JohnA Posted May 3, 2000 Share Posted May 3, 2000 How is the shape of a horn and the curve of its sides calculated? Is there a good design manual for horns? I have a design in mind and I want to calculate the size and shape required. John Quote Link to comment Share on other sites More sharing options...
pzannucci Posted May 4, 2000 Share Posted May 4, 2000 John, If you do some searching online, you can come across some calculators or programs you can download. They will do the calculations based on various parameters and the type of expansion, be it tractrix, exponential, or others. The only problem with these programs are that they are not real explanatory but it's a start. If it is a bass horn, you'll have to figure out how to fold it. Peter Z. Quote Link to comment Share on other sites More sharing options...
JohnA Posted May 4, 2000 Author Share Posted May 4, 2000 I'll keep looking, but I didn't find anything last night. John Quote Link to comment Share on other sites More sharing options...
pzannucci Posted May 4, 2000 Share Posted May 4, 2000 John, I will send you, via e-mail if you like, what I have found. I just need to scrounge around. Other than a couple of Java applets I have come accross, I do have a couple of executables that can be used. I have the source code and that is the only way I could figure out what parameters it wanted to come up with its tables. If you just come across source code for an application and you are not a programmer, let me know the link also since I too am interested in something for my future projects. Peter Z. Quote Link to comment Share on other sites More sharing options...
Ray Garrison Posted May 4, 2000 Share Posted May 4, 2000 John, Did you start by checking out the horn speakers page at http://invalid.ed.unit.no/~dunker/horns.html ? I just took a look, one of the links leads you to http://www-user.uni-bremen.de/~carnivor/ where there's some interesting horn calculation software posted. Post your design? Ray Quote Link to comment Share on other sites More sharing options...
jwgorman Posted May 4, 2000 Share Posted May 4, 2000 John are you just looking for an equation? Am I missing something? More importantly hows come you gets the cool purple star and the "elite member" moniker? Are you the Green Beret of the BB users? "One hundred men will test today, but only John, gets the purple star..." jwgorman Quote Link to comment Share on other sites More sharing options...
Ray Garrison Posted May 4, 2000 Share Posted May 4, 2000 Elite member boundry occurs at 300 posts. Take a look at the buys on the ProMedia board for some examples of higher level classifications. Ray Quote Link to comment Share on other sites More sharing options...
JohnA Posted May 4, 2000 Author Share Posted May 4, 2000 I'm not having the luck I expected on ebay finding something for the rear channels, so I want to see what I can gin up myself. I was thinking about a K-33 firing into a J-shaped horn about 5 feet tall and the mid and tweeter on top. Maybe the horn would need to be a "C" to get it long enough. To find out, I need the design equations and a drafting board. I just noticed the new star. John Quote Link to comment Share on other sites More sharing options...
pzannucci Posted May 5, 2000 Share Posted May 5, 2000 John, The link that Ray posted is one of the links I was going to send you. If you're not a programmer, I have built the full screen version of the open source software on that page, if needed. Peter Z. Quote Link to comment Share on other sites More sharing options...
oosting Posted May 5, 2000 Share Posted May 5, 2000 John, Olsen in his "Modern Sound Reproduction" has a section on horns whith the equations for exponential hrons. He also shows some examples of base horn folding. You can probably find it in a local library. If you want, I can email you a Excel spreadsheet that will calculate the expansion curve. The calculation is the easy part, designing and building these things is hard. Ed Quote Link to comment Share on other sites More sharing options...
JohnA Posted May 5, 2000 Author Share Posted May 5, 2000 Ed, I'd like to have the spreadsheet. I've got a cabinet maker in mind for the building. I need to see if the size will work out, though. The La Scala bass horn is pretty short, so I ought to be able to do it. John Quote Link to comment Share on other sites More sharing options...
pzannucci Posted May 5, 2000 Share Posted May 5, 2000 As long as you're not going below 50hz or so, the size and length will be containable. The problem you will have is with impedance and how to get reasonably smooth response from a small short horn. The smaller they are, the harder they are to smooth out let alone folding to not have bad response. I have built several in the past and the cuts and assembly can be trying. Hope you have a good cabinet maker and can apply liberal bracing to avoid resonances. Peter Z. Quote Link to comment Share on other sites More sharing options...
JohnA Posted May 5, 2000 Author Share Posted May 5, 2000 I think 50 to 60 Hz is plenty. All I think I need is a pair of 6' tall La Scalas. John Quote Link to comment Share on other sites More sharing options...
JRklipsch Posted May 5, 2000 Share Posted May 5, 2000 John, I saw a folded horn design at www.decware.com I don't know if that will suit your purpose. John Quote Link to comment Share on other sites More sharing options...
oosting Posted May 6, 2000 Share Posted May 6, 2000 John, I put a copy of the spreadsheet at: http://www.ameritech.net/users/oosting/exponentail_horn.xls. It calculates the horn cross seectional area and side lenght of a exponentail horn with a square corss section. All you need to do is input the cuttoff frequency, the effective driver size (13 inches for a 15 inch driver), , the compression ratio (driver area divided by throat area) and the mouth factor. The mouth factor is 1 for a horn mouth in free space, 2 for a horn mouth placed on the floor, 4 for a hron mouth up against a wall and 8 for in a corner. Note: the LaScala's have a compression ratio of 3.7. Ed CORRECTION: http://www.ameritech.net/users/oosting/Exponentail_Horn.xls Quote Link to comment Share on other sites More sharing options...
Dick Posted May 6, 2000 Share Posted May 6, 2000 Ed, Your web page seems to be unlisted... ------------------ Dick Hemmings Quote Link to comment Share on other sites More sharing options...
JohnA Posted May 7, 2000 Author Share Posted May 7, 2000 ED, I've got your spreadsheet. Thanks! I have a drawing that shows the slot the La Scala woofer fires through (throat?) is 13" x 3". That would give a compression ratio of 3.4. Is that accurate? I can't reach that far into the bass horn and it too much trouble to dissamble one right now to check. If so, I can build a 45" J-horn and set a La Scala top end on it and have a stunning rear surround. Your calculations are for a square horn, is rectangular expanding to square acceptable? It is most important that the area expand exponentially for the horn to have proper performance, is it not? John Quote Link to comment Share on other sites More sharing options...
oosting Posted May 7, 2000 Share Posted May 7, 2000 Yeah, you're right. I must have had a brain cramp! The effective driver area of the LaScala woofer is 132.7 sq in (13 inch effective diameter). The throat area is 39 square inches. That gives a compression ratio of 3.4. Thanks for correcting me. As far as I know, the essential thing for the horn to perform correctly is that the area increases exponentially from the throat to the mouth. The LaScala starts out as a 3 by 13 inch rectangle and ends up as a 23 inch square. And, it seems to work quite well. Are you looking at making one fo the horn's dimensions constant? For example make it 12 inches thick from the throat to the mouth? It would start as a skinny rectangle and end up as a large square or even a really fat rectangle at the mouth? It would be much easier to build that way. Ed Quote Link to comment Share on other sites More sharing options...
pzannucci Posted May 8, 2000 Share Posted May 8, 2000 I believe for an exponential design (I lost my book that had all the expansion rates for exponential bass horns) and I believe that the expansion was in the 40%-50% per foot range to an effective cut off of around 45-50hz. There are games that can be played such as the size of the horn is the full size of the horn mouths including an area for the enclosure in the middle of the mouth. So you can build something like a Belle and the mouth size also contains the enclosure in the middle as part of the mouth size. Just that the smaller the openings and shorter the horn, the worse the response is. Peter Z. Quote Link to comment Share on other sites More sharing options...
JohnA Posted May 8, 2000 Author Share Posted May 8, 2000 Peter, Ed, The idea is to build a J-shaped (L-shaped?), unfolded bass horn with the mouth against the floor, and place the HF section on top of that. The woofer would fire downward, its back air chamber would be between the HF section and the bass horn. I'd hope to make the footprint about 2' x 2' and have the left and right sides parallel. I'd try to vary the front and rear to achieve expansion. Since it would be tall, stability will have to be addressed. The killer for this whole project might be cost. If I can buy La Scalas for the same price, why bother? Even Cornwalls on stands would perform the way I want. John Quote Link to comment Share on other sites More sharing options...
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