When Apple debuted the original iPhone Dock back in 2007, the accessory’s appeal was obvious: people would want to use the iPhone upright by their computers or stereos, and could really benefit from a cleanly designed, affordable mounting solution to do so. Apple bundled the iPhone Dock with the first iPhone, then pulled it from the box of the less expensive iPhone 3G and 3GS, releasing the iPhone 3G Dock as a smaller but otherwise nearly identical sequel. Now there’s the iPhone 4 Dock ($29), which has remarkably dropped even further in size while preserving the same functionality and pricing as its predecessor, though a key difference in the new iPhone — its need for a case — unfortunately reduces the Dock’s appeal.

Apple seems to delight in making both its devices and accessories as small as possible, so the fact that the glossy white plastic iPhone 4 Dock is so downright diminutive isn’t a complete shock—the company has released iPod nano and shuffle docks that were smaller, but like the iPhone 4 itself, this is the tiniest iPhone dock to date. When it’s placed next to the company’s three-year-old iPod- and iPhone-agnostic Universal Dock, the difference is stark: the iPhone 4 Dock has a footprint of only 2.38” by 1.68” versus the Universal’s 3.15” by 2.6” measurements, nearly an inch smaller in each direction. Only a few millimeters of white can be seen off to the sides and front of the iPhone 4, with around 1.2” of plastic at the back to support the device as it reclines. On the rear surface are the same two ports—one for a Dock Connector cable, one for a 3.5mm audio cable—and each dock’s bottom has a soft gray rubber pad to keep it from slipping on a flat surface.
Like the iPhone 3G Dock but unlike the original iPhone Dock, the iPhone 4 Dock ships without any other items in its package; you have to self-supply the syncing, charging, audio, or video accessories you want to use with it.
Despite these similarities, there are some important differences between the iPhone 4 and Universal Docks. The line out port on the iPhone 4 Dock is fixed rather than variable, such that attempts to adjust the volume of the iPhone 4 via its buttons do not result in changes to the audio output level from the Dock; the volume slider disappears entirely in iPod mode, for example. By comparison, Apple’s Universal Dock includes an IR sensor that’s missing from the iPhone 4 Dock, sometimes enabling a remote control to change volume levels, the latter reflected in the output from its variable line out port—oddly, iPhone 4 sometimes allows volume attenuation to work with the Universal Dock, and sometimes doesn’t. This is due to some subtle electronic differences between the authentication chips found in Apple’s accessories, as well as the software of its iOS devices, which have recently started to exhibit compatibility issues that may remain buggy until a subsequent release of iOS 4—or longer.
For the time being, we can say that haven’t discovered any Dock Connector accessories that don’t work with the iPhone 4 Dock, but there are so many potentially incompatible items now that it’s hard to perform any sort of broad-based testing. It suffices to note that the most commonly attached electronic accessories—charging, syncing, video, and audio cables—all appear to work fine with the iPhone 4 Dock for the time being, though Apple is mostly concerned about having the Dock connect to computers and AV systems with its own cables, which work without complaint.
Due to the higher quality output of the Dock’s line-out, users looking for a way to attach the new iPhone to a home stereo system will find that the Dock provides a better-sounding and more stable mounting solution than just connecting an audio cable to the iPhone 4’s headphone port.
What doesn’t work fine with the iPhone 4 Dock are cases, and that’s where the accessory will be problematic for many users. Apple’s prior iPhone and iPhone 3G Docks were similarly tailored to fit just those iPhones without any protective cases, which wasn’t considered to be a major issue for some people—Apple used to suggest back then that cases weren’t really important. But due to the iPhone 4’s new shatter-prone glass body and antenna attenuation issues, many users now feel that cases are necessary to keep the new device working right and feeling safe, and even Apple CEO Steve Jobs has suggested as much in recent communications to end users. Unfortunately, the designers of the iPhone 4 Dock apparently didn’t get Jobs’ memo, so even Apple’s own Bumper cases don’t fit inside this accessory. It’s worth noting that the earlier Universal Dock works with Bumpers and numerous other, better iPhone 4 cases as well.
One potential difference between the Universal and iPhone 4 Docks turned out to be a non-issue. As with the iPhone and iPhone 3G Docks, the iPhone 4 Dock was designed with special accommodations for the iPhone’s bottom-mounted speakerphone features: there are small mesh grates inside the iPhone 4 Dock’s well that match the microphone and speaker mesh panels on the iPhone 4, as well as a special waveguide vent on the Dock’s bottom that lets audio flow out and in without distortion.