Ew, sulphur alert! Definitely a gassy, cabbage-like top note that I've also previously encountered in some Tomatins, Tomintouls and Juras. This could stem from spirit sulphur or sherry casks treated with sulphur candles; since the Macallan distillate is usually immaculate, I'm going with the latter: a deficient cask. The nose is pretty much ruined by this, I'm afraid to say. You can still detect the Macallan distillery character behind the sulphury off note, but it's a struggle.
Sadly, the palate is affected as well, especially the initial attack. Pity, really, because this has a good body and the juiciness that is typical for the age.
The finish is lackluster as well, missing any and all cocoa / coffee notes. Instead, there's a residual alcoholic whiff along some sweetness and slight acidity.
I really wanted to like this, especially since I absolutely adore the 18-year-old Speymalt bottlings, but in all honesty, this is crap.