7 ply birch plywood... junk or??

[deez283 10+ year member]

Getting ready to build a Box and a friend told me he has a sheet of Birch plywood.. I went and checked it out, it apears to be 7 layers and looks nice but is this stuff any good for sub boxes??

Should I use it or just run over to HD and buy a sheet of 3/4" MDF??

any insight?

Click to read more...

 

[deez283 10+ year member]

nobody has tried this stuff???

 

[helotaxi 5,000+ posts]

Without a picture of some kind, its impossible to tell what you're talking about.

If it's the stuff I think that it is, there's nothing wrong with it. It's not Baltic Birch but it's fine for an enclosure. Just like with any enclosure, make sure that you brace any large surfaces and it will work fine.

 

[deez283 10+ year member]

Without a picture of some kind, its impossible to tell what you're talking about.
If it's the stuff I think that it is, there's nothing wrong with it. It's not Baltic Birch but it's fine for an enclosure. Just like with any enclosure, make sure that you brace any large surfaces and it will work fine.

Yeah it's not Baltic just standard 7 ply birch from Home depot that runs 45.00 a sheet...

I just wanted to get some opinions before I use it for a sub box... after searching around I've found lots of info on the baltic but not so much on the 7 ply.. I've always used MDF but figured if I could get this free then why not? but at the same time I want a quality box that sounds right so I have no problem buying the MDF if it's much better to use.

 

[helotaxi 5,000+ posts]

Properly braced, that should yield about the same results as properly braced MDF. Box should be lighter as well. I've used that stuff before with pretty good results.

 

[RAM_Designs 5,000+ posts]

Hell, I'm using 5-ply right now on my single 10" box since that's all I had laying around the afternoon I felt like making a box...seems fine to me, no reason to complain.

 

[Sarthos 10+ year member]

Any wood you find should work so long as the frame is designed strong. I used oak cabinet board braced with 2x4s and that made a solid box, but it was pretty heavy.

 

[deez283 10+ year member]

Alright guys, thanks for the insight I'll go scoop it up from him when he gets off work tonight.

 

[matt_bennett05 10+ year member]

Agree w/ all above! I had the OWNER of a stereo shop tell me this morning that MDF have a better "sound" to it than ANY other material... and that Birch sounds like *****....ERR??? I prefer birch myself... reeeallly wanted to argue but it would have been pointless to a smart @$$ know-it-all...

 

[Mitch86 5,000+ posts]

MDF is a little more forgiving as far as cutting and rounding over and such. Birch ply likes to "chip". But in my experience it works just as well as MDF. But as mentioned, make sure to brace any large areas. (the same with any material)

 

[FIMPALASS 10+ year member]

Baltic birch is way stronger than MDF.

Got the below info from-

http://www.talkaudio.co.uk/index.php...d=91&itemid=26

Mechanical properties:-

In laymen’s terms, strength is an indication of how much load a material will withstand before failure and stiffness is how much the material will flex, or deform, when subjected to a given load.

We are not really interested in the ultimate strength of our sub boxes as they seldom fail, so the material strength is of little use. However, we are interested in how much a box will flex. Therefore, we will concentrate on the stiffness of sub box materials.

Eb = Modulus of elasticity in bending.

Eb describes how stiff a material is under bending. The higher the number, the stiffer the material is and the less it will flex. It allows us to easily compare the stiffness of different materials.

The following properties are all based on 18mm sheet materials:

Birch faced ply:-

Eb = 2700 N/mm^2 perpendicular to grain

4600 N/mm^2 parallel to grain

Density = 11.6 kg/m^2

Birch ply:-

Eb = 3400 N/mm^2 perpendicular to grain

4600 N/mm^2 parallel to grain

Density = 12.4 kg/m^2

MDF:-

Eb = 2200 N/mm^2

Density = 10.8 kg/m^2

It can be seen from the above, that the plywood properties are directional depending on the orientation of the grain. For the purposes of this analysis, we can assume the stiffest properties as sub box panels are generally supported on all four edges. MDF is a homgeneous material and the mechanical properties are identical in any direction.

Comparing the Eb values given above it can be seen that the birch based plywood is over twice as stiff as the MDF. Therefore, if two identically sized sub boxes were fabricated, one from 18mm MDF and the other from 18mm birch ply, the MDF box would flex twice as much as the birch ply box.

That’s quite an improvement from simply using a different material for your enclosure.

 

[FIMPALASS 10+ year member]

I just noticed your from WA. If you have a dunn lumber near you go there and get some quality Baltic birch. The stuff at home depot just has birch on the outter layers and usually a lesser grade wood in the middle.

 

[deez283 10+ year member]

I just noticed your from WA. If you have a dunn lumber near you go there and get some quality Baltic birch. The stuff at home depot just has birch on the outter layers and usually a lesser grade wood in the middle.

Yeah, only place for lumber nearby is Depot and a levee lumber and neither carry Baltic..

If I were to go buy it I'd just get the 3/4" MDF I always use but a friend offered a new sheet of the 7 ply birch he bought from home depot for free so I thought I'd get some opinions on weather it would be good for a sub box..

 

[helotaxi 5,000+ posts]

Free wood is the best kind unless it's particle board.

I'm pretty sure that stuff is exactly what I used for this box:

 

[RAM_Designs 5,000+ posts]

^^^what's the specs on that? Looks pretty low tuned.