Re: Re: details
This annoys me no end. I thought it was MDF but no, ply does it too. Difference with ply is you see very faint impressions of the grain. So no easy fix by switching materials. What you should be looking is either more patience or better paint products.
I've found leaving the cabinets for at least a month after initial spraying helps greatly because paint continues to shrink and cure for up to 12 months after applying. The first few of weeks are where the biggest changes happen though. Just before Christmas, after showing signs of what your talking about, I went over the LGT I sprayed in August last year with 2000 grit and very lightly block sanded and polished out. It still looks as good now as it did then so there's definitely some time factor involved. But 2K paints really are the way forward here, the chemical reaction of curing is accelerated greatly.
BTW didn't you lambaste me about all that joint expansion stuff when I resorted to veneering over joints in laminations? BTW that worked a treat too. Back then you implied MDF was pretty stable but it doesn't sound like you consider that to be the case anymore?
MJL21193 said:
This annoys me no end. I thought it was MDF but no, ply does it too. Difference with ply is you see very faint impressions of the grain. So no easy fix by switching materials. What you should be looking is either more patience or better paint products.
I've found leaving the cabinets for at least a month after initial spraying helps greatly because paint continues to shrink and cure for up to 12 months after applying. The first few of weeks are where the biggest changes happen though. Just before Christmas, after showing signs of what your talking about, I went over the LGT I sprayed in August last year with 2000 grit and very lightly block sanded and polished out. It still looks as good now as it did then so there's definitely some time factor involved. But 2K paints really are the way forward here, the chemical reaction of curing is accelerated greatly.
BTW didn't you lambaste me about all that joint expansion stuff when I resorted to veneering over joints in laminations? BTW that worked a treat too. Back then you implied MDF was pretty stable but it doesn't sound like you consider that to be the case anymore?
Re: Re: details
Always? Even with the pilot hole done right?
You just knew someone was going to call you a lair
Bunch of screws:
Side panel removed with a few of the holes visible, no with splits. Not a great shot for illustrating this but I don't have anything more suitable to show. I'm trust worthy though
My guess is either I'm lucky or your doing something wrong if your MDF always splits. On occasion I get splits though and MDF is well known for this - you ain't making this up in other words.
MJL21193 said:
Always? Even with the pilot hole done right?
You just knew someone was going to call you a lair
Bunch of screws:
An externally hosted image should be here but it was not working when we last tested it.
Side panel removed with a few of the holes visible, no with splits. Not a great shot for illustrating this but I don't have anything more suitable to show. I'm trust worthy though
An externally hosted image should be here but it was not working when we last tested it.
My guess is either I'm lucky or your doing something wrong if your MDF always splits. On occasion I get splits though and MDF is well known for this - you ain't making this up in other words.
Re: Re: Re: details
"Lambaste"? I haven't heard that one since the nuns in elementary school.
Yes, and I still don't have problems with joints. The front baffle on these was painted so many times, over such a long period (May to August?) that there was definitely enough dry time. TBH, maybe I'm blaming it on the wrong thing. Could be the original solvent based urethane paint underneath the waterbased that is causing the problem. I don't know.
It hard to see it under normal light conditions, but it's one of those things that can drive me nuts. I will find time this summer to remove the drivers and re sand and re polish, hopefully this solves the problem and I don't cut through anywhere.
I recently did something from HDF, and painted that. Three weeks later, it still looks perfect, after only a brief hand polish. Granted, I didn't screw around with different paints, but went with the WB urethane on top of one coat of SB urethane to seal.
I'm keeping my eye on it, and I will most likely be using HDF as a paint base from now on.
ShinOBIWAN said:
"Lambaste"? I haven't heard that one since the nuns in elementary school. Yes, and I still don't have problems with joints. The front baffle on these was painted so many times, over such a long period (May to August?) that there was definitely enough dry time. TBH, maybe I'm blaming it on the wrong thing. Could be the original solvent based urethane paint underneath the waterbased that is causing the problem. I don't know.
It hard to see it under normal light conditions, but it's one of those things that can drive me nuts. I will find time this summer to remove the drivers and re sand and re polish, hopefully this solves the problem and I don't cut through anywhere.
I recently did something from HDF, and painted that. Three weeks later, it still looks perfect, after only a brief hand polish. Granted, I didn't screw around with different paints, but went with the WB urethane on top of one coat of SB urethane to seal.
I'm keeping my eye on it, and I will most likely be using HDF as a paint base from now on.
Attachments
Re: Re: details
This is very interesting, because different paints seem to yeild different results. Just a few weeks ago, I was looking at various paints, and this one paint that is also used on cars is really funny, if you look at it staight on, the reflection image can have some unsmoothness; if you look at the reflection from less than 30 degrees angle, the the reflected line is really straight. For wood paints, the smoothness is the same regardless what angle you look at it from.MJL21193 said:
Re: Re: Re: details
Oh, but the flavour!
That looks like 1" MDF, not 1/2"! Course it doesn't split.
I don't normally use screws anyway, just heaps of glue and airgun nails.
soongsc said:
Too much sauce and lacking a bit in juice.
Oh, but the flavour!
ShinOBIWAN said:
Always? Even with the pilot hole done right?
You just knew someone was going to call you a lair
Bunch of screws:
My guess is either I'm lucky or your doing something wrong if your MDF always splits. On occasion I get splits though and MDF is well known for this - you ain't making this up in other words.
That looks like 1" MDF, not 1/2"! Course it doesn't split.
I don't normally use screws anyway, just heaps of glue and airgun nails.
Re: Re: Re: Re: Re: Re: details
only ten years? try 35; after which the woman is quite likely well justified to be simply tired of your BS - and less vile on her worst day than most of us achieve before breakfast. I know my wife certainly is both.
give any of these threads enough time and they're guaranteed to meander OT
sorry for the interruption, now back to our regularly scheduled program:
Shin and John - nice work on the painted MDF - dozens of times harder to achieve nice results here than simply veneering and lacquering plywood. After one attempt, I've never had the patience to try the former again.
MJL21193 said:
Some, but mostly they were Nasty.
Nuns take a vow of chastity, so they are like the woman you are married to for 10 years - vile.
only ten years? try 35; after which the woman is quite likely well justified to be simply tired of your BS - and less vile on her worst day than most of us achieve before breakfast. I know my wife certainly is both.
give any of these threads enough time and they're guaranteed to meander OT
sorry for the interruption, now back to our regularly scheduled program:
Shin and John - nice work on the painted MDF - dozens of times harder to achieve nice results here than simply veneering and lacquering plywood. After one attempt, I've never had the patience to try the former again.
An externally hosted image should be here but it was not working when we last tested it.
Re: Re: Re: Re: details
Good to hear the joint problem hasn't changed, more work is never fun. For a minute there I thought you'd noticed what I'd been experiencing.
The whole spraying wood thing is pretty fussy stuff isn't it. Spraying metal's is far less work - those car body shop guys don't know they're born.
I'll have to give HDF a try, over here they call it medite. Its a fair whack more expensive than MDF though and upto nearly the same price as the premium quality marine ply.
Interesting enclosure you show. Cardioid but are those ports I see?
MJL21193 said:
Good to hear the joint problem hasn't changed, more work is never fun. For a minute there I thought you'd noticed what I'd been experiencing.
The whole spraying wood thing is pretty fussy stuff isn't it. Spraying metal's is far less work - those car body shop guys don't know they're born.
I'll have to give HDF a try, over here they call it medite. Its a fair whack more expensive than MDF though and upto nearly the same price as the premium quality marine ply.
Interesting enclosure you show. Cardioid but are those ports I see?
Re: Re: Re: Re: details
Its 3/4", I wouldn't fancy my chances with 1/2". I don't see many projects using 1/2" except for small bookshelves. 3/4" seems the minimum and the norm. 1" is nice but weighs a ton.
Screws are a PITA, like yourself I try to avoid but in this case I wanted pressure applied over the whole surface whilst the glue dried and this was easier than struggling with clamps.
MJL21193 said:That looks like 1" MDF, not 1/2"! Course it doesn't split.
I don't normally use screws anyway, just heaps of glue and airgun nails.
Its 3/4", I wouldn't fancy my chances with 1/2". I don't see many projects using 1/2" except for small bookshelves. 3/4" seems the minimum and the norm. 1" is nice but weighs a ton.
Screws are a PITA, like yourself I try to avoid but in this case I wanted pressure applied over the whole surface whilst the glue dried and this was easier than struggling with clamps.
Re: Re: Re: Re: Re: details
It was ten years, 12 years ago. Then 5 years, 4 years ago. Just finishing up #3 - 3 years. I just can't seem to find the right one.
C'est la Vie!.
The painting is tough when you don't do it often and have no formal training for it. My early attempts were quite simply disgusting. Practice and some research got me half-way decent anyway, but a pro would put mine to shame.
Metal won't move under the paint, so they are one up there. I thought about plastic laminate, like formica as the base for flawless paint over MDF, but I'm thinking the HDF is the best solution. Has better properties than MDF too.
That is not a speaker, but a sub amplifier enclosure. The "ports" are heatsink chimneys. Look it over here. About half done at this point.
chrisb said:
It was ten years, 12 years ago. Then 5 years, 4 years ago. Just finishing up #3 - 3 years. I just can't seem to find the right one.
C'est la Vie!.
The painting is tough when you don't do it often and have no formal training for it. My early attempts were quite simply disgusting. Practice and some research got me half-way decent anyway, but a pro would put mine to shame.
ShinOBIWAN said:
Metal won't move under the paint, so they are one up there. I thought about plastic laminate, like formica as the base for flawless paint over MDF, but I'm thinking the HDF is the best solution. Has better properties than MDF too.
That is not a speaker, but a sub amplifier enclosure. The "ports" are heatsink chimneys. Look it over here. About half done at this point.
Re: Re: Re: Re: Re: Re: details
Well, HDF/Medite probably is the best wood product solution overall for < 0.7 Qts driver cab designs IMO if I were to use other than plywood or metal.
WRT to dealing with the instability of wood products I got good long term results from adding a flex agent to the various sprayed automotive coating systems I used, with DuPont acrylic enamel being my preference, but I haven't kept up with coating systems since I was forced to quit spraying in '89, so imagine there's better choices today or at least less hazardous ones.
Nice amp case BTW.
GM
MJL21193 said:
Well, HDF/Medite probably is the best wood product solution overall for < 0.7 Qts driver cab designs IMO if I were to use other than plywood or metal
. WRT to dealing with the instability of wood products I got good long term results from adding a flex agent to the various sprayed automotive coating systems I used, with DuPont acrylic enamel being my preference, but I haven't kept up with coating systems since I was forced to quit spraying in '89, so imagine there's better choices today or at least less hazardous ones.
Nice amp case BTW.
GM
Re: Re: Re: Re: Re: Re: Re: details
Turns out that acrylic Enamel or Acrylic Laquer are still the best, and still hazarous. The water borne acrylics can be used with sucess, but its a real pain on MDF. You have to seal it well and water based seals don't work so well. A two part epoxy primer, then acrylic works best for me.
GM said:
Turns out that acrylic Enamel or Acrylic Laquer are still the best, and still hazarous. The water borne acrylics can be used with sucess, but its a real pain on MDF. You have to seal it well and water based seals don't work so well. A two part epoxy primer, then acrylic works best for me.
Re: Re: Re: Re: Re: Re: Re: details
It used to be similar (been a while since i bought any) ie 15-25% more than MDF (ie if you ignore that we get MDF for free), but the recent warm winter weather in the Baltic has pushed the price up close to double what it was a year ago. Even so, materials cost is but a drop in a bucket compared to manufacturing costs.
dave
ShinOBIWAN said:
It used to be similar (been a while since i bought any) ie 15-25% more than MDF (ie if you ignore that we get MDF for free), but the recent warm winter weather in the Baltic has pushed the price up close to double what it was a year ago. Even so, materials cost is but a drop in a bucket compared to manufacturing costs.
dave
Re: Re: Re: Re: Re: Re: Re: details
Thanks GM,
The first paint I tried for this, a few years ago was just gloss black alkyd rust paint. This would take forever to dry, and never get really hard, so I wouldn't see joint cracks or any of this other nonsense. It was too flexible.
Then I switched to urethane based paint, and this still took a long time to dry, but ended up with a harder finish.
Last summer, I ordered waterbased urethane paint from Sherwin Williams, from their industrial coatings division. It's amazing stuff, harder than any solvent based 1K I tried (but not as hard as 2K automotive paint). Sprays on smooth, dries very fast (5 minute flash on a warm day) and is very durable. It waterbased, so easy clean up, no hazardous fumes.
For this use (speakers and such) I don't see the reason to use anything else.
GM said:
WRT to dealing with the instability of wood products I got good long term results from adding a flex agent to the various sprayed automotive coating systems I used, with DuPont acrylic enamel being my preference, but I haven't kept up with coating systems since I was forced to quit spraying in '89, so imagine there's better choices today or at least less hazardous ones.
Nice amp case BTW.
GM
Thanks GM,
The first paint I tried for this, a few years ago was just gloss black alkyd rust paint. This would take forever to dry, and never get really hard, so I wouldn't see joint cracks or any of this other nonsense. It was too flexible.
Then I switched to urethane based paint, and this still took a long time to dry, but ended up with a harder finish.
Last summer, I ordered waterbased urethane paint from Sherwin Williams, from their industrial coatings division. It's amazing stuff, harder than any solvent based 1K I tried (but not as hard as 2K automotive paint). Sprays on smooth, dries very fast (5 minute flash on a warm day) and is very durable. It waterbased, so easy clean up, no hazardous fumes.
For this use (speakers and such) I don't see the reason to use anything else.
Re: Re: No More Re's!!
Here's the way I see it: With the drivers mechanical motion you have inertia. The lower frequencies need a longer excursion of the cone to produce the same spl as a higher frequency at a lower excursion. The further the cone travels, the more opposing force, therefore more kinetic energy to deal with. It's easy to visualize when you think about how a long throw woofer will make a box "walk", as opposed to a midrange or tweeter that, even if hanging in free air, will not move very much (if at all).
I agree about the driver flanges. It's not practical to leave it loose on the baffle. I do like Dave's solution, where the magnet is directly coupled to a brace. This channels the mechanical energy from the driver into the box structure, and not into the baffle.
The question remains: What happens to this energy if there is nothing to dissipate it? (such as panel damping).
gedlee said:
Here's the way I see it: With the drivers mechanical motion you have inertia. The lower frequencies need a longer excursion of the cone to produce the same spl as a higher frequency at a lower excursion. The further the cone travels, the more opposing force, therefore more kinetic energy to deal with. It's easy to visualize when you think about how a long throw woofer will make a box "walk", as opposed to a midrange or tweeter that, even if hanging in free air, will not move very much (if at all).
I agree about the driver flanges. It's not practical to leave it loose on the baffle. I do like Dave's solution, where the magnet is directly coupled to a brace. This channels the mechanical energy from the driver into the box structure, and not into the baffle.
The question remains: What happens to this energy if there is nothing to dissipate it? (such as panel damping).
Re: Re: Re: No More Re's!!
If the box doesn't flex and resonate and is coupled solidly to the floor, there will be little to dissipate. Most of the energy will be emitted as the acoustic output of the driver, since the effective mass of the box will include that mass of the support beneath it.
This case is similar to the case of "coupling" a driver solidly to the baffle. If it's not tightly coupled, the driver frame can move (the old equal and opposite reaction), hence the cone motion will suffer. If the box is not tightly coupled (more often the case with a 2-way on a stand), then the box can move. A solid floor standing box on a concrete floor will give you some of the best coupling for the box. It's like adding mass to the box itself. Put it on a stand and you may see some additional resonances arise. The key is to prevent the box baffle from moving at all.
Dave
MJL21193 said:
If the box doesn't flex and resonate and is coupled solidly to the floor, there will be little to dissipate. Most of the energy will be emitted as the acoustic output of the driver, since the effective mass of the box will include that mass of the support beneath it.
This case is similar to the case of "coupling" a driver solidly to the baffle. If it's not tightly coupled, the driver frame can move (the old equal and opposite reaction), hence the cone motion will suffer. If the box is not tightly coupled (more often the case with a 2-way on a stand), then the box can move. A solid floor standing box on a concrete floor will give you some of the best coupling for the box. It's like adding mass to the box itself. Put it on a stand and you may see some additional resonances arise. The key is to prevent the box baffle from moving at all.
Dave
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