This is probably a really dumb question... but iMacs are a complete mystery to me, and since they are different from what I am used to, they obviously can't be any good.

I purchased for SWMBO a pretty nice USB headset (w/microphone) for her 24" iMac. She previously used headphones that weren't USB, that plugged into the microphone and headphone jacks in the back of the computer.

Now, of course, with the old headphones disconnected, the audio plays through the internal speakers. What do I do to convince the iMac to play audio through the USB headset?

tanstaafl.

When you plug in a USB sound device, it's not the same as a headphone jack. It's like plugging in a whole new sound card.

Somewhere in the operating system you will find a setting to control which output is the "default" audio output for the operating system. It will let you choose which sound card is the default one.

Don't know how that's handled on the mac. In Windows you right-click on the volume icon in the taskbar and select "playback devices", where it gives you a list of all the sound cards installed on the system. From there you select one and set it as default. I'm sure there's something similar in the Mac's control panel, somewhere in the audio devices configuration.

Note: the above assumes that the USB audio device that you plugged in actually works on the mac at all (ie, it loaded the correct soundcard device drivers for the usb soundcard that you plugged in). If not, you gotta solve that problem first.

Assuming that those USB headphones are correctly installed with the correct device drivers running on the mac, then this theoretically should be your answer:

http://support.apple.com/kb/PH4397

Yes, that did the trick... except that it assumed that I actually knew anything at all about an iMac or any other Apple device. It turns out that to get to the "Apple Menu" which is more or less the equivalent of the Windows Control Panel, you click on the little bitty Apple logo at the top left of the screen.

Who knew?

Thanks, Tony.

tanstaafl.

Doug, this may be a handy guide to keep bookmarked, it helps translate Windows activities to OS X activities:

https://www.apple.com/support/macbasics/pctomac/

Yeah, agreed that "Apple Menu" isn't particularly intuitive to direct newbies to that icon, but hey, at least that particular Apple menu has existed unchanged in the same spot since (I think?) all the way back to the first Mac or maybe even the Lisa.

Think of how many instruction sheets had to change (and become significantly more wordy) when, in Vista, Microsoft changed the "Start" menu to the "Shiny spherical button in the corner of your screen that contains some version of the windows logo" menu. Or similarly for the Microsoft Office line of products, which now have two or more different text-less menus in their upper left corner which replace what used to be the "File" menu.

Sometimes iconography makes things harder for everyone except the localization crew.

Can you think of any logical reason why the headset would work properly when plugged directly into a USB port on the back of the computer, but not work when plugged into a 4-port USB hub which in turn is plugged directly into the back of the computer?

Curiouser and curiouser.

tanstaafl.

Hubs, especially unpowered hubs, aren't reliable.

-jk

The headset is powered from the USB port it is plugged into.

An unpowered USB hub (one that does not have its own separate power supply) must not only power itself from the computer's USB port, it must also provide power to the USB headset. Often there just is not enough power available to go around.

Some USB hubs are cheaply designed and/or cheaply made, the hub may not meet 100% of the USB standards, or may only comply with a deprecated or incomplete version of the USB spec.

I've also seen cases where some devices will work when plugged into USB 3, but not when plugged into USB 2. Not devices that require the extra speed, note. In my case, it seems to be something in the EHCI stack in Linux, on this particular Intel motherboard, with this particular FTDI cable, whether plugged into a hub or not. Still, works with a USB 3 port, and I've got plenty, so, meh.

Not saying that's a problem with this particular device on this particular Mac, but it's something worth checking: if you have USB 2 and USB 3 ports, try both.

I'm going to put my money behind K447's answer.

If the USB hub is unpowered (ie there is not a wall wart power brick powering it) then there's your problem.

Those fancy headphones need a power amplifier to make their fancy newfangled rock n roll sounds the kids seem to love these days.

Plug the headset directly into the iMac.

Click the Apple Menu then press Option (alt). First menu choice should change from "About this Mac" to "System Information...". Pick System Information.

On the left, find USB. Then on the right find the headset. It will have information like this:

There may be an Extra Operating Current field as well, though this tends to be spotted only on devices pulling extra power to recharge a battery (such as an iPhone).

Note the numbers. Then unplug the headset, plug in the hub, and plug in the headset. Go to the File menu, pick "Refresh Information". Find the headset again now under the hub and note the numbers.

As others have said, it's likely a power issue.

http://support.apple.com/en-us/HT4049 is a good Apple support article detailing USB power and the information I posted above.