The 1840 is more significant [than the 1440] in that it provides just the perfect stepping stone between the $300 headphones to the $1K models.
For most listening tastes, the Shure SRH1840 is a safe bet, if not the perfect headphone for those who want a well-rounded (but still detailed) listening solution. For more particular or niche tastes, however, other headphones may offer a more tailored sound.
-Major HiFi(Jul 2016)
the SRH1840 headphones are comfortable and light, and the sound will surely thrill demanding audiophiles.