Newly derived morphologically complex words have played a prominent role in research on morphological productivity and lexical innovation (e.g. Baayen 1989, 1996; Plag 1999; Muhleisen 2010). Most of the attention concerning the properties of such words has been devoted to their phonological, morphological, semantic and syntactic properties (see, for example, Bauer et al. 2013 for such analyses). This paper takes a look at the phonetic properties of affixed words, testing Hay’s (2003) ‘segmentability hypothesis’, according to which newly derived words are expected to show less phonetic integration, hence less phonetic reduction, of the affix involved than established forms. This hypothesis is based on the idea that morphological segmentability negatively correlates with phonological integration. To date there is only one study that clearly confirmed the segmentability hypothesis (i.e. Hay 2007), while other studies have failed to replicate the effect (see Hanique and Ernestus 2012 for an overview). The present study investigates the issue with data from the Switchboard corpus for five affixes of English: un-, locative in-, negative in-, dis- and adverbial -ly. Using different measures of morphological segmentability, we demonstrate that the durations of the two prefixes un- and dis- (unlike the durations of in- and -ly) largely support the segmentability hypothesis. With un- and dis- prefixed words, prefixes that are more easily segmentable have longer durations.