Making sub boxes...

[T!mmy]

well I have two questins....

when making a normal mdf box, is it better to just cut all the angles at a 90 degree (straight) and overlap your edges or to cut them all on 45s making the joint "split" the corner of the box?

when making a fiberglass box which has NO true edges or anything...how do you calculate the airspace?

Thanks
Brian

 

[Beelzebubba]

I always cut them on 45s...I suppose it doesn't matter as the box was eventually covered so it didn't need to look neat.

I have no Idea on the fiberglass enclosure. My experimentation with fiberglas ended up sounding like s**t.

 

[venger]

I'd do less 45's as possible cause you are dealing with less wood and less complication. I think he most important part of the 45's is making it so flush you can't see light through the peices when you hold them together before you do any glue, staple, screw, or caulking.

google this: speaker box airspace calculator. With the fiber glass mold I'd say you are going to have to pretend the design is as square or retangular as possible thus giving approximate measurements, perhaps shortening the lengths some to compensate for the roundness of the mold edges. Who knows maybe somebody has a better idea.

 

[T!mmy]

I had an idea that I think someone told me awhile back but wasnt sure how to gauge it...taking packing material and putting them in a bag or something until you have the right amount and then tying that off. then use that as a rough idea for how much airspace

 

[Beelzebubba]

I had an idea that I think someone told me awhile back but wasnt sure how to gauge it...taking packing material and putting them in a bag or something until you have the right amount and then tying that off. then use that as a rough idea for how much airspace

It's good for a rough idea, they'll be some unaccounted for airspace between the packing material though so it won't be exact.

 

[T!mmy]

sand then

 

[Beelzebubba]

I'd do less 45's as possible cause you are dealing with less wood and less complication. .

I wouldn't have tried them without a table saw. Trying to do a piece of 4 foot long MDF with a jigsaw? OMG no. I know how well I work with power tools and there would have been gaps and a slight S curve all the way down it.

 

[venger]

nah i didn't mean anything like that. as stated by someone else you are covering it with carpet. if i had a choice for a particular corner, i'd go 90, i think its a better seal and stronger. remember the long term.

 

[T!mmy]

well I've got all the woodworking tools I could possibly ever need... just wanting to figure out the best way

 

[kingstonrock]

To guage the volume of a weird shape, the easiest thing is to fill it with packing peanuts. Then pour those packing peanuts into a cardboard box, the length and width are the dimensions of the box and the height is the depth of the peanuts. This method will be plenty accurate b/c the airspace b/w peanuts is accounted for in calculating the volume of the cardboard box.

Eric

 

[kingstonrock]

Also: 90 degree cuts are your best bet for getting a good seal; and be sure to pre-drill all screw holes, otherwise the MDF will be prone to splitting.

 

[420GREEN]

And use a good wood glue for all the seams, liquid nails in a tube is the shiat(fills in all the unsightly gaps and imperfections)................or it will rattle apart and sound like crap.....

 

[charles_00Civic]

I cant remeber when or where, but i posted on how to make fiberglass sub bozes. Looks relaively easy and you can put them anywhere and they'll mold amazingly well.

 

[T!mmy]

Also: 90 degree cuts are your best bet for getting a good seal; and be sure to pre-drill all screw holes, otherwise the MDF will be prone to splitting.

I think we're going to try 45 degrees...my grandpa is going to help me and he can do all that s**t extremely well...he should be able to get it accurate enough that it sits perfectly inthere...and since it would be a 45 it would be stronger...

 

[T!mmy]

btgw...having to make some minor alterations to the original box dimensions...what is the formula for getting airspace?

 

[jdmspivic]

OR you can always jsut call the manufacturer of the company that makes the sub and ask them on their recomendation and they will give u EXACT MEASUREMENTS! but 90 degree cuts are always better locks more air in that way. just be sure to glue and staple and silicone after your done.

 

[T!mmy]

OR you can always jsut call the manufacturer of the company that makes the sub and ask them on their recomendation and they will give u EXACT MEASUREMENTS! but 90 degree cuts are always better locks more air in that way. just be sure to glue and staple and silicone after your done.

like I said...36" is the recommended width of the box (By JL Audio), although 36" is too wide for my CRX. Therefore I am chopping an inch off but it has to be added somewhere else to keep the same airspace.

 

[jdmspivic]

make angles to fit you hatch just make the box in a shape that will fit the car and keep the space be creative.

 

[loccusst]

DO NOT do 45....you will not get a good seal as stated before. Just butt the pieces of wood together to make a simble 90 degree angle. Use many screws along with wood glue. Don't forget to brace and to take the bracing as well as the sub into consideration when calculating volume. Also polyfill inserted into the box will make the sub think it is in a much larger box than it already is. The peanut trick is used by the pros too. Don't worry about the looks of the box...that's what carpet is for and you can always put a trim piece to make the box flush with your trunk. A fiberglass box is a whole nother discussion.

 

[kingstonrock]

The formula for volume of a rectangular box is simply length*width*height. Divide by 1728 (12^3) to get convert from cubic inches to cubic ft.

Also, as for ensuring that the box is sealed, you can line the inner edges with a bead of silicone. As a precaution, if your driver has a foam (instead of rubber) surround, do not mount the driver in the box until the silicone has cured overnight, the fumes *may* damage the foam material the speaker's surround is made from. I say *may* b/c there is no real proof to this, it is mainly just hearsay, but IMO why risk it?

Eric