Different wood types to build a box

[The enD 467]

How does one choose the wood he wants to build his box out of? I see pretty much every one using MDF for theirs, but what about other types? Currently I know three types and I am not completely sure about their pros and cons.

Particle Board

cons - not accousticly dead, breaks easy if bend, crumbles at edges,

pros - pretty light and cheap

MDF

cons - porous, adds significant weight to the box, lots of dust when cut

pros - quite strong, easy to work with, small channels can be made so it bend but it still holds it structure

Plywood

cons - price

pros - light and strong - all you want from wood for boxes

Am I wrong about the stated properties of these materials? How should I base my choice on wood? If I have the money to buy the most expensive type - plywood?

[antonmiller 8]

MDF is fine, unless your chasing tenths on the meter, i would go with mdf, birch can be kerfed much easier than mdf as well. and birch is the strongest/lightest, ive heard of people gaining close to half db building the same box that was mdf out of birch.

[slim2fattycake 85]

stay away from particle boards...

[The enD 467]

stay away from particle boards...

Can you expand you answer. I would like to know why not only take it as a given.

[slim2fattycake 85]

it is the least durable of all engineered wood and it is not that much cheaper than MDF. It breaks apart in clumps really easy and it swells and sags when introduced to moisture. And you have to be extra careful using screws in it as the structure is really weak. You definitely need more bracing than compared to MDF as well.

[///M5 2,833]

Structural Integrity is the name of the game. Particle board sucks for it, MDF is pretty good, and Void Free 11+ layer ply is extremely good for it. None of them preclude the necessity of bracing though, but some materials make it much easier.

Look at B&W Matrix bracing and realize that is exactly how a speaker should look. Obviously the layout of the bracing can vary, but theirs is NOT overkill.

[shizzzon 461]

u dont want the most expensive plywood, hehe. Marine ply is the most i've seen . $265 per sheet @0.75in thick. Good luck with that...

Since we are on the subject of wood choices...

I've been using Birch for a little bit because it's only $7 more a sheet than MDF is.

I will be chasing tenths on the meter and had planned on using Hardwood for my next build.

Anyone have any criticism on this?

I'm assuming Hardwood is gonna be more dense and i assume weigh more than MDF(and Birch).

It's $48 a sheet here.

I would like to try Oak but it's too much for my tastes right now. $66 per sheet here.

[///M5 2,833]

u dont want the most expensive plywood, hehe. Marine ply is the most i've seen . $265 per sheet @0.75in thick. Good luck with that...

Since we are on the subject of wood choices...

I've been using Birch for a little bit because it's only $7 more a sheet than MDF is.

I will be chasing tenths on the meter and had planned on using Hardwood for my next build.

Anyone have any criticism on this?

I'm assuming Hardwood is gonna be more dense and i assume weigh more than MDF(and Birch).

It's $48 a sheet here.

I would like to try Oak but it's too much for my tastes right now. $66 per sheet here.

Your goals are different and independent from the reasons I cited above. Regularly a dead enclosure (read well built, braced, etc..) won't be as loud as a poorly built one. It will completely depend on its signature resonance which you can predict, but will require some serious Finite Element software and even then regularly need some real world measurements to optimize. Considering a single sheet of Oak at $66 is too expensive then the whole process of changing materials will be as well as you will have to experiment many times to gain tenths. No golden rule here.

[Jay-C76 333]

that last picture is actually laminate veneer.. (used for furniture making)

It is very dense and heavy as hell!

I built an enclosure for two 12's once out of the same material.

You'll need a good, sharp, carbide blade for that stuff.

The smoke from cutting will make you gag too! LOL

[The enD 467]

Thanks for the replies, all.

In the best scenario I'll go with plywood, aero ports, lots of bracing from M5's advice.

wow

[shizzzon 461]

Maybe i dont follow M5's advice?

A really well built enclosure will not be as loud as a poorly built.

Disregarding typical builds...

A design made out of 4" thick concrete on all 6 sides vs a single layered box out of mdf will yield lower pressure output because of it's high resonance?

Is this what you are implying, similar scenario?

This is completely the opposite from what most of us competitors do.. We brace and brace and brace the box and the car to make it solid as a rock.. and the numbers go way up.

I think i need a new elaboration.

[helotaxi 46]

You can't simply lump all plywoods together. Void free baltic birch is great stuff. Pine underlayment sucks. The price can be informative but isn't the final word in suitability. Oak ply will be heavy and fairly dense but regular oak ply isn't void free. Event the $60+ a sheet stuff isn't void free.

[cheese20323 13]

So what you guys are saying that MDF is like the best in price and performance(strength).....

[helotaxi 46]

So what you guys are saying that MDF is like the best in price and performance(strength).....

It's a good balance. It holds glue well. Edges can be nicely formed with a router. It cuts very cleanly. The finished surfaces are extremely smooth which makes it nice to paint once you seal the end grain.

It really isn't that strong though. You have to watch splitting it running screws into the edges or dinging up the corners by bumping it against something.

[Kanaworm$ 292]

BJ at Fisher Customs used(s) Trupan Light.

Supposedly lighter and just as acoustically dead as mdf.

[helotaxi 46]

Trupan is good stuff except that it is hard to come by and expensive. It bends much better than any of the others. It was developed for cabinet makers to bend around curved faces on counter pedestals and so forth.

[Adrian_D 520]

We brace and brace and brace the box and the car to make it solid as a rock.. and the numbers go way up.

I think i need a new elaboration.

I braced the box..and lost big time

[kirill007 52]

We brace and brace and brace the box and the car to make it solid as a rock.. and the numbers go way up.

I think i need a new elaboration.

I braced the box..and lost big time

It also depends on the freqeuncy and the way the air flows.

The loudest freqeuncy shouldn't be the same as before, the resonant freqeuncy changes so you need to use a different freqeuncy to get higher numbers.

And u need to brace so u don't obstruct the airflow too much.

[shizzzon 461]

are we trying to debate the differences between density vs rigidity?

I've been told it's best for competition to make an enclosure more rigid than dense. Of course, i got no explanation as to why...

However.. depending on how rigid an enclosure is and how it's attached, wouldn't it make the material inside the box more dense anyway?

Example- 2 layers of mdf for all 6 sides. On the outside, 1 layer of 2x4s on all 6 sides. Now, this won't really make the box rigid unless the 2x4s are anchored but it would make the enclosure more dense...

so if the 2x4s were anchored.. it would be both more dense and rigid.. correct?

I've seen installs where users have poured concrete in between their walls and side of the vehicle to fill any empty voids so the wall is physically part of the vehicle now and well installed, hehe.

Let's look at NDMStang's steel cage for his truck...

That's gonna make any design rigid as hell... but i do not assume it will do terrible...

I may understand part of what you guys are saying...

If the resonance of the box continues to increase internally but the resonance of the car remains the same, their can\will be a loss of output? is this what you are referring to?

If this is true, then wouldnt just retuning the port help a lot more?

Seriously, when building a wall, you can't build it, test it, then add external bracing later on... It wouldnt be a real wall or reliable bracing.

So we basically just build it as large as possible, well built n braced with some trickery calculations on how it's built then do port testing, car testing and box testing.

[helotaxi 46]

Rigidity and density have nothing to do with each other. 20 layers of MDF is no more dense than 1. HDF is more dense than MDF, that simply means that for a piece of each the same size the HDF will weigh more. Birch ply is less dense than MDF but more rigid.