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MaximRecoil
05-10-2003, 11:17 PM
I want to build a sealed box. I want to build it out of something burly. I was thinking something along these lines:

1 inch MDF or 1 inch HDF (High Density Fiberboard) or 2 inch Baltic Birch Plywood.

Anyone ever used any of these materials/thicknesses building a subwoofer box? Any advantages/disadvantages of HDF as compared to MDF?

As far as the 2" birch plywood goes, that is a material that is commonly recommended for building home audio subwoofer enclosures (recommended by Drew Daniels, who was Applications Engineer at JBL Professional from 1984 to 1989 no less)

I'm sure that 3/4" MDF would be fine but I still want to use the thicker material just because.

Jimi77
05-10-2003, 11:35 PM
If you're going to go that thick I'd mix and match. I'd do 1" thick - 1/2 of Baltic Birch (light & Strong), glued to 1/2 MDF (Dense and acoustically dead).

MrBurns
05-10-2003, 11:37 PM
I've had the idea of concrete boxes floating around my head for years, but never gotten around to experimenting. They are dense and dead. They should be great.

Giga357
05-11-2003, 12:33 AM
I wouldn't think concrete would be dead. I could very well be wrong however

MaximRecoil
05-11-2003, 12:37 AM
Originally posted by Giga357
I wouldn't think concrete would be dead. I could very well be wrong however
Concrete is the ultimate. Look at any home or club sound system that cost $100,000+ to put together and you will find that the subwoofer enclosures are built out of 6 inch thick poured concrete (poured around 2 inch baltic birch plywood speaker mounting rings).

Edit: Hot Damn! This is my 100th post and I am officially a "Senior Member" lol thmbup

TCPMPN
05-11-2003, 12:41 AM
concrete doesnt flex either so its good for high spl

sandt38
05-11-2003, 01:22 AM
HDF I don't reccomend... MDF is cool. Birch rules. Birch enclosures require less than 1/2 of the bracing and weigh considerably less.

IMHO 3/4 birch = 1 1/4 MDF easy. I reccomend it and it alone for world class enclosures.

mcchicken
05-11-2003, 01:31 AM
I agree with Sandt here....BB is much more rigid than MDF....it's been said that it is 3 times more rigid.....and just happens to be much lighter. Density has very little to do with what makes for quality enclosure material.....rigidity is VERY important.

MaximRecoil
05-11-2003, 01:31 AM
Originally posted by sandt38
HDF I don't reccomend... MDF is cool. Birch rules. Birch enclosures require less than 1/2 of the bracing and weigh considerably less.

IMHO 3/4 birch = 1 1/4 MDF easy. I recommend it and it alone for world class enclosures.
Just so we are on the same page here; you are talking about birch plywood as opposed to solid birch plank right?

mcchicken
05-11-2003, 01:40 AM
Baltic Birch....comes in 5'x5' sheets.

94StealthRT/TT
05-11-2003, 01:42 AM
Shouldn't the wood be naturally acoustically dampened?

In this case MDF is better then birch?

94StealthRT/TT
05-11-2003, 01:44 AM
Originally posted by sandt38
HDF I don't reccomend... MDF is cool. Birch rules. Birch enclosures require less than 1/2 of the bracing and weigh considerably less.

IMHO 3/4 birch = 1 1/4 MDF easy. I reccomend it and it alone for world class enclosures.

Seth,

I'm building my enclosure for my 15A...

When and where did you come to grips that Baltic birch is better?

Is that what your using for you Brahma?

sandt38
05-11-2003, 12:54 PM
Originally posted by 94StealthRT/TT


Seth,

I'm building my enclosure for my 15A...

When and where did you come to grips that Baltic birch is better?

Is that what your using for you Brahma?

I just happened to be asking for a lighter material and someone suggested the Birch. I got a hold of a sheet and hefted it, allowed it to sag in the middle (testing rigidity), and looked it over really good. It looked like a nice wood, with a massive ridgidity advantage. And I'd say about a 30% savings in weight.

I tried it in a Shiva enclosure, and built the same enclosure with MDF. I used no bracing. It was obvious the birch was better. No panel flex with the birch, while the flex was obvious with the MDF. The birch box was exceptionally lighter too, it seemed to have a better all around sound (I suspect it was due to panel flex of the MDF). With my playing around with enclosures I am using simple MDF right now. I have another project I will be starting soon that I am in the process of design layout. That should be the finished product in the Nat and in it I will use Birch. I have a MDF enclosure built of the same size I will use for placement testing, and assurance of the SQ of what I am looking for. The final design though will use Birch and plexi with some blue neon to integrate the design with the ZRS-10 I will be adding soon.

Big Bas 83
05-11-2003, 01:34 PM
Is this baltic birch something I can find at Home Depot? Is it significantly more expensive than MDF???

kbog
05-11-2003, 03:10 PM
Originally posted by Big Bas 83
Is this baltic birch something I can find at Home Depot? Is it significantly more expensive than MDF???

yes.yes.

Big Bas 83
05-11-2003, 04:02 PM
LOL thanks.....

how much more? I know a sheet of MDF cost $18 dollars at home depot, but i dont remeber the size of it... do you have any idea for a price on a comparably sized birch?

kbog
05-11-2003, 04:13 PM
Well, part of the reason I posted that way is because I forgot. I remember looking at both about 2 months ago. I was mainly concerned with weight and the Birch was lighter, but I also looked at price and saw the birch was more. I may be in HD today though and I will let you know exactly...

NERV
05-11-2003, 05:16 PM
Slightly OT question.. how durable is MDF to say.. particle board?

The WeaseL
05-11-2003, 05:39 PM
Originally posted by NERV
Slightly OT question.. how durable is MDF to say.. particle board?

Although I'm a bit of a n00b when it comes to box design, I can tell you that MDF > Particale board I believe.

kbog
05-11-2003, 06:04 PM
MDF will be magnitudes better than particle board, but marine grade plywood will be more rigid than both I believe.

Just got back from HD:

2'x4' 3/4" MDF - $6.47

2'x4' 3/4" Birch Ply - $14.97

So it is more than twice as much.

jayselle
05-11-2003, 06:26 PM
if you want to stop flexing and have a sturdy box, i would recommend double layering with 3/4"....dont buy one inch mdf...its way to heavy to work with....and using wood glue to create double layered 3/4" mdf is much stronger..

i have been double layering my high power enclosures for awhile and there is no flexing at all, i do not even have to add internal bracing (but still do), i also recommend 2.5" drywall screws every three inches along with the wood glue

i would like to work with birch, but its just too expensive....and lets face it putting screws into double layered 3/4" mdf will be a lot easier than 0.5" birch

The_spacemonkey
05-11-2003, 06:53 PM
Originally posted by mcchicken
I agree with Sandt here....BB is much more rigid than MDF....it's been said that it is 3 times more rigid.....and just happens to be much lighter. Density has very little to do with what makes for quality enclosure material.....rigidity is VERY important.

on the contrary, it has alot to do with it. Higher the density, lower the resonance.


and concrete would be better than cement for an enclosure due to the fact that the composite matrix and partical phases work together to create a more rigid, but less brittle structure.

jjagger
05-11-2003, 11:03 PM
The current issue of some audiophile magazine (on your Barns and Noble shelf right now), features Do It Your self high end system, using concrete (or cement) as enclosures. I do not remember the name of the magazine tho...

As far as which wood, I think layering birch with MDF is defenantly the way to go! Birch by itself is VERY not sound dead. So you have a strong structure that leacs a lot of sound. If you want to go all the way, layer birch ply with MDF, and add some type of sound foam. Black Hole is by far the very best for this, but it is sooo $$$$. Check it you on Parts Express just for kicks. Brace and seal for good measure.