Jared530
I'd like to know aswell....
mokedaddy
5,000+ posts
professional idiot
Its about the same strength, just lighter in weight and more expensive.
ask the mythbusters.
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
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
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
10+ year member
OG
I only use birch for my boxes and I have had good luck thus far...but agreed it is not necessary for car audio.
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
10+ year member
OG
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. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif my 2.5cuft sealed box I use now is about 20 lbs.
iamamp3pimp
5,000+ posts
Bass Heads Entertainment
birch > MDF
Void free or not.
Void free or not.
Blazin_Jason
10+ year member
CarAudio.com Elite
Didn't it start cause TCAB? //content.invisioncic.com/y282845/emoticons/laugh.gif.48439b2acf2cfca21620f01e7f77d1e4.gif
supa_c
5,000+ posts
Abministrator
I prefer plywood, oak or birch.
Its cheap if you get it from lowes with a $10 off coupon //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif
Its cheap if you get it from lowes with a $10 off coupon //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif
So how do those two compare to a fiberglass enclosure for a car?
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.
Most likely, but I'm not sure.
But not everyone has coupons silly. //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif
...They don't. Completely different uses.
lilmaniac2
5,000+ posts
Ask Me about SI Mag V4!
i use birch because its much easier to work with and its lighter and easier to ship
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