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-   -   Cabinet Material??? (http://www.diyaudio.com/forums/multi-way/28234-cabinet-material.html)

FrankRoss 14th February 2004 09:37 PM

Cabinet Material???
 
A few years ago when I built my first speaker cabinets I purchased "3/4" MDF" from a specialized lumber store (actually a lumber mill).

Today I purchased from Lowes what was labeled as 3/4" MDF, but this stuff is COMPLETELY different than what I purchased a few years ago.

The MDF I bought years ago was a very dense "particle" board. It was heavy, rigid and made for a very strong cabinet (NOT to be confused with "chip board").

But this stuff from Lowes is more like a very dense paper, which when banged flakes off at the edges. The sales people at Lowes insists that it's definately MDF. After it was cut, the residue is like very fine baby powder.


Is what I purchased at Lowes the right stuff for my new cabinets? Will it or won't it break apart when I try to put the lug bolts near the speaker opening for mounting the speakers? I'm really confused and would appreciate any explanation, and opinions of what the best material for cabinets would be.

(the new cabinets will be 36" wide X 52" high X 19" deep.)

Please help!

leadbelly 14th February 2004 11:08 PM

From your description, it sounds like what you have purchased recently is MDF and what you purchased years ago was actually particleboard. MDF looks like pressed sawdust, there is no visible woodchip pattern. It's not that uncommon a mistake; some of the home reno shows on TV misidentify it as well, which drives me crazy.

FrankRoss 14th February 2004 11:46 PM

Still Confused
 
Please bear with me, I'm a novice...

The original Bozak Concert Grand cabinets were made of a dense particle board with plywood baffles. That is why I used dense particle board for the first pair that I made a few years ago.

So I understand, the 1/4" pressed-paper MDF that I JUST PURCHASED is what I really should use???

Also, since this new MDF doesn't seem as strong as the fine-grained particle board, how should I attach the speakers to the baffle? Once I cut the 13 inch hole for the woofer, the 4 mounting studs for the speakers will only be 1/4" away from the edge. Will the MDF break apart close to the edge?

I'm really nervous about using this new MDF, since I'm only accustomed to working with true hardwoods and very dense and heavy particle boards (not chip-board).

I can already see the edges of the 3/4" MDF flaking apart and I haven't even started to work with it yet! Do you have any tips/tricks to working with MDF?

moses 15th February 2004 12:19 AM

MDF is easy to work with. It has no grain or particle orientation, likewise it can be cut with just about anything, along with planed or jointed(tho not recommened), routed, shaped, and makes an extremely strong bond with PVA glue. Also note if what you have is MDF it will be heavier then particle board or plywood, 100-110lbs a sheet depending on the manufacturer. It has a decent screw hold capability, tho screwing into the ends of MDF will often cause it to split if you don't pre-drill. You can also use (void free)Baltic Birch which Lowes probably has too.

leadbelly 15th February 2004 12:25 AM

Well, I don't know what the speaker you refer to even looks like, so I can only speak in generalities.

Yes, MDF is weaker in tension and compression than a high grade particleboard. However, 3/4" thick (meaning 3/4" wide glue surface) is generally considered strong enough for all boxy, rectangular speakers. When the speaker design starts to impinge on the glue surface area, something else must make up for the lost strength. That is why you see some speaker designs, say with a large round-over radius, where techniques like corner braces, batting strips behind the joint, or a baltic birch and MDF sandwich are used.

If you are only 1/4" from the edge when mounting the driver, than means the entire side piece is behind the hole.Just pick out a generous screw length and pre-drill with drill bit 1 or 2 sizes smaller.

As for working with MDF, yes, you can ding the edges, but it also holds a very nice edge when milled. I just handle the pieces as gently as I can.

pne123 15th February 2004 12:31 AM

I am new to building speaker cabinets but not to woodworking.
W/ that said, you bought mdf at lowes. Did you you really get 1/4" thick or is that a typo? If so, you are way to thin. I used 3/4 and doubled it up to make 1.5" on the baffle.

If you use any screws, predrill them all first or it will destroy the mdf. I use threaded inserts for all driver mounting. All you have to do is drill a hole and screw in the insert. Any good hardware store should have them. I go to orchard.

any hardware 1/4" from an edge is to close.

mdf cuts clean but is hard on your blade.

oh yea, use alot of glue. it really soaks it up. especially where it has been cut.

here is shot of the very begining of my first project

http://dodgetrucks.org/photopost/dat...7small-med.jpg

hope this helps

FrankRoss 15th February 2004 01:25 AM

Sorry, that (1/4") was a typo - I did purchase 3/4" MDF.

I'm still confused. I always try to do as much research as I can ahead of time, that's why I'm stumped. Searching the Internet for MDF info, from what I can see according to the pics, it is what I bought years ago - very fine particles of wood glued together. There is no grain, but fine wood particles are very evident.

I know that OSB and chip board are strips or small flakes of wood glued together. But what I understand "particle" board to be is just that - very small particles of wood glued together to form a sheet.

The MDF from Lowes does not look like Medium Density Fiberboard. To me, it looks (and acts) like recycled paper glued together. It looks more like white plastic than anything else, but "feels" like ordinary paper compressed together. The edges flake off very easily. This is why I'm concerned about using it to make cabinets that weigh around 175 lbs. each (175 lbs. is NOT a typo).

If the MDF is prefered due to its accoustical properties, I will attempt to use it. I just hope what I bought is actually what everybody here (and Lowes) is refering to as MDF.

Finally, why are most of the manufactured cabinets that I see made of particle board, such as McIntosh, KEF, Martin Logan, etc...???

I won't keep going on about this and will end my post here, but as much info as you can offer would be appreciated.

pne123 15th February 2004 02:26 AM

http://www.lungster.com/l/speakers/mdffaq/mdf.html

check out this link.

he does have one picture of mdf. not very good one since it is veneered.

has partical board right next to it.

pne123 15th February 2004 02:30 AM

this is mdf.

http://dodgetrucks.org/photopost/data/66mdfsample.jpg

Tiggerfip 15th February 2004 02:35 AM

I bought my MDF from Home Depot or a local lumber yard because I think there are some differences in the quality of MDF. I personally prefer Plum Creek brand.

As noted - real mdf has no grain, no fibers, no texture at all. It is great because it has no voids - great for speakers. There is another type of MDF on the market which is sold at Limback's in Seattle, WA which is easier to mill and produces a better edge without sanding - it has a specific name I can not remember at the moment. When cut MDF is horrible for the woodworker. Just ask any finish carpenter - we hate the stuff because of the fine dust it produces when cut; it gets everywhere even with a Fein or Wap vacuum hooked up to your table saw.

No - there is no way that Lowe's carries void free birch plywood much less the 13ply birch plywood that would be optimal for speakers if you do not like to veneer. You can get it here in Seattle at specialty wood products stores - i.e. Crosscut Hardwoods, Blackstock Lumber, etc...


I think I am at a loss about the particle board though. When I think of particle board I think of the light weight product used in inexpensive and sometimes expensive furniture sold at Ikea and elswhere. I am sure the speaker manufacturers use it because it is very inexpensive - and it light so the manufacturing process is not hendered by 100 pound plus sheets of material to move around.

P.S. As far as connections go with MDF I prefer butt joints and when possible I use hurricane nuts (t-nuts without prongs) which stay in very nice or when I do not have access to the back of the sheet like when I am attaching a base to the edge of a 3/4 sheet the brass inserts. But be sure to use the course outer thread inserts - not the fine outer threads with MDF. They go in and hold much better.


P.S.S. Try reading this:

http://www.lungster.com/l/speakers/mdffaq/mdf.html


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