1.5" MDF

[almareaktiva]

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.

[williamrschneider]

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.

[williamrschneider]

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.

[williamrschneider]

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.

[jml]

Re: 1.5" MDF


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

cheers

[johnnail]

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

[zach_t]

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.

[johnnail]

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

[kec]

What design is that Will? *NM*

[JustinG]

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.

[williamrschneider]

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.

[williamrschneider]

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.

[williamrschneider]

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.

[williamrschneider]

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).

[almareaktiva]

Re: 1.5" MDF


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