Amplifier boost modelled in WinISD
The first step is to specify the type of boost.
To model amplifier boost in WinISD, use the Parametric Equaliser.Access it by selecting the EQ / Filter tab and click the "Add" button to get this screen.
This example is a Jaycar Amp with 6dB of boost @ 35hz.
The software defaults to a Q of 2.0 which is what I have used to model my designs.
Other values may be more appropriate though - here is how SPL changes with different values for Q
The second step is to set the correct System input power.
WinISD takes whatever you set as the "System Input Power" and then adds the boost. The result of this process must not exceed the maximum power of your system.
This means that the "System Input Power" must be set lower than the maximum power by an amount equal to the boost. To work out how much to reduce the power, you need to convert "Boost in dB" into a "Power ratio"
Power ratio = 10 ^ ( Boost in dB / 10 )
|
Boost
in dB
|
Divide
maximum power by:
|
|
1
|
1.3
|
|
2
|
1.6
|
|
3
|
2.0
|
|
4
|
2.5
|
|
5
|
3.1
|
|
6
|
4.0
|
|
7
|
5.0
|
|
8
|
6.3
|
|
9
|
7.9
|
|
10
|
10.0
|
In this example, we are boosting by 6dB, so from the table we see that we must set the "System Input Power" equal to one quarter of our maximum power. For example, the "Blast Furnace" is designed for 240w maximum power, so set the Input power to 60w
As a check that you have got it correct, load a second copy of your project, remove the boost and set the System Input Power equal to your maximum power. Compare the SPL at the boost frequency for the two projects - they should be the same.
Here's our example continued. Red line is 240w with no boost. Green is 60w with 6dB boost @ 35hz. Notice how the two curves are equal at the boost frequency of 35hz.
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