greg928gts Posted January 15, 2009 Share Posted January 15, 2009 Note: If you're looking for more updated information, search for the thread "Tractrix horn calculator #3" by greg928gts. I decided to start another thread, since the other one got so confusing. I have learned a lot about these calculators and building wooden midrange tractrix horns in the last couple of weeks, thanks to JC and the time he's spent emailing with me. Thanks JC. I'm going to build a wooden midrange tractrix horn for my Khorns. This horn will take a 2" driver and it will fit under the tophat so the Khorn can stay stock looking. I will integrate it into the front grill frame (motorboard) to use all the space possible (vertically) under the tophat. The horn will be 24" wide, so there will be space for a tweeter on the side, like with the ALK Trachorn setup. This ends up being a full tractrix design with no compromise for size. This type of horn build is done with the top and bottom pieces of the horn set at an angle, but flat (not curved); and the sides are curved. The combination of the top and bottom angles and the curved sides, built according to the tractrix calculation, provides an area of expansion down the horn that is tractrix. The calculator I'm using is from this website http://volvotreter.de/dl-section.htm It is in an excel spreadsheet program, so it's easy to modify and add things to it, which is nice. I've started modding it for my own use by adding calculations that convert the metric to standard, and I've added information and notes that are helpful to me. The tractrix calculator is for general use, meaning that it is designed to give basic tractrix expansion, regardless of type of construction. JC has showed me his way of using only the information that is necessary from the program, and then doing the rest of the calculations myself to fit the particular type of horn build that I'm doing. The picture below shows the parameters of the horn, some of which I've entered, that the calculator is using. Greg Click on this picture to see a larger version that is easier to read. Quote Link to comment Share on other sites More sharing options...
greg928gts Posted January 15, 2009 Author Share Posted January 15, 2009 After entering the information into the tractrix calculator to get the desired horn size and Fc, There are only two columns to look at for figuring; the “Distance From The Throat” and the “Area” of expansion (tractrix). Knowing the throat size, the mouth size and the length of the horn, a trapezoid can be drawn on graph paper that shows the vertical cross-section (vertical height) of the horn. This is the center vertical plane of the horn. See picture below. Measure the height of the trapezoid (horn) at each 1” increment (Length Of Horn - Distance From The Throat) and enter those measurements into another column in the spreadsheet (Height in inches – numbers in red on the right in the diagram) We now know the Area at each of the 1” increments and we know the Height of the horn at each of the 1” increments, and with that information we could calculate the Width of the horn, which would give us the curve of the sides of the horn. However, calculating the width based on the height and area at the 1”increments means we will be getting the curve of the horn at the center horizontal plane of the horn, and while that information may be useful for some, for the purposes of cutting the tops and bottoms of the horn from pieces of wood, we need the “flare” curve of the horn. What we are calling the flare curve is the inside joint where the curved side of the horn meets the top of the horn. This curve is a little longer than the curve at the center plane of the horn because as it curves out, it also angles with the top and bottom angled pieces of the horn. So if we want to know the “flare” curve of the horn, an adjustment is needed in the calculations. That adjustment is made by using the “Distance From The Throat” column in the spreadsheet to calculate the width based on a different set of numbers than simply the 1” increments down the center of the horn. That different set of numbers comes from measuring the length of the angled side of the trapezoid (black numbers on the left in the diagram). Greg Quote Link to comment Share on other sites More sharing options...
greg928gts Posted January 15, 2009 Author Share Posted January 15, 2009 Measure the length of the angled side of the trapezoid (which is the top angled piece of the horn) and note the total length of that angled line. It will be a little longer than the center length, or length of horn. At each 1” increment (Length Of Horn - Distance From The Throat), measure and note the length of the angled side of the trapezoid. You’ll notice that each of these measurements is a little longer than the corresponding center line measurement, noted in the diagram above as “Location of flare where the width calculation is used”. Use these numbers to figure the width of the horn in the step below. On the spreadsheet, use the “Distance From The Throat” column to find a number that is equal to (or nearly so) each of the measurements from the step above. Make a new column and convert the Area in square mm to Square inches for each. Use the Area to divide the Height measurements into. This will yield the Width of the horn at each of the 1” increments (distance from the throat) which has been adjusted to give us the “flare” curve of the horn. Enter those numbers into a new column on the spreadsheet (Width in inches). Using each of the Width measurements, plot another diagram showing the “flare” curve of the horn. This is the pattern used to cut the top and bottom pieces of the horn. In the diagram below, note how the measurements along the center line are not 1” increments, they are the larger numbers obtained by measuring the angle of the trapezoid, this is what adjusts the curve for the “flare”. Thanks to JC for the diagrams and for the many emails explaining all this to me. Hopefully I've conveyed this in a way that makes sense. It probably won't make complete sense until you've done it once or twice. I'll probably forget by the time I get to do this again and I'll have to refer back to this thread! Greg Quote Link to comment Share on other sites More sharing options...
capo72 Posted January 16, 2009 Share Posted January 16, 2009 Yes!!!!!!!!!!!!! Quote Link to comment Share on other sites More sharing options...
tigerwoodKhorns Posted January 16, 2009 Share Posted January 16, 2009 I am not using top hats so I can go with a horn that is taller. You used 250 hz for a 400 HZ crossover, that should be plenty of cushion. Is there any advantage to using a larger horn, like 225 hZ? Do you have the profile for a 1" driver? Do you have an updated spreadsheet that you can email? Thanks for doing all of this legwork. Quote Link to comment Share on other sites More sharing options...
jwc Posted January 16, 2009 Share Posted January 16, 2009 Is there any advantage to using a larger horn, like 225 hZ? The idea of the bigger midhorn at 225 was to try and get the XO point possibly lower to 300hz and also "potentially" get "better" low midrange sound. Greg needed a horn to fit in a top hat and use a 400Hz XO. That type of upgrade for someone will be somewhat like upgrading to ALK's Trachorn except that a 2" throat option is there as well as "the biggest mihorn to fit in a khorn top hat" and still fit a tweeter. Greg....nice write up to sum up all those emails and phone conversations. jc Quote Link to comment Share on other sites More sharing options...
Guest " " Posted January 16, 2009 Share Posted January 16, 2009 "the biggest mihorn to fit in a khorn top hat" and still fit a tweeter" are you going to put the tweeter vertically in the horn like the old k-5-j. it seems like we went full circle...I wonder if the k-5-j is 2" throat if I pull off the throat adapter... Quote Link to comment Share on other sites More sharing options...
greg928gts Posted January 16, 2009 Author Share Posted January 16, 2009 I am not using top hats so I can go with a horn that is taller. You used 250 hz for a 400 HZ crossover, that should be plenty of cushion. Is there any advantage to using a larger horn, like 225 hZ? Do you have the profile for a 1" driver? Do you have an updated spreadsheet that you can email? Thanks for doing all of this legwork. I think there can be problems with a horn that is too big for the given crossover point being used, but I'll let others comment on this. I've wondered the same thing. Is the sound different, and possibly better with a 225hz horn crossed over at 800hz? No 1" driver profile, you'll have to download the program and start figuring. When I enter all the numbers and clean up the spreadsheet, I'll post it here. Greg Quote Link to comment Share on other sites More sharing options...
greg928gts Posted January 16, 2009 Author Share Posted January 16, 2009 "the biggest mihorn to fit in a khorn top hat" and still fit a tweeter" are you going to put the tweeter vertically in the horn like the old k-5-j. it seems like we went full circle...I wonder if the k-5-j is 2" throat if I pull off the throat adapter... I'm going to use a Beyma CP-25. Greg Quote Link to comment Share on other sites More sharing options...
Guest " " Posted January 16, 2009 Share Posted January 16, 2009 " Is the sound different, and possibly better with a 225hz horn crossed over at 800hz? " This could wind up being a pretty matrixed question. a. A 225hz tractix horn crossed over at 300hz, 400hz, 800hz would certainly sound different b. a 225hz tractix horn crossover at 400hz using a 6db per octave crossover or a 12db, 18db per octave crossover would also sound different c. aside from the high pass crossover values re: (a) and (, there's the bandpass values if we are talking 3-way so.....(d) and (e) would apply d. a 225hz tractix horn with a bandpass of 4000hz would sound different than one with a band pass of 5800hz e. a 225hz tractix horn with a bandpass using a 6db per octave crossover would sound different from 12db, 18db, etc. Quote Link to comment Share on other sites More sharing options...
jwc Posted January 16, 2009 Share Posted January 16, 2009 I think there can be problems with a horn that is too big for the given crossover point being used, but I'll let others comment on this. I've wondered the same thing. Is the sound different, and possibly better with a 225hz horn crossed over at 800hz? I disagree with this. I have more than one example but let's say a K401 XO'ed at 700Hz sounded way better than a K600 XO'ed at 600 or 700 Hz. In fact...Gothover and I are gonna stir up even a bigger horn with a lower Fc and XO it at 400 or 500Hz. jc Quote Link to comment Share on other sites More sharing options...
Guest " " Posted January 16, 2009 Share Posted January 16, 2009 " K401 XO'ed at 700Hz sounded way better than a K600 XO'ed at 600 or 700 Hz." yeah...the betterness on the low end would be there for sure with a gentle sloping xover.....which is probally what sounds better Quote Link to comment Share on other sites More sharing options...
DrWho Posted January 16, 2009 Share Posted January 16, 2009 ....which is probally what sounds better I disagree. I think it's the better pattern control and lower distortion. Quote Link to comment Share on other sites More sharing options...
tigerwoodKhorns Posted January 17, 2009 Share Posted January 17, 2009 I have more than one example but let's say a K401 XO'ed at 700Hz sounded way better than a K600 XO'ed at 600 or 700 Hz. In fact...Gothover and I are gonna stir up even a bigger horn with a lower Fc and XO it at 400 or 500Hz. I have different motives. My greedy engineering side takes over. Whenever I design something, I want to have as many "options" as possible without unecessairily complicating the design. Here my design goal is versitility. I already have an active dividing network so I can change crossover points and slopes with the push of a button. I want to be able to use many different midrange drivers if I feel like experimenting. So the ability to accomodate 1", 1.4" and 2" drivers as well as crossover points as low as maybe 300 to 350Hz is the goal. My bass bins can accomodate a 24" wide horn, I think that the depth of the horn will be the limiting factor because I want the ability to be able to rotate the top section to fine tune the imaging for the listening position while having proper corner loading. I look forward to the spreadsheet. Quote Link to comment Share on other sites More sharing options...
jwc Posted January 17, 2009 Share Posted January 17, 2009 I have more than one example but let's say a K401 XO'ed at 700Hz sounded way better than a K600 XO'ed at 600 or 700 Hz. In fact...Gothover and I are gonna stir up even a bigger horn with a lower Fc and XO it at 400 or 500Hz. I have different motives. My greedy engineering side takes over. Whenever I design something, I want to have as many "options" as possible without unecessairily complicating the design. Here my design goal is versitility. I already have an active dividing network so I can change crossover points and slopes with the push of a button. I want to be able to use many different midrange drivers if I feel like experimenting. So the ability to accomodate 1", 1.4" and 2" drivers as well as crossover points as low as maybe 300 to 350Hz is the goal. My bass bins can accomodate a 24" wide horn, I think that the depth of the horn will be the limiting factor because I want the ability to be able to rotate the top section to fine tune the imaging for the listening position while having proper corner loading. I look forward to the spreadsheet. Are you wanting the plans for the 223 tractrix or the one Greg has shown above? jc Quote Link to comment Share on other sites More sharing options...
tigerwoodKhorns Posted January 17, 2009 Share Posted January 17, 2009 Are you wanting the plans for the 223 tractrix or the one Greg has shown above? jc What are the dimensions of the 223 HZ horn? width, height and depth? I assume that the 223 hz horn is designed with the proper offset described above. I want to be able to do with this horn is build adapters top fit a 1.4" driver and a 1" driver (which I have right now - Phenolic JBL 2470's). Do the calcualtions allow the horn to be extraolated to these sizes? Thanks. Quote Link to comment Share on other sites More sharing options...
jwc Posted January 17, 2009 Share Posted January 17, 2009 The 223 is 17.5" deep plus the baffle. 24 wide x 12 H The throat is 2 x 2. You could make your own adapter ot you could make the appropriate extension of the horn to make it down to 1.4 or 1. jc Quote Link to comment Share on other sites More sharing options...
Guest " " Posted January 17, 2009 Share Posted January 17, 2009 " I disagree." What else is new....if you were not here to disagree with the opinions of others...I would not recognize this place....your techno babble does not dis-entitle others to their opinions. a more tactful approach would be to just simply state your opinion and leave it at that. Quote Link to comment Share on other sites More sharing options...
DrWho Posted January 17, 2009 Share Posted January 17, 2009 I don't see claiming causation as being an opinion. Quote Link to comment Share on other sites More sharing options...
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