consistent Posted May 11, 2007 Share Posted May 11, 2007 Hi All, I decided that I should attempt to make a tractrix horn the way ALK and a few others suggest except I know absolutley nothing about wood working and all that stuff! So I ended up taking the easy way out by cutting (butchering more likely) top and bottom pieces of the horn from 'almost' 1 inch MDF and using premium quality cardboard (1.7mm thickness) and layering this 4 times with super strong Canadian wood glue. The result was amazing, didn't think it could be done. I put a strip of 7mm MDF on the edge of the mouth of the horn frame and again on the top of the frame. I then cut out a cardborad piece to fit snuggly into the frame, glued it in then cut down the sides then repeated this 4 times and viola a tractrix horn! I am going to try and load up pictures, I am also not very good at this. I am in a Linux environment using Open Source (gimp) so here it goes. Quote Link to comment Share on other sites More sharing options...
consistent Posted May 11, 2007 Author Share Posted May 11, 2007 ...and here is another in the early stages Quote Link to comment Share on other sites More sharing options...
consistent Posted May 11, 2007 Author Share Posted May 11, 2007 ...and another Quote Link to comment Share on other sites More sharing options...
consistent Posted May 11, 2007 Author Share Posted May 11, 2007 ...and a more sexy picture, sorry no women or men! Quote Link to comment Share on other sites More sharing options...
consistent Posted May 11, 2007 Author Share Posted May 11, 2007 ...and finally after the undercoat and now the 'black' Well that seemed to go well! Gimp works. I am using the AK4 and I don't think the change from the 401 to the tractrix is that dramatic when placing the tractrix in the same position as the 401. Some things are more noticeable and others are not, until I move the whole kit around facing into the listening area. I am using Bob's tweet and put that on the vertical rather than the assumed horizontal. That makes a difference in greater focus of instrumentation and voicing in the top end. The tractrix is postioned facing the listener and then moved slightly back with the tweet on top of it ( I have taken the 'top hats' off the Khorn to allow for this). Now I get a dramatic change, so pinpointed with what seems to be a wider soundstage and centre point. I am liking it! Quote Link to comment Share on other sites More sharing options...
PrestonTom Posted May 11, 2007 Share Posted May 11, 2007 This is an intriguing project. I saw something similar on another forum. They had used bendable plywood and 1/8 luan rather than cardboard. They also showed some cutting jigs since there are some funny angles on the thicker pieces. I assume you had a similar headache. Congratulations! Do you have a way of measuring the frequency response and dispersion? Also, are you going to try and smooth the transition between the driver (round) and the throat entrance (square). Some have suggested a malleable substance (clay or plaster of paris) at that transition. What are your thoughts? Good Luck, -Tom Quote Link to comment Share on other sites More sharing options...
Guest " " Posted May 11, 2007 Share Posted May 11, 2007 That looks good. How long did it take you? Quote Link to comment Share on other sites More sharing options...
consistent Posted May 11, 2007 Author Share Posted May 11, 2007 Hi Tom, I was thinking about testing but would need to call on an old friend who I haven't seen in years. I'm not sure what that transition will do. I have done only some around the opening (wood workers plaster) and I notice that the 401 leaps from round to square. I have not put the 401 washer into the tractrix as it seems the sound loses pitch. I would also love to test 'washer or no washer'. The headache was my intolerance at the glue not drying quick enough. The cardboard was easily cut, per layer, with a sharp cutting knife. Cheers Quote Link to comment Share on other sites More sharing options...
consistent Posted May 11, 2007 Author Share Posted May 11, 2007 It took a few weekends on and off. I think that what I know now I could half the time, maybe 2 days allowing for glue to dry and a further day for the paint as I now have the jigs and sizes of motor boards. Quote Link to comment Share on other sites More sharing options...
Guest " " Posted May 11, 2007 Share Posted May 11, 2007 'The headache was my intolerance at the glue not drying quick enough." Do you think contact cement would be a better option? Quote Link to comment Share on other sites More sharing options...
Daddy Dee Posted May 11, 2007 Share Posted May 11, 2007 Wow, Those look great. Congrats on your craftsmanship. I had the privilege of having a pair of quite similar, though made with plywood, from 3dZapper. the sound was indeed impressive, and IMO, an improvement over a K400/401. Also, have to say, as an audio skeptic, I was surprised at the improvement. \ Quote Link to comment Share on other sites More sharing options...
consistent Posted May 11, 2007 Author Share Posted May 11, 2007 I think contact cement may work better although the wood glue is easier to work with and clean up Quote Link to comment Share on other sites More sharing options...
consistent Posted May 11, 2007 Author Share Posted May 11, 2007 Yeah, a little scepticism is healthy. The improvement is good but not earth shattering and that may well be my design! Quote Link to comment Share on other sites More sharing options...
djk Posted May 11, 2007 Share Posted May 11, 2007 " and using premium quality cardboard " RCA did this on many of their horns, including the bass horn on their double 15" model (Ubangi). Quote Link to comment Share on other sites More sharing options...
Spongeworthy Posted May 11, 2007 Share Posted May 11, 2007 Cool project. Thanks for sharing. I may actually try this. I also sell adhesives for a living so I have some materials that will cure very quickly. Quote Link to comment Share on other sites More sharing options...
consistent Posted May 13, 2007 Author Share Posted May 13, 2007 Its well worth the effort. Once you work out the frame the cardboard just slips in and after 4 layers it is just like wood and has good density Cheers Quote Link to comment Share on other sites More sharing options...
Daddy Dee Posted May 14, 2007 Share Posted May 14, 2007 Consistent, Have you got plans/drawings for that horn? Quote Link to comment Share on other sites More sharing options...
consistent Posted May 14, 2007 Author Share Posted May 14, 2007 Yep, It was from an old thread I think ALK and a few others contributed to. I did up my templates based on them. Originally it came out of Bruce Edgars calcs and ideas for a 2" lens. Al has some pics on his website. Also recently there was a thread on a magnificent pair being built...I can't remember who it was I'll have to do a search. My system recently died and I lost a lot of info and am now using Open Source (Suse) rather than Windows and just starting to find my way around. Cheers Quote Link to comment Share on other sites More sharing options...
tigerwoodKhorns Posted May 15, 2007 Share Posted May 15, 2007 I have a 4' x 8' sheet of that bendable wood. I was going to eventually fabricate a pair. I want to be able to veneer them. That will be the trick. When you say cardboard do you actually mean cardboard or just flexable board like they sell at the home depot (like what is used for the bottom of drawers on cheap cabinets). Quote Link to comment Share on other sites More sharing options...
consistent Posted May 15, 2007 Author Share Posted May 15, 2007 Hi, I really mean cardboard! When you use multiple layers it works like ply. Even a mate of mine was not convinced I used cardboard and I had to show him the off cuts. Lots of glue and multiple layers, works a treat. Do the 'knock test' and it sounds like ply or MDF Cheers Quote Link to comment Share on other sites More sharing options...
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