holding a box together

[evo2k3 10+ year member]

look...i am at about the upper bounds of my knowledge hear, but ill stick the idea out anyways. How is mfd porus by nature....think of how it is made, basicly compresed saw dust and glue/epoxy. I really dont think mdf will leak air by nature. Plus fiberglass is epoxy, how does adding more of it make it more sealed? just a question, thats what makes sence to be. I mean i have glassed seems where the cap was a touch to big for silcon and it works great for the seams, but the only thing i can see it doing is stifening the box up a bit and making it look nice. just my 0.02.

 

[paikiah 5,000+ posts]

Originally posted by evo2k3 look...i am at about the upper bounds of my knowledge hear, but ill stick the idea out anyways. How is mfd porus by nature....think of how it is made, basicly compresed saw dust and glue/epoxy. I really dont think mdf will leak air by nature. Plus fiberglass is epoxy, how does adding more of it make it more sealed? just a question, thats what makes sence to be. I mean i have glassed seems where the cap was a touch to big for silcon and it works great for the seams, but the only thing i can see it doing is stifening the box up a bit and making it look nice. just my 0.02.

Well, lemme change what I said...

I HEARD MDF was porous, so I was advised to do something either in the inside or outside, if my box were to handle great amounts of power... but I'm no professional...

glass can't be porous, right? that's why I'm saying maybe that's why YOu were advised to use fiberglass inside...//content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif afterall, a lot of canoes, and the jetski hulls are made of fiberglass...it's not porous...//content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

if the walls of the box leaks, you can apply a thin fiberglass layer to prevent any possible leakage, that's what I think it is....//content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[evo2k3 10+ year member]

by point is just that I really think the seems are going to leak far before you are able to puch air through mdf....because is a part fiberglass.

 

[Savant 10+ year member]

Originally posted by evo2k3 look...i am at about the upper bounds of my knowledge hear, but ill stick the idea out anyways. How is mfd porus by nature....think of how it is made, basicly compresed saw dust and glue/epoxy. I really dont think mdf will leak air by nature. Plus fiberglass is epoxy, how does adding more of it make it more sealed? just a question, thats what makes sence to be. I mean i have glassed seems where the cap was a touch to big for silcon and it works great for the seams, but the only thing i can see it doing is stifening the box up a bit and making it look nice. just my 0.02.

Porus doesn't mean 'leak air'.. it means little cavaties on the surface (more or less).. your skin is porus but your lungs work because your chest is a vaccume inside.. if porus meant leak, we wouldn't be able to breath..

That said, fiberglass + resin is very low on the porus scale.. you can put water on it and it won't seep in... MDF will **** up water even though there is glue/epoxy/whathaveyou holding it together.. the 'bulk' of the material is wood.. with fiberglass, the bulk is glass and solid plastic..

Putting 'fiberglass' in a box (meaning layering a buildup with resin etc).. Not sure you will gain anything there.. it might have a higher resonance (reflect sound better) than the MDF and prevent some of the sound from getting absorbed by the wood (it might muddy the sound a bit, the glass might help keep it crisp).. but I doubt you would really notice much difference.. Putting Fiberglass Insulation in the box.. now that's a totally different matter.. that's like putting in fill (that's what it is actually, just not called 'fill'..).. I forget exactly how that works.. I think fill is supposed to make the woffer think there is 'more' volume in the box, which is counter intuitive since you filled up space.. I just know my buddy (way back when) would put insulation (filler) in his enclosures once in a while.. not sure it really made a difference.. Perhaps that's what was meant by the suggestion to you?

 

[ramos 5,000+ posts]

Yes MDF is porous. Using your own example think about how it's made. It is basically wood particles compressed together under extreme preasure. Then soaked in a formaldahyde glue. That's pretty much all there is to the process of manufacturing it. No special care is taken to make sure the particles are perfectly aligned so that it is airtight. How could it not be porous ? For an even better example look at an edge after you cut it. //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

If you make your cuts straight and clean. Then really all you need to use is a good urethane glue to hold the enclosure together. All I use is gorilla urethane glue and 1 1/4 brads. . I can build a box using nothing but glue. And I would bet you North America tat yo will break the MDF before The glue lets go. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[ramos 5,000+ posts]

Now if your talking about putting actual Fiberglass cloth or mat it will greatly increase the strength of the enclosure. But it really wouldn't make any audible difference. If your talking about just brushing some resin on the inside. You won't gain any strength. But you will seal it up pretty well. You might actually gain a few db's on a meter. But I still doubt there would be any audible difference. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[Savant 10+ year member]

Originally posted by ramos Yes MDF is porous. Using your own example think about how it's made. It is basically wood particles compressed together under extreme preasure. Then soaked in a formaldahyde glue. That's pretty much all there is to the process of manufacturing it. No special care is taken to make sure the particles are perfectly aligned so that it is airtight. How could it not be porous ? For an even better example look at an edge after you cut it. //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

 

If you make your cuts straight and clean. Then really all you need to use is a good urethane glue to hold the enclosure together. All I use is gorilla urethane glue and 1 1/4 brads. . I can build a box using nothing but glue. And I would bet you North America tat yo will break the MDF before The glue lets go. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

Hmm.. so I really don't need 27 screws on a 12x12 top-plate if I'm using liquid nails? I mean, does the glue really cure that hard that you don't get any usefulness from the screws?..

*grumbles about buying a second box of screws and adding 50 lbs of weight to each box in threaded madness*

 

[evo2k3 10+ year member]

Originally posted by Savant Hmm.. so I really don't need 27 screws on a 12x12 top-plate if I'm using liquid nails? I mean, does the glue really cure that hard that you don't get any usefulness from the screws?..

 

*grumbles about buying a second box of screws and adding 50 lbs of weight to each box in threaded madness*

kind of the same thing i told you in the other thread....lol....you need screws or clamps to hold the glue as it cures....I suppose brads would work well if you had a air gun for it, but putting them in by hand is probably hard that usuing a screw gun (a more common home workshop tool) to run screws into pilots. When you use brads, do you have any trouble with the would splitting? I also think it is safe to say that we all agree air is not going to leak through the side of a box. and the fiber glass can add strength and appearence...that pretty much some it up?

 

[nswartley 5,000+ posts]

actually MDF stands for 'medium density fiberglass': it is not just wood

 

[ramos 5,000+ posts]

Nope no splitting what so ever. And you are correct. The screws or brads in my case. Are basically there to hold the enclosure together until it dries. Of course you leave them in. Every little bit helps. But believe me the brunt of the blow is being taken by the glue. Remember though. When your using MDF. The best adhesive you could possibly use is a urethane wood glue. There are several different brands availiable at home depot, Lowes or any place like that. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

And

M edium

D ensity

F iberboard

There is also

LDF - Low Density Fiberboard

HDF - High Density Fiberboard

and various light weight versions of each. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[Savant 10+ year member]

Originally posted by nswartley actually MDF stands for 'medium density fiberglass': it is not just wood

Nope.. medium density fiberboard.. like particleboard, only it's not made with 'particles', it's made with 'fibers'.. smaller chunks, packs better, denser, less brittle, etc etc etc.. I'll bet dollars to pennies that there is no glass in MDF at all..

 

[Savant 10+ year member]

Originally posted by evo2k3 kind of the same thing i told you in the other thread....lol....you need screws or clamps to hold the glue as it cures....

But you made fun of me so I discounted everything you said

And, I like to get confirmation on most things I hear, so don't be offended //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

 

[evo2k3 10+ year member]

Originally posted by ramos M edium

D ensity

F iberboard

 

There is also

 

LDF - Low Density Fiberboard

HDF - High Density Fiberboard

 

and various light weight versions of each. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

yup yup....not fiberglass...that doesn't even make sence...think about....and no offense takin savat....just givin you a hard time //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif .

 

[nswartley 5,000+ posts]

i think its safe to say i got shot down //content.invisioncic.com/y282845/emoticons/frown.gif.a3531fa0534503350665a1e957861287.gif

 

[violator5spd 10+ year member]

what diameter hole do i need to cut out for my re se's?? i know its less than 12"...maybe something closer to 11?