Thickness of veneer on MDF?
#11
I'm designing a couple of speaker cabinets of the totally-closed, sealed, infinite-baffle type (12" woofer, 6" mid and a tweeter arrangement) that would be around 45" h. X 17" wide X 15" deep - close to 5 cubic feet in volume.  Common audio lore says solid wood is a no-no, plywood not very good, MDF or particle board better, 3/4" absolute minimum thickness for sides and back, 1" minimum for front baffle with the speaker cutouts, lined copiously with fiberglass insulation.

I have had fits trying to apply veneer smoothly to particle board, at least the stuff one can find easily, and somewhat better luck with MDF.  However, the micro-thin veneers are quite expensive (for the quantities needed for this project) and are difficult to prepare and finish properly.  I have a large supply of very nice hardwoods, which could be resawn and planed down to 1/8".  Have cherry and oak (also walnut, although I would rather not build this with that wood).  Also have poplar which could be used as the backing layer.  I do NOT have a wide belt sander.

The concept would be to laminate 1/8" hardwood over 1/2" MDF with a backing of 1/8" poplar, for the sides, and 1" MDF or two layers of 1/2" MDF for the front (which is covered with grill cloth) and the back (which is not visible).  Hopefully this "would not ring like a cheap acoustic guitar", as one audiophile put it, and better yet would be stable.

Searching around for thickness of veneer reveals two schools of thought - no thicker that 3/32", and 1/8" would be fine - and general agreement that one of the urea-formaldehyde resin glues would work better than yellow glue, contact cement, etc., for this application.

What do you think?  Is this likely to be a stable composite considering that the interior is totally sealed and not subject to humidity changes, etc.?
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#12
(08-25-2017, 09:21 PM)GaryMc Wrote: I'm designing a couple of speaker cabinets of the totally-closed, sealed, infinite-baffle type (12" woofer, 6" mid and a tweeter arrangement) that would be around 45" h. X 17" wide X 15" deep - close to 5 cubic feet in volume.  Common audio lore says solid wood is a no-no, plywood not very good, MDF or particle board better, 3/4" absolute minimum thickness for sides and back, 1" minimum for front baffle with the speaker cutouts, lined copiously with fiberglass insulation.

I have had fits trying to apply veneer smoothly to particle board, at least the stuff one can find easily, and somewhat better luck with MDF.  However, the micro-thin veneers are quite expensive (for the quantities needed for this project) and are difficult to prepare and finish properly.  I have a large supply of very nice hardwoods, which could be resawn and planed down to 1/8".  Have cherry and oak (also walnut, although I would rather not build this with that wood).  Also have poplar which could be used as the backing layer.  I do NOT have a wide belt sander.

The concept would be to laminate 1/8" hardwood over 1/2" MDF with a backing of 1/8" poplar, for the sides, and 1" MDF or two layers of 1/2" MDF for the front (which is covered with grill cloth) and the back (which is not visible).  Hopefully this "would not ring like a cheap acoustic guitar", as one audiophile put it, and better yet would be stable.

Searching around for thickness of veneer reveals two schools of thought - no thicker that 3/32", and 1/8" would be fine - and general agreement that one of the urea-formaldehyde resin glues would work better than yellow glue, contact cement, etc., for this application.

What do you think?  Is this likely to be a stable composite considering that the interior is totally sealed and not subject to humidity changes, etc.?
I think it would be fine based on what you propose. I wonder about the use of poplar on the interior; in fact under the circumstances I am not even sure you need an interior balance sheet I have seen a lot of speakers made without the interior sheet that work just fine.
Let us not seek the Republican Answer , or the Democratic answer. Let us not seek to fix the blame for the past. Let us accept our own responsibility for the future  John F. Kennedy 



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#13
Joe gave you the answer, I wouldn't use the interior sheet either and I would use the UF glue. But don't think the interior will not be subject to humidity changes. If for no other reason the speaker cones are porous to humidity; but in this case it doesn't really matter.
I started with absolutely nothing. Now, thanks to years of hard work, careful planning, and perseverance, I find I still have most of it left.
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#14
Triggers another old memory.

When I had my shop some kid came in one day wanting me to make a couple large speaker boxes for him to put in the back seat of his junker $1000 car. He had already bought the speakers and had definite ideas of how he was going to mount them in the boxes.

He had cash so I did so of course.

Think I used a double thickness of MDF and glued, glued, glued -- with absolutely no chance of stray vibrations from loose joints or panels.

To save money he painted the exterior to match his car as I remember.

He left happy and never came back; so I guess it turned out well.
A laid back southeast Florida beach bum and volunteer bikini assessor.


Wink
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#15
Same here, for something around 1/8" veneer I would only use UF or epoxy glues.  And I would veneer both sides as it will keep things balanced during the construction process.  Epoxy might allow you to have no bowing problems unless your shop RH changes, but IMO it's easier to do both sides and then not have to worry about it. 

Also, if you have to edge seam your veneer to get the width you need, I recommend you glue those seams with yellow glue.  That will make handling easier, and prevent glue bleed through and any chance of seam separation when you glue it to the substrate. 

Since you have no drum or wide belt sander, and if your planer can't make 1/8" veneer w/o destroying it, then make it 1/4" thick, glue it on to your substrate, and then plane the whole assembly down on both sides until you have 1/8", or whatever you want.  If you have a well tuned bandsaw, however, you should be able to cut veneer of consistent thickness that is smooth enough to glue down w/o further processing.   However, you get your veneer it needs to be of consistent thickness for it to be pressed against your substrate during lamination, the exception to that being the top sheet in a vacuum bag where the bag will follow any differences.  But that won't be the case with the veneer on the bottom if it's lying on a rigid caul, nor will it be the case for a mechanical press.  I get around this problem by using an 1/8" thick piece of rubber foam on top of the bottom caul. 

John
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#16
Thanks for the replies and great tips.  I will get into this after some of the fall chores are done.

FYI, I have a pair of Bozak B302A "Century" 3-way speaker systems purchased in 1972.  Bozak made some of the finest speakers in the world up through the late '70s, and are highly sought after to this day.  The B302A actually was the smallest system Bozak made until late in the game when "bookshelf" speakers became all the rage.

[Image: Tag%20on%20back_zpse1xdklun.jpg]

These are boxy, roughly a cube 2 ft. on a side weighing about 85 lbs. each and still sound fantastic, but that boxy configuration plus dark walnut cabinets and a greenish, greyish, goldish grill no longer fit into our decor.  I want to make tower-style cabinets with equivalent volume in a lighter wood with a "neutral" grill color like black.  At the same time I would move the tweeter assembly up higher as opposed to near the bottom in the original cabinet.
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#17
I am not an audiophile, and have never made a speaker enclosure, always just bought some already made so I could listen to them before plunking down my $$$$$$.

That said I had a friend who owned a cabinet shop, and possibly 1/3 of his business was making speaker cabinets, evidently his were very good. I was chatting with him at lunch one day,. and I asked him about the speakers. He shrugged, and said once he found something that worked, he repeated it, over and over, and over..........

Then added that absolutely anything you do when making a speaker box has some effect on sound coming from it, then add the speakers and you have another 1000 year conversation. I didn't get the impression that lucking into a good sounding speaker was easy to do.
Worst thing they can do is cook ya and eat ya

GW
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#18
I maybe should add that veneering just the exterior only works if you build the enclosure first  

I too am not an audiophile but I have made enclosures in the past and as Steve said once you see what was done initially you can mimic the OEM 

All bets however are off if the intent is to change the configuration 

YMMV
Let us not seek the Republican Answer , or the Democratic answer. Let us not seek to fix the blame for the past. Let us accept our own responsibility for the future  John F. Kennedy 



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#19
For speakers, I can't recommend this stuff, Better Bond Heat Lock, more. I used it over decade ago 2006 and still holding strong, I built Adire Audio 281 towers and center channel of similar dimensions. 3/4 MDF, glued and screwed, butt joints. I covered in quartersawn Makore veneer. Rolled it on both surfaces, let it dry, position, iron it on. I used a razor to flush trim. I agonized similarly about contact cement, wood glues, hide glue, UF, veneer bagging. Don't over think it. This stuff felt so easy to use it was criminal. No issues with contact cement and positioning headaches while trying to hold it above the surface of a large panel. Get the veneer glue roller too. worth it.

Also the Jasper 200 circle cutting jig is worth the $$ too IMO. You can plunge a circular recess then cut the circle out. I got perfect results everytime. Good luck. Speaker building is fun!

Pics
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#20
(08-28-2017, 10:20 AM)smithgl12 Wrote: For speakers, I can't recommend this stuff, Better Bond Heat Lock,  more. I used it over decade ago 2006 and still holding strong, I built Adire Audio 281 towers and center channel of similar dimensions. 3/4 MDF, glued and screwed, butt joints. I covered in quartersawn Makore veneer. Rolled it on both surfaces, let it dry, position, iron it on. I used a razor to flush trim. I agonized similarly about contact cement, wood glues, hide glue, UF, veneer bagging. Don't over think it. This stuff felt so easy to use it was criminal. No issues with contact cement and positioning headaches while trying to hold it above the surface of a large panel. Get the veneer glue roller too. worth it.

Also the Jasper 200 circle cutting jig is worth the $$ too IMO. You can plunge a circular recess then cut the circle out. I got perfect results everytime. Good luck. Speaker building is fun!

Pics

That glue won't work with 1/8" thick veneer.  It's for thin commercial veneer where the heat can easily transfer through. 

John
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