Making a box is harder than one might think.

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One option for spraying that is easy but you have to want a textured finish is to use truck bed paint. I know you can get it in the states and the Uk. Gives a great pro looking finish BUT, only in black over here and you do need to keep it dust free.
Used it recently on the round surround to the grid on a sub I built
 
No point showing the Home Depot link. I have been using this stuff since th elate ‘70s. It was supplied standard with the then available KEF diy speakers.

Dave

Kef Konstruction Series?

I just missed their availability. I know I missed something good though, from the few examples I have seen.

Well this is a first for me. Having got my mdf boxes ready for covering, they have expanded. Perhaps just 1% but when a 36mm baffle gets 1/3rd of a mm thicker, it casts a shadow I could hide in. Well... I want to hide in.

I think the moisture from applying carpet underlay with pva did it. I set them up to air, but perhaps should of used a fan. I didn't even attach any to the front baffle. There isn't an area over 2" between braces. To move is really something. I'm concerned how much stress the glue is now under.

Only time will tell, but I will seal boxes before putting so much glue in again. That's for sure.
 
nothing wrong with MDF - for patterns, templates and spacers :rolleyes:
Nothing wrong with MDF - as long as you have a few spare pairs of lungs, and don't mind significant health risks:
MDF ... is a compound of wood dust and scrap bonded together by a resin containing formaldehyde - a recognised carcinogen. When MDF is cut, sanded, shaped or machined in any way, it releases clouds of dust particles coated with formaldehyde. The particles, much smaller than those emitted by most other commonly used woods, can be inhaled deep into the lungs.

<snip>

Recent studies from the International Agency for Research on Cancer, part of the World Health Organisation, concluded that wood dust is carcinogenic to humans and that formaldehyde is 'probably carcinogenic to humans'.

The agency also quoted evidence that short-term exposure to formaldehyde could cause irritation to the eyes, nose and throat. For builders and furniture makers who use MDF daily, the current exposure limit in the UK set by the Health and Safety Executive is two parts per million - more than 20 times that of other European countries such as Germany and Sweden.
Source: Deadly secret of DIY dream material - background | UK news | The Guardian

If you Google for "MDF formaldehyde" or "MDF health risks" you will turn up a lot more material on the subject.

Formaldehyde is the stuff used to preserve tissues in biological research; among other things, it can cause bone necrosis and pneumonia, seriously damage internal organs, and even kill outright, as this article from the Journal of Experimental Medicine explains: THE TOXIC EFFECTS OF FORMALDEHYDE AND FORMALIN

-Gnobuddy
 
Kef Konstruction Series?

Well this is a first for me. Having got my mdf boxes ready for covering, they have expanded. Perhaps just 1% but when a 36mm baffle gets 1/3rd of a mm thicker, it casts a shadow I could hide in. Well... I want to hide in.

Only time will tell, but I will seal boxes before putting so much glue in again. That's for sure.

This is the issue I was relating to you earlier. You'd think only water based glues would do this but no, anywhere that any wet glue is applied to the "end grain" of mdf it will expand and hold it's new shape.
Once you realise it's going to happen you can usually allow for it and finish sand later.
It even happens when spring a solvent based aerosol paint finish so must be sealed, sanded and sealed again before final finish.

In answer to the title of this thread, Making a box is easy, making it perfect isn't.;)
 
So I’ve reached the stage of getting about 4 coats of gloss black sprayed on my boxes and I’m wondering what next to get that piano gloss finish. The speakers have that slight orange peal, faint brush stroke finish. Would people recommend doing a wet or dry sanding now with a high grit (1600?) paper next? Or should I just keep on with more top coats or a higher grade sand paper. Don’t want to mess up these stages!!
 

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So I’ve reached the stage of getting about 4 coats of gloss black sprayed on my boxes and I’m wondering what next to get that piano gloss finish. The speakers have that slight orange peal, faint brush stroke finish. Would people recommend doing a wet or dry sanding now with a high grit (1600?) paper next? Or should I just keep on with more top coats or a higher grade sand paper. Don’t want to mess up these stages!!

Actually, the orange peel finish you now have can look very attractive - but if you want to go for the full piano finish it will be quite a challenge. You would have to wet and dry sand down the surface by hand, working through the grits starting somewhere around 600 and gradually working up to 2000. Make sure the paint is fully hardened before you start. And change the paper frequently.

Then you can start varnishing. Or, if so inclined, give a final spray coat, and leave aside the idea of a piano finish for another build some other time.

tapestryofsound
 
I'm in the process of finishing my cabinets right now and though I do not want the piano gloss finish, I went with a black satin and will finish with a coat or two of clear. I am using the rattle cans which is not ideal but I am getting pretty good results. Started by sanding all sides with random orbital sander until all joints (butt joints in my case) were flush. Then sealed gaps and end grains with wood glue. Sanded smooth. Two coats of primer. Sand with 320. Two coats of paint. Sand until smooth with 320. Third coat. Sand with 600. Fourth coat. Sand with 1000. Final coat, wet sand with 1000. Finally hit it with 2 clear coats. I found a wealth of information in this thread....

Best way to finish MDF -

Techtalk Speaker Building, Audio, Video Discussion Forum
 
So I’ve reached the stage of getting about 4 coats of gloss black sprayed on my boxes and I’m wondering what next to get that piano gloss finish. The speakers have that slight orange peal, faint brush stroke finish. Would people recommend doing a wet or dry sanding now with a high grit (1600?) paper next? Or should I just keep on with more top coats or a higher grade sand paper. Don’t want to mess up these stages!!


Develop a method using a small area on the back of one of the speakers. I would try very fine sandpaper or wet/dry on a pad, either orbital sander or by hand, then maybe go to something like T cut.
 
So I started wet sanding last night using an 800 grit. My heart was in my mouth as the wet sanding seemed to be pretty quickly removing most of the black finish!! I’m just not sure if I was doing this right. I think possibly using too much water? I was trying to use almost no pressure, but still the layers seemed to be flying off.

I think the biggest problem for me is not knowing how good (good enough) is at each stage. I feel I could have sanded more but then I would have ended up with no black paint left! Anyway on with another coat of black and they look better than last time, I’m guessing bit more sanding then another coat? I know someone said it would be a challenge, I guess my worry is knowing when enough is enough?

Really annoyingly I clipped one of the speaker cases on the garage door frame on my way back into the garage, so I have a chip to repair as well!!
 

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