A small ported two-way whose measured performance is good for its price: both Klippel measurements show a reasonably flat listening window (within ±3.3–3.7 dB from 300 Hz to 5 kHz), wide and even horizontal dispersion from the waveguide, and usable bass to about 47 Hz (−6 dB). Sources agree on the wide sweet spot, a deep soundstage for the size, and strong value. They split on how neutral it is — Amir and several owners call it close to flat, while Erin, MusicRadar and others hear a forward 1.5–2 kHz region, a resonant mid-bass or a mildly flattering balance — and on whether mixes made on it can be trusted. Nearly everyone agrees the tweeter hisses; what divides them is distance: at an arm's length on a desk many find it a real annoyance or a reason to return it, while from about 1.5–2 m or with music playing most can't hear it. Output is capped by a limiter around 96–102 dB at 1 m, so it suits nearfield use rather than filling a large room.
About this product
The 5-inch model of JBL's 3 Series MkII powered nearfield monitors: a 5" woofer and 1" soft dome tweeter in JBL's Image Control Waveguide, two 41 W Class D amps, a rear port, XLR and TRS inputs, and Boundary EQ and HF Trim switches. Sold one cabinet at a time. Not the 6.5" 306P MkII or 8" 308P MkII beside it, and not the original LSR305 it replaced. A pair sells for about $300 in the US as of September 2026, though US single-unit stock is patchy.
JBL's 305P MkII, introduced at the start of 2018, is the refresh of the LSR305 — the 5-inch powered monitor that made JBL's waveguide design, borrowed from its flagship M2, affordable to bedroom producers. Its trick is the tweeter's shaped horn, which keeps the sound consistent as you move off-axis, and it has spent most of a decade near the top of every "first studio monitors" list at roughly $150 a cabinet.
It was also the very first speaker Audio Science Review measured, and it has since been measured again by Erin's Audio Corner, so few budget monitors are as well documented. The data says the same thing the fans do about its dispersion; the arguments are about everything else — a hiss from the tweeter, a lively 1.5–2 kHz region, a resonant mid-bass, and whether a pair around $300 is still the default in a field with Kali, Adam and Yamaha in it.
