Problems playing audio through USB speakers, fixes

We've recently received a rash of reports indicating problems playing sound through USB-connected speakers -- especially after updating to Leopard. Some users experience an odd phenomenon where sounds refuse to play through USB speakers, but upon disconnecting the speakers, a queued up series of sounds plays through the internal speakers, as if the sounds were clogged in the USB channel then pushed in rapid succession through the internal speaker once USB speakers are taken out of the loop.

As described by MacFixIt reader Dave:

"When I boot, the sound works fine, including new message sounds for Mail. However, after a time, either due to sleep, use of other applications (Safari?), etc. the sound stops completely. I checked Sound in the system preferences, and all looks normal, but it acts like it has been muted - but isn't. Over time, in checking for a bad connector, I found that if I unplug the USB cable for the display (and other peripherals, including speakers), the internal speakers play a string of all the missing sounds that had been held back, or stored somehow; and then the external speakers start working again."

"I went to system preferences and changed the sound output from external to internal speakers - instead of unplugging the USB cable between the monitor and the laptop. It produced the same result, the internal speakers sequentially played a series of sounds sent messages, checked email, etc. So it acts as if the sound "data" is being blocked and held, and I'm beginning to think it is triggered by one of the things turned off during sleep; such as screensaver, disk shut down, display turned off, etc."

So in many cases, the solution may be to simply disconnect and reconnect USB speakers to regain sound throughput.

In other cases, the problem may be underpowered USB speakers. We've previously reported various other issues caused by a lack of adequate USB power, usually solved by disconnecting other power-drawing USB devices from the same bus or adding an externally powered USB hub.

One additional suggestion: you might try running USB Prober. It is located in /Developer/Applications/Utilities, provided you have installed the Xcode developer tools. (These are probably present on your Tiger installer DVD, if you have one, but the best way to obtain them, if you have a broadband Internet connection, is to go to http://developer.apple.com, join the Apple Developer Connection as a free online member, and log in to obtain the most recent Xcode tools installer as a 1GB download.) Apparently, just running USB Prober does some sort of USB reset that can "wake up" unresponsive USB ports.

Finally, outdated firmware or drivers may be precluding recognition for some devices. Try checking your device manufacturer's Web site for the latest downloads.

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