93 .

mtx site enclosure construction

i don't stick to using a golden rule. but is a good example of why i said stay away from square enclosures. the equation above will help determine your final shape.

 

[Bosaliniee 10+ year member]

thanks for the help, i built it the only way it would fit in my trunk it sounds good but im not sure if i could have made it sound any better by building it another way, its 17h x 18w x 17.5d exterior dimensions with 3/4 mdf. do you think i should put polyfill in it or anything? i will post a pic up once i get a chance didnt have my camera at the garage i used and its been raining all day so i couldnt do it when i got home(no garage here)

 

[PV Audio 5,000+ posts]

That may be, but..

...illustrating the effect of enclosure shape on cabinet difraction..

Sphere

Cube

Beveled Cube

Rectangle

Beveled Rect.

Cylinder

Again, I don't really know what I'm reading, so I may be wrong. Either way, a rectangle is obviously ideal for a car trunk, seeing as there is no room for 30" cubes in cars //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[PV Audio 5,000+ posts]

BTW, the beveled cube is above the standard one, I don't have the book with me right now; i took that off an online version from torrentspy.