That was a rather unhappy surprise. But there were pleasing surprises as well. The first was when I'd spotted the HDMI inputs and outputs. The second was when in use, it became clear that the soundbar was capable of generating its own on-screen messages. Adjust the volume and a bar indicator appears on the screen for a second or two. Likewise for changing the bass boost or the surround mode. That worked at all resolutions, even with 3D video.
JBL hasn't put a Bluetooth selection key on the remote, although all the other inputs score keys. But you don't have to walk over the the soundbar to change to Bluetooth. There's a simple workaround. Just turn the soundbar off, then start playing music from the paired device and the soundbar will switch back on in Bluetooth mode. Only one device can be paired at a time.
The system sounded really quite good, both with movies and music. I watched a couple of episodes of The Walking Dead, and within seconds forgot that I was using this system rather than the AU$20,000 worth of gear I normally use. But The Walking Dead doesn't have a lot of surround, and this system doesn't do such a good job there. The front sound stage though was well balanced and solid in performance. Music was tonally balanced with a very slight tendency towards brightness, while voices in movies were clear and coherent. The whole system when quite loud as well, filling my largish office with plenty of clean sound.
A couple of aspects of performance were strange. For one thing, there was a lag between the audio starting — say, the start of a song — and the subwoofer kicking in. Not just the lag in waking up after the system had gone to sleep, but even after the briefest of interruptions, such as skipping a track. I timed it at about 0.9 seconds before the subwoofer would join in with the soundbar. That doesn't look like a long time, but it was quite disconcerting in listening.
Likewise, the soundbar itself seemed to take a fraction of a second to latch onto an incoming digital signal, so at the start of each song on a CD it missed the first beat or two of each track (except for those tracks which flowed on without a break from the previous one).
Properly balanced, the unit delivered a remarkably wide frequency response of 40 hertz to 20,000 hertz. At the listening couch in my office the upper bass/lower midrange was recessed by about four decibels compared to the treble, which made the system a touch bright and made the subwoofer more obvious when its level was too high. Measured up close the subwoofer was good down to about 36 hertz, which is pretty impressive for what is quite a low cost unit.
What a pity about those operational issues. Because, aside from them, the JBL Cinema SB400 is not just a good soundbar and subwoofer combo, but a HDMI and Bluetooth-enabled home theatre in a box.