Al Klappenberger Posted February 5, 2005 Share Posted February 5, 2005 Guys, Some of you have noticed that I have been hinting about the development of a true wooden Tractrix squawker horn replacement for the K400 and K500 horns in the Klipschorn, Belle Klipsch and LaScala. The design was copied from an article that appeared in Speaker Builder magazine written by Bruce Edgar. The picture shows Bruce's version of the horn for 4 inch cone drivers. I simply wrote a computer program to duplicate his procedure. The picture shows the prototype horn being test fit for size in the top section of Khorn. The horn was to be provided mounted in a completely new drop-in front frame (motor board), black grill cloth and front surface mounting adapters for the K77 or Beyma CP25 tweeters. Adapters were also to be provided for the K55 driver or any 1 Inch throat driver such as the Altec 902. The curves shown below the picture compare its response to the ALTEC 511b and the Klipsch K400 horns. The curves where done outdoors and are therefore anechoic. As the curves show, the horn is quite flat down to 400 Hz and usable down to 300 Hz to help protect the driver. Listening tests have been done and the sound was described as very similar to a "fully damped Altec 511b". HOWEVER: I have been trying for months to find a wood shop that will make them for me locally. I have found two extremes. One extreme is a small wood shop that is unable to make them because of the compound angles involved or long delay times. There other type is a big shop with CNC milling machines that require large volumes to make it practical. The cost would be out of sight to make them in small quantities. My other possibility is to have a CNC equipped shop make the parts in quantity and I find a small shop to assemble them or assemble them myself. HELP! Before I can do anything to get these made I need to know what kind of interest this is in them and what quantity I can expect. This will determine the price. I apologize to Klipsch for utilizing their forum for what would seem to be a sales pitch, but I don't believe my business web site will give me enough of an idea of the demand quickly enough. If the demand for the horn is low, I may simply release the design for the DIY crowd, but these are NOT easy to build. The single prototype in the picture took me a week to make! Al K. Quote Link to comment Share on other sites More sharing options...
BEC Posted February 5, 2005 Share Posted February 5, 2005 Al, I have a connection with a very cooperative local cabinet shop that has state of the art CNC equipment. I will approach them with this project of yours if you want me to do that. Bob Crites Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted February 5, 2005 Author Share Posted February 5, 2005 Bob, Thanks for the offer. I may need to take you up on that, but the idea of having these made out of town scares me. There are too may details to be explained that are difficult to show on a drawing. I am afraid that I need to be able to guide whoever builds them in person. Even making the top and bottom "plates" requires not only following the tractric curve but keeping a second precise angle on the edge as well to make them fit to the sides. Al K. Quote Link to comment Share on other sites More sharing options...
michael hurd Posted February 5, 2005 Share Posted February 5, 2005 Al, what materials are you considering offering these horn in? It looks like you used MDF for the prototype, and it does machine well, but you might consider many layers of veneer epoxied together into a large block, this would also work quite well. After coating the outside, it would not have any problems with humidity or water like mdf does. You should also ask around on the board here, there are plenty of people in the plastics industries, you might be able to get a horn formed out of RRIM, or other durable plastic. Quote Link to comment Share on other sites More sharing options...
BEC Posted February 5, 2005 Share Posted February 5, 2005 Al, What you are describing is exactly where a CNC router does outstanding work. Of course programming that all in to the computer is the challenging part. If the drawing can be produced with the required precision, that programming is made a lot easier. By the way, this woodworking CNC router is not limited to wood. I have had this guy make plastic parts for me on it. Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted February 5, 2005 Author Share Posted February 5, 2005 Guys, Here are two drawings showing how the new horn is to be mounted in new grill frames for both the Khorn and Belle. The networks shown are the extreme-slope models so as to verify that the maximum possible size networks will fit. The tweeter shown is the Beyma CP-25 for the same reason. The horn is just tall enough to fit in the Khorn but the Belle will require simple raiser strips to lift the top woodwork by a small about. Al K. Quote Link to comment Share on other sites More sharing options...
michael hurd Posted February 5, 2005 Share Posted February 5, 2005 Al, take a look at www.woodhorn.com , they have a guide to properties of different types of plastics. Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted February 5, 2005 Author Share Posted February 5, 2005 Michael, The prototype is made of particle board on the top and bottom. The sides are 4 layers of 1/8 inch masonite with semi-hard adheasive between them for damping. I suspect the final version will be two layers of bendable plywood with damping adheasive between them. Bruce Edgar mentioned in his article that a single layer of plywood casue resonances. The throat adaptor is also particle board. I suspect that other methods of making this horn will cost even more, especially if I try to make it look pretty. I have looked at the woodenhorn.com web site. Did you see their prices? The idea is an ugly beast that doesn't cost a mint hidden inside the top compartment that sounds super! Hopefully the final thing will look a lot better than my hand made prototype though. Bob, Yes, but I need to order a large quantity of top and bottom "plates" and of the throat adaptors to make this cost effective. The throat adaptor must transition from a 1 inch square to a 1 inch round over 3/4 inch distance to maintian tractrix expansion at the throat. This is also a job for either a CNC or a hand file, which is how I did it! To give you a hit of the problem, the only cost quote I got for this project was over $300 for EACH horn (fully assembled) in small quantities! This would be my cost! Al K. Quote Link to comment Share on other sites More sharing options...
michael hurd Posted February 5, 2005 Share Posted February 5, 2005 Once a CNC program is written, all you have do do is mount the block of material, and start the mill. It does the rest for you. The cost of programming ( the initial cost ) is high, but after that, the cost goes down substatially. Quote Link to comment Share on other sites More sharing options...
BEC Posted February 5, 2005 Share Posted February 5, 2005 Al, Just a guess, but after a successful prototype, I think this cabinet shop would be quoting a price that would be a lot less than that. It would be based on material plus machine time at $60.00 (I think) per hour. That would be for all the cut out pieces. Assembly, if they did it would be more. I can't imagine that it would be more than $100.00 per pair for the pieces before assembly. I could of course be way off on that. Bob Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted February 5, 2005 Author Share Posted February 5, 2005 Bob, That pricing sounds good. I will still have to make, or have mdae, the two types of grill frames, tweeter brackets and tack on the grill cloth. The total price for all that would probably be quite reasonable. The quote of $300 was for finished horns at a quantity of a set of two each week using the CNC. That is what I would expect the quantity to be at best. Am I right? I could easily store large quantites of parts, like the top and bottom plates in a flat pile, but I have no room to store complete horns! This is what I am hoping for at this point. Al k. Quote Link to comment Share on other sites More sharing options...
michael hurd Posted February 5, 2005 Share Posted February 5, 2005 Two each week! Is that assembled? No wonder they want so much. Even if they were a solid block of material, I doubt that they would take over an hour each to machine, and if they were a solid block, then there would be no assembly required. The throat adapters would take a little bit longer, but if you find a source for the aluminum billet, they should take 15-20 minutes each, tops. Quote Link to comment Share on other sites More sharing options...
BEC Posted February 5, 2005 Share Posted February 5, 2005 Al, I know that you would need to order parts from the cabinet shop that would use complete 4 X 8 sheets of material on each order. The program for the CNC router determines the most efficient use of material and that would pretty much determine the minimum order. If you want a number that ends up just using 1/4 of the last sheet, you still pay for that sheet. Bob Quote Link to comment Share on other sites More sharing options...
michael hurd Posted February 5, 2005 Share Posted February 5, 2005 Have you given a thought to making a male plug mold of your prototype and then using that to produce a fiberglass version? Resin and cloth are cheap, but the mold has to be finished very smooth, then waxed really well. A shop that speciallizes in composites and glass would be your best choice, as they can apply a gel coat with a spray gun, and then laminate cloth and resin over the mold. This would leave a smooth inside finish in the horn. Quote Link to comment Share on other sites More sharing options...
michael hurd Posted February 5, 2005 Share Posted February 5, 2005 Al, pm Tigerwoodkhorns, he bought some transformers and is building his own alk's. In another thread, he mentioned that he has access to a cnc machine shop, however he is located quite a ways away from you. Even if you could just find out about the throat adapters, check it out. Quote Link to comment Share on other sites More sharing options...
JJkizak Posted February 5, 2005 Share Posted February 5, 2005 Once you get the exponential curve dimensions then you can bandsaw the curved portions out of blocks of wood and the flat portions out of regular boards. (that is if there are flat portions for the top and bottom). Then glue the whole thing together. Wood tap the end with the threads to screw on the driver and the mounting flange can be one piece of flat wood cut out with a router and also glued or fibreglassed which is incredably strong. JJK Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted February 5, 2005 Author Share Posted February 5, 2005 Guys, The idea of making a mold and using it to generate the final horn of fiberglass sounds good. but I don't know what that would take. It is totally out of my area of expertice. In short, I wouldn't know how to begin! I have a friend who had somebody do that for him to make a square mouth tractrix. I might discuss the idea with him. JJK, You don't quite realize the detials of the top and bottom plates. They can not simply be cut out of a flat piece of board with a jigsaw without major filing on the edges after it is fastend to the building fixture. That is how I did it BTW. The angle keeps the edges from being flat against the curved swides. The cutter must be held at a precise angle that causes an continuous change in angle as you move from the throat end to the mouth. The other way is to cut them, one at a time, on a band saw with the plates mounted on a wedge. That is how Bruce Edgar suggested it be done in his article. Al K. Quote Link to comment Share on other sites More sharing options...
michael hurd Posted February 5, 2005 Share Posted February 5, 2005 Al, I sent you a p.m. Quote Link to comment Share on other sites More sharing options...
tigerwoodKhorns Posted February 5, 2005 Share Posted February 5, 2005 Al, I have access to an Ingersol Rand Waterjet CNC machine at a good frind's shop. I will be in the shop after my caps arrive building, you guessed it, a set of "special" ALK's. I designed, fabricated and installed the relays and interface between the control system and the mechanical devices on the CNC machines for my friend's shop at no cost. I have free reign to build whatever I want there. If you have the specs, I can prep CAD drawings of the top and bottom plates and cut some out. Please note that the waterjet (basically the same machine as the router that Bob mentioned, but a lot bigger and equipped with a 75,000 psi pump and abrasive injector) can only cut objects in 2 dimensions. However, you top and bottom plates appear to be 2D. Do you have a router? I could fab plates of 1/8" steel or aluminum that can be templates. Just run a router around the sides and you have your tops and bottoms (if they are 2-d). The throat piece is a different story. I would fabricate a mold that you can pour material into to make that. Fabricate a mold out of an aluminum billet or other suitable material, and there has to be an easy way to make say, a plaster piece and then coat it with some sort of resin like the stuff used for fiberglass. Or maybe some form of plastic can be used for the piece like the stuff used in hot glue guns. Al, this is kind of funny. My order of stereo projects is: 1. Build ALk's. 2. Build false corners. 3. Build a swivel base for the squaker and tweeter for my K-Horns. You beat me to item 3!! Let me know. I will be there in a few weeks builoding my ALK's and I can cut some pieces out at the same time. Chris Quote Link to comment Share on other sites More sharing options...
tigerwoodKhorns Posted February 5, 2005 Share Posted February 5, 2005 ---------------- On 2/5/2005 12:41:47 PM Al Klappenberger wrote: You don't quite realize the detials of the top and bottom plates. They can not simply be cut out of a flat piece of board with a jigsaw without major filing on the edges after it is fastend to the building fixture. That is how I did it BTW. The angle keeps the edges from being flat against the curved swides. The cutter must be held at a precise angle that causes an continuous change in angle as you move from the throat end to the mouth. The other way is to cut them, one at a time, on a band saw with the plates mounted on a wedge. That is how Bruce Edgar suggested it be done in his article. Al K. ---------------- Sorry Al, I didn't see the above. How about this: Make the tops and bottoms out of three 1/8" pieces of wood that approximate the transition when stacked (put two pilot holes in each to achieve the proper alignment). Then you can fill the edge in with fiberglass resin. Give it a quick sanding when it is done and you should have your transition! (This model, as you know, is simpele integration from calculus). Chris Quote Link to comment Share on other sites More sharing options...
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