I am having a very hard time obtaining a sheet of mdf. It just seems like fate is against me. My question is how much of a difference will I see if I use plywood for my box design but seal the inside with resin?

 

No matter how well you may think it is sealed, you will still have air leaks. Plus MDF is a stronger wood anyway and can take much more abuse than plywood. Try checking around at your local Home Depot or some place like that in your area.

Dave

 

plywood and mdf are completely different animals. Local audio shops will have it, some hardware stores have it, circuit city would most likely have it.....

 

MDF isnt wood. its like sawdust glued together. A lot more dense and heavier than plywood. makes a shitload of dust when you cut it too...

look @ home depot for it. thats where i get all of mine. $17.99 for a 4'x8' sheet

 

You should be able to get MDF at any home improvement store or lumber yard. I have used plywood before and it sounds hollow, because the plywood resonates a lot.

 

Ok cool. Thanks for all the help guys.

 

Where do you guys find MDF sheets that will fit inside a car. Four feet is too wide, 3 feet would be a squeeze but it would work.

BTW, when I had my first car I built several boxes from plywood. Properly braced there was not much of a difference in sound or spl. I used information from the loudspeaker cookbook to calculate resonant frequency of the boxes panels, so the bracing would be much more effective.

MDF may be better, there is always some debate, but plywood is not a show stopper either. Plywood is more resistant to water than mdf and particle board.

 

Home depot or any good lumber supply will typically slice the 4 x 8 up for you into whatever sizes you need to fit inside your car - you could even have them cut to your final dimensions which will save you having to mess with it when you get it home, especially if you don't have good table saw.
There is usually no charge for the cuts, just pay for the sheet.


[Modified by D'Ecosse, 10:16 PM 2/12/2003]

 

just do a fiberglass box there super easy and cheaper in the long run

 

Yeah I got my MDF last night. Home Depot sliced it so I could fit it in my car. I just had them quarter it. It was $17.99.

Thanks guys.

 

any one ever see mdf get made in a factory? It's pretty cool.

 

I'd like to see how you came to that conclusion.....

 

I'd go with mdf. If you have the extra cash and know how to lay fiberglass then go with that cause it'll look a lot better.

 

easy mdf is $20.00 a sheet and thats kinda cheap! Fiberglass is about $30.00; but then add in the price for bondo (to cover the inside of the box) and carpet (for the outside) on the box and take in to account the water moisture effect. I built my fb box for about 45.00 total and it will out stand a mdf box, its lighter and looks a hell of a lot better


[Modified by xXxS_SxXx, 7:50 PM 2/13/2003]


[Modified by xXxS_SxXx, 7:51 PM 2/13/2003]

 

I have no doubt that the fiberglass box is better. I was going to try it to go with a non angular shape but I decided that a standard mdf box will better suit my needs at this time.

 

So, let's try this again....

In your previous post, you said that the fiberglass box is cheaper in the long run then the MDF box, apparently now you are switching your stance?

A fiberglass box is significantly more expensive IMO for a few reasons. It takes a lot more "tools" to get the job done. Factor in the time that it takes (time = money), and a MDF box will always win in the cost/performance analysis.

Here's how I would realistically price materials for a 'glass box in the spare tire well:
Gallon of Resin 25
Yard of both knytex + cloth 20
Small panel of MDF (gotta mount that sub to something): 5
Masking material (tape, foil, etc): 10
8-10 disposable Paint brushes: 5
Box of rubber gloves: 15
Pint of bondo: 10
That's a subtotal of around $90

The rest (glue, screws, caulk, adhesive, and some type of finishing material) is going to be a wash between the two...meaning regardless of material choice you will need them. I didn't even account for mixing cups, spreaders for the bondo, a respirator (that's a must) or the fleece and sand paper that you will need if you intend to make the baffle 'glass as well. That's a bare minimum of what it would take to march down to your local hardware store, and get started with glassing.

A MDF box
Wood: 15
Sub Total: $15

ummmm....that's it...everything else that you need to build a wood box, you need for the fiberglass one. I guess you could throw in that 5 dollar terminal cup for extra measure, but all things considered I think you get my point:

The bottom line, where I come from $90 is a whole lot more then $15

Fiberglass is expensive....that's the reality, but don't let the expense deter you....once you get started with it, you will never turn back...you will think of a ton of things to build out of it. Thankfully, the cheaper Bondo brand resins and cloths/mats come in smaller packages so that you can experiment.

BTW, I HIGHLY recommend you guys try out Dynaglas - this stuff rocks for cosmetic panels....try it, you'll like it. Steve Brown from Apline swears by it!!


[Modified by rcurley55, 6:25 AM 2/14/2003]

 

you miss read my post i meant 20.00 is a cheap price for mdf
well i built my fiberglass box for less then 50.00 and it is tied in to the trunk so it doesnt look like it doesnt belong there like a mdf box does

as far as your prices go:
Here's how I would realistically price materials for a 'glass box in the spare tire well:
Gallon of Resin maybe 2: 20.00
Yard of both lycra and fibeglass 3/4oz matting and material:35.00 maybe 40.00 depend on if you can get it on sale.
Masking material (tape, foil, etc): stuff around the house
Pint of bondo(pints a little thin): 10
That's a subtotal of around $60

but what ever its a pointless battle mdf = alot of extra weight and you'll probally change it after a while any way so why not do it right the first time!

i totally agree with this statment
....once you get started with it, you will never turn back...you will think of a ton of things to build out of it.




[Modified by xXxS_SxXx, 12:48 AM 2/14/2003]

 

Same here. Home Depot for less than $20. It's really heavy though.

 

question, is it labeled MDF (mediem density fiberboard)? its differnt than particle board right?

 

yes its different in stead of big wood chips like particle board mdf is made of saw dust like particles put under pressure wth a glue like substance does this answer your question?

 

When you go to home depot, just ask for mdf. It is labeled MDF.

Anyone ever try an HDF box?

 

fiberglass resin for less than $20 a gallon? I wan't to know were you are getting it for. The cheapest I have found is like $25 a gallon. Also for a wooden box you will need glue $5.00 and Screws $5.00 as well as carpet $15.00 then you need a circular saw $50 then you need a Jig saw $30 then you need a drill $30 then you need something to attach the carpet to the box with like spray glue $5.00


[Modified by 18gTeg, 4:58 PM 2/17/2003]

 

Who cares??? Either way the price of the box is less than $100 (not counting tools) unless you're getting really elaborate. For under $100 who cares??? Do which best meets your needs I say.

 

Sorry for trying to help you out on what things cost. If you didn't want people to reply then don't bother posting.

 

I know what things cost. This wasn't even what I was asking... I just don't see why this had to turn into a fiberglass vs. mdf war...