I don't think you've ever heard high end subwoofers if you could make this statement.
My listening experience comes from my own vehicle where I would swap out and test subs from friends and my own collection. Each sub had its own characteristics and I could hear a difference in accuracy and SPL.
I'm currently running a Dynaudio Esotar 1200 in a 2 cu ft sealed box and it's the best I've ever heard in my car. I went from testing various IDQ, Focal K2 and JL w7 and w6 subs all in proper boxes. The sub bass coming from the Dynaudio is smooth, accurate and goes really low.
80hz is a null spot not incorrect time alignment
You could produce sub freqs using any cheap subwoofer but accurate and smooth transition doesn't come cheap. You could get SPL for cheap though.
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