I always use the same ratio of coffee to water when brewing, but it seems that there is a difference in taste between a single cup pour-over, a 12 cup pot, and a 96 oz urn. And the smaller the batch, the better it tastes. What could be the reason for this?
i'm not sure it's extraction time here as per Jean-Philippe Allard's reply.
Why would extraction time be longer or shorter if the grind size is the same, and we assume the same temperature of water and the same ratios.
That said - what perhasp Jean-Philippe Allard may be getting at is that there extraction time as a variable can change. IT may take three minutes for your pour over and longer or shorter for your urn
and extraction method does affect flavour.
also the actual drinking temp may be different - coffee really changes taste as it cools.
Also another factor is temperature - it may be easier to control water temp in one scenario over the other. SO your 12 oz may be a pour over but what is the urn? shower over a basket? big press?
A different kind of comparison may be: same grind and different size of pour over - like a v60 01 vs a v60 02 using your grind/ratio - and of course your pour technique.
Hope that helps.