Bear in mind that there is some spingback when you use spinning. It takes a few times to be able to get the stable dimentions.
gedlee said:
It is a two part mold. And yes, the walls (wall?) are too thin or rather, I would like them thicker myself. The edge of the lip is 1/8" thick, but the rest is ~1/4". Seemed sturdy enough until I mounted the CD, thought the weight would crack it. It's fine though, I've even given it a few good shakes, but were I to do it again, the walls would be significantly thicker.
I'll post pics of the mold, I should have some time tomorrow. It's constructed as per Patrick Bateman's method (as I know it) of stacking thin sheets of smaller and smaller diameter - I used MDF - then sanding and shaping with a polyester filler. It's crude and inaccurate (and takes time), but I was curious so... The plug isn't too bad though, however, the back is quite ugly.
Oh, and I just realized I neglected to mention the size. It's 11".
That method of making a mold works fine for a small number of parts, but the mold won't hold up over time. I would not use the poly at anything less than 1/2" from what I have seen, my waveguides are 1" thick. The poly is not brittle, but its not very strong either. I don't think that I'd ship a CD mounted on a waveguide only 1/4" thick.
You can imagine the work involved in making something at the 15" size.
You can imagine the work involved in making something at the 15" size.
I would really like to build a big beautiful white elliptical glassfiber waveguide...BUT, I also know a skilled man who makes wooden art bowls, and I am tempted to ask him to turn a couple of waveguides...think I need to talk with him...design will be 18"/12"/1"CD, probably 🙂
😀 There was a man here...one I took lessons from...who had a lathe which would allow the turning of ellipsoidal work. My interest in that machine stirred too late. It vanished after the auction.
One of the interesting aspects of a segmented plug is that it can be expanded ad infinitum. 😀
One of the interesting aspects of a segmented plug is that it can be expanded ad infinitum. 😀
gedlee said:
Having only cast one, I can't comment on the durability. How and why does the mold eventually fail?
Mold:
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Oh, and why would anyone ship a CD mounted on a waveguide?
@dfdg
as a production item perchance? such as the completed Nathans, Abbeys and Summas that Earl makes.
Nice work on the mold there, think I'll be biting the bullet and just buying from Earl as I just dont have the capability to make something accurate enough.
Nick
as a production item perchance? such as the completed Nathans, Abbeys and Summas that Earl makes.
Nice work on the mold there, think I'll be biting the bullet and just buying from Earl as I just dont have the capability to make something accurate enough.
Nick
durability
so... this is now a thread about production quantities of CD horns? I thought all the fuss was about how difficult it is to make JUST ONE horn as a DIY-er.
My bad, I guess....
Seems dfdg has made a perfectly viable horn using a pretty straightforward DIY method, and a bit more finish work on the mold would provide a perfectly acceptable horn as good as what geddes sells for $200.
The "experts" seem to provide lots of negatives wrt making these by any means as a DIY-er, it would seem... no agenda there
John L.
so... this is now a thread about production quantities of CD horns? I thought all the fuss was about how difficult it is to make JUST ONE horn as a DIY-er.
My bad, I guess....
Seems dfdg has made a perfectly viable horn using a pretty straightforward DIY method, and a bit more finish work on the mold would provide a perfectly acceptable horn as good as what geddes sells for $200.
The "experts" seem to provide lots of negatives wrt making these by any means as a DIY-er, it would seem... no agenda there
John L.
Your bad for thinking it's some kind of big deal I guess. Do what you're going to do, we'll pay attention and think about it so where's the conflict? If I wasn't such a procrastinator I'd have made my own waveguide by now. What did you make?
dfdg said:
I ship assembled speakers all over the world.
Mold failure depends on the heat generated within the cast. The greater the heat the shorter the molds life span. MDF is not very solid with regard to temperature and humidity and it expansion and contraction causes stress cracks in the filler and eventual failure. I've ruined molds on the first cast when the material overheated.
Those are very good looking molds. You have obviously done this before. You said that you made those by hand.
I really don’t see what the issue is here. You guys are making the molds far too difficult. Once you decide on what size waveguide you want, just make a reusable mold using Smooth-on mold and casting products.
www.smooth-on.com
You should be making a waveguide first, then use that waveguide to make your mold. Most of you guys are doing this a$$-backward.
http://www.youtube.com/v/MJ9lgZ3V90o
I would use the same technique as in the above video. It’s not that difficult. The most difficult part is making your first waveguide. I just turn my own on my lathe using templates as guides. I can hold +/- 1mm or better on my lathe easy. They look like this:
www.smooth-on.com
You should be making a waveguide first, then use that waveguide to make your mold. Most of you guys are doing this a$$-backward.
http://www.youtube.com/v/MJ9lgZ3V90o
I would use the same technique as in the above video. It’s not that difficult. The most difficult part is making your first waveguide. I just turn my own on my lathe using templates as guides. I can hold +/- 1mm or better on my lathe easy. They look like this:
@ Auplater
I was replying to a specific query, of course this thread is about small quantities of WG's (2 one would assume, 1 would be a of limited use in STEREO)
Nick.
I was replying to a specific query, of course this thread is about small quantities of WG's (2 one would assume, 1 would be a of limited use in STEREO)
Nick.
moi?
Big deal? Not from here, this is just a hobby, remember? It's a little tiresome watching the constant deference to the "sacred cows" here, though, especially after repeated efforts have been made by same to discredit viable techniques.
I've made lots of stuff, I guess you haven't read the whole thread?
http://www.diyaudio.com/forums/showthread.php?postid=1606914#post1606914
Yeah, I know, Nick... but I was taken to task about the excessive costs, dangers, and complexity of EF for DIY-ers by the powers that be, and now mold longevity in production runs is an issue?
BTW: I agree completely with JLH re: overly complex, and said as much early in the thread, for which I was also taken to task. So be it.
John L.
poptart said:
Big deal? Not from here, this is just a hobby, remember? It's a little tiresome watching the constant deference to the "sacred cows" here, though, especially after repeated efforts have been made by same to discredit viable techniques.
I've made lots of stuff, I guess you haven't read the whole thread?
http://www.diyaudio.com/forums/showthread.php?postid=1606914#post1606914
Yeah, I know, Nick... but I was taken to task about the excessive costs, dangers, and complexity of EF for DIY-ers by the powers that be, and now mold longevity in production runs is an issue?
BTW: I agree completely with JLH re: overly complex, and said as much early in the thread, for which I was also taken to task. So be it.
John L.
JLH said:
I think that there would be dozens of viable ways to make waveguides each with different skill sets and equipment required. I simply try and point out what some of the apparant flaws might be for each approach - based on the fact that I have made hundreds of waveguides. Some methods work better for small runs others for larger runs. Some might cost more in tooling some more in materials. What you are showing is the "pro" method and is the same as what I do, but it takes a lot of tools and skills to perform. There is no one "right" method, but there can be some serious flaws with some of them.
Some people seem to be very touchy about "their" technique not being my favorite one.
John
Fair enough, just thought I'd state where i was coming from, I thought you were having a go.
Nick.
ps: Just spunked a pile (for me) some new subs, maybe nathans for xmas? 🙂
Fair enough, just thought I'd state where i was coming from, I thought you were having a go.
Nick.
ps: Just spunked a pile (for me) some new subs, maybe nathans for xmas? 🙂
Re: durability
The accuracy is the difficult part. The technique I used I don't think will get there. Maybe with a lathe...
I would have to disagree even without seeing geddes guide in person. It would need a lot more finish work. And even then I seriously doubt the accuracy would be there even after one put in a lot more time and effort.
It terms of materials costs, I had everything but the polyurethane on hand from other little projects. But otherwise it would be not be cheap and when you factor in the time spent, it's not a viable route if the choice is between fabrication or purchase and cost is a paramount.
As a DIY challenge/curiosity project, it's okay, that was my motivation.
Didn't realize they were fully assembled.
Well, I didn't use my feet. 🙂 Used a router to cut circles for stacking. Shaping, sanding by hand. I've worked with fiberglass and wood before, but strictly as a hobbyist. Never made a mold before or casted anything from a premade mold.
No lathe.
Grumpy_Git said:
The accuracy is the difficult part. The technique I used I don't think will get there. Maybe with a lathe...
auplater said:
I would have to disagree even without seeing geddes guide in person. It would need a lot more finish work. And even then I seriously doubt the accuracy would be there even after one put in a lot more time and effort.
It terms of materials costs, I had everything but the polyurethane on hand from other little projects. But otherwise it would be not be cheap and when you factor in the time spent, it's not a viable route if the choice is between fabrication or purchase and cost is a paramount.
As a DIY challenge/curiosity project, it's okay, that was my motivation.
gedlee said:
Didn't realize they were fully assembled.
gedlee said:
Well, I didn't use my feet. 🙂 Used a router to cut circles for stacking. Shaping, sanding by hand. I've worked with fiberglass and wood before, but strictly as a hobbyist. Never made a mold before or casted anything from a premade mold.
JLH said:
No lathe.
I see the speakers both assembled and as kits. The assmebled ones have to go all over the world. They need to stand up to this when the CD is mounted.
Here is a pic of how I turned my 345Hz Tractrix horns,14" outside dia,2" throat,from glued up layers of MDF.
It would have been a bit easier if I had cut out the inside circles first,rather than turning a solid piece.The boring bar is only 3/4",so a bit flimsy,but works OK if you don't try to take a heavy cut.
Keep turning till the guide bar hits the pattern.You don't have to keep stopping to check with a template.
I turned the outside freehand,but the pattern could be made to include the outside,too.
http://img507.imageshack.us/my.php?image=0000001kv5.jpg
It would have been a bit easier if I had cut out the inside circles first,rather than turning a solid piece.The boring bar is only 3/4",so a bit flimsy,but works OK if you don't try to take a heavy cut.
Keep turning till the guide bar hits the pattern.You don't have to keep stopping to check with a template.
I turned the outside freehand,but the pattern could be made to include the outside,too.
http://img507.imageshack.us/my.php?image=0000001kv5.jpg