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In the Forum: Horn-Loaded Speakers
In the Thread: Macondo’s Midbass Project – the grown up time.
Post Subject: About my horn skeleton.Posted by Romy the Cat on: 6/25/2010
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Here I would like to share some basic ideas about the skeleton of the horn. This is just a view from 50.000 feet but it will give some illustration what is brewing in my mind.
The one side of the triangular horn will be flat and will sit at level of the house sealing (attic floor). Two other sides of the triangular horn are curved. They are not continuously curved (I do not think I need to bend if for such a low frequency). They rather are a sequence of 7-12 flat panels (circle’s chords) that are mounded at different angle and by changing the angle they shape the hyperbolic curve.
Here are my more or less final circulations in metric: Hyperbolic at 0.6, Throat = 249cm (7' diameter), 45Hz, ¼ size
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Distance
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Area
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0.0
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249.0
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1.0
|
251.5
|
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2.0
|
254.0
|
|
3.0
|
256.6
|
|
4.0
|
259.2
|
|
5.0
|
261.9
|
|
6.0
|
264.6
|
|
7.0
|
267.4
|
|
8.0
|
270.2
|
|
9.0
|
273.0
|
|
10.0
|
276.0
|
|
11.0
|
278.9
|
|
12.0
|
282.0
|
|
13.0
|
285.1
|
|
14.0
|
288.2
|
|
15.0
|
291.4
|
|
16.0
|
294.6
|
|
17.0
|
298.0
|
|
18.0
|
301.3
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|
19.0
|
304.8
|
|
20.0
|
308.2
|
|
21.0
|
311.8
|
|
22.0
|
315.4
|
|
23.0
|
319.1
|
|
24.0
|
322.8
|
|
25.0
|
326.6
|
|
26.0
|
330.5
|
|
27.0
|
334.5
|
|
28.0
|
338.5
|
|
29.0
|
342.6
|
|
30.0
|
346.7
|
|
31.0
|
350.9
|
|
32.0
|
355.2
|
|
33.0
|
359.6
|
|
34.0
|
364.1
|
|
35.0
|
368.6
|
|
36.0
|
373.2
|
|
37.0
|
377.9
|
|
38.0
|
382.6
|
|
39.0
|
387.5
|
|
40.0
|
392.4
|
|
41.0
|
397.4
|
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42.0
|
402.5
|
|
43.0
|
407.7
|
|
44.0
|
413.0
|
|
45.0
|
418.4
|
|
46.0
|
423.8
|
|
47.0
|
429.4
|
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48.0
|
435.0
|
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49.0
|
440.7
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50.0
|
446.6
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51.0
|
452.5
|
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52.0
|
458.6
|
|
53.0
|
464.7
|
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54.0
|
470.9
|
|
55.0
|
477.3
|
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56.0
|
483.8
|
|
57.0
|
490.3
|
|
58.0
|
497.0
|
|
59.0
|
503.8
|
|
60.0
|
510.7
|
|
61.0
|
517.7
|
|
62.0
|
524.9
|
|
63.0
|
532.1
|
|
64.0
|
539.5
|
|
65.0
|
547.0
|
|
66.0
|
554.6
|
|
67.0
|
562.4
|
|
68.0
|
570.3
|
|
69.0
|
578.3
|
|
70.0
|
586.5
|
|
71.0
|
594.8
|
|
72.0
|
603.2
|
|
73.0
|
611.8
|
|
74.0
|
620.5
|
|
75.0
|
629.4
|
|
76.0
|
638.4
|
|
77.0
|
647.6
|
|
78.0
|
656.9
|
|
79.0
|
666.3
|
|
80.0
|
676.0
|
|
81.0
|
685.8
|
|
82.0
|
695.7
|
|
83.0
|
705.9
|
|
84.0
|
716.2
|
|
85.0
|
726.6
|
|
86.0
|
737.3
|
|
87.0
|
748.1
|
|
88.0
|
759.1
|
|
89.0
|
770.3
|
|
90.0
|
781.6
|
|
91.0
|
793.2
|
|
92.0
|
805.0
|
|
93.0
|
816.9
|
|
94.0
|
829.0
|
|
95.0
|
841.4
|
|
96.0
|
854.0
|
|
97.0
|
866.7
|
|
98.0
|
879.7
|
|
99.0
|
892.9
|
|
100.0
|
906.3
|
|
101.0
|
919.9
|
|
102.0
|
933.8
|
|
103.0
|
947.9
|
|
104.0
|
962.2
|
|
105.0
|
976.8
|
|
106.0
|
991.6
|
|
107.0
|
1006.7
|
|
108.0
|
1022.0
|
|
109.0
|
1037.5
|
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110.0
|
1053.4
|
|
111.0
|
1069.4
|
|
112.0
|
1085.8
|
|
113.0
|
1102.4
|
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114.0
|
1119.3
|
|
115.0
|
1136.5
|
|
116.0
|
1154.0
|
|
117.0
|
1171.7
|
|
118.0
|
1189.8
|
|
119.0
|
1208.1
|
|
120.0
|
1226.8
|
|
121.0
|
1245.8
|
|
122.0
|
1265.0
|
|
123.0
|
1284.6
|
|
124.0
|
1304.6
|
|
125.0
|
1324.8
|
|
126.0
|
1345.4
|
|
127.0
|
1366.4
|
|
128.0
|
1387.6
|
|
129.0
|
1409.3
|
|
130.0
|
1431.3
|
|
131.0
|
1453.7
|
|
132.0
|
1476.4
|
|
133.0
|
1499.5
|
|
134.0
|
1523.0
|
|
135.0
|
1546.9
|
|
136.0
|
1571.2
|
|
137.0
|
1595.8
|
|
138.0
|
1620.9
|
|
139.0
|
1646.5
|
|
140.0
|
1672.4
|
|
141.0
|
1698.8
|
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142.0
|
1725.6
|
|
143.0
|
1752.8
|
|
144.0
|
1780.5
|
|
145.0
|
1808.7
|
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146.0
|
1837.3
|
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147.0
|
1866.4
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148.0
|
1896.0
|
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149.0
|
1926.1
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150.0
|
1956.6
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|
151.0
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1987.7
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152.0
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2019.3
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153.0
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2051.4
|
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154.0
|
2084.1
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155.0
|
2117.3
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156.0
|
2151.0
|
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157.0
|
2185.3
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158.0
|
2220.2
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159.0
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2255.7
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160.0
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2291.7
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161.0
|
2328.3
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162.0
|
2365.6
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163.0
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2403.5
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164.0
|
2441.9
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165.0
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2481.1
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166.0
|
2520.9
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167.0
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2561.3
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168.0
|
2602.4
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169.0
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2644.2
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170.0
|
2686.7
|
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171.0
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2729.9
|
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172.0
|
2773.8
|
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173.0
|
2818.4
|
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174.0
|
2863.8
|
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175.0
|
2909.9
|
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176.0
|
2956.8
|
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177.0
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3004.5
|
|
178.0
|
3052.9
|
|
179.0
|
3102.2
|
|
180.0
|
3152.3
|
|
181.0
|
3203.2
|
|
182.0
|
3254.9
|
|
183.0
|
3307.5
|
|
184.0
|
3361.0
|
|
185.0
|
3415.4
|
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186.0
|
3470.7
|
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187.0
|
3526.9
|
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188.0
|
3584.0
|
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189.0
|
3642.0
|
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190.0
|
3701.1
|
|
191.0
|
3761.1
|
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192.0
|
3822.1
|
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193.0
|
3884.1
|
|
194.0
|
3947.1
|
|
195.0
|
4011.2
|
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196.0
|
4076.4
|
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197.0
|
4142.6
|
|
198.0
|
4209.9
|
|
199.0
|
4278.4
|
|
200.0
|
4348.0
|
|
201.0
|
4418.7
|
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202.0
|
4490.6
|
|
203.0
|
4563.7
|
|
204.0
|
4638.0
|
|
205.0
|
4713.5
|
|
206.0
|
4790.3
|
|
207.0
|
4868.4
|
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208.0
|
4947.8
|
|
209.0
|
5028.4
|
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210.0
|
5110.4
|
|
211.0
|
5193.8
|
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212.0
|
5278.6
|
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213.0
|
5364.7
|
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214.0
|
5452.3
|
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215.0
|
5541.4
|
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216.0
|
5631.9
|
|
217.0
|
5723.9
|
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218.0
|
5817.4
|
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219.0
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5912.5
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220.0
|
6009.2
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221.0
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6107.5
|
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222.0
|
6207.3
|
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223.0
|
6308.9
|
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224.0
|
6412.1
|
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225.0
|
6517.1
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226.0
|
6623.8
|
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227.0
|
6732.2
|
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228.0
|
6842.5
|
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229.0
|
6954.6
|
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230.0
|
7068.5
|
|
231.0
|
7184.3
|
|
232.0
|
7302.1
|
|
233.0
|
7421.8
|
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234.0
|
7543.5
|
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235.0
|
7667.2
|
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236.0
|
7792.9
|
|
237.0
|
7920.8
|
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238.0
|
8050.7
|
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239.0
|
8182.8
|
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240.0
|
8317.1
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241.0
|
8453.6
|
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242.0
|
8592.4
|
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243.0
|
8733.5
|
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244.0
|
8876.9
|
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245.0
|
9022.8
|
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246.0
|
9171.0
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247.0
|
9321.6
|
|
248.0
|
9474.8
|
|
249.0
|
9630.5
|
|
250.0
|
9788.8
|
|
251.0
|
9949.7
|
|
252.0
|
10113.3
|
|
253.0
|
10279.6
|
|
254.0
|
10448.7
|
|
255.0
|
10620.5
|
|
256.0
|
10795.2
|
|
257.0
|
10972.8
|
|
258.0
|
11153.4
|
|
259.0
|
11336.9
|
|
260.0
|
11523.5
|
|
261.0
|
11713.2
|
Since I would like to keep the proper hyperbolic curve then the bends in each curved side will be almost in logarithmic scale as hyperbolic curve changes a lot in the end of the profile. Here is some twist however. I would like to take advantage of my triangular shale and to make the first and second bendable surface to have asymmetrical bends (chords). If you look at the image then you will clearly see that chords on one side of the “bendable surfaces” are in the middle of the chord on another side. Doing this, I will increase smoothness of my opening. It will not be complicate to do it but it will be a bit pain in ass to circulate the sq area.
After a long contemplation about the material for the horn I have my leading idea of something that I call “Soft Shell Boat” approach. I did contemplated many different approaches, starting from very cheap and frugal (like most of the DIY Californians do) to very much overbuilt approach (two layers with sand between them). Considering my specific case and reasonable weight limitation on my attic I think my “Soft Shell Boat” approach will work very nice. The idea is to build an inverted boat hull with ribs outside. The Soft Shell will be most likely ¾ Russian plywood birches. Each connection between the chords will have before and after a set of ribs (brasses) made from 2x2 and 2x4 (asymmetrical). The 2x4 of the any nearby chords will be connected by 2x2 and 2x4 (asymmetrical as well). The whole idea do not use very strong surface of the horn is to let the very massive ribs to care the load across the horn surface. If everything will go as I plane then it will be no more than one sq feet of plywood in free hanging mode. The image below illustrates the idea for 4 chords (divisions between the chords are think black lines and the ribs are thick lines). For sake of simplicity the chords in the image are made with no angles.
Rgs, Romy the Cat
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