Which Material Is Heavier...

[Derek Arita]

Weight is an issue in what I'm trying to build. I need to know which is heavier, 3/4" furniture grade birch ply (Baltic Birch Ply?) or 3/4" MDF? I asked this in another thread, but it kind of got lost. Hope someone knows the answer.

[Jeff Nolan]

MDF is 680–830 kg/m3 and birch core plywood is 680-700 kg/m3... but if you go with poplar core plywood then you are down around 500 kg/m3.

[Derek Arita]

MDF is 680–830 kg/m3 and birch core plywood is 680-700 kg/m3... but if you go with poplar core plywood then you are down around 500 kg/m3.
Is poplar core plywood as stiff? Is it easy to find?

[Jeff Nolan]

What are you trying to accomplish? Weight is one factor in selecting sheet goods but the application itself is a far bigger concern. Also, there really isn't anything called "furniture grade" in plywood... sheet goods are graded according to the size and quantity of knots on the face veneer and whether they are filled. Letter grades A-D are assigned for both the front and number grades for the back, hence A-1 is knot free and well sanded on both sides while A-3 is intended to be used with only the front side visible.

[Prashun Patel]

Not sure why yr getting the runaround.

MDF will be way heavier than it's equivalent volume in plywood - cabinet grade, underlayment or otherwise.

MDF will be stable than ply but won't support heavy loads.

Cabinet grade plywood seems to be a BORG defined term. It just means it has a birch veneer on one side that has no voids, and then an 'ugly' birch veneer on the other side. But it says nothing about the voids that might be present between the veneers.

[Frank Drew]

I bought a sheet of 1" MDF, 5'x9' as I remember it; it was about the heaviest, certainly the most awkward thing I've ever moved into my shop by myself. For starters, it had wedged itself tight into the bed my full-sized pickup truck and I had a hell of a time getting it out.

That stuff is HEAVY!

[Van Huskey]

If you ask the question "is MDF heavier than ______" the answer is always YES (except for one thing), even if the blank has words like tungsten, gold, platinum or lead in it. The stuff is stupid heavy, but one thing is heavier, if you fill that blank with HDF, thats the one time the answer is NO.

[Derek Arita]

Thanks! I appreciate the help. I'm using it to build a speaker enclosure in a small car and weight is an issue.

[Eric Gustafson]

Thanks! I appreciate the help. I'm using it to build a speaker enclosure in a small car and weight is an issue.

MDF is the preferred material for speaker enclosures.

[Jeff Nolan]

I'd go with baltic birch... yeah MDF is preferred for enclosures but part of that is that it is cheap. A good multi-core void free plywood like BB or ApplePly will give you sound quality that is on par with MDF... and let's keep in mind that this is a car not a sound studio. On the plus side, BB is marginally lighter and easy to work with.

[Joe Kieve]

All of the above on MDF. No one has mentioned the dust created when cutting or sanding. It gets everywhere... so wear a dust mask when cutting and sanding. It's also tough on saw blades. They'll wear out quicker on MDF than on plywood.
We used to use a lot of 3/4" MDF in the shop I worked in years ago and we got it in 5' X 10' sheets. It was all two men could do to lift a sheet.

joe

[Van Huskey]

MDF is the preferred material for speaker enclosures.


Generally true mainly due to its uniform density, but there are some esoteric audiophiles who swear by Russian Baltic Birch, I dunno never have seen any raw labeled as such, but mabe a lot is from Russia I just don't know it. It is funny when a budding audiophile finds out that the $20,000 speaker they are lusting after is just "upper east side" particle board covered by 1/32 or less of that beautiful exotic wood.

One place you can save weight in a speaker enclosure is elegant bracing. Most people just use the same 3/4" MDF 'cause they have the sheet but by dropping down to often a very thing bracing material as long as the bracing system is well designed. The extra cost and sparse weight savings are why I would pick MDF, though of no audible superiority in a car I do fnd that is superior to any plywood in a critical listening environment, I have yet to see a cabinet made from ply that was as objective dead as a MDF one. The plywood cabinets, even the ones that are more expensive than German cars tend to "sing".

[Justin M Rovang]

They also use fiberglass as well.