Mid Bass Horn Design 80-800 Hz

[GM]

When I built my 825 clones in '64 all I had was a hand and hole saw, so just back cut the side flares, and filled in the gap with a putty made from glue and sawdust to stiffen the glued and screwed joint. They never cracked from moving them several times during the ~6 yrs I had them and even withstood the extra pressure of loading 411s in them when I converted them to a two way for my neighbor at the time.

Since it worked so well, I did all horns this way except for the conicals that had fixed angles I could cut on my radial arm saw.

[bfish]

Originally posted by GM:
...a hand and hole saw...

<font size="2" face="Verdana, Helvetica, sans-serif">I'm trying to picture how you'd work one of those...ain't coming up with anything pretty either...

[GM]

With a great deal of elbow 'grease'.

[Steve Mac]

I guess you go to war with the army you have...
I built a jig for the router base:
Router Base 1
Router Base 2
Router Base 3

If I hold the router base edges in sync with the parallel lines drawn on the wedge faces as it's cut, theoretically it'll work. I'm just frightened of ruining the perfect edge on the face. I'm also sick and tired of not getting this done quicker.

[bfish]

I'm rooting for ya! (he said, as he stubbed his toe for the umpteenth time on a 2+ year old project of his own).

[jnorv]

Question on cutting the horn end pieces on an angle. Calculating the shape is fairly simple but how did you compensate for the angle when you did your router cuts. It looks like it might be setting in there at about a 15 degree angle and short of a 5 axis router table I am at a loss on how to do that cut. In the end it might not make that much difference to the final fit.

Jim N

[Steve Mac]

Originally posted by Jim Norvell:
That should work in theory. I would use some making tape on the upper edge to reduce splintering. By scaling your drawing and making some calc's, it looks like you might have to take off about 1/4 inch at the mouth. I think I would make a couple of passes instead of just one. It is hard to tell from your pictures but do you have a ball bearing contour follower at the top of the bit instead of the end?

Jim N

<font size="2" face="Verdana, Helvetica, sans-serif">I have this bit...it may be barely long enough...maybe not...it's awful close.

I don't know if I'm going to do it but I was milling around Home Depot looking for ideas and I bought a sheet of tin. I was thinking to sandwich it between two pieces and use a jig saw to slice it out, file it clean, and then remove the top piece clamping the metal over the piece to be cut with parallel lines drawn just once...on the metal...and that would save time, and then I would have maybe some protection during the removal of material process.

Tin Pic

I picked up a coping saw in case I start feeling Ahmish...

[jnorv]

That should work in theory. I would use some making tape on the upper edge to reduce splintering. By scaling your drawing and making some calc's, it looks like you might have to take off about 1/4 inch at the mouth. I think I would make a couple of passes instead of just one. It is hard to tell from your pictures but do you have a ball bearing contour follower at the top of the bit instead of the end?

Jim N

[bfish]

Originally posted by Steve Mac:
...I picked up a coping saw in case I start feeling Ahmish...

<font size="2" face="Verdana, Helvetica, sans-serif">They'd use a drawknife, a reeeally, reeeally sharp one.

<font color="#FFFFFF" size="1">[ December 12, 2007 02:48 AM: Message edited by: bfish ]</font>

[Steve Mac]

A draw knife eh?...Ya know if I cut one more curve based on the bottom edge of the angle top face I could do just that...just hew out the difference between the two edges...hmmmm