Hi all, this is my first post on diyaudio! I've seen the other MDF prep threads, but there's some questions I couldn't find the answer to.
Anyways, I'm building 4 subwoofer enclosures with 3/4" MDF and trying to do it right (or right as I can) this time and the more I look into it the more my head spins. I'm a perfectionist and this is the first time I'm painting a box rather than carpeting, and I think I now understand why they're carpeted. I've been to HD, amazon, and partsexpress so much I'm sick of it and just going to make due with the things I've already bought.
Thanks in advance for any help.
Anyways, I'm building 4 subwoofer enclosures with 3/4" MDF and trying to do it right (or right as I can) this time and the more I look into it the more my head spins. I'm a perfectionist and this is the first time I'm painting a box rather than carpeting, and I think I now understand why they're carpeted. I've been to HD, amazon, and partsexpress so much I'm sick of it and just going to make due with the things I've already bought.
- MDF SEALING: I settled on the zinsser cover stain but so many of you push shellac or bin(shellac). Can anyone tell me why one would be better than the other in regards to sealing/application/and post-prep (ex. sanding smooth)? Ultimately does it really matters which I use?
- APPLICATION METHOD: I've always done aerosol, but it's been getting costly with the number of cans. I was thinking of foam rolling the next 3 enclosures instead. As far as sealer/primer/color/top coat, is there a difference between rolling and spraying as far as build/application/cure time/texture/post-prep?
- PAINTING WITH ENAMEL: Because of the oil based cover stain, I went with Krylon glossy paint + primer aerosol (was told it was an alkyd-enamel/oil enamel mix) because it had the color I wanted and was cheap. I'm going to let the sealer cure for 7 days before applying the color/top coat. Due to the recoat time restrictions with the enamels (recoat < 4 hrs or >24 hrs), what's the best way to approach # coats, recoat times, and sanding to try to obtain a piano finish? Will doing 2 coats with 1 hr drying in between then waiting 24 hrs, sanding, and repeating work? The transition between color and topcoat will be 1 coat paint, 1 coat top coat, then continue as top coat.
Thanks in advance for any help.
I think the shellac products are better for sealing, they dry quicker too and have better adhesion. But what you have will do the job.
Foam roller is a good method. It will let you get down a good build of primer than can be flatted back generously. It will take longer to dry and be initially more work flatting the texture back but it should be quick enough. Using spraycans would cost a fortune and probably end up taking just as long as you would need many more coats for the same thickness.
You might have a problem trying to flat and buff an enamel topcoat. They cure over a long time and are not designed to be flatted back at any point. I'd consider returning the cans for a lacquer gloss finish.
Foam roller is a good method. It will let you get down a good build of primer than can be flatted back generously. It will take longer to dry and be initially more work flatting the texture back but it should be quick enough. Using spraycans would cost a fortune and probably end up taking just as long as you would need many more coats for the same thickness.
You might have a problem trying to flat and buff an enamel topcoat. They cure over a long time and are not designed to be flatted back at any point. I'd consider returning the cans for a lacquer gloss finish.
Forgot to add, the shellac sealers are just sealers, they are not sandable primers with build. I doubt the Cover Stain has any build or sanding properties either, that's not what it's meant for. You need an automotive primer for building and sanding.
As much as I hate both paint finishes and MDF for speakers, on the few occasions I've done that, I found the following:
1) Spray guns - with a little practice either turbine or compressed air driven HVLP guns will yield far better results than brush/roller - particularly on curved or faceted surfaces. You can get decent results and high product yield with a $50 gravity feed HVLP gun from your local autobody shop, or you can spend over $1000 on a pro-rig
2) High solid catalyzed primer/sealers such as ML Campbell Clawlock, and their Resistant paint or tinted Magnamax lacquers are widely used hereabouts by the high end residential kitchen cabinet trade. They are formulated specifically for wood finishing.
3) The more time and products you spend on the filling, priming / sanding, ( at least 2 coats) the better your final results. The primer/sealers are much easier to sand down than most of the high durability finish paints / catalyzed lacquers/conversion varnishes.
4) As a personal aesthetic, I prefer the duller sheen finishes, down to as low as 15dg sheen, whether on solid wood / veneers or painted finishes. The higher the gloss, the more work and the final result is prone to scratching, crazing and generally a pain to keep clear of smudges, etc.
1) Spray guns - with a little practice either turbine or compressed air driven HVLP guns will yield far better results than brush/roller - particularly on curved or faceted surfaces. You can get decent results and high product yield with a $50 gravity feed HVLP gun from your local autobody shop, or you can spend over $1000 on a pro-rig
2) High solid catalyzed primer/sealers such as ML Campbell Clawlock, and their Resistant paint or tinted Magnamax lacquers are widely used hereabouts by the high end residential kitchen cabinet trade. They are formulated specifically for wood finishing.
3) The more time and products you spend on the filling, priming / sanding, ( at least 2 coats) the better your final results. The primer/sealers are much easier to sand down than most of the high durability finish paints / catalyzed lacquers/conversion varnishes.
4) As a personal aesthetic, I prefer the duller sheen finishes, down to as low as 15dg sheen, whether on solid wood / veneers or painted finishes. The higher the gloss, the more work and the final result is prone to scratching, crazing and generally a pain to keep clear of smudges, etc.
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Thanks for the info. I was thinking of switching to a lacquer but the only spray I found was Rust-Oleum Specialty 11-oz. Lacquer Gloss White Spray Paint-1904830 at The Home Depot. I have no idea if zinsser cover stain is an enamel or lacquer so I don't know if this would work. Would using a shellac or shellac based sealer make it easier to work with lacquer or enamel over cover stain? I was told that if I fully cured any layer that it wouldn't matter what I put on top of it. If I went with a lacquer color coat I'm guessing I should stay with a lacquer clear like the minwax lacquer clear?
Also, It drives me crazy how companies don't say whether it's a lacquer or enamel and how hard it is to find that info using google. Are short recoat times indicative of enamels? For now, can you suggest an aerosol system that's compatible all the way through the sealer, primer, color, and top coats? Lastly, enamel's aren't designed to be flattened, but does that mean that they can't be? Am I just trying to defy the physics of the paint?
Chrisb, thanks for the info but you're on another level from where I am right now. I know HVLP is the way to go and guns are cheap but I don't currently have a compressor. I plan to buy both in the near future but for now I'm stuck with aerosol or roll on.
I like the idea of hardwoods for home audio for looks, but I'm just using MDF for car audio for its acoustic properties. I designed the boxes the way I want, and I'm trying to squeeze every bit of SQ that these drivers will give me. I even went so far as to coat the interior with a rubber. I guess it makes sense, but it leaves me wondering why MDF isn't used exclusively in home audio.
Can you please enlighten me? I guess I've fallen into the believe what you read crowd. What would be best and why?
"you gotta be a lil crazy to stay sane..."
Care for a little religiosity thrown into your audiophila? 😉
This has been discussed to death - short synopsis could be:
density vs stiffness - and all that derives therefrom
Certainly MDF has some advantages of lower cost and "easier" machinability - but it's not without its dark sounding and noxious handling characteristics.
This has been discussed to death - short synopsis could be:
density vs stiffness - and all that derives therefrom
Certainly MDF has some advantages of lower cost and "easier" machinability - but it's not without its dark sounding and noxious handling characteristics.
Sticking to woofers.
1/ If you push any potential panel resonances up in frequecy such that they are above the passband of the woofer then the resonances will never get excited. Stiff, light panel material with short spans is the receipe for this.
18 mm quality ply has about the same stiffness as 32 mm of MDF and is a whole lot lighter.
2/once 1 is satisfied then one needs to prevent cabinet ballooning. Stiff, short panels best for this.
3/ Due to all the impedance transitions across plies plywood is better damped than essentially homogenous MDF.
MDFs primary advantage is that it is cheap (to buy, tool and finish). Commercial manufacturers did so well at promoting MDF that it has become so ingrained that even many talented speaker designers believe it could be no other way.
dave
chrisb and planet10, thanks for helping me out. I've read so many threads on wood choice including this one you were in (http://www.diyaudio.com/forums/subwoofers/178508-what-best-wood-speaker-enclosures.html) and settled on MDF. Is it common belief that something like birch ply is better but the same people use MDF anyway? TBH, ply sounds hard to work with and that scares me a little as my wood working skills are very lacking but improving with each build. Either way, it sounds like a personal preference to pick the lesser of two evils whether that'd be cost, tool, sound, finish, etc. based.
As far as birch ply goes, would this be the type to use? 18mm, (3/4 in.), 4ft x 8ft, Sandeply Hardwood Plywood-454559 at The Home Depot
As far as birch ply goes, would this be the type to use? 18mm, (3/4 in.), 4ft x 8ft, Sandeply Hardwood Plywood-454559 at The Home Depot
Finding quality ply at Home Depot is hard if not impossible. The standard baltic birch has 13 plies in 18mm (often called 3/4"), the US supplied ply we prefer to use has 15 plies. As a metric, the more plies the better.
dave
dave
availability- aye, that's the rub
One needn't read too many of my posts to discover that being employed in the commercial millwork trade for the past 20+yrs gives me access to a wide range of material selection - and pricing that can distort my sense of cost for the average DIYer.
As Dave notes, and others could probably corroborate, availability of the finer quality materials often employed in the commercial trade can be difficult, and certain regional. In my trade at least, "domestic" - i.e. North American production is not necessarily the sole arbiter of product quality, or even consistency.
Big box chain store such as HD, Lowes, Canada's Rona, and too many regional players to name tend to cater to the LCD , and the market for $80-100 per sheet plywood is certainly too limited for their bean counter's comfort zone (turn-over of required volumes would suck). But I digress as usual.
Try looking for local wholesale suppliers to the millwork/ kitchen cabinet trades, and in US or Canada, brands such as Murphy, States, or Columbia - those are the big three from which we select locally. And don't be surprised to find a loquacious sales rep to reveal that the "platform" core of much of the domestic "finished" multi-ply product is of European source. For example, much of "Baltic" birch is literally from the Baltics - cover sheets on lifts of 5x5 ply are clearly labelled "Russia" - which raises some questions.
One needn't read too many of my posts to discover that being employed in the commercial millwork trade for the past 20+yrs gives me access to a wide range of material selection - and pricing that can distort my sense of cost for the average DIYer.
As Dave notes, and others could probably corroborate, availability of the finer quality materials often employed in the commercial trade can be difficult, and certain regional. In my trade at least, "domestic" - i.e. North American production is not necessarily the sole arbiter of product quality, or even consistency.
Big box chain store such as HD, Lowes, Canada's Rona, and too many regional players to name tend to cater to the LCD , and the market for $80-100 per sheet plywood is certainly too limited for their bean counter's comfort zone (turn-over of required volumes would suck). But I digress as usual.
Try looking for local wholesale suppliers to the millwork/ kitchen cabinet trades, and in US or Canada, brands such as Murphy, States, or Columbia - those are the big three from which we select locally. And don't be surprised to find a loquacious sales rep to reveal that the "platform" core of much of the domestic "finished" multi-ply product is of European source. For example, much of "Baltic" birch is literally from the Baltics - cover sheets on lifts of 5x5 ply are clearly labelled "Russia" - which raises some questions.
Hah, you guys are on a different level. I'm a novice DIY building simple car sub enclosures, working in my garage with the little tools I have, and using a friend's table saw. I'm glad I learned something that I could put to use later when I've gotten the proper woodworking tools and honed my skills...
On the original topic, I think I've figure out how I'm gonna finish this first box to get it out of the way. For the other three I think I'll roll-on coverstain, rattle rustoleum filler primer (roll if I can find locally), haven't decided on color, and roll minwax polyurethane. I hope it works... I'll post pics of my success or failure and my thanks to you guys when I'm done 🙂
On the original topic, I think I've figure out how I'm gonna finish this first box to get it out of the way. For the other three I think I'll roll-on coverstain, rattle rustoleum filler primer (roll if I can find locally), haven't decided on color, and roll minwax polyurethane. I hope it works... I'll post pics of my success or failure and my thanks to you guys when I'm done 🙂
It's all very well recommending sprayguns and catalysed paints, but that is a significant investment in equipment and the unaware spraying catalysed paints is a major health risk.
I do have spray equipment now as I build speakers and do automotive work as hobbies. There is no doubt it's way easier and the results are better. And for more than a few pairs of cabinets it works out cost effective.
MDF has it's downsides, but for a painted finish it's better than plywood as there is no grain to fill.
OK on to your paint questions. Enamels usually have a slower drying time than lacquers. Putting shellac over Cover Stain to then prime over would be stupid, just use one or the other. Cover Stain claims to be an enamel. I'm afraid I can't recommend you any specific spraycans to use as your brands in the USA are all different to here in the UK. But I can tell you the polyurethane you mentioned is an enamel so not suitable to be flatted and polished.
Starting again what I would recommend is to seal the wood with Zinsser BIN. The Cover Stain will do as you already have that. Just make sure it's fully cured, overnight would be good. Then get an automotive lacquer primer tin from an auto paint store (jobbers you call them over there) and roll that on. It won't need any thinners. From the same paint store they will either have on the shelf or will be able to custom fill for you spraycans of lacquer single stage paint in a solid colour. They will also be able to sell you the wet and dry paper, blocks, polishes and pads etc you will need for finishing.
Don't forget, getting the wood right before putting any paint on is key. Once you starting painting all the imperfections will show up - don't think the primer will allow you to hide anything.
I do have spray equipment now as I build speakers and do automotive work as hobbies. There is no doubt it's way easier and the results are better. And for more than a few pairs of cabinets it works out cost effective.
MDF has it's downsides, but for a painted finish it's better than plywood as there is no grain to fill.
OK on to your paint questions. Enamels usually have a slower drying time than lacquers. Putting shellac over Cover Stain to then prime over would be stupid, just use one or the other. Cover Stain claims to be an enamel. I'm afraid I can't recommend you any specific spraycans to use as your brands in the USA are all different to here in the UK. But I can tell you the polyurethane you mentioned is an enamel so not suitable to be flatted and polished.
Starting again what I would recommend is to seal the wood with Zinsser BIN. The Cover Stain will do as you already have that. Just make sure it's fully cured, overnight would be good. Then get an automotive lacquer primer tin from an auto paint store (jobbers you call them over there) and roll that on. It won't need any thinners. From the same paint store they will either have on the shelf or will be able to custom fill for you spraycans of lacquer single stage paint in a solid colour. They will also be able to sell you the wet and dry paper, blocks, polishes and pads etc you will need for finishing.
Don't forget, getting the wood right before putting any paint on is key. Once you starting painting all the imperfections will show up - don't think the primer will allow you to hide anything.
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DO NOT, I repeat, DO NOT use sandeply. It is utter crap. If you must, spend the extra $5 and get birch or oak plywood from lowes or home depot. way better grade of wood. I speak from experience. the inner plies of sandeply are really low grade crap and have almost no strength to them. they like to come apart when you cut or round them.
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Great advice Richie, am sure I'll come back to your previous thread 🙂
BTW Jeff I'd recommend high quality birch ply too on future builds, as advised previously at least 13-ply (18mm) with no/few voids. MDF is good for beginners to learn because its easy to cut etc. yet Birch Ply is far better sounding.
BTW Jeff I'd recommend high quality birch ply too on future builds, as advised previously at least 13-ply (18mm) with no/few voids. MDF is good for beginners to learn because its easy to cut etc. yet Birch Ply is far better sounding.
To elaborate on what richie said above, while they can seal open "pores" on machined MDF edges, even mulitple coats of high solids sealer / primers are no substitute for proper filling/ sanding of joint lines, fastener holes, etc.
It's also worth noting, that while not to quite the same extent as plywoods, not all MDF is created equal - and that most definitely applies to its machining and painting characteristics.
It's also worth noting, that while not to quite the same extent as plywoods, not all MDF is created equal - and that most definitely applies to its machining and painting characteristics.
Thanks all. I'm gonna try a build with some JBL 2235H's I came across. You guys have me really nervous now with proper quality wood selection.
Btw, I feel all the pain expressed on this site about seams now cause my first box is driving me crazy. Most are invisible at the final coat primer stage (but will probably show up in the future) except one 4" seam that's just blatant. I tried coating the entire box in bondo but my mixing application skills are a bit lacking and ended up with non-drying areas and horrible texture on a 1/4 of the box. Bought an orbital sander to remove everything. I'll try that again when I get better with bondo.
Just started my second enclosure and really wishing I had a table saw with a sled and a jointer. I don't think the cuts will make for even seams. Going to see how well I can hand sand an even surface, hah. Also used a ton of wood glue to see if that'll help fill the gaps.
"you gotta be a lil crazy to stay sane..."
Btw, I feel all the pain expressed on this site about seams now cause my first box is driving me crazy. Most are invisible at the final coat primer stage (but will probably show up in the future) except one 4" seam that's just blatant. I tried coating the entire box in bondo but my mixing application skills are a bit lacking and ended up with non-drying areas and horrible texture on a 1/4 of the box. Bought an orbital sander to remove everything. I'll try that again when I get better with bondo.
Just started my second enclosure and really wishing I had a table saw with a sled and a jointer. I don't think the cuts will make for even seams. Going to see how well I can hand sand an even surface, hah. Also used a ton of wood glue to see if that'll help fill the gaps.
"you gotta be a lil crazy to stay sane..."
Btw, I think that most my joints don't show at the initial stages because of the glue. I'm not using any special joints, just edge to surface, and when sanding the joints flat the glue seems to sand perfectly flat with the MDF. Does this work as well as bondo for covering seams?
Also, I'm still using screws instead of clamps. I've been using the MDF dust/glue method to fill screw holes. These again seem to sand seamlessly. Is there a better method or is this acceptable? Don't wanna hear anything about clamps from you guys just yet, lol. I'll be getting them in the near future for the 3rd box build. I'm literally experimenting step by step so I can experience my own expected failures and learn from them.
"you gotta be a lil crazy to stay sane..."
Also, I'm still using screws instead of clamps. I've been using the MDF dust/glue method to fill screw holes. These again seem to sand seamlessly. Is there a better method or is this acceptable? Don't wanna hear anything about clamps from you guys just yet, lol. I'll be getting them in the near future for the 3rd box build. I'm literally experimenting step by step so I can experience my own expected failures and learn from them.
"you gotta be a lil crazy to stay sane..."
I used Atlas brand acrylic enamel spray bombs ($5/can) for my black piano gloss studio monitors and they turned out nice. Especially after 3M 1000 grit wet sand and turle wax polish.
Heres pics, first one is unsanded. Second is sand and polish : first round.
https://db.tt/wcKzm8iH
https://db.tt/30KVEsYk
Both pics are on Dropbox.
Heres pics, first one is unsanded. Second is sand and polish : first round.
https://db.tt/wcKzm8iH
https://db.tt/30KVEsYk
Both pics are on Dropbox.
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