You'll find an unexpected feature on the bottom of the RDP-XF100iP: a removable battery pack. It's a nice feature to have, if you ever wanted to stock up on extra packs for an extended time away from a wall socket or as a measure against obsolescence when the rechargeable battery eventually wears out.
Our favorite feature of the RDP-XF100iP is its sound quality, but we'll get to that in a minute. Compared with other portable speakers, the one feature that really sells the RDP-XF100iP (aside from its sound quality) is its FM radio. Our Editors' Choice offers a better price and a more compact design than the RDP-XF100iP, but it doesn't offer a radio. The has the radio, but lacks the sound quality. You could jump up to a serious boom box like the , but then you're losing the compact design. The Sony RDP-XF100iP sits right in that Goldilocks zone of price, sound, and portability, and if you consider FM radio a necessity, it's a great choice.
Another little feature we're happy with is the inclusion of a remote control. The remote has all the functionality found on the top of the RDP-XF100iP, and actually responds a little faster than the button controls. The range of the IR remote isn't great, but you can expect the typical 15- to 20-foot distance.
The RDP-XF100iP is a testament to Sony's reputation for sonic innovation and sound quality. It's not the most balanced or restrained system, but if you want an impossibly big, rich sound from a compact system, the RDP-XF100iP is tough to beat in this price range.
The RDP-XF100iP's biggest sonic trick is its guttural low-frequency punch. Right out of the box, with EQ flat on our iPod, basslines and kick drums fill out the mix in a dramatic and unexpected way. We imagine that Sony engineers must have pulled this off using some creative speaker porting or a passive radiator, because the low-end sound has a similar acoustic quality to the Yamaha NX-B02 or systems.
If you do decide to sweeten the sound with some of the integrated speaker EQ, expect that you will hear a little low-end distortion at high volumes, but it's nothing unlistenable. Overall we're impressed by how loud the RDP-XF100iP is able to get, even while running from its internal battery.
Battery life is rated at 7 hours from a full charge, either listening to the radio or an iPod or iPhone. By comparison, the Logitech S715i delivers 8 hours of playback time, though the audio quality takes a hit when it runs off batteries; the RDP-XF100iP maintains an awesome sound on or off its power supply.