This is how I solved the problem of standing waves with my M3s and yammie sub in my living room. I stuffed the sphincters of the M3s with foam. All issues disappeared without using any EQ.

I don't understand where he gets the numbers of 7 feet for speaker distance and 19 feet for sub distance. Those must be examples.

House of the Rising Sone
Out in the mid or far field
Dedicated mid-woofers are over-rated