I recently had a conversation regarding how the Irish of Clonduff was pronounced, my attempts at replicating the dialect condemned as "sounding like a Donegal accent."
Like in much of the North, it is believed by many that the phonology of the local Irish is preserved in the English dialect.
At best, this can only be partially true, given that English has far fewer sounds than Irish and that English has been the dominant venacular in Clonduff for circa 150 years (although remanants of the language were to be found in the 1940s).
Unfortunately, we do not have any recordings of Clonduff Irish or any Gaelic dialect in County Down.
We do however have recordings of other East Ulster Dialects, the closest being from Omeath in County Louth, approx eight miles as the crow flies.
The body of Omeath recording includes that of Brian Mac Cuarta, who interestly lived in Clonduff from the age of 7-20 (information from Ciarán O Duibhín's site - http://www.smo.uhi.ac.uk/~oduibhin/cainnteoir/oirghialla.txt)
Brian lived in Hilltown at a time when possibly even a majority of people spoke Irish but when it had all but ceased to be transmitted to children, who knows, he may have been influenced by the dialect, a recording of Brian can be found here, the recording done in 1931, he was 84.