MDF and it's little secrets

[srm51555]

I've been researching how to safely handle MDF before starting to build my DIY M2 cabinet and have read a lot of information featuring safety issues with formaldehyde content through the board "gassing" and particle inhalation when working with it unfinished. I understand this is the miracle wood for speakers, but do not want to over look the fact that this wood can be gassing the air all over the house (living in Wisconsin the summers are only 2 months of the year and the rest of the year the house is sealed up, not really but it seems like it :p ) My original plan was to have someone precut the panels because I don't have a proper dust collection system and I was going to cut the holes and assembly/brace the cabinet. Would painting the cabinet with a non-latex based paint seal in all of the bad stuff (both inside and out? or is there a safer alternative that can be used? Thanks, Scott

[audiomagnate]

I've been researching how to safely handle MDF before starting to build my DIY M2 cabinet and have read a lot of information featuring safety issues with formaldehyde content through the board "gassing" and particle inhalation when working with it unfinished. I understand this is the miracle wood for speakers, but do not want to over look the fact that this wood can be gassing the air all over the house (living in Wisconsin the summers are only 2 months of the year and the rest of the year the house is sealed up, not really but it seems like it :p ) My original plan was to have someone precut the panels because I don't have a proper dust collection system and I was going to cut the holes and assembly/brace the cabinet. Would painting the cabinet with a non-latex based paint seal in all of the bad stuff (both inside and out? or is there a safer alternative that can be used? Thanks, Scott

You're still going to get sawdust, and that's where the bad stuff is. Outside with a good mask and a dust collection system and you should be fine.I had a small speaker manufacturing facility right after college (KAS Audio) with neither and breathed the stuff in all day and I'm still here to talk about it...

[macaroonie]

MDF has found a happy home in the loudspeaker world but it is the pits to work with unless you have the proper gear.
I would suggest you use Baltic Birch plywood with BB/ BB faces ( not pristine outer veneers ) It's more expensive than MDF but is actually pleasant to work with and has dimensional stability in line with what MDF offers.
In the context of an M2 build the uplift in cost is negligible.

[srm51555]

Thank you both, A proper shop is what I lack unfortunately, so the Baltic Birch does sound nice to use.

[badman]

Yes, use Baltic birch, it's a better material. MDF can be fine once it's sealed but the sawdust is misery squared, and sealing the edges carefully MUST be done to get nice results.

[NickH]

mdf doesn't out gas just siting there. Plus I honestly thing the exposure concentration from dust inhalation isn't that high. The process of cutting it is probably the cause from friction heating. That being said inhaling any particulate isn't good. The first time I worked with mdf I didn't wear a mask and my allergies were going nuts for a week. The dust mask does help.

You be the judge but I wouldn't be too worried about the formaldehyde when your working with it once and a while. Not like its a job. See if the OSHA specifics exposure levels if our really worried.


I personally like mdf over plywood. Once I found confirmat screws that is.

Nick

[macaroonie]

Yes, use Baltic birch, it's a better material. MDF can be fine once it's sealed but the sawdust is misery squared, and sealing the edges carefully MUST be done to get nice results.

^^^ This.

This may not apply in your case but watch for it , I was using BP recently and although there are stringent standards that apply to this type of ply I noticed variations in general quality.
Finnish seems to be the best with Latvian and Russian just behind. I did get a couple of boards that were Polish , they seemed to be less well put together. More knots and plug repairs and seemingly less dense.
This makes sense as the more northern trees will be slower growth and hence denser with tighter grain.

Grading : http://www.wolstenholme.com/plywood-products/baltic-birch/grading/

[Champster]

I've found through experience that when you're cloning, it is best to minimize the changes to the original. Otherwise, what you wind up with is very different than that which you were trying to copy. So with that said, if you're building a M2 Clone, this is from the brochure:

M2 Enclosure
Small Footprint
Extended Bass PerformancePatented Low Frequency Port Design
Extended low frequency performance and high SPL can be theformula for unwanted resonance. The M2 enclosure is constructedof rigid 1" MDF and with the aid of JBL’s interferometer, extensivelybraced for rock-solid stability at the system’s full rated power. Theenclosure incorporates a JBL patented Slipstream port design withinternal flares that ensure low frequency efficiency while eliminatingnoise caused by port turbulence. Architecturally elegant, the M2enclosure occupies a relatively small footprint, and can betransported to various working environments,

[srm51555]

Grading : http://www.wolstenholme.com/plywood-products/baltic-birch/grading/

Good to know Thanks


I've found through experience that when you're cloning, it is best to minimize the changes to the original. Otherwise, what you wind up with is very different than that which you were trying to copy. So with that said, if you're building a M2 Clone, this is from the brochure:

The M2 enclosure is constructedof rigid 1" MDF and with the aid of JBL’s interferometer, extensivelybraced for rock-solid stability at the system’s ,

This has also been a factor in my decision process.

Does anyone know at what thickness does the BB have to be to exhibit the same Speaker cabinet producing qualities?

[Champster]

Does anyone know at what thickness does the BB have to be to exhibit the same Speaker cabinet producing qualities?

I don't know that answer, but one other thing to consider is that mftrs (JBL included) make decisions regarding materials partly based on profitability. BB is far lighter than MDF and saves a ton of money on freight. When you ship as many boxes as JBL, it makes a sizable difference in your bottom line. For us hobbiest, we shouldn't give the financial aspect to weight a moments notice. If you wear a dust mask, eye protection and hearing protection, there is no reason not to go with MDF. It is easier to cut, makes a better painted finish and is much more dense than BB. But that said, these are YOUR speakers and you should do what YOU want.

[badman]

I don't know that answer, but one other thing to consider is that mftrs (JBL included) make decisions regarding materials partly based on profitability. BB is far lighter than MDF and saves a ton of money on freight. When you ship as many boxes as JBL, it makes a sizable difference in your bottom line. For us hobbiest, we shouldn't give the financial aspect to weight a moments notice. If you wear a dust mask, eye protection and hearing protection, there is no reason not to go with MDF. It is easier to cut, makes a better painted finish and is much more dense than BB. But that said, these are YOUR speakers and you should do what YOU want.

MDF is less expensive and shipping doesn't negate that. It is, however, easier to paint, if you use care on the edges

[Mr. Widget]

MDF does continue to out gas formaldehyde for some time after the woodworking is done. This is why there is hospital grade formaldehyde free MDF. Beyond that, I believe many of the multi-ply birch plywoods use formaldehyde based glue as well.

As for ideal speaker building materials I like a combination of the two.


Widget

[just4kinks]

Nobody has mentioned yet how MDF will dull your blades. And even a few drops of water will cause it to blister, a lot and it will degrade and fall apart.

+1 for baltic birch.

[4313B]

I can't stand baltic birch. I'm glad some of you guys like it. I personally prefer to walk on it. Like Mr. Widget, I have used a combination of baltic birch and MDF on a few projects in the past.

I've never had any issues with MDF. JBL turned me on to NovaPly when I was around 15 years old and I've never looked back. Prior to that I was using mahogany in junior high wood shop class, not a very good wood to build loudspeaker enclosures from :rotfl:

[srm51555]

Nobody has mentioned yet how MDF will dull your blades. And even a few drops of water will cause it to blister, a lot and it will degrade and fall apart.

+1 for baltic birch.

I forgot how awesome your 4345's turned out. What thickness BB did you use? My plan for today was to sandwich two 0.75" sheets together to hopefully achieve a similar deadness of MDF. Bracing would be the same as the stock M2.

[cooky1257]

If you were working MDF day in day out it's wise to be very cautious(ply too btw) but one off projects in an open garage say, I wouldn't be too worried except when routing, mask is mandatory

really. Edges are an issue in finishing-so I veneer or only have exposed edges on the rear.

[NickH]

Did some research on this out gassing problem. And the problem is not limited to mdf. These glues are used to make interior and exterior grade plywoods too. The rates of out gassing do increase with temperature. But as I thought these rates are very small. Max rates for mdf are around 2 milligrams per square meter. But the rates for plywood aren't much lower. The rate of outgassing decreases with time. I don't know if its linear rate of change or not though, but I'd bet its logarithmic.

I'd bet most of this stinkyness happens while its sitting at the store or during transportation to the store. That being said a dust mask won't do anything to protect you from the formaldehyde while your working with the material. You needs a respirator that filters organic compounds.

Nick

[cosmos]

It's sad really.. MDF is nice material in most respects to work with, but virtually any time I spend a good part of the day cutting it, I get sick for a few days after.. and I mean stay home from work sick with massive headache and flu like symptoms, even with a dust mask and collection going. I have now banned it from my workshop.

I will have to check out Novaply and hospital grade MDF. Never heard of either material before. Thanks!

4313B, do you know where to get Novaply locally?

[just4kinks]

I forgot how awesome your 4345's turned out. What thickness BB did you use?

I used 1" (actually 24mm) throughout with more bracing than the stock design.


My plan for today was to sandwich two 0.75" sheets together to hopefully achieve a similar deadness of MDF. Bracing would be the same as the stock M2.

Have you considered doing something fancy like sandwiching a layer of damping material in there as well?

[Mr. Widget]

It's sad really.. MDF is nice material in most respects to work with, but virtually any time I spend a good part of the day cutting it, I get sick for a few days after.. and I mean stay home from work sick with massive headache and flu like symptoms, even with a dust mask and collection going. I have now banned it from my workshop.

I will have to check out Novaply and hospital grade MDF. Never heard of either material before. Thanks!

4313B, do you know where to get Novaply locally? Look for Medite II. It is a brand of US made formaldehyde free MDF. Also, you may want to get a powered respirator. I use one and while a bit bulky you can wear it all day without getting a hot sweaty face.


Widget

[rdgrimes]

A number of flooring materials also have Formaldehyde in them.

[srm51555]

I used 1" (actually 24mm) throughout with more bracing than the stock design.
Have you considered doing something fancy like sandwiching a layer of damping material in there as well?

I have not, any suggestions for me or others reading?


If you were working MDF day in day out it's wise to be very cautious(ply too btw) but one off projects in an open garage say, I wouldn't be too worried except when routing, mask is mandatory

really. Edges are an issue in finishing-so I veneer or only have exposed edges on the rear.

I found a friend that will CNC the baffle, so that will reduce the working time with it even more. Now it's just controlling the gassing. Painting seems to be the easiest, with sealing the edges with drywall compound before painting. I keep on coming back to MDF when thinking about Mr. Widget's experiment with equivalent plywood cab's vs MDF cab's and clearer midrange from the MDF. Also I haven't found anything to support the fact that if I went thicker it would deaden the cabinet, but the BB does look pretty. All I know I better make my decision soon, it's getting colder by the day here. This might be a can of worms but does everyone glue/screw or just glue?

[srm51555]

Look for Medite II. It is a brand of US made formaldehyde free MDF. Also, you may want to get a powered respirator. I use one and while a bit bulky you can wear it all day without getting a hot sweaty face.


Widget


Did some research on this out gassing problem. And the problem is not limited to mdf. These glues are used to make interior and exterior grade plywoods too. The rates of out gassing do increase with temperature. But as I thought these rates are very small. Max rates for mdf are around 2 milligrams per square meter. But the rates for plywood aren't much lower. The rate of outgassing decreases with time. I don't know if its linear rate of change or not though, but I'd bet its logarithmic.

I'd bet most of this stinkyness happens while its sitting at the store or during transportation to the store. That being said a dust mask won't do anything to protect you from the formaldehyde while your working with the material. You needs a respirator that filters organic compounds.

Nick


If anyone else has any safety tips or tricks please let us know this is all good stuff

[hsosdrum]

I have not, any suggestions for me or others reading?


Auralex makes a limp-mass vinyl sound deadening material for room isolation. It's designed to serve as meat in a drywall sandwich—perhaps it could also be used as the meat in an MDF sandwich?

http://www.auralex.com/product/sheetblok-sound-barrier/

[4343]

... This might be a can of worms but does everyone glue/screw or just glue?

I've done both, the screws are used when I want to make something permanent, I leave them off for experiments. One (unfinished) experiment even has a few panels that were edge glued because they were not big enough. Still holding after 5 years.

You could do a ply shell with MDF lining if you really want the look of the ply, or just need durability for transport. That's what I did for some PA boxes, not a complete liner, but the baffle and slot ports are all MDF, while the outside is all Baltic Birch. I used a case of Liquid Nails coating the inside and all the braces. Easily passes the knuckle test, it's very dead. And it turns out 4 2226's + 2446 can simulate real drums set pretty well using trigger pads...

[Mr. Widget]

You could do a ply shell with MDF lining if you really want the look of the ply, or just need durability for transport. That's what I did for some PA boxes, not a complete liner, but the baffle and slot ports are all MDF, while the outside is all Baltic Birch. I used a case of Liquid Nails coating the inside and all the braces. Easily passes the knuckle test, it's very dead. And it turns out 4 2226's + 2446 can simulate real drums set pretty well using trigger pads...This reminds me of some subs I built a few years ago for our late friend Scott Fitlin. There are a couple of interesting features to the project.

http://www.audioheritage.org/vbulletin/showthread.php?9812-2242H-Subs-for-Big-Bass (http://www.audioheritage.org/vbulletin/showthread.php?9812-2242H-Subs-for-Big-Bass)


Widget

[DavidF]

I have not, any suggestions for me or others reading?



I found a friend that will CNC the baffle, so that will reduce the working time with it even more. Now it's just controlling the gassing. Painting seems to be the easiest, with sealing the edges with drywall compound before painting. I keep on coming back to MDF when thinking about Mr. Widget's experiment with equivalent plywood cab's vs MDF cab's and clearer midrange from the MDF. Also I haven't found anything to support the fact that if I went thicker it would deaden the cabinet, but the BB does look pretty. All I know I better make my decision soon, it's getting colder by the day here. This might be a can of worms but does everyone glue/screw or just glue?

I generally use MDF for projects. It is cheaper (especially if you make mistakes like I do), generally easier to find and does not splinter like ply. The big thing to learn in working with MDF is that its working surfaces are soft. As mentioned above it creates a fine dust and it sure does dull cutting tools (esp. router bits). But it is the relative softness that is the issue. It cannot be used effectively to provide a finish surface. It will show tooling marks, bumps and dings. Never go near it with a power belt sander. I always use wood veneer as the finish to MDF that provides a good flat surface and covers up surface issues.

As to screws v. glue, I always go with glue and clamps whenever possible. Screws are OK for assembly to set the glue if you don't want or need to invest in a host of clamps. Just don't count on them to hold permanently (for that reason I pull out all screws in the final assembly) and take care with drilling in MDF panel edges.

MDF is a dense material giving it some mass potential in mitigating resonance but it is not very stiff. Quality plywood has better stiffness but is not as dense. I tend to brace an MDF cabinet more so than I would using a good plywood. If you are considering a large enclosure (in terms of width and height) I would recommend using a heavy ply for the baffle and MDF for the remaining panels. Depending upon the design, the driver baffle holes can eat up a good part of the surface area so the stiffness can be important.

Again, it you are intending a painted finish MDF, be prepared for a lot of work to prep the surfaces. I am not sure about drywall compound as a filler. I worry about shrinkage. If you have used it before with good results, then fine.

Finally, I always spray paint the interior. More to capture the dust than to prevent gas seepage.

Good luck and make always make it fun...

[Ducatista47]

When it comes to cutting panels, you might seek a real, non Big Box locally owned lumber yard. There is one near me (a few miles down the street) here in Peoria, Illinois.

It has a cabinet shop and they charge $35/hour to cut. I purchased two sheets of 3/4 inch very high quality MDF and an hour from them for close to $100. I had sketched out the cuts on a piece of paper, old school. Every piece was perfect. They fit on the back seat of my subcompact sedan. I bought a router and a ton of clamps and using Macaroonie's method built what might be the most solid cabinets in the state. Per Ian's advice the baffles were two panels screwed and glued for a 1 1/2 inch thickness.

I don't know how rare a lumber yard like this one is these days, but worth looking for and definitely worth finding. I know this one will disappear when the elderly owner passes away. Lacking any such luck, look for a stand alone cabinet shop, probably much easier to find. Why buy all the dust collection equipment and professionally sized table saw & specialty blade for an occasional project?

Clark

PS Not trying to discourage having a full shop if you do a lot of this. I have visited SAEMAN's (Rick's) shop and it is a wonder what he has done with a tiny garage space. My jaw dropped at the baffle templates (Delrin?) he has made for 4345s, 4350s, etc. Only one is needed for each as you turn it around to get the other channel.

[srm51555]

I've decided to go with the 1" MDF and use the Widget BB "sandwich" later when finishing them. This was a hard decision so thanks for all of your help. The Baltic Birch projects are beautiful, but acoustically I felt I needed to mirror the M2 as close as possible. Having the MDF cut and baffle CNC'd by the people with the proper tools eliminates much of the "dirty work". Maybe Speaker exchange should offer a knock down kit :hmm: . Paining the wood inside and out should eliminate much of the emissions created. In the end if I decide to build another cabinet it's not like I can't find another JBL woofer that like's ~5cf of space. :rotfl: