There are many ways to accomplish this:

1. Download the RealTraps tones and plot a graph or import into Excel. You will need an spl meter to accomplish, takes about an hour.

2. Use RoomEQWizzard free software from Home Theater Shack forums. You will need a HTPC and SPL meter and decent soundcard.

3. Use the Velodyne SMS-1 subwoofer EQ system which will create a graph with included mic.

4. Plus many other products available.

In most cases you are taking the readings from the listening position.

3.

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