Diving in - a pair of DR250s

[Grant Bunter]

Tonight was what I called "3 glue Tuesday"

I cut apart an old pillow, stuffed the area around the horn throat, and hot-melt glued the first set of PVC pipes on. Then I got out the PL and attached the second horn sheath. Then I assembled the melded array. 3 joints, 3 different kinds of glue. This left me with two questions:

1) Do I have to trim (or sand) the hot melt glue at the PVC pipe/wood boundary? Or can I leave a little bump?

No, don't worry about trimming. Bumps are fine. Just make sure they are sealed.

2) Does the tweeter array have to be without any holes at the glued joints? (I know it no longer seals the driver chamber, but for the tweeters to work well...)

Not for function. As you've said, the melded array now sits in a module that seals the driver chamber.
You might like to make sure there are no holes for aesthetic reasons though, especially if you don't plan to put on grille, or hide the inner parts of the cab with foam on the grille.

[billkatz]

Tonight was what I called "3 glue Tuesday"

I cut apart an old pillow, stuffed the area around the horn throat, and hot-melt glued the first set of PVC pipes on. Then I got out the PL and attached the second horn sheath. Then I assembled the melded array. 3 joints, 3 different kinds of glue. This left me with two questions:

1) Do I have to trim (or sand) the hot melt glue at the PVC pipe/wood boundary? Or can I leave a little bump?

No, don't worry about trimming. Bumps are fine. Just make sure they are sealed.

Thanks - got the second set of reflectors in.

2) Does the tweeter array have to be without any holes at the glued joints? (I know it no longer seals the driver chamber, but for the tweeters to work well...)

Not for function. As you've said, the melded array now sits in a module that seals the driver chamber.
You might like to make sure there are no holes for aesthetic reasons though, especially if you don't plan to put on grille, or hide the inner parts of the cab with foam on the grille.
I'm planning on no grills with an "interesting" color for the piezos. I'm going to let my son choose. The holes, if any are left, are pin size so you can't see them - so if there are any at this point, I'll leave them.

Thanks for your help

[billkatz]

Tonight I attacked the part that has worried me the most since I started this - the module cleats: small, with a radius and odd angles. I finally came up with an approach, and I think it worked pretty well. First I put on the 24" radius milescraft router jig, and by measuring the top and bottom panels, found where the pivot had to be relative to the back edge of the cleat - basically continuing the radius of the other cleats.

Then I took my "comb" of cleats and cut them off square against the table saw fence. I laid them out allowing an inch of extra ply against the fence.
Next, I built a little jig/sled that would hold them in the correct position to make the 45 degree cut at the other end:

The parts came out well-matched and appear to be the right size. Here they are stacked at the bottom of the cabinet:

Now I have to figure out how I want to attach the module - whether I want to make another 16 in order to use the "hifibob" pocket screw attachment method, or the nacelles.

Then, as a final test, I did a dry fit of the whole front end, including the array:

And here's where I ran into problems! I'm really glad I tested this. While everything appears to fit well, I can't get the tweeter array in or out with the module faces in place. I noticed in the printed plans (but not in the sketchup) that the picture on page 21 does show an angle cut on the inside of the faces. Perhaps this is what's needed?

Has anyone else run into this problem?

The final parts I need for the module are the little top and bottom braces. The plans recommend they be cut at a 3 degree angle on the bottom - but the parts are installed at a 45 degree angle to the top/bottom. Do I need to jig up a compound angle for these parts?

[Grant Bunter]

This was my array


I didn't swap around the elements like you did, and found the same thing as you, that the array catches. I do note in sketchup all the piezo element tabs face towrds the back plate.

I had to angle it slightly to put it in and take it out. It's the tabs on the elements that are catching most likely. In my case, I bent them down (carefully) so they didn't come to be quite as wide.

Yes, you do need to shape the upper and lower middle segments of the module down for clearance, as explained in the plans.

To get a better idea, put the cab on it's back, and centre the array (so there's an equal gap between top and bottom). If it doesn't catch then, it was simply the array was sitting to low...

[escapemcp]

This was my solution:



Used a Dremel round sanding bit to achieve this (in minutes).

[hifibob]

great looking build..You will definitely have a scene of accomplishment once completed..

[billkatz]

great looking build..You will definitely have a scene of accomplishment once completed..

Thank you. I have been coveting your CNC as I have been making the tiny parts like the module sheath braces. Watching your video of DR parts magically appear is humbling after a couple hours of routing and sawing.

[billkatz]

This was my solution:

Used a Dremel round sanding bit to achieve this (in minutes).

Oooh - an excuse for another tool. Last week was the multi-tool/sonic saw attachment for my Makita cordless tools. The Dremel solution looks very tidy. Off to the hardware store for a Dremel and a pipe coupler for the ports.

[hifibob]

great looking build..You will definitely have a scene of accomplishment once completed..

Thank you. I have been coveting your CNC as I have been making the tiny parts like the module sheath braces. Watching your video of DR parts magically appear is humbling after a couple hours of routing and sawing.

Haha it does make it easy but definitely takes the fun and therapeutic zone I get into while building. I can't wait to hear your impressions once fired up.

[billkatz]

I made a little progress tonight. I trimmed the horn sheaths with my new sonic saw:

I also glued up the first bits of my first module. I used a couple long clamps to hold the back of the module to the horn, taped down some wax paper, and clamped module cleats to the top and bottom. Then I glued the cleats in, and glued and shot some brads to hold the module faces on.

The next step will be to add the middle cleats.
I also trimmed the module sheaths to size.

I also discovered a small problem with my second cabinet as I trimmed the module back to fit. It appears that my sheath braces are slightly wider at the top than the bottom - giving the front of the horn a bit of a trapezoidal shape. When I build the module there will be a slight misalignment of about 1/8" on either side at the top of the module top. You can see the alignment here:

I hope this slight step in the horn curve will not negatively affect things. I don't see any way to easily fix this alignment.

[Grant Bunter]

I guess all you can do is check the measurement/width of the backing plate at top and bottom.
It looks to be equally spaced though oversized at the top (compared to your arcs), but if it is the correct size at the bottom, it is possible the backing plate cuts are not square...

[ncgrove]

...it is possible the backing plate cuts are not square...

The ones on my DR250s certainly aren't square, but everything turned out fine as far as I'm concerned. A healthy dose of Duratex will make it impossible for anyone but yourself to notice.

[billkatz]

I guess all you can do is check the measurement/width of the backing plate at top and bottom.
It looks to be equally spaced though oversized at the top (compared to your arcs), but if it is the correct size at the bottom, it is possible the backing plate cuts are not square...

Unfortunately the module back is exactly square, it is the front of the woofer compartment (made of 4 individual sides) that is wider at the top than at the bottom. (I can easily confirm that by rotating the module back 180 degrees). At this point I'm just going to push forward. I think I can see the finish line from here!

[Grant Bunter]

Unfortunately the module back is exactly square, it is the front of the woofer compartment (made of 4 individual sides) that is wider at the top than at the bottom. (I can easily confirm that by rotating the module back 180 degrees). At this point I'm just going to push forward. I think I can see the finish line from here!

Arrrr ok, understood. I thought it was the backing plate.
haha, don't start to race now the finish line is getting closer...

[escapemcp]

The finishing line is a mirage... it's still a long way off. Slow, steady & methodical will do you grand.