AirPort audio dropouts with AirTunes when using 802.11b cards; screeching

A number of readers have recently begun reporting an issue where an AirTunes audio stream drops out when running an Airport Extreme base station in mixed 802.11b/g mode and streaming music from a Mac running an 802.11b Airport card (not and AirPort Extreme card).

Other readers are experiencing the problem with only an AirPort Express on the network.

Set AirPort card to 802.11b only The most common cure for this problem appears to be setting both the AirPort Express and any AirPort Extreme base stations also involved in streaming to 802.11b-only mode rather than 802.11b/802.11g.

This can be accomplished with the AirPort admin utility (located in Applications/Utilities on a standard Mac OS X installation) for AirPort Extreme Base stations, and in the Airport Express configuration application under the wireless settings section for the AirPort Express.

A poster to the Apple Discussion forums writes "I have a 800mhz 15" Powerbook and initially when I set up my new AX unit I did not add it to my Airport Base Station, just as a stand alone unit. I had no issues. Only when I added it to my original base station did the problem with audio dropping occur, although only on the powerbook not my desktop unit. I first when into the settings and changed the channels from 10 to 1 and that did nothing. Then I changed my airport card setting from b/g compatible (I believe it defaulted to that) and set it to b only, and I've been currently cranking out some Van Halen for the last hour with absolutely no interruptions."

Likewise, a MacFixIt reader writes "I had the same problem. I solved it setting Airport Extreme Base Station from default b/g to b only. No audio drop out in the last two hours."

Still, some readers are having the dropout problems with any 802.11b (non-Extreme) AirPort cards despite 802.11g or 802.11b settings. One user writes "All the older Airport-based Macs suffer sporadic drop-offs with Airtunes, whether at 'b only' or 'b/g compatible' settings for the base and express stations [...] On the other hand, the newer Airport-Extreme-carded Macs stream flawlessly at either 'b' or 'b/g' settings, even for music shared from the older Macs.

Unfortunately, setting your base station or AirPort Express to 802.11b will (as expected) result in a dramatic speed drop for AirPort Extreme users on the network. In fact, even setting the base station or AirPort Express to ?802.11b/g Compatible? will result in a speed drop for 802.11g users, as explained by Apple in the AirPort FAQ:

"When '802.11b/g Compatible' mode is selected in the AirPort software, the AirPort Extreme Base Station supports not only systems with AirPort Extreme Cards, but also systems with AirPort Cards or other 802.11b or 802.11g Wi-Fi Certified cards. AirPort-enabled systems and other 802.11b Wi-Fi Certified products operate at a maximum speed of 11 Mbps. AirPort Extreme users will experience speeds less than 54 Mbps when they are sharing the network with 802.11b users. When only AirPort Extreme ? enabled systems and Windows PCs with 802.11g Wi-Fi Certified cards are accessing the AirPort Extreme Base Station, all users can achieve data rates up to 54 Mbps.

Turn on interference robustness Several readers have reported that turning on interference robustness (an option in the drop-down AirPort menu) reduces the occurrence of audio dropouts.

Audible screeching with AirPort Express Meanwhile, MacFixIt reader Morgan Gordon reports an unconfirmed audible screeching issue when streaming to a home stereo system:

"I've been using my Airport Express for about two weeks now as a remote device connected to my first generation (pre-snow, really first gen!) airport base station (wireless data sharing is not enabled). I am using the optical output on the Airport Express to connect it to a discreet Denon dolby digital / PCM decoder box I've had for years. Frequently, the Airport Express will generate an incessant and unprovoked screeching tone when iTunes -- and likewise, Airtunes -- is not even active. I've discovered only two ways to solve this issue: 1) open iTunes and play a song over Airtunes forcing a connection to the Airport Express device; 2) unplug and reboot the Airport Express device. I suppose it's possible that this problem is the result of incompatibilities between the old original Airport base station and the newer Airport Express base station, but I've heard no reports of this happening to other users of Airport Express devices."

If you are experiencing a similar problem, please drop us a line at late-breakers@macfixit.com.

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