From one piece The Importance of Bed Depth 3 beliefs, in the piece's order there
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korrents.com
A deeper coffee bed reduces astringency by trapping long molecules on particle surfaces, not by pore-size filtration.Their words
the coffee bed would act on these molecules by filtering them out a bit like oxygen adsorbers keep oxygen in; it just provides a gigantic maze of free surface area for them to stick on, and hopefully the microscopic fluid velocity is gentle enough to not drag them along.
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Their words
the depth of a coffee bed, contrary to the width of the coffee bed, is a variable that impacts the flavor of the coffee being brewed significantly, and in a way that you cannot easily compensate for by changing other brew variables.
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korrents.com
Dripper diameter, with other brew variables held fixed, does not change extraction or taste — only batch size.Their words
changing the dripper diameter, keeping all other important variables fixed, has no impact on the brew mechanics and the resulting cup, in an "idealized" scenario