Formant values vary with the type of speech, gender of the speaker, and speech community (the Netherlands or Flanders). Below are some reported average F1/F2 values.

F1	mixed	female	male
Netherlands	801	986	795
	771	912	738
			670
Flanders	826	868	717
	807

F2	mixed	female	male
Netherlands	1498	1443	1301
	1509	1572	1409
			1425
Flanders	1506	1640	1429
	1511

wordgroup	phonological context	soundfile	waveform/spectrogram
in de la van de kassain the drawer of the cash desk	word-final		[click image to enlarge]
brooden kaasbreads with cheese	pre-obstruent		[click image to enlarge]
van het opdoemende gevaarfrom the looming danger	pre-liquid		[click image to enlarge]

wordgroup	phonological context	soundfile	waveform/spectrogram
in mijn la liggen (...)in my drawer lie (...)	word-final		[click image to enlarge]
tomaten en verse kaastomatoes and fresh cheese	pre-obstruent		[click image to enlarge]
daar is geen gevaar voorfrom that no danger is expected	pre-liquid		[click image to enlarge]

A possible feature specification of /a/ is -high, +low, +tense, -round, +back.

/a/ is most profitably seen as an A-class vowel, and as an alternant of the B-class vowel [ɑ] (see Phonology of /ɑ/). From the argument above, it follows in any case that /a/ and /ɑ/ differ only in whatever feature it is that distinguishes A from B-class vowels. However, in this particular case, the vowels seem closer to each other than other pairs of A and B-class vowels. For instance we find variation that is not otherwise attested in such pairs. E.g.:

This variation is at least partially regional and has not been seriously studied; it seems to us for instance, that [ɑ] at the end of the word is only found in Flanders. What exactly determines the reason why some a[a]’s can be realized as [ɑ]'s or vice versa, whereas others cannot, is not clear. Also otherwise, the two vowels seem sometimes to change position. For instance, the generalization that intervocalic fricatives are voiced after a tautomorphemic A-class vowel and voiceless after a B-class vowel has exceptions exactly with this pair:

Unlike other A-class vowels, there is no glide insertion after /a/ before another vowel. Instead, a glottal stop is inserted in words such as chaos[xaʔɔs]chaos.

When placed before an /r/ consonant,  in the same foot, the vowel lengthens to [aː] (Gussenhoven 1993).

Like other A-class vowels /a/ can occur at the end of a syllable; and like other A-class vowels /ø/ tends to not occur before two non-coronal consonants, with the exception of the numeral twaalftwelve and placenames such as MaarnMaarn.