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View Full Version : Birch>MDF??



Jared530
01-27-2007, 07:32 PM
I was trying to search the threads to find out if birch was actually the same strength as MDF, or if t was stronger. Can anyone help me out?

gc86
01-27-2007, 07:38 PM
I'd like to know aswell....

mokedaddy
01-27-2007, 10:32 PM
Its about the same strength, just lighter in weight and more expensive.

azbass
01-27-2007, 10:36 PM
ask the mythbusters.

T3mpest
01-27-2007, 10:40 PM
Straight from the man himself, Dan Wiggins

In general marine grade plywood (or Baltic birch, apple ply, or any other void-free plywood) is superior for subwoofer use. The reason: stiffness.
Subwoofer cabinets WILL talk - they will vibrate. The key is to keep the cabinet from vibrating in the frequency range of the subwoofer. There's two ways to do it: push the resonance of the cabinet above the pass band of the driver, or push the resonance of the cabinet below the pass band of the driver.

To push the resonance above the pass band, we need to make the cabinet stiff. Stiffen something, and it resonates at a higher frequency. In this case, plywood is MUCH better than MDF. Plywood is simply stiffer than MDF, and that's why it is used for sub-flooring, cabinetry bases, and other strength-critical uses. It is the lamination of cross-oriented layers of wood that gives you the strength. No matter how you try to bend it, some of the wood fibers are in tension, which is where they are strongest.

To push the resonance below the pass band, we need to make the cabinet heavy. Add mass to something, and it resonates at a lower frequency. This is where MDF is better - it is much denser than plywood, and as such will take less thickness to lower the resonant frequency of the box. Of course, making a wall thicker also increases the stiffness, which runs slightly counter to the addition of the mass; the resonance still lowers, but not as fast as one would expect.

Overall, it's easier to make a box sufficiently stiff to not resonate below 300 Hz, than it is to make a box heavy enough to not resonate above 15 Hz. Bracing and stiff wall materials raise the resonance - bracing ADDS stiffness (as well as physical strength to hold up a driver, for instance).

Additionally, we need to consider the internal loss. As sound passes through material boundaries, it loses energy. The more layers, and the greater the changes in density, the more energy is lost. MDF is a VERY homogeneous material - it has little internal loss. Plywood, on the other hand, has multiple layers and has considerably higher internal loss. So acoustic waves will be better attenuated by plywood than by MDF.

And in the automotive world it is, IMHO, superior to MDF in two other significant ways: weight and water resistance. Less weight is always good - better gas mileage, easier to build/move, etc. And plywood doesn't swell and turn to mush, like MDF. In fact, marine grade plywood is VERY water resistant. No problems living in damp conditions in car trunks, or getting rained on occasionally.

Overall, if you don't mind paying an extra $25 a sheet for the material, I'd go with a quality void-free plywood (marine grade, Baltic birch, apple ply) over MDF, especially for subwoofers in cars. Lots of benefits, and only one real drawback (the slightly higher cost).

Dan Wiggins
Adire Audio

PV Audio
01-27-2007, 10:56 PM
Plywood is worthless in car audio, as I've said many times. Wiggins is 100% correct, but that is irrelevant to car audio applications. Plywood won't make you louder, bracing MDF will still be just as good, the weight of MDF also makes it more resistant to vibrations, MDF costs less, if you're dunking your enclosure in a pool then you have problems beyond what we can help you with. There is no reason whatsoever to use plywood other than aesthetic or personal purposes. 99% of people won't be able to tell the difference when carpeted, and you'll only be impressing yourself. Now, for home audio, that's a completely different story, but for trunk beaters, save your money and get MDF.

slick rick
01-27-2007, 11:02 PM
I only use birch for my boxes and I have had good luck thus far...but agreed it is not necessary for car audio.

PV Audio
01-27-2007, 11:07 PM
Don't get me wrong, I love plywood, especially cabinet grade oak and birch plywood. It routers like butter and comes with a natural finish that doesn't need to be "finished". However, I will never even consider using it for car audio unless someone wants a stain finish. It's too expensive to have zero PRACTICAL advantages that cannot be replicated with MDF. I honestly don't understand what this new plywood bandwagon is all about, it seems as though the placebo effect is in high order.

slick rick
01-27-2007, 11:13 PM
Don't get me wrong, I love plywood, especially cabinet grade oak and birch plywood. It routers like butter and comes with a natural finish that doesn't need to be "finished". However, I will never even consider using it for car audio unless someone wants a stain finish. It's too expensive to have zero PRACTICAL advantages that cannot be replicated with MDF. I honestly don't understand what this new plywood bandwagon is all about, it seems as though the placebo effect is in high order.

Agreed. I did it to be different (kept the wood bare) and to "save" a bit of weight. My 3.7cuft box for my ava 15 weighed 39 lbs. Not bad. :) my 2.5cuft sealed box I use now is about 20 lbs.

iamamp3pimp
01-27-2007, 11:32 PM
birch > MDF

Void free or not.

Blazin_Jason
01-27-2007, 11:37 PM
I honestly don't understand what this new plywood bandwagon is all about, it seems as though the placebo effect is in high order.

Didn't it start cause TCAB? :laugh:

supa_c
01-27-2007, 11:43 PM
I prefer plywood, oak or birch.
Its cheap if you get it from lowes with a $10 off coupon :D

95bat
01-27-2007, 11:49 PM
So how do those two compare to a fiberglass enclosure for a car?

PV Audio
01-28-2007, 12:25 AM
birch > MDF

Void free or not.
Pimp, if you can give me ONE reason to stop using MDF and use birch plywood for car subwoofer enclosures, just ONE reason that will make me justify its more than 2x price increase, I'll consider it. However, since I cannot see any whatsoever, it's going to take a lot of convincing. It's just not worth the money for car audio.

Didn't it start cause TCAB? :laugh:
Most likely, but I'm not sure.

I prefer plywood, oak or birch.
Its cheap if you get it from lowes with a $10 off coupon :D
But not everyone has coupons silly. :D

So how do those two compare to a fiberglass enclosure for a car?...They don't. Completely different uses.

lilmaniac2
01-28-2007, 12:28 AM
i use birch because its much easier to work with and its lighter and easier to ship

supa_c
01-28-2007, 12:35 AM
The no dust should make it an automatic win anyways.
I hate cleaning up mdf dust

slick rick
01-28-2007, 12:35 AM
Didn't it start cause TCAB? :laugh:

I hope not. I got the idea from some guys over at the ole SI.net years ago. :)

95bat
01-28-2007, 12:41 AM
...They don't. Completely different uses.

Don't people use fiberglass for subwoofer enclosures?

PV Audio
01-28-2007, 01:06 AM
Yes they do. But a tank and a Ferrari are both modes of transportation...just used completely differently. :)

95bat
01-28-2007, 02:33 AM
While I understand your analogy, I don't understand the reasoning behind it :P

Jared530
01-28-2007, 03:05 AM
the reason why i was asking this was because im going to build a new box for my xxx. And my MDF box by itself was a talk, it lowered the back of my carat least 3 inches. I wanted something lighter. If birch was almost identical strength compared to MDF then im going to get it, i dont mind paying the extra 15-20$ for it.

supa_c
01-28-2007, 03:28 AM
Its considerably lighter, almost 1/2 the weight

PV Audio
01-28-2007, 10:26 AM
If you don't mind paying the money, then go for it.

95bat, what I'm saying is that you wouldn't use fiberglass in the same situation where you could use actual wood. You use fiberglass when you need to get the most space out of your car, or when you want to try something innovative. Wood enclosures are just the industry standard, and aren't particularly special unless it's a different kind of enclosure.

bjfish11
01-28-2007, 11:31 AM
Basically, when all said and done, the only differences you will notice between the two is weight and amount of dust left behind. Ive never used Birch for a sub box, but Ive worked with it at work before. I dont totally agree with the "it cuts easier, routes easier" stuff. But then again, I havent worked with MDF in over 3 or 4 years. I use Trupan.
Here is some info I gathered up between Trupan and Birch awhile back (keep in mind Trupan weights approx 80% as a sheet of MDF.)


I gathered up some info on baltic birch 13 ply vs. trupan, and here is what I got.

Weight---
Trupan- 2.25 lbs. per square foot.
Birch- 2.16 lbs. per square foot

Price (my cost)---
Birch is roughly $.25 more per square foot.


The reason I compared square footage is because the Brich I have easy access to comes in 5x5 sheets (which ***** to handle) vs. 4x8 sheets.

In case your wondering, a 4x8 sheet of trupan weights in at 72 lbs and a 5x5 birch weighs 54 lbs.

Im gonna stick with using trupan. I dont feel the price is worth the very minimal weight difference you will get. However, if its wanted for a build, I would be more than happy to get it.

Shyne151
01-28-2007, 03:26 PM
Basically, when all said and done, the only differences you will notice between the two is weight and amount of dust left behind. Ive never used Birch for a sub box, but Ive worked with it at work before. I dont totally agree with the "it cuts easier, routes easier" stuff. But then again, I havent worked with MDF in over 3 or 4 years. I use Trupan.
Here is some info I gathered up between Trupan and Birch awhile back (keep in mind Trupan weights approx 80% as a sheet of MDF.)


I gathered up some info on baltic birch 13 ply vs. trupan, and here is what I got.

Weight---
Trupan- 2.25 lbs. per square foot.
Birch- 2.16 lbs. per square foot

Price (my cost)---
Birch is roughly $.25 more per square foot.


The reason I compared square footage is because the Brich I have easy access to comes in 5x5 sheets (which ***** to handle) vs. 4x8 sheets.

In case your wondering, a 4x8 sheet of trupan weights in at 72 lbs and a 5x5 birch weighs 54 lbs.

Im gonna stick with using trupan. I dont feel the price is worth the very minimal weight difference you will get. However, if its wanted for a build, I would be more than happy to get it.

Is trupan available at home depot or lowes? i have to build a box for my new car soon, and i don't want the *** end to sag like my monte did.

PV Audio
01-28-2007, 03:39 PM
No, you need to go to a high-quality lumberyard to find it. It comes in two weights as well.

azbass
01-28-2007, 03:43 PM
meh, in car. mdf for the win.

in home, and stained, birtch. etc. ftw

tommyk90
01-28-2007, 03:58 PM
The only real benefit that MDF has over GOOD birch is the cost savings.

I've worked a lot with both, and for a person like me who has to move around heavy boxes all the time for SPL testing, birch is a lifesaver.

For example, i had a 4 cube box for a pair of 10's. Because of the dimensions, it was nearly 3/4 of a sheet of 4x8 MDF. With the subs in, the whole package weighed well over 100 pounds.

For my single 15" box (the sub weighs more than both the 10's i had combined), i used birch. the box was about the same size, and only half the weight. Made things MUCH easier to move around.

But I agree with everyone for the most part. If weight isn't an issue, then there's no real point to getting birch. For my teammate joe's box, since his box needed 3 sheets of wood, we used birch for it and saved well over 100 pounds.

supa_c
01-28-2007, 04:42 PM
Ive never seen birch in 5x5 sheets, you must have a weird distributor.

joetama
01-28-2007, 05:13 PM
Hmmm.... I'm thinking about trying birch in my next box now just for the **** weight savings......

PV Audio
01-28-2007, 05:19 PM
Bingo. There's no point in using birch at all in car audio unless you'd be using a LOT of wood. Otherwise, save your money. I'm not going to lie, birch and oak ply look **** beautiful when stained, poly'd and wet sanded.

Hey B&W, I'ma be building some new x-overs for those towers I made. What kinda slope do ya think? PM me with your response.

joetama
01-28-2007, 05:24 PM
Bingo. There's no point in using birch at all in car audio unless you'd be using a LOT of wood. Otherwise, save your money. I'm not going to lie, birch and oak ply look **** beautiful when stained, poly'd and wet sanded.

Hey B&W, I'ma be building some new x-overs for those towers I made. What kinda slope do ya think? PM me with your response.

PM sent.... Sorry for the weird spellings, I'm bored and it entertained me....

bjfish11
01-28-2007, 05:26 PM
Ive never seen birch in 5x5 sheets, you must have a weird distributor.

Thats the only thing we carry in a Baltic Birch. Its mainly used to make drawers for cabinets. I dont know why it comes that way, but im sure there is a good reason. Its a ***** to carry though, so I hate it.