I have a thought on how I can test the frequency output from the B&O amp to the factory subwoofer and would like your thoughts.

If I connect my digital multimeter in place of the stock sub and play a 60hz test tone I should see voltage because the amp is passing it. Now if it did the for various frequencies say 20, 40, 60, 80, 100, 120 etc I should be able to see where I no longer get voltage thus telling me where the stock amp crosses over the sub channel.

I my theory solid?