Note: In my tests with the original SoundLink Wireless Mobile I couldn't adjust the volume with an iPhone 3G, so it's possible to run into some snafus depending on how ancient your phone is.
At the launch for the original product, Bose talked about the engineering challenges of getting good sound out of a very compact speaker, and a Bluetooth one at that, as Bluetooth compression diminishes sound quality.
If you want to see what's going on inside the speaker, the design for the speaker's four low-profile neodymium transducers (mid- and high frequencies) and dual-opposing passive radiators (bass) are detailed on Bose's Web site.
While the cutting-edge hardware design is the biggest factor behind the speaker's sound, there's also a nice piece of software running in the background to process what's coming into the speaker and make it sound as good as possible going out.
As I said in my review of the original speaker, the results are shockingly good: the speaker plays incredibly loudly for its size. This thing can actually fill a medium-size room with sound and easily blows away the smaller Jawbone Jambox ($179 list). What's also impressive is that the sound doesn't distort at higher volumes. You can crank the Bose and it does just fine, with the bass holding together well and without any rattling or shaking of the speaker.
I played a wide variety of music on the speaker. With the Wilco album "The Whole Love," the mellower, acoustic guitar tracks sounded rich and detailed, like what you'd get from a larger speaker. I then hit it with some rock and pop tracks from David Guetta, Rihanna, and Pitbull. It all sounded quite good for a Bluetooth speaker this size, though sound quality will vary according to the recording quality of the track (poorly recorded tracks can have a harsh edge to them).
The new neodymium transducers are supposed to give the speaker a more "natural" sound. Doing an A/B test with the original SoundLink Mobile, I noticed a very slight difference for the better. For instance, with our old standby test track, Snoop Dogg's "Drop It Like It's Hot," the heavy bass line still sounded slightly restrained at higher volumes but the bass response on the new speaker seemed a touch tighter and more refined.
As I did with the SoundLink Wireless, I jury tested the speaker with a few other editors here at CNET, and all of them came away impressed by how loud it played for its size and how full the sound was, particularly for a small Bluetooth speaker.
Once again they noted that the bass didn't have quite the oomph they would've liked, but it's just not fair to expect subwoofer-level performance from a speaker the size of a hardcover book.
Since the original Bose SoundLink Wireless came out more compact, portable Bluetooth speakers have it the market, including the highly rated Jawbone Big Jambox. In fact, I've gotten several e-mails from readers asking me whether they should buy the SoundLink Bluetooth Mobile Speaker II or the Big Jambox. My short answer is that they're both very solid (and fairly expensive products) that most people will not regret buying. In terms of sound, it's hard to declare one a clear winner over the other because their sound is dependent on room placement and personal taste (also, the Jambox has two different sound modes).
I'm slightly more partial to the Bose because I like the form factor better, especially for travel. That said, if the speakerphone capabilities are important to you, the Big Jambox is going to be the better choice.
If you're comparing this speaker with smaller products like the original $179 Jambox, this Bose is a little more than twice as heavy, but it sounds much better and plays much louder. Likewise, the Bose is bigger and more expensive than the very compact Soundmatters FoxL v2, but the Bose sounds better than that model, too.
Logitech, meanwhile, offers a compelling alternative with the $250 UE Boombox. It offers comparable (or even slightly better) sound quality. But it's bigger than the Bose and has unique styling that will appeal to some more than others.
Finally, you can also step up to a more expensive portable AirPlay speaker such as the Libratone Zipp. That speaker uses Wi-Fi for streaming audio and overall sounds better than the Bose, with slightly clearer sound and bigger bass (it plays louder, too). But the Libratone only streams music from iOS devices and computers running iTunes.
In the end, while the SoundLink Bluetooth Mobile Speaker II may no longer be in a class by itself, it remains an impressive, well-built product. If you're on the fence about getting one, it's worth noting that Bose offers a 30-day money-back guarantee on the product, so you can try before you're fully committed, which is a good thing considering the speaker is fairly pricey at $300 (or $350 with the leather cover). Not everyone will think it's worth that kind of dough, but I suspect most people won't suffer a case of buyer's remorse.