I was speaking if you read my sentence about sellers of "upgrade" half the time useless when acoustics is not care for ( Not just room acoustics by the way )
Guess why and how i modify the speakers i just bought ? Acoustics knowledge ..Upgrade unnecessary... The venthole design of most speakers is not done as it must be done because of cost and esthetics... Same for the tweeter physical design in many case...
I modified all my bookshelf speakers for stupendous improvement... Acoustics rules...
However, contrary to the claim made by @mahgister above I don’t see how that should negatively impact sellers of audio equipment - quite the opposite