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toddalin
12-26-2005, 02:59 PM
I redid the testing on my L200 and center speaker cabinets and the results are included below. I tried to reduce the influence of the room in these measurements and the data are much more linear. I hope this is of interest. I'll olso retest and print results once the 2235's /W15GTI are installed.

In this case, measurements were obtained at a distance of 0.825 inch from the woofer dust cap and toward the center of the port, in-line with the baffle board. (A piece of paper was laid on the baffleboard, the mic is moved in unti it touched the paper, and the paper was removed.)

The first table represents the L200 cabinet with a D130 reconed by OCS as a 130A. Initially the woofer level was brought up to 100 dBL (no weighting) and all other measurements are taken relative to that level.

The Relative Port contribution was then considered with respect to the area of the woofer. For the L200 cabinets one port was measured and the other was assumed to be the same. The calculation is:

Measured Port spl+10*LOG((2*(2^2*3.14159))/(7.5^2*3.14159))


The total freq response is calculated as:


10*LOG(((10^(Cone spl/10))+(10^((Rel Port spl)/10))))


The calculation does not include provisions for phase angle in port contribution.

Frequency Cone spl Port spl Relative Port spl Composite Freq Response
180 100.0 90.3 81.8 100.1
160 99.1 90.5 82.0 99.2
140 97.3 90.8 82.3 97.4
120 98.8 90.8 82.3 98.9
100 99.2 90.9 82.4 99.3
90 99.5 91.6 83.1 99.6
80 99.5 92.5 84.0 99.6
70 100.7 94.7 86.2 100.9
60 95.4 94.9 86.4 95.9
50 87.9 94.9 86.4 90.2
45 79.7 95.1 86.6 87.4
40 76.5 95.5 87.0 87.4
35 80.8 94.8 86.3 87.4
30 81.4 94.0 85.5 86.9
25 80.2 90.5 82.0 84.2
20 78.1 86.3 77.8 81.0



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The center cabinet includes two 130As each mounted in a 4 cubic foot outter cabinet. For this testing, only one of the woofers was used. It is assumed that if the other woofer were used alone, similar results would occur except that the contribution of the two outter ports would be reversed.

A 4" diameter, 9.5"-long port leads out the baffle board and a second similar port leads to a 2 cubic foot central cabinet. For the center cabinet a similar port also leads out the baffle board. Testing was performed in the same manner as for the L200 cabinet except that the contribution for each of the three ports was assessed individually and added to the total. Ports 1, 2, and 3 represent the port in the woofer chamber, the central port, and the port in the far woofer chamber.

Freq Cone Port 1 Relative Port Port 2 Relative Port Port 3 Relative Port Composite
180 100.0 89.3 77.8 81.1 69.6 71.8 60.3 100.0
160 100.1 89.2 77.7 80.5 69.0 75.4 63.9 100.1
140 99.1 86.4 74.9 84.5 73.0 81.0 69.5 99.1
120 99.6 88.6 77.1 78.8 67.3 65.0 53.5 99.6
100 98.6 88.9 77.4 86.7 75.2 80.3 68.8 98.7
90 98.4 89.0 77.5 84.1 72.6 77.5 66.0 98.4
80 97.8 89.5 78.0 80.7 69.2 71.9 60.4 97.9
70 97.2 89.4 77.9 82.2 70.7 74.3 62.8 97.3
60 92.6 88.7 77.2 88.5 77.0 82.6 71.1 92.9
50 88.5 92.2 80.7 88.1 76.6 83.9 72.4 89.5
45 84.9 92.1 80.6 87.9 76.4 85.0 73.5 86.9
40 80.0 91.4 79.9 87.1 75.6 86.0 74.5 84.2
35 78.7 90.3 78.8 86.4 74.9 85.9 74.4 83.2
30 78.5 89.7 78.2 86.0 74.5 85.1 73.6 82.8
25 78.5 89.0 77.5 85.0 73.5 83.6 72.1 82.2
20 78.2 87.4 75.9 84.0 72.5 81.9 70.4 81.3



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