DrForinor Possibly, but I’m joining the rank of the confused. 😉
I would have expected the IMS 14-18 gram basked to be marked “IMS 14 - 18 grams”, which is the tapered one. And I would not have expected an IMS basket to be marked “La Marzocco”… but if I understand you correctly, the “original” basket is the tapered one marked IMS 14-18, and the “La Marzocco” one is the ‘new’ straight one, which is causing you trouble.
I’m not surprised that they extract differently - the hole numbers and diameters seem to be quite different (I calculated 630 holes for the “original” and 820 for the “new”, but that’s based on the holes being distributed uniformly within a dodecagon). It would be interesting to see the ‘real’ specs in terms of open areas, but I suspect the ‘new’ basket has quite a higher flow than the original, so I would expect you need to grind quite a bit finer. However, if you grind ‘too fine’ you’ll just get bitterness.
Have you tried decreasing the dose in the ‘old’ basket? And tinkering with grind there? I am afraid that if you change too many variables at once (basket - and thus flow and shape, and thus thickness of the puck, going thinner; dose - decreasing again the thickness) it will be difficult to understand what is actually driving the poor result.
All this said, I can’t understand how a basket with a smaller or very similar volume (there isn’t much difference in height between the clip ridge and the bottom of the baskets, but the old one is quite tapered, thus smaller volume) has a higher recommended dose… it may be that the ‘La Marzocco’ basket is simply the ‘wrong’ basket for the Lelit.