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HamCall (October 1991)
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HamCall (Whitehall Publishing)(1991).bin
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lpads.txt
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1990-10-14
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LOUDSPEAKER "L" LOSS PADS
dB 4 ohms 8 ohms 16 ohms
loss R1 R2 R1 R2 R1 R2
-------- ---------------- ---------------- -----------------
1 .44 32.8 .87 65.6 1.74 131
2 .82 15.5 1.65 30.9 3.29 61.8
3 1.17 9.70 2.34 19.4 4.67 38.8
4 1.48 6.84 2.95 13.7 5.91 27.4
5 1.75 5.14 3.50 10.3 7.00 20.6
6 2.00 4.02 3.99 8.04 7.98 16.1
7 2.21 3.23 4.43 6.46 8.85 12.9
8 2.41 2.65 4.82 5.29 9.63 10.6
9 2.58 2.20 5.16 4.40 10.3 8.80
10 2.74 1.85 5.47 3.70 10.9 7.40
11 2.87 1.57 5.75 3.14 11.5 6.28
12 3.00 1.34 5.99 2.68 12.0 5.37
13 3.11 1.15 6.21 2.31 12.4 4.62
14 3.20 1.00 6.40 1.99 12.8 3.99
15 3.29 .87 6.58 1.73 13.2 3.46
16 3.37 .75 6.73 1.51 13.5 3.01
17 3.44 .66 6.87 1.32 13.7 2.63
18 3.50 .58 6.99 1.15 14.0 2.30
19 3.55 .51 7.10 1.01 14.2 2.02
20 3.60 .44 7.20 .89 14.4 1.78
Loss pads are useful for passive crossover design to adjust the relative
output levels of system drivers of differing sensitivities, for attenuation of
horns in clusters driven by single amplifiers, and so on.
The circuit used to produce attenuation is the same as that produced by
conventional rotary type variable L-pads but offer fixed resistor stability in
trade for not being adjustable.
To implement a fixed L-pad attenuator, use the rule of thumb that the two
resistors should have a wattage rating equal to the available power divided by
the total resistor value and then multiplied by the value of each individual
resistor, for example, a 6 dB pad for an 8-ohm driver driven by a 100 watt
source calls for an 8 and a 4 ohm resistor. The required power rating of each
resistor is found by dividing 100 watts by 12 (the total ohms of both
resistors), and then multiplying the resulting number (8.33) by 8 (66.7) and
then by 4 (33.3). To check on yourself, add the power ratings you get for the
two resistors, and you should get the original power rating (100 watts for
this example).