Nothing specific. I'd say the WL2 now has quite an old WLAN chipset but if the HFA handsets are fine.... can't be that. If you're using the same codec and sample size as the HFA and it's on the same subnet, I can't think of an explanation for it. So you could check/compare CGWB config if you're using a different STMI card for the SIP phones but from what you've said it'll be the same, and you'll have set codecs and QoS/DSCP as you want it in the phone. WLAN sniffer may help, but problems like this are always a pain in the ass.