Bert Doppenberg's two-way horn

Member: Bert Doppenberg, Holland
Drivers: PM2A
Horn contour: Tractrix

The bass horns:

• Drivers: First I used the B139 drivers from KEF. The horn was designed for this driver. For various reasons, I Later turned to several smaller units to cope with the throat of the horn (354 cm2). The speakers are 8 x Monacor SP60 each channel. They are cheap and do the trick! Sensivity 96dB/1Watt and a respons from 32Hz-150Hz within +/- 5 dB!
• The cut-off frequency is 16,7Hz (because the hornmouths are acoustically coupled to eachother, otherwise it would have been 23,7Hz). The lenght off the bass horn is 3.67 mtr, and the mouth area = 0,8569 m^2.
• The material I used was plywood (18mm). The horns are buried in sand under the wooden floor of my listening room.
• Click here for Bert's own article on these basshorns

The midrange horns:

Have been caculated with a cut-off of 150Hz. Using the output from the club's 'ad hoc' software, I ended up with a 40cm long tractrix horn, with a throat area of 254,470 cm^2 and a mouth area of 3881,512 cm^2.

Click here for Bert's own article on the midrange horns

Pictures:

• The basshorns
• Front view of one of the mid horns
• The system

The horn expansion:

d(mouth,X)	area(X)	square(X)	radius(X)
0,000	254,470	15,952	9,000
1,003	269,385	16,413	9,260
2,013	285,323	16,892	9,530
3,029	302,336	17,388	9,810
4,014	319,841	17,884	10,090
5,003	338,490	18,398	10,380
6,028	359,010	18,948	10,690
7,021	380,134	19,497	11,000
8,014	402,572	20,064	11,320
9,006	426,386	20,649	11,650
10,024	452,391	21,269	12,000
11,010	479,165	21,890	12,350
12,018	508,306	22,546	12,720
13,019	539,130	23,219	13,100
14,013	571,709	23,910	13,490
15,022	606,989	24,637	13,900
16,020	644,224	25,382	14,320
17,007	683,494	26,144	14,750
18,004	725,835	26,941	15,200
19,007	771,416	27,774	15,670
20,014	820,415	28,643	16,160
21,004	871,968	29,529	16,660
22,012	928,330	30,469	17,190
23,018	988,685	31,443	17,740
24,000	1052,090	32,436	18,300
25,009	1122,210	33,499	18,900
26,006	1197,044	34,598	19,520
27,005	1278,093	35,750	20,170
28,001	1365,723	36,956	20,850
29,005	1461,675	38,232	21,570
30,010	1566,491	39,579	22,330
31,010	1680,745	40,997	23,130
32,010	1806,545	42,503	23,980
33,004	1944,694	44,099	24,880
34,001	2099,286	45,818	25,850
35,008	2274,981	47,697	26,910
36,006	2473,579	49,735	28,060
37,003	2704,398	52,004	29,340
38,004	2982,179	54,609	30,810
39,001	3334,667	57,747	32,580
40,002	3881,512	62,302	35,150