Dahlberg  Audio  Design.
"The tall neodymium ribbon". Part 2

Now we are down to woodworking. The drawing on your right shows one of my latest constructions in profile. The shaded area is detachable and in this version also mounted to the magnetic circuit (those bolts are not in the drawing). The black lines show speaker-fabric. You will need it, strangely enough not even grownups can keep there fingers to themselves. There are two measurements that say 25mm and that makes it easy for the construction of a gluing, and routing jig. Just use a one inch square steel pipe of sufficient length.
The steel pipe has to be cleaned and painted to prevent it from discoloring the wood during gluing.
Apart from what's showing in the drawing some connecting parts will be made. For starters some blocks 87x25x15mm preferably from the same wood. 25 and 15 is not absolutely crucial. Some covers over and under the opening to finalize it. Here you can use almost anything just as long as it isn't magnetic.

The finished result as a drawing.

We are starting of with some "U-profiles", these ones are made from oak.

Use appropriate amounts of regular white wood glue. Don't leave it for to long or else the glue may stick to the steel pipe. 30 minutes is sufficient.

"U-profiles" 

You will need some tools...

These ones work so-so but they are fast

You can take a little of before routing.

When that's done it's time for routing and that will be done with the pipe as a guide. Some hand tools may also come in handy. The pictures should be helpful enough when describing how to do this. Simulate the routing before you start the machines and please be careful about your fingers.
 
Copy routing. Angled routing. Make sure that you measure carefully.

 

Ok.

The last part of the "U-profile"  will not be glued. Instead it's attached  with screws. To get the right drilling depth I'm using a little helper, look at the pictures. When that's done you just finish of the routing. Same procedure as last with the steel pipe in place. 
Some marking. Drill with depth limitation. Barely through the first layer  but no more. 

Ok, now it's time to turn the parts into a left end right side tweeter/driver. On the outside you are supposed to glue an additional 8mm strip of oak. Due to the fact that the drivers are supposed to be a mirror imaged pair it's quite important to keep track of how you are putting it all together. Lay them side buy side, it helps.

Gluing is done without the detachable part of the u-profile.  At this point you will have to use the clamps again, you can not get to many of these. Just keep it up as earlier, appropriate amounts of glue and look closely at the pictures about how too set the clamps. Access glue is easily removed later with a sharp knife.

The angled routing is not done on this profile yet but is still possible. after the next moment it's not so take care of this now. Just as earlier with the steel pipe and so on. Now it's time to glue the wooden blocks that are holding the two halves together.

Widening of a U-profile.

Set a few clamps to eliminate the risk of sideways slipping as well.

The blocks are made from what's left of earlier bits and pieces. 88x15x26mm will work just fine. Let the magnetic circuit lay in place during assembly, that way you are sure that it will fit later on. Once again, keep track of what's left/right and up/down.

Blocks, 88x26x15mm. Just the 88mm's that are important.

The u-profiles are glued together, keep track of left/right and up/down.

 

Now we have the magnetic circuit and the wooden parts. Time to put them together. 

The magnetic circuit will attach to the removable backside.

Start of by placing the magnetic circuit where it's supposed to be. Then we attach the oak strips with the small wood screws. Then set a clamp over the sides to hold the wood against the steel. Mark where the holes will be drilled to attach the backside to the magnetic circuit. 
Drill down through the oak and in to the steel to make a mark, don't move anything during this procedure. Make sure that you mark wish strip goes where.

When you are done with this you can remove the oak strips and the magnetic circuit. Drill and tap to finish this part.
When you are done you mount the strips to the steel.

Magnetic system in place. Mark for the holes.
Predrill... Drill and tap.
Now it's just the backside left. The pictures should be a sufficient description. Just make sure that the short pieces you glue are not to long. It has to fit in the front section. I'm using the same 44x8 mm oak strip for this as well. The covering lids are also made from the same oak strip. The sharp edge is rounded of and the rest is done with the router, look at the pictures. Just keep an eye on them when gluing, they may slip sideways if you are unlucky.

Make sure about sufficient length and placement.

Same as earlier ;-) .

Some routing again.

Seems too fit.

Now it's just the fun stuff left. Making them look good as well. The sanding and so on is usually no problem but cutting them too the right length and angle is a little bit trickier. If you use sufficient tools for it should work just fine though.

Make sure that it does not slip sideways. I don't now what this tool is called in English but it works. 

This I like, ... God tools help a lot at this stage.
And now it's time for the internal wiring. The principle is shown in this sketch, the gray lines illustrating the aluminum strips of the ribbon and the red lines of course showing the actual wiring. Too make sure what's  "positive"  and "negative" you use a 1.5V battery. If the ribbon is moving forward when the battery is connected, the connection connected too "+" is the positive one. 

Principle sketch for the internal wiring.

The driver at the pictures above already have the speaker cloth assembled. I have just stampled it at the short ends. Burn through the cloth at the  assembly  holes with your solder iron.

I'm using a regular 1/2inch copper pipe as a tube for the internal wiring, works just fine and is easy too find. 

Cable sleaving looks nice as well. It's easier too  work with if you are a little generous with the length.  The tube is just pressed in too place, remember this is not a handle. 
The wiring is by own choice, I'm using cat-5 right now. 

 

Make sure that you follow the principle sketch when soldering.

Drill a hole.

Internal wiring.

Find these at your plumbers Cable sleaving looks nice
Cat-5 is what I'm using for this project. A little bit too close too the screws but no real problem anyway
 

All done!

Now it's just ribbon manufacturing left :-)

Part 1   Part 3

Bengt Dahlberg & HiFiForum.nu except: Logos and Trademarks are property of their owners. All Rights Reserved