[The following review applies to both the MacAlly PodDuo and the XtremeMac iPod Audio Splitter.]
It's great to enjoy your music in solitude, but sometimes you want to share your tunes and speakers aren't an option. In these situations, you need to be able to connect two sets of headphones to your iPod. You could buy a cheap headphone splitter at RadioShack, but iPod users have a couple better options in the form of MacAlly's $10 PodDuo and XtremeMac's $13 iPod Audio Splitter. Both products were designed with iPods in mind, and we can report that both do their jobs well with no discernible loss in sound quality. Which you should choose depends on which iPod you have and which case(s) and/or accessories you use.
[Note that with any headphone splitter, you'll get the best audio quality if you use two identical pairs of headphones -- such as two sets of Apple's stock iPod earbuds -- or two pairs that have the same impedance (two 32-ohm sets, for example). If you mix and match impedances, the audio quality of one or both sets of headphones can suffer.]
The XtremeMac Audio Splitter works only with 3G or later iPods and the iPod mini due to the adapter's reliance on these models' headphone/remote jack -- the bottom of the Audio Splitter features a small plastic nub that fits into the remote jack in order to prevent the Audio Splitter from rotating or shifting while attached. The resulting two headphone jacks are located on the top of the adapter, just above where the iPod's actual headphone jack resides. Because these jacks are oriented vertically, the Audio Splitter protrudes quite a bit above the iPod's body. In addition, because of its thick base, the Audio Splitter won't work with many iPod cases that cover the top edge of the player. Finally, because the Audio Splitter covers the iPod's remote jack, you cannot use the remote and the Audio Splitter at the same time. However, the Audio Splitter's shape and size make it an ideal fit for the iPod mini -- it's the same thickness as the mini and its rounded edge fits flush against the mini's own.
MacAlly's PodDuo takes a different, not-so-iPod-mini-matching, approach that makes it a bit more versatile. The PodDuo is shaped like a simple T adapter that plugs into the headphone jack of any iPod model and provides two jacks, one on each side. Like the Audio Splitter, it blocks the iPod's remote jack. (In theory, you could connect the PodDuo to the iPod remote's own headphone jack, but this would be fairly awkward.) However, because the PodDuo doesn't require an iPod with a 3G/4G/mini remote jack, it can be used with all iPods. For this same reason, it can also be used with iPod accessories that provide a standard headphone jack, such as Griffin's iTalk microphone attachment, and with many iPod cases that the XtremeMac splitter cannot. The downsides to the PodDuo are that it tends to spin/rotate a bit when tugged by connected headphone cables, and because its headphone jacks are located on each side, headphone plugs tend to protrude quite a bit past the edges of your iPod. This effect is especially bad when used with the iPod mini, since the mini's headphone jack is all the way to the right-hand side of the player -- the PodDuo itself protrudes nearly an inch over the edge of the mini.
Our recommendation? If you have an iPod mini, the XtremeMac Audio Splitter is the perfect match, although you need to ensure that any case you use with your mini provides full access to the top of the iPod. If you have a full-size iPod, or need to use the splitter with any other accessory that provides a headphone jack, MacAlly's PodDuo is likely a better fit.--Dan Frakes
Provides two headphone jacks for an iPod or other portable music player