The older A33 sounded very good for its size and price class, but I noted in its review that it fell down a little bit with certain tunes. Well, TDK's engineers apparently read the review and tweaked the sound for the better. It now doesn't distort on any of the tracks I mentioned in my previous review, which doesn't seem like a coincidence.
More broadly speaking, this is a speaker that plays very loudly for its size, has some nice punch to its bass, and offers a reasonable amount of detail, though its treble performance isn't all that great. Overall, it's a fairly pleasant sounding speaker, and it fared better in our tests than many speakers in this and greater price ranges. There's very little stereo separation, but that's par for the course for this type of speaker where the drivers are so close together.
A lot of people wonder how this compares to the($199.99), another weatherproof speaker that I like a lot, and I think their sound is pretty close. The Boom is a smaller speaker, so it's a little easier to transport, and it has nearly double the battery life (15 hours compared to the Trek Max's 8 hours). The other small advantage to the UE Boom is that you can pair two of them together. But the Trek Max does offer that USB charging port and costs $50 less.
I also think the cylindrical Boom and its "360-degree" sound is a little better suited to outdoor use than indoors (it's truly designed to be an outdoor speaker). On the other hand, the TDK's bass performance can be improved by placing the speaker near a wall or something that allows for some reflection. Properly placed, the TDK arguably holds the edge for indoor listening.
If you're willing to give up something in the sound-quality department, TDK also makes the smaller A26, which weighs in at 12.2 ounces and features Bluetooth 4.0 technology (the A33 and Trek Max use Bluetooth 2.1). It charges with a common Micro-USB cable rather than an AC adapter (battery life is rated at 6 hours). I haven't tried that speaker yet, but it's down to around $80 online.
Finally, if you're looking to go even smaller, there's the Trek Micro ($59.99), which is similar tospeaker and other "micro" Bluetooth speakers.
In final analysis, TDK has basically eliminated most of the shortcomings I noted in my review of the A33 and even improved the rated battery life by a couple of hours, upping it to 8 hours. The Trek Max isn't perfect, but at half the price of the, it's arguably one the best portable Bluetooth speakers for the money, especially if you're looking for a speaker you plan on using indoors and outdoors.