jwc Posted December 19, 2008 Share Posted December 19, 2008 Jeremy. Yes that JBL 2482 would be a great match if not one of the best. Too bad thay don't make that anymore. Do you know if JBL continues to make disphragms for those. Another good one would be the 2485J....which also is no longer produced. I would be glad to run curves on those horns or drivers. Everyone needs to remember I'm not a pro or anything. But I can take the Horns outside and run pink noise through them. I find my results are reliable or at least useful. I'll do axis and off axis. I don't have as much time to build anymore but I have time and interest for testing designs i'm interested in. jc Quote Link to comment Share on other sites More sharing options...
gaspr Posted December 19, 2008 Share Posted December 19, 2008 The layout you are showing with the curve of the horn I assume is in the center of the horn, so how did you go about figuring what the curve of the top and bottoms would be? They are slightly different no? Good question Greg. After giving this some thought, I think that the curves on the top and bottom pieces should be traced directly from the template. If you can imagine the "wavefront" at any point in the horn as a bulge or a bubble, it starts to make some sense...at least to me.[*-)] Quote Link to comment Share on other sites More sharing options...
Deang Posted December 19, 2008 Share Posted December 19, 2008 I forgot about Great Plains -- they make a nice monster driver that goes that low. http://www.greatplainsaudio.com/downloads/390series.pdf Quote Link to comment Share on other sites More sharing options...
jwc Posted December 19, 2008 Share Posted December 19, 2008 I forgot about Great Plains -- they make a nice monster driver that goes that low. http://www.greatplainsaudio.com/downloads/390series.pdf Yes...but that has 1.4" exit....not 2". I guess we could use an adapter. jc Quote Link to comment Share on other sites More sharing options...
awsjr Posted December 19, 2008 Share Posted December 19, 2008 the GP drivers are very similar to the the Altec 292- 8A with the phenolic diaphragm....the 292-8A are rated 300hZ to 7000hZ....1.4 dia throat....I have used these drivers on some Altec 805 horns....what about using a mid-range driver like the JBL LE-5 instead of a compression driver ?....between this thread and Jeremy's thread this looks like a good Christmas holiday project.... Quote Link to comment Share on other sites More sharing options...
Marvel Posted December 19, 2008 Share Posted December 19, 2008 The LE-5 breaks up too easily and wouldn't work very well. I thought of trying one of the Galaxy Audio 5"drivers. They handle a lot of power and could easily handle the freq. range. I also have four of them sitting in my storeroom. [*-)] How much gain do you get from the horn? Bruce Quote Link to comment Share on other sites More sharing options...
awsjr Posted December 19, 2008 Share Posted December 19, 2008 I dont know what divisions JW used, but when I measured his template, I used 1 Inch Divisions. 223 HZ horn info: Mouth internal height 12" Not to scale, Reccomend build 1/2 flair then mirror for accuracy. Length 17.5" I also reccomend adding 1 inch front and rear of the flair to be trimmed after complete. Throat 2" 17.5"------------------------------------------------------------------------------------------------ 12.25 .25 inches to be trimmed when complete. 17" ------------------------------------------------------------------------------11.02" 16" --------------------------------------------------------------------- 7.565 15" -------------------------------------------------------- 5.53" 14" ------------------------------------------------ 4.73" 13" ------------------------------------------ 3.88" 12" --------------------------------------- 3.25" 11" ----------------------------------- 2.79" 10" --------------------------------2.41" 9" ---------------------------- 2.06" 8" -------------------------1.8" 7" ----------------------1.58" 6" --------------------1.41" 5" ---------------- 1.25" 4" -------------- 1.13" 3" ------------ 1.05" 2" ----------- 1.0" 1" ---------- .98" 0" ----------- 1.0" the numbers are off as posted....see the attached plot.... Quote Link to comment Share on other sites More sharing options...
Guest David H Posted December 19, 2008 Share Posted December 19, 2008 the numbers are off as posted....see the attached plot.... I remeasured the horn very carefully and was a little confused why my numbers were off but the template was perfect. Turns out the metal machinist ruler I made the divisions with was just over an inch and was throwing the numbers off. Fortunately I used the same ruler on my template therefore the template is correct. Thanks, I just plotted this on graph paper to check the result, and there appears to be errors at lines 16 and 17. I will double check the numbers, but looks like line (17) should be approximately 10.02 and (16) 7.06. I threw this together rather quickly as a guide and didn't double check the numbers. JW do you still have the actual plot ? Quote Link to comment Share on other sites More sharing options...
greg928gts Posted December 19, 2008 Share Posted December 19, 2008 Greg, I hope I am understanding your questions corectly. First I cut the bell shaped top and bottom sections, the sides are then mounted in a holding jig that is clamped to my saw table. The side angles are then hand sanded in with 40grit adhesive back 14"x2" automotive longboard sand paper that is attached to a 14"long piece of 4" pvc pipe. This process only takes a few minutes to sand, and because both pieces are being sanded simutaneously I get a near perfect fit every time. I am attaching a pic to give you an idea. I like the way you've figured out how to sand the angles, I might give that a try. I bought a bandsaw that had enough of an opening so that I could cut the top and bottom pieces with them set on a jig to hold them at the proper angle. Then I found that I couldn't get a good enough cut with the bandsaw, so sanding was necessary. So I set up a small drum sander on my drill press and adjusting the table up and down I'm able to sand with the pieces held in the same jig. Your way is so much easier! If the calculated curve is the center of the horn and you cut the tops and bottoms to that curve, the center of the horn will no longer be the same as the calculated curve. The tops and bottoms are actually a different curve so that the center stays true to the calculation. I'm sure the calculation program could be adjusted to give us the proper curve of the top and bottom pieces. I did it by holding a pencil in the vertical position and transcribed the curve from one of the top pieces (held in my jig) to graph paper, then by trial and error making adjustments until I had it very close. Mostly by error! Greg Quote Link to comment Share on other sites More sharing options...
greg928gts Posted December 19, 2008 Share Posted December 19, 2008 I don't know if you have seen it or not before Greg, but I have attached a link to the thread I posted when I went through this build. I think you should be able to see the way I handled a couple of the questions you are dealing with. Your skills are way beyond mine so this should be no problem for you. http://forums.klipsch.com/forums/t/93132.aspx Jeremy Thank you Jeremy, yes I've read through the thread a couple of times. I would pose the same observation to you, that if the tops and bottoms are cut to the calculated curve, then the center curve of the horn is no longer the same as the calculated curve. SPINDLE SANDER! Who the heck has a spindle sander in their shop?!! Geeez. [] Greg Quote Link to comment Share on other sites More sharing options...
Guest David H Posted December 19, 2008 Share Posted December 19, 2008 If the calculated curve is the center of the horn and you cut the tops and bottoms to that curve, the center of the horn will no longer be the same as the calculated curve. The tops and bottoms are actually a different curve so that the center stays true to the calculation. I'm sure the calculation program could be adjusted to give us the proper curve of the top and bottom pieces. I did it by holding a pencil in the vertical position and transcribed the curve from one of the top pieces (held in my jig) to graph paper, then by trial and error making adjustments until I had it very close. Mostly by error! I did not account for any change when I built the horns because the material to be removed is from the outside of the top and bottom pieces and I don't think the inside flair is affected. Quote Link to comment Share on other sites More sharing options...
jwc Posted December 19, 2008 Share Posted December 19, 2008 JW do you still have the actual plot ? Mine is drawn out large on graph paper with multiple plots in millimeters. There isn't a way to put on this message board. jc Quote Link to comment Share on other sites More sharing options...
Guest David H Posted December 19, 2008 Share Posted December 19, 2008 JW do you still have the actual plot ? Mine is drawn out large on graph paper with multiple plots in millimeters. There isn't a way to put on this message board. jc Ok I will go back and re-measure then repost to the board. Quote Link to comment Share on other sites More sharing options...
capo72 Posted December 19, 2008 Share Posted December 19, 2008 I have scanned my graph paper plot and printed out copies full scale. I could mail copies to someone who might want to work off my plot. Mine is done in mm and has hundreds of points. I also could do an Autocad plot when I get back to work Monday. Jeremy Quote Link to comment Share on other sites More sharing options...
greg928gts Posted December 19, 2008 Share Posted December 19, 2008 If the calculated curve is the center of the horn and you cut the tops and bottoms to that curve, the center of the horn will no longer be the same as the calculated curve. The tops and bottoms are actually a different curve so that the center stays true to the calculation. I'm sure the calculation program could be adjusted to give us the proper curve of the top and bottom pieces. I did it by holding a pencil in the vertical position and transcribed the curve from one of the top pieces (held in my jig) to graph paper, then by trial and error making adjustments until I had it very close. Mostly by error! I did not account for any change when I built the horns because the material to be removed is from the outside of the top and bottom pieces and I don't think the inside flair is affected. Ah, o.k., I think we're talking about two different things. I understand what you're saying here, that by sanding the edges of the top and bottom pieces while they are sitting in the jig, so that the side pieces will fit tight and flush to the tops and bottoms, the curve of the horn will not change. I believe you are correct as you've stated, because the material taken off is towards the outside of the horn. What I was referring to is the difference in the actual curve of the top and bottom pieces (which both share one curve) as compared to the curve at the center plane (which is what the drawing of the curve is supposed to represent). At least that's what I think. I'm hoping someone else here will comment on this. When I first started playing around with this, I cut the curves of the top and bottom pieces according to the layout. But then I realized that when the top and bottom pieces are set at the angle, the curve in the middle was different than the layout. So I assumed that adjustments had to be made to the top and bottom curves to account for the angle. The adjustments would be such that the curve in the middle plane of the horn would be according to the layout. This is hard to explain. Greg Quote Link to comment Share on other sites More sharing options...
Marvel Posted December 19, 2008 Share Posted December 19, 2008 Erik Forker has a column in his spreadsheet that has 'stretch' values for the sides, since those are curved, but I think still along the centerline. If those could be calculated, you should be able to adjust/calculate for the angle of the top and bottom as well, so you could draw out the curves with the wood flat on your table. Quote Link to comment Share on other sites More sharing options...
jwc Posted December 19, 2008 Share Posted December 19, 2008 Greg. I think i know what you are asking. Look at his jig from the side with the bottom and top of the horn mounted to it. Basically, the jig is 17.5 inches tall (length of the horn) 12 inches at the base (height of horn) 2 inches at the top of jig (throat). basically draw that trapezoid (jig) out on graph paper. Then draw a straight line from the middle of the jig at the 2" center from the top to the center of the 12" inch center at the base. Along that straight line....measure off one inch increments. At each of those incriments, draw a perpendicular line out to the side walls of the trapezoid. measure that line. So..at 2" from the throat...lets say the height of the horn (length from one side trapezoid to the other) is 3". OK.....now go back to you tractrix calculation and find out what the area of the tractrix horn is supposed to be at 2" from the throat. let's say it is 6 sq inches. OK ::: Well the height of the horn at 2" from the throat is 3". So the flare width at 2" from the throat must be 6 sq in / 3 in = 2 inches. So when drawing out your tractrix flare. the width of that flare 2" from the throat is 2". What you have drawn out on graph paper at the end of the day is the trapezoid repesenting the constant vertical expansion of the horn. This is also the jig in the end. At 1" increments you have measured the hieght of the horn. Then you go back and use that height to divide the tractrix calculated area at that point of the horn. You get now the required horizontal measurement to make the tractrix curve correct. Does this make sense??? The sand technique that he describes works as it is the most "inner" portion of the top and bottom that provides the correct measurement. So when you sand off the outer edges to be flush with the inner edges, you can lay down the horn side walls against a flat surface to glue or nail. jc Quote Link to comment Share on other sites More sharing options...
greg928gts Posted December 19, 2008 Share Posted December 19, 2008 So when drawing out your tractrix flare. the width of that flare 2" from the throat is 2". You lost me right there. Regarding the curve that is plotted out on the graph paper. Are we supposed to use the curve as a guide for cutting the tops and bottoms of the horn? Is that the curve at the center plane of the horn, or is that the curve of the inside corner of the horn where the side meets the top of the horn from the throat to the mouth? Those are two different curves, which one is being represented by the graph paper drawing? Greg Quote Link to comment Share on other sites More sharing options...
Guest David H Posted December 19, 2008 Share Posted December 19, 2008 Greg I think median flair has already been accounted for, because the vertical flair and length have already been calculated. Quote Link to comment Share on other sites More sharing options...
greg928gts Posted December 19, 2008 Share Posted December 19, 2008 Greg I think median flair has already been accounted for, because the vertical flair and length have already been calculated. Does that mean that the curve drawn on the graph paper is the curve of the inside joint where the top piece joins the side piece? If so, then we can say that the curve drawn on the graph paper can be used as a template to cut out the top and bottom pieces of the horn without adjustment. Greg Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.