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The reason why there is no energy shortage nor will there ever be is because energy is being preserved and conserved and only changes form. It never gets lost or increased.
To solve this problem we will apply the concepts related to wavelength as the rate of change of the speed of the wave over the frequency. Mathematically this is

Here,
v = Wave velocity
f = Frequency,
Replacing with our values we have that,

\lambda = 0.68m
The distance to move one speaker is half this

Therefore the minimum distance will be 0.34m
It takes more work to use a meat grinder