Hypsometry. Modal Synthesis.

When I’m traveling I carry an AirPort Express with me, for instant wifi-ication of the world. Right now I’m staying in a friend’s apartment in Brooklyn, which already has wifi but whose stereo is not connected to the network. So, I figured it’d be simple enough to use the AirPort Express to connect the two, and thus my laptop, right?

Wrong. So, for posterity’s sake, and for the sake of my brain the next time I need to know how to do this, here’s how to do this properly, at least in the circumstances I encountered:

Restart the AirPort Express by holding down the reset button for a bunch of seconds. (The documentation says to hold the button down for 5 seconds to get a hard reset, but I found that only worked sometimes. Hence my vagueness.)

Open up the AirPort Utility application and use the manual setup controls to configure the base station.

Go to the Wireless tab of the AirPort section of the controls, and choose “Join a wireless network” as the Wireless Mode. Choose the correct network from the Network Name list (waiting for it to refresh its list, and retrying as needed). Then choose the appropriate Wireless Security setting from the drop-down menu.

And that’s the first part of the trick. For no obvious reason, the AirPort Utility isn’t as smart as the regular AirPort interface, and is unable to properly determine what security a given network is using. So you need to figure the appropriate security setting out on your own.

The router my friend uses is a Westell 327W, presumably configured in a fairly default way. The password is a 10 digit string of numbers and letters, which indicates that the network is secured using 40-bit WEP with a hexadecimal password. The fact that it’s 10 digits long indicates this. If the password were 5 characters long, it would be a 40-bit ASCII password; if the password were 13 characters long, it would be a 128-bit ASCII password; if the password were 26 characters long, it would be a 128-bit hexadecimal password.

Despite the simplicity of these distinctions, it turns out that AirPort sometimes has trouble telling what type of WEP password you’ve given it. To get around that strange inability, you need to either enclose the password in double quotation marks, to indicate an ASCII password, or prepend a hexadecimal escape ($ or 0x), to indicate a hexadecimal password.

So, given that the network here uses a 40-bit hexadecimal password, prepend $ to the 10 digit string of numbers and letters, and enter it in the Wireless Passsword and Verify Password fields.

Go to the Base Station tab, still within the AirPort section of the controls, and choose a name for the base station, as well as a password.

This, in theory, should suffice. But a quick check of the AirPort Express’s settings – in the Summary tab of the AirPort section of the controls – showed that the base station was still planning on connecting to the network using Ethernet, per its default settings. Turns out that displaying the Internet section of the controls clues the AirPort Utility in to the actual current settings, so just click on that, then go back to the AirPort Summary display and make sure your settings are correct.

Once everything looks good, click Update. Wait while the machines do their little dance, then jump into iTunes, choose your new set of speakers from the list, and listen to your music.