Klein + Hummel O 300 Active Studio Monitors and O 800 Active Subwoofer

The Klein + Hummel O 300 is one of the nicest studio monitors I’ve heard: You have to jump to larger models, audiophile makers, or mastering-grade speakers for better performance. The horizontal design is smart. And combined with a proprietary wave guide implementation, the O 300s produce an accurate sweet spot in nearly any production environment.

The speaker is an active 3-way model fabricated from premium materials. The 8" woofer is lightweight polypropylene; the midrange comes from a 3" treated fabric dome, and the high-frequency driver is a combination of titanium (for accurate transient response) and fabric (for smoothness). All drivers are magnetically shielded. The horizontal form makes it easy to get your ears at tweeter level, though K+H tells us that doing so narrows the sweet spot significantly. (Note to speaker makers: Engineers want horizontally-capable monitors. Meter bridges and speaker stands are often too high to get tweeters at ear level without tilting speakers down, leading to comb filtering.)

Each of the drivers has its own amp with high quality crossovers—critical for proper phase and frequency response. We noticed none of the frequency bumps or dips associated with poorly-implemented crossover technology.

The driver protection scheme doesn’t limit all potential spikes, as this could include musically-important transients, but limits (as indicated by a blinking K+H logo) only when a voice coil is in danger of thermal overload or a power amp could overheat. Well done.


At the risk of sounding like an audiophile mag reviewer, I’d describe the O 300 as detailed, wide-ranged, and effortless—no ear fatigue here. Playing our favorite commercial CDs revealed depth and width in the soundstage. It seemed we could hear where the horn section players were standing on Calexico’s “The Black Light,” and double kick lines were punchy and defined in Lamb of God’s “As the Palaces Burn.”

At the micro level, the O 300s produced extensive detail. This was a great help for catching potential tracking issues. From a ticking pendant timepiece, to low-level HVAC noise, to where sampled piano notes looped, nothing got past the O 300s.

While the O 300s didn’t lack low end, Dave Hidek, our chief mixing engineer, wanted a sub’s extension and accuracy beyond the ported cabinet’s frequency response, which extends to 33Hz. Enter the O 800: Designed as a component to this system, we could skip the obligatory crossover point setup as the sub’s 24dB/octave Linkwitz-Riley filter (at 90Hz) dovetailed perfectly with the O 300s, and the rear-panel level and low cut controls allowed fine-tuning the O 800 for our room. The driver features a long-excursion design type (a full range of about 40mm), which contributes to an articulate low end that is delightfully free of tubbiness, while helping to avoid damage to the cone. If anything, the sub was a little too much for rock and country applications in our room; however, H, a visiting rap engineer, was very pleased with the output, and the sub does have a level control, which makes situations like this a bit more manageable. If you’re looking for a sub (whether with K+H mains or not), consider the O 800—it provides a great mix of extension and precision. And while cosmetically attractive, the fine-mesh wire also protects the loudspeaker cone from the wayward foot. Smart!


Reviews often pigeonhole monitors as either “accurate” (and possibly fatiguing over long hours) or “pleasing,” which may gloss over sonic problems. The O 300 proves that a speaker can deliver the best of both worlds, as this design is both revealing and a pleasure to use. Granted, the O 300 won’t produce the “ear-bleed” levels of some other monitors (though they play to a max SPL in half space at 3-percent THD/1m of 112.8dB/SPL and adding the sub adds another 10dB above that), but that won’t matter to pros who value their hearing. And while not K+H’s fault, the U.S. dollar’s weakness vs. the Euro will put a damper on North American sales. But minor items aside, these are some of the best mixing speakers I have ever heard. It was a sad day here at Treelady when we had to return them.

Product type: High-end, three-way monitor speakers (and sub-woofer).
Target market: Recording studios and mastering suites.
Strengths: Accurate, yet pleasing sound reproduction. Non-fatiguing. Horizontal design fits contemporary studio setups. Wave guide implementation provides accurate sweet spot without comb filtering. Voice coil protection circuitry.
Limitations: Dollar vs. Euro exchange rate makes them pricey. Not as loud at max volume as competing monitors.
List price: O 300 $2,495 each, O 800 $2,795