Disclaimer: my basis for comparison as near-field monitors are mainly IK Micromonitors and ILoud MTMs which I own, and a couple Dynaudio models in various sizes which I am quite familiar with. I have seen reviews here which compare the JBLs to portable BT speakers by this company. If you apply this as frame of reference, YMMV.
I bought the JBL104 based on good reviews and a seemingly lower price at Thomann than elsewhere, looking for inexpensive but still decently resolving, solidly built monitors that would work well in a multimedia setup used by kids.
The first major turnoff is the JBL startup jingle upon powering on, which is the same as used in some of their bluetooth speakers. Here it is played at what feels like max volume, making the speakers rattle with effort. Killed by your own startup sound? Not unlikely it would seem. Thankfully, if you leave them on and let them sleep when unused, they will not make any sound upon wakeup. Same goes for Bluetooth - you get a grille-rattling noise upon connection, but when it reconnects, it's blessed silence.
I started them off via Bluetooth with a range of sources, including the recent Google Chromecast. They sounded like a failed buy off the bat; with a boomy, low quality bass protruding everywhere, shrill highs which carry very little detail and a dead midrange, with the tiny in-built amp clearly struggling with the midwoofers which seem far too large for its capabilities. It's the type of sound that makes you want to increase the volume in an effort to actually hear something.
The input selector allows you to choose between a number of sources (kudos there) or have them all on at once - a nice move by JBL. Connected via RCA inputs they do come alive to an extent, showing there is potential in the mids to come a little to the front. But it is also the type of speaker/amp combo that has you endlessly fiddling with the EQ in your source between tracks, because what works on one will sound awful on another. The ever-present bass is the biggest culprit (needs to be cut by 6dB or more starting at 150-180 Hz to become remotely linear).
All in all, still not sure if they are a keeper. I would definitely cry if I paid the average price they go for these days - for that you can have a pair of refurbished Micromonitors which are in a completely different league.
