The Manchurian Candidate (1962)

One of the worst 5.1 "remixes" I’ve heard. It’s just a rechannelled version of the original mono mix, and it’s phasey as hell. Extremely annoying and completely unnecessary. For a while, the mono mix was available only on the DVD, but both the MGM BD and the DVDs were derived from the same master, and are thus frame-accurate after a quick delay/trim.

The mono track on the Arrow BD is presumably from the same source as the MGM DVD mono track (both being from the same dated master), but without any filtering at the authoring stage. It certainly sounds more detailed, but there is a very audible amount of mid-frequency rustling running throughout, as well as (strangely) some very low-frequency thumping that intrudes upon the dialogue very annoyingly every few seconds. In fact, the MGM/Arrow mono tracks are generally monstrously bassy, rendering the score almost unintelligible at times.

The mono track on the Criterion blu-ray is an ENORMOUS improvement. The rustling is gone and everything is MUCH more detailed. Curiously (given that this is Criterion), hardly anything has been done to attenuate or eliminate the high-frequency hiss present, either, but it sounds all the better for it.
It's quite likely that the audio for the new restoration was sourced from lower-generation materials than the audio on the now very dated MGM master. Sounds bloody marvellous.