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 ) 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 ) 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-...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-...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

[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.