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Thread: 1.5" MDF

  1. #1

    Default 1.5" MDF


    Whats the best way to join/seal together 2 pieces of .75" mdf for a 1.5" baffle? Again, thanks to all you awesome people for your help.

  2. #2
    Join Date
    May 2007
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    Athens, Ohio USA
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    1,097

    Default Re: 1.5" MDF *PIC*




    > Whats the best way to join/seal together 2
    > pieces of .75" mdf for a 1.5"
    > baffle?

    I used ordinary Titebond wood glue. I made both pieces slightly oversized, routed the driver holes in each piece separately (it's tough trying to route through 1-1/2" of material!), and glued and clamped overnight.

    After the rest of the box was finished, I attached the baffle and used a 2" flush trim bit to make the sides match the box.

    Here's a picture of the newly routed baffle attached to the box..

    With thick baffles like this, pay attention to the area behind the woofer to ensure enough air flow. I heavily chamfered the back of this baffle before I was done.

  3. #3
    Join Date
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    Default Re: 1.5" MDF *PIC*




    One more thing...

    Registering both baffle halves and the box (which had a 1/2" plywood piece that the baffles faced against) required some precision. I used a pair of slotted pins to align everything before routing or trimming anything.

    The 1/8" holes for the pins were drilled with the plywood and both baffle halves clamped together. The hole did not go clear through to the front of the baffle.

    The pin also aided the glue-up of the baffle halves by preventing them from slipping out of alignment when clamped together. If they had slipped, the driver holes would not align. This addresses part of your original question.

    I know this sounds a little vague, so here's another picture that may shed a little light on the subject. This picture was made AFTER all the holes had been routed, but it shows the pin clearly. At various times I removed the pins to work on the baffles - like when I routed the driver holes, but the finished speakers still have them installed. When I take the baffles off of the box, they go back together EXACTLY the same each time.

  4. #4
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    Default Re: 1.5" MDF *PIC*




    I can't seem to post enough today!

    Here's a picture of the nearly finished speakers. The front baffle is 1-1/2" thick made up of two pieces of 3/4" MDF. You can't tell it's glued together at all.

  5. #5

    Default Re: 1.5" MDF


    That's a nice looking cabinet my friend. Both aesthetically pleasing and appears to be very inert.

    cheers

  6. #6
    Join Date
    Aug 2006
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    Tri-Cities, WA
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    716

    Default Re: 1.5" MDF


    > I can't seem to post enough today!

    > Here's a picture of the nearly finished
    > speakers. The front baffle is 1-1/2"
    > thick made up of two pieces of 3/4"
    > MDF. You can't tell it's glued together at
    > all.
    HOw much did you chamfer the rear of the baffle? I can't really tell from the photo. Darned nice looking speaker cabinet you've made, though. Very nice work.

    John

  7. #7
    Join Date
    Oct 2005
    Location
    New Hampshire
    Posts
    452

    Default Re: 1.5" MDF


    Great looking cabinet, how did you finish the baffle?

    Another option is to build the box with 0.75" material, flush trim another set of 0.75" pieces to it. Once the second set is flush trimmed, glue in place...this leaves the corners "short". Fill with a 0.75"x0.75" piece of stock, glued in. Then flush trim that. This gets you out of flush trimming 1.5" thickness. I have done this with the second layer being veneered plywood and solid wood corners.


  8. #8
    Join Date
    Aug 2006
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    Tri-Cities, WA
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    716

    Default Re: 1.5" MDF


    > Whats the best way to join/seal together 2
    > pieces of .75" mdf for a 1.5"
    > baffle? Again, thanks to all you awesome
    > people for your help.
    Like it's suggested by Mr. Schneider, alignment pins can be the fix for this obstacle. He is right....it IS difficult to router through 1.5" of mdf...or any other material for that matter. It is far easier to router the front baffle and then the back half and finally join them. Alignment is the problem and the alignment pins solve that problem. I typically use 1/8" drilled holes and pins. I at least pin two diagonally opposing corners of the material. Clamp both pieces to be joined and drill all the holes for alignment pins, circle pin holes for the driver rebates, etc. Then mark which sides of the two panels that face each other for future reference. You might also mark the material as Baffle 1 and Baffle 2. Unless you drill all the holes using a drillpress and positioning jigs, you won't be able to drill both baffles the exact same...so mark which second layer of mdf goes to which baffle...just to avoid mating problems later. Once you have the driver rebates cut and the through-holes cut as well, you can then apply a smooth coat of glue to both surfaces to be joined. I like to use glue-ing cauls...these can be something as simple as 2" X 2" oak staves...this is to keep the two mdf surfaces as flat as possible during glue operation. I use 1.5" X 1.5" aluminum angle that is 1/4" thick. It gives really good stiffness I typically use two on top, two on the bottom and clamp on the cauls. If you have mdf that is slightly cupped (minor warping due to leaning against a wall or something), then make sure the low part of the cup is towards the glue joint for both pieces....cups should oppose each other. This way, the middl of the board joins naturally as you press the pieces together....the bowed gap should be around the edges....clamps can take care of those. Glue-ing the opposed cups or minor warpage can make the warpage neurtralized in all the worst cases of warpage. Just a tip.
    The chamfer on the back to allow for driver airflow should be to within 1/4" meeting the rebate for the front. This will leave about 1/4" of "tunnel" through-hole....before the flare into the cabinet airspace. No driver is gonna get congested with that. I use scallops, indexed to coincide with the openings of the driver used. This gives me a little extra "meat" left of the mdf where the screws are gonna go.

    John

  9. #9

    Default What design is that Will? *NM*




  10. #10
    Join Date
    Apr 2007
    Location
    Chicago-ish
    Posts
    1,034

    Default Re: 1.5" MDF


    What brand/type of paint did you use on that? Is it some sort of satin finish? I can't seem to decide how to paint my big ol' sub.

  11. #11
    Join Date
    May 2007
    Location
    Athens, Ohio USA
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    Default Re: What design is that Will?


    The drivers and crossover parts are from the North Creek Echo kit and the cabinet plans were based upon information in the kit. I modified the plans a bit to suite my preferences.

    This inexpensive start was my first taste of speaker building, and I'm hooked now.

  12. #12
    Join Date
    May 2007
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    Athens, Ohio USA
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    Default Re: 1.5" MDF


    > How much did you chamfer the rear of the
    > baffle?

    I bought a 3/4" 45 degree chamfer bit to do that. It goes almost to the front half of the baffle.

    The original plans provided very little airflow around the plywood woofer hole for a shielded driver, and even the 3/4" chamfer bit didn't provide enough extra room. Because it's inside the box and out of sight, I used a rough rasp to enlarge the opening. Live and learn.



  13. #13
    Join Date
    May 2007
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    Default Re: 1.5" MDF *PIC*




    > Great looking cabinet, how did you finish
    > the baffle?

    Heh, it went through a lot of iterations before I settled on Krylon Semi-Flat spray paint.

    I had some Zinser primer meant for sealing drywall and primed the baffle first with a thick, rolled-on coat of that stuff. MISTAKE! It doesn't sand well and clogs the sandpaper easily. It does fill voids well, but subsequent work was painfully slow.

    After I sanded it down smooth, I tried a Krylon Satin paint, didn't like that, so I sanded that down, primered with Krylon black printer and finally the Semi-Flat black Krylon. That's what I settled on.

    The box was maple veneer stained with General brand honey stain, and four or five coats of Minwax semi-gloss polyurethane.

    Here's a picture showing the entire box painted with the Zinser stain block (or whatever it was) that I used for the first primer. The baffle had been taken on and off after painting, but notice how closely the pins align the baffle with the rest of the box. The joint was almost invisible because of the good alignment.

  14. #14
    Join Date
    May 2007
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    Athens, Ohio USA
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    Default Re: 1.5" MDF *PIC*




    Here's another picture of the boxes and baffles during construction. You can clearly see the front baffles are made of two pieces, and you can see the plywood face/brace for the box. Looking carefully, you can spot the holes in the plywood for the pins (there are also 4 larger holes for the mounting screws in each corner).

  15. #15

    Default Re: 1.5" MDF


    Thanks alot guys for all the info. Here goes to cutting the pieces for my first speaker.

  16. #16
    Join Date
    May 2007
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    Athens, Ohio USA
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    Default Re: 1.5" MDF *PIC*




    John:

    Clearly you've done more woodworking than I have and have foreseen problems with gluing that I haven't encountered yet. Perhaps the small size of my baffles kept me out of trouble.

    My approach to gluing was dead simple - glob on a bunch of glue and toss a bunch of clamps at it. Wipe up what squeezes out. See pic...

    I like the idea of a small paint roller to distribute glue evenly. That makes a lot of sense, and I'll probably adapt that to my next project.

    Thanks for your comments.

  17. #17

    Default Re: 1.5" MDF


    > Heh, it went through a lot of iterations
    > before I settled on Krylon Semi-Flat spray
    > paint.

    > I had some Zinser primer meant for sealing
    > drywall and primed the baffle first with a
    > thick, rolled-on coat of that stuff.
    > MISTAKE! It doesn't sand well and clogs the
    > sandpaper easily. It does fill voids well,
    > but subsequent work was painfully slow.

    > After I sanded it down smooth, I tried a
    > Krylon Satin paint, didn't like that, so I
    > sanded that down, primered with Krylon black
    > printer and finally the Semi-Flat black
    > Krylon. That's what I settled on.

    > The box was maple veneer stained with
    > General brand honey stain, and four or five
    > coats of Minwax semi-gloss polyurethane.

    > Here's a picture showing the entire box
    > painted with the Zinser stain block (or
    > whatever it was) that I used for the first
    > primer. The baffle had been taken on and off
    > after painting, but notice how closely the
    > pins align the baffle with the rest of the
    > box. The joint was almost invisible because
    > of the good alignment.

    So you painted and finished the box and baffle separately before glueing them together? How did you prevent the glue from messing the finish?

  18. #18
    Join Date
    May 2007
    Location
    Athens, Ohio USA
    Posts
    1,097

    Default Re: 1.5" MDF


    > So you painted and finished the box and
    > baffle separately before glueing them
    > together? How did you prevent the glue from
    > messing the finish?

    The baffle isn't glued to the box. It's removable. It's held by the four corner screws against the face of the box. To ensure a good fit, I "lapped" the mating faces of both box and baffle on a sheet of sandpaper double-stick taped to a large flat surface. The fit is very tight and close.

  19. #19
    Join Date
    May 2007
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    Athens, Ohio USA
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    Default Re: 1.5" MDF *PIC*




    Here's the back-side view that shows the roll pin on one corner of the just-glued baffles. Sorry about sharpness, but you'll still get the idea how it registers the two pieces of MDF closely so that the driver holes align precisely.

  20. #20
    Join Date
    Oct 2005
    Location
    Ellicott City, MD
    Posts
    22

    Default Re: 1.5" MDF

    Provided Link: http://i168.photobucket.com/albums/u...s/IMG_1376.jpg


    > I can't seem to post enough today!

    > Here's a picture of the nearly finished
    > speakers. The front baffle is 1-1/2"
    > thick made up of two pieces of 3/4"
    > MDF. You can't tell it's glued together at
    > all.

    WOW! Much better job than I'm doing on my Echoes!



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