I thought you were using a saw, are you 😕
If you using a router sharpen the bit, don't know about routers much though.
If you using a router sharpen the bit, don't know about routers much though.
Found some interesting exotic BB to add to someone collection.
http://www.environmentalhomecenter.com/shop.mv?CatCode=PRODUCT&ProdCode=EUROPLY
1 1/4" thick, 23 layers, only 240$ per sheet!
http://www.environmentalhomecenter.com/shop.mv?CatCode=PRODUCT&ProdCode=EUROPLY
1 1/4" thick, 23 layers, only 240$ per sheet!
Re: Re: Re: Tips from the dark side
Average MDF (what ever that means) moe is more like about 530,000 lbs/in^3 or psi/in^2 is the units of moe first off. I maybe have gotten them wrong too sorry. Baltic birch maybe 1.8e+6 lb/in.^3 parellel to the what most call grain, if you find a really good piece. Moe of birch parellel to the grain might be like (guessing, but very weak probably) 200,000 lbs./in.^3 (even that is high i would suspect). I never seen it speced for a piece of lumber since lumber is long and grain runs length-wise. We are talkin about plywood, so sheet grain is perpendicular to every adjacent sheet. Therefore, you have 200,000 (example) and 1.8e+3 (if u very lucky) lbs./in.^3. So the result is somewhere inbetween. Also keep in mind thickness increase stiffness. If measuring parellel to outside grain of plywood you might get 700,000 lbs./in.^3, but measuring parellel to the outside grain you might get 400,000 lbs./in.^3. So the Wisa Birch plywood specs I found it was actually less stiff parellel to the plywood facesheets grain than MDF. Baltic Birch is maybe slightly stronger though, I suspect.
You have to understand the molecular structure of wood to understand how a piece functions. Or at least remember some basics wood properties and know how a piece of plywood is assembled. I you do not have that knowledge you make statements like one is stiff or harder or denser when you really don't know.
simon5 said:
Average MDF (what ever that means) moe is more like about 530,000 lbs/in^3 or psi/in^2 is the units of moe first off. I maybe have gotten them wrong too sorry. Baltic birch maybe 1.8e+6 lb/in.^3 parellel to the what most call grain, if you find a really good piece. Moe of birch parellel to the grain might be like (guessing, but very weak probably) 200,000 lbs./in.^3 (even that is high i would suspect). I never seen it speced for a piece of lumber since lumber is long and grain runs length-wise. We are talkin about plywood, so sheet grain is perpendicular to every adjacent sheet. Therefore, you have 200,000 (example) and 1.8e+3 (if u very lucky) lbs./in.^3. So the result is somewhere inbetween. Also keep in mind thickness increase stiffness. If measuring parellel to outside grain of plywood you might get 700,000 lbs./in.^3, but measuring parellel to the outside grain you might get 400,000 lbs./in.^3. So the Wisa Birch plywood specs I found it was actually less stiff parellel to the plywood facesheets grain than MDF. Baltic Birch is maybe slightly stronger though, I suspect.
You have to understand the molecular structure of wood to understand how a piece functions. Or at least remember some basics wood properties and know how a piece of plywood is assembled. I you do not have that knowledge you make statements like one is stiff or harder or denser when you really don't know.
According to that review, the average MOE of a MDF sheet 3/4" thick is 2991 N/mm^2 versus 2254 N/mm^2 for particleboard of the same thickness.
I'd need to find a similar review of MDF versus BB plywood.
http://www.ifss2003.org/pro/topic - 6.pdf
The review start at the page 50, results are at the page 53.
I'd need to find a similar review of MDF versus BB plywood.
http://www.ifss2003.org/pro/topic - 6.pdf
The review start at the page 50, results are at the page 53.
The difference in MOE of mDF, 350,000psi vs. 500,000 psi is based on the thickness of the MDF. the 350,000 psi rating is usually for 1.25" thick, and 500,000 is a high grade .75" thickness MDF.
763 and 624 g/cm^3 wow pretty dense 
There's different kinds of MDF and plywood you have to remember. With plywood grade or money is very impotant part of the proformance, also thickness of sheets and number of them for a given thickness of plywood is important. MDF also varies, but quality is easier to control.
No BB vs MDF sheet will tell you which is stiffer or harder or denser (to a lesser degree), unless they are the specific types that you are going to buy. MDF hardness seems to vary from harder than baltic birch to softer. MDF moe vs plywood moe can vary a lot depending on quality of plywood (number of sheets, grade of wood, thickness of sheet, thickness of actual piece, orientation of grain, etc.), but also make up of the MDF. In some cases I found and mentioned moe of MDF was better than Birch plywood perpendicular to grain (18 mm, 13 ply). I already went over moe enough I feel. All MDF I found are denser than Birch plywood.
For 1.25" Medite got 470,000 lbs./in^3 for the Medite (I or II forgot) spec sheet I was looking at. MOE does not change for MDF too much. I accept it to be farely uniform in make up. I was comparing roughly 3/4" pieces of birch and MDF.
Look at the specs of the specific wood (and manufacture specs if you can too) you are going to buy. And don't let people here tell you general statements about woods. That is the best advice I can give.
There's different kinds of MDF and plywood you have to remember. With plywood grade or money is very impotant part of the proformance, also thickness of sheets and number of them for a given thickness of plywood is important. MDF also varies, but quality is easier to control.
No BB vs MDF sheet will tell you which is stiffer or harder or denser (to a lesser degree), unless they are the specific types that you are going to buy. MDF hardness seems to vary from harder than baltic birch to softer. MDF moe vs plywood moe can vary a lot depending on quality of plywood (number of sheets, grade of wood, thickness of sheet, thickness of actual piece, orientation of grain, etc.), but also make up of the MDF. In some cases I found and mentioned moe of MDF was better than Birch plywood perpendicular to grain (18 mm, 13 ply). I already went over moe enough I feel. All MDF I found are denser than Birch plywood.
mbutzkies said:
For 1.25" Medite got 470,000 lbs./in^3 for the Medite (I or II forgot) spec sheet I was looking at. MOE does not change for MDF too much. I accept it to be farely uniform in make up. I was comparing roughly 3/4" pieces of birch and MDF.
Look at the specs of the specific wood (and manufacture specs if you can too) you are going to buy. And don't let people here tell you general statements about woods. That is the best advice I can give.
I agree that MDF is denser, just want to use plywood in my next projects with subwoofers to save weight and use stiffer wood to push resonances higher in the passband.
I'll still use MDF for speakers because of the better damping and you can't push the resonances you must damp them.
I'll still use MDF for speakers because of the better damping and you can't push the resonances you must damp them.
I make my cabinets either from Baltic Birch ply (Finland kind with 11 layers for 15 mm/0.6") or MDF.
The Baltic birch is definitly MUCH harder than MDF, the difference is quite large (say huge), it's also stiffer. The density is often more or less the same but from time to time the MDF has a higher density. For use at home MDF is advisable because of the higher density and many agree that it "sounds" better.
Knowing the above however it shouldn't be suprissing that for proffesional audio (PA) Baltic birch is the standard, in the industry as well for the diy'er. The (Finland) baltic birch is without doubt the overal stronger material. With MDF for instance I can double the dept with my router to that of the birch. Making one cab out of each material will take away any doubts that you might have.
Mvg Johan
Rademakers said:
Tell me measurements and I will believe you.
These are samples I found:
MDF is 1000-1500 Janka and birch is about 1260, what else can I say? Janka is how many lbs. it takes to embed a .44" half-sphere into the wood.
Also for the 11 layer 15 mm Wisa (England manufacture I think) birch plywood, MDF is about the same stiffness perpendicular to grain if not stiffer. The MDF I looked at Medite was stiffer perpendicular to the grain of the plywood.
I not giving my opinion here. This is how the products I looked at preformed in tests.
These results also make a lot of sense if you know the molecular structure of wood and a little about plywood. Or understand that wood is not very stiff at all in the radial or tangential directions.
I wish some one would believe me
I would like to note that the more you pay for the Plywood the better the MOE will be, but hardness and density will not change much. Paying more for MDF will probably not get you too much more MOE, but I am not certain.
The 350,000 psi MOE is an ANSI 208.2 spec governing MDF.
when you order Premium MDF you generally get Ansi 208.2 spec'd product. Branded MDF usually has the 500,000 psi MOE you talk about, and then most suppliers only carry 3/4 unless you special order, where the common 208.2 mat'l is easily available.
Generally, The thicker the panel the lower the MOE, and the more likely they will just meet and not exceed the spec.
As far as I know georgia pacific is the most common supplier.
when you order Premium MDF you generally get Ansi 208.2 spec'd product. Branded MDF usually has the 500,000 psi MOE you talk about, and then most suppliers only carry 3/4 unless you special order, where the common 208.2 mat'l is easily available.
Generally, The thicker the panel the lower the MOE, and the more likely they will just meet and not exceed the spec.
As far as I know georgia pacific is the most common supplier.
hm, wasn't the starter of the thread looking for some more hands-on pointers in working with plywood?
@Topicstarter: So in theory MDF is harder to work with but in practice however you will find more resistance coming from the (fins) baltic birch, making the use of good tools a key element.
I wouldn't saw the panels myself unless I had very good equipment, like the ones they use at the woodshop as otherwise it can splinter or get burnmarks.
It can also splinter when you drill holes in it, so put a piece of scrapwood underneed.
One downside of Baltic birch is that the toplayer can come off under certain circumstances. Glue doesn't realy soak in because it can't get by the glue layer in between. So to make the strongest glue-connections, you can enlarge the surface area or cut the panels under an angle of 45 degrees. It's not completely neccesary because as soon as the cabinet is completed it will have much more strenght. But if you aim for the best construction just keep it in mind.
Benefit of the cutting under 45 degrees (in the woodshop) is that you can make the cabinet in just a few hours while using nothing but glue and clamps.
When using screws into the sides of the panels you should pre-drill the holes with an drill 1 or 2 mm smaller (as with MDF).
Did you actually test the same birch as stated in my post? I don't think you did as I see a lot of different names coming by and strange theory.
Mvg Johan
I wouldn't saw the panels myself unless I had very good equipment, like the ones they use at the woodshop as otherwise it can splinter or get burnmarks.
It can also splinter when you drill holes in it, so put a piece of scrapwood underneed.
One downside of Baltic birch is that the toplayer can come off under certain circumstances. Glue doesn't realy soak in because it can't get by the glue layer in between. So to make the strongest glue-connections, you can enlarge the surface area or cut the panels under an angle of 45 degrees. It's not completely neccesary because as soon as the cabinet is completed it will have much more strenght. But if you aim for the best construction just keep it in mind.
Benefit of the cutting under 45 degrees (in the woodshop) is that you can make the cabinet in just a few hours while using nothing but glue and clamps.
When using screws into the sides of the panels you should pre-drill the holes with an drill 1 or 2 mm smaller (as with MDF).
If the theory doesn't match the reality the conclusion should be that there is something wrong with the theory.
Did you actually test the same birch as stated in my post? I don't think you did as I see a lot of different names coming by and strange theory.
That's why every layer is turned 90 degrees clockwise compared to the previous layer.
I do not doubt the outcome or the tests, I do doubt your conclusions and for good reason. Think about it for a sec. One day you will find yourself on the other side of the line and realize the limits of science. Or limmited science for that matter.
Mvg Johan
Rademakers said:
No theory just numbers. Go find numbers then talk.
Rademakers said:
Birch is not baltic birch if I remember, but is close enough to prove my point. Go find baltic birch. $250 piece is impressive, but who will buy it? Moe goes up with price. Moe depends more on the quality of wood used more than species of Birch. Don't believe me I only studied wood building materials four 3 years at university. How long you study wood for? What you do, hammer nails into wood your whole and think you are an expert?
Rademakers said:
No, that is not why. Wow, you are really expert, eh?
Rademakers said:
Not my tests. Out come is in the numbers I posted. No conclusions just numbers
http://www.google.com/url?sa=t&ct=r...97.pdf&from=cov&t=agc&ei=ypofQ8DxB8XqaNqNoMQD
http://www.google.com/url?sa=t&ct=r...wood.com/MediteII.pdf&ei=L5sfQ969M63OaIHgrYwN
Some more numbers...
This birch plywood is rated at 2 170 000 PSI.
http://www.hardwoodinfo.com/species_guide/display_species.asp?species=yellowbirch#
Click on the Strength and mechanical properties link.
This birch plywood is rated at 2 170 000 PSI.
http://www.hardwoodinfo.com/species_guide/display_species.asp?species=yellowbirch#
Click on the Strength and mechanical properties link.
FWIW, all these numbers being thrown about are (perhaps 
) useful, but what about the relative sound differences of BB compared to MDF?, bearing in mind it's possible to fashion perfectly good cabinets using either medium!
) useful, but what about the relative sound differences of BB compared to MDF?, bearing in mind it's possible to fashion perfectly good cabinets using either medium!On the last project that I used ply, even the tiny brad nail holes (which I filled) show up when I started to lacquer. I promised myself to never use any nails/screws and use wood filler again.
With that said, I think someone had brought up a good idea. Cut at 45degress and just simply glue and clamp overnight.
I don't really understand why some would argue over the density of mdf and bb ply. If you simply need to make the cabinets stronger, just BRACE!!!
There might be a difference in how each cabinet would sound, but I'm not an expert in that.
With that said, I think someone had brought up a good idea. Cut at 45degress and just simply glue and clamp overnight.
I don't really understand why some would argue over the density of mdf and bb ply. If you simply need to make the cabinets stronger, just BRACE!!!
There might be a difference in how each cabinet would sound, but I'm not an expert in that.
Working with (machining) Baltic Birch plywood
With respect to cutting it on a table saw, I would recommend a high quality 80 tooth TCG grind or modified ATB saw blade, and ensure it is kept sharp I prefer the FS Tool brand or Leitz- if you can get them... feed slowly at an even pace.. Same principle with router bits - use high quality bits (avoid most Asian made bits, which frequently have inconsistent grind and carbide quality) and feed slowly and evenly.
Oh, and wear eye and hearing protection :>)
I bought 5' x 5' sheets of Baltic birch (3/4") to build my Avalanche 18 subwoofer cabinet out of... :>)
Best of Luck!
Bruce
With respect to cutting it on a table saw, I would recommend a high quality 80 tooth TCG grind or modified ATB saw blade, and ensure it is kept sharp I prefer the FS Tool brand or Leitz- if you can get them... feed slowly at an even pace.. Same principle with router bits - use high quality bits (avoid most Asian made bits, which frequently have inconsistent grind and carbide quality) and feed slowly and evenly.
Oh, and wear eye and hearing protection :>)
I bought 5' x 5' sheets of Baltic birch (3/4") to build my Avalanche 18 subwoofer cabinet out of... :>)
Best of Luck!
Bruce
With all these figures being quoted over this long posting, would those (Jimmy154, simon5, mbutzkies) like to put their figures (only, please) in a separate post? I"m not sure what the different measurments available are, but density, hardness (ie. how hard to put a dent in it), elasticity (how hard to bend it), compression (how hard you can sqeeze it) and breaking point (how many people can stand on it) could be of great help at some stage.
I must admit that although the ply is prettier to work with (I love it when you do 45 degree trimming on it), I find that 1" MDF seems deader to me for my boxes. Maybe it's the glue.
Sorry if this is a bit off-topic🙂
I must admit that although the ply is prettier to work with (I love it when you do 45 degree trimming on it), I find that 1" MDF seems deader to me for my boxes. Maybe it's the glue.
Sorry if this is a bit off-topic🙂
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