Photos: Mark Ewing.
Horst Klein and Walter Hummel set up their Stuttgart company to make studio monitors and PA loudspeakers back in 1945, but my only experience of K+H monitoring to date has been the O 300D system (reviewed SOS October 2004). That particular model — a compact, three-way active design, with a sealed cabinet and digital inputs — is still available, and still provides seriously impressive reference-quality monitoring, despite its modest dimensions. In fact, I was so impressed that I was reluctant to return them after that review, and have been tempted to buy a pair ever since. So when I was offered the chance to audition the O 300D's junior sibling, I was very eager indeed.
The two-way O 110 model is a reflex-loaded design, with corner ports either side of the tweeter. Each MDF cabinet measures 268 x 170 x 190mm (giving an internal volume of about 6.5 litres) and weighs 5kg so, although compact, these certainly aren't flimsy. The cabinets are finished in a hard-wearing, anthracite enamel paint (white and silver finishes are also available) and metal grilles protect the drivers. The steel amplifier chassis set into the rear carries a modest heatsink, the (fixed voltage) mains and signal connectors, and a pair of threaded inserts to facilitate wall-mounting. A comprehensive array of brackets and other mounting hardware is also available.
The speaker's front baffle is made from a material referred to as 'Low Resonance Integral Moulding' (or LRIM), which has been machined to produce an elliptical waveguide for the tweeter. This ensures mechanical time alignment between tweeter and woofer, while also controlling the dispersion: wide horizontally, for good imaging; narrow vertically, to minimise reflections from the mixing console surface.
The magnetically shielded 145mm bass driver has a sandwich-membrane diaphragm which, combined with an unusually long voice coil, is claimed virtually to eliminate harmonic distortion. The 25mm composite tweeter is cleverly engineered, too, apparently combining the transparency of titanium with the low distortion characteristics of a fabric dome.
Each driver has its own amplifier and both are conservatively rated at a continuous 50W (for THD below 0.1 percent). Separate protection limiters in each amp are optimised for the characteristics of their respective drivers, and their activity is indicated by the illuminated K+H logo on the front panel blinking on and off.
The active crossover is tuned to 2.5kHz with fourth-order slopes, but the low-frequency (LF) response can be fine-tuned to suit the room. The bass roll-off can be increased below about 500Hz by 0, 2.5, 5 or 7.5dB to compensate for boundary loading, and a gentle, bell-shaped cut can be applied to the lower mid with 0, 1.5, 3 or 5dB settings. The overall free-field response is given as 56Hz to 24kHz ±3dB, which is surprisingly respectable for such a small box, and the published frequency plots are remarkably flat. The waterfall spectral decay also shows a clean, fast decay above 400Hz, and very good damping of the port and LF driver. The rated maximum SPL is 107dB at one metre for three percent THD — which is more than enough for a nearfield!
As with most K+H professional monitors, there are various input options. The review model was the basic version, with an electronically balanced input on an XLR. A rear-panel control allows the sensitivity to be adjusted from +6 to -18dBu. However, an input transformer can be specified as an option, if required, and the 'D' model adds a digital input. Unusually, this shares the same physical input XLR, to accept AES3 or S/PDIF signals. A screwdriver switch on the rear panel is used to determine whether the analogue or digital input is used, and in the case of the latter, it also selects the left, right, or mono sum of the digital channels. The internal D-A converter accepts sample rates from 32 to 96kHz with 24-bit resolution, and a BNC socket provides an unbalanced digital 'through' facility to link with a second monitor.
I assume that the O 110 D's digital input facility is similar to that of the O 300D and, if so, despite the unusual arrangement, it should work perfectly and with excellent sound quality.
Initially, I rigged the O 110s alongside a pair of similarly-sized PMC DB1 monitors (powered by Flying Mole amplifiers), as these are a familiar reference for me. I used them both during a SADiE editing session for a choral CD and was immediately impressed with the scale, depth and accuracy of the stereo images the K+H monitors produced, and the wide 'sweet spot' listening area they allowed. The sound was transparent and neutral, detailed and precise — but without any 'hyping'. In fact, their sound character has a lot in common with the venerable British designs from the likes of ATC, Harbeth and, indeed, PMC.
Later, I played a wider variety of material through the little K+H monitors and was impressed further by their capabilities. Solo voices were portrayed in a very lifelike way, with solid, three-dimensional images and a complete absence of coloration. Bass instruments were also carried surprisingly well (although obviously without the weight of a larger monitor) and serious quantities of air were being moved through those corner ports! Bass guitars were tuneful — not one-note affairs — and kick drums were clearly defined and solid.
However, it is worth noting that the O 110 speaker only really delivers its best when the monitoring level is above a certain threshold. Like most reflex cabinets, lower listening levels appear to reduce the efficiency of the bass driver significantly, resulting in a rather bass-light balance. This was the one area in which the O 110 lost out significantly to PMC's DB1 (it is hardly a fair comparison, since PMC's speakers are virtually unique in being able to maintain an almost constant spectral balance regardless of listening level, thanks to the strange characteristics of the 'Advanced Transmission Line' design they use). For those who require deep, powerful bass, the K+H O 800 subwoofer forms a perfect partner for the O 110s, and includes the appropriate crossover filtering.
The overall tonality of the O 110 seems to be voiced fractionally brighter than the DB1 at the extreme high-end, but this only draws attention to itself when listening at silly volumes, whereupon it can sound a bit strident. Overall, though, these diminutive monitors are extremely clean, accurate, well-balanced, and very impressive: they are certainly well worth auditioning.
Most monitors that match the sonic quality of the K+H O 110s cost significantly more, but on the list would be the ATC SCM20As, Harbeth Monitor 20s, PMC DB1s and Geithain ME25s.
2.1 Monitor System
This interesting monitor system uses the natural roll-off of the satellite speakers to provide the crossover with the subwoofer.
Studio Nearfield Reference Monitors
Building to a price inevitably entails compromises. The art is in choosing the right ones...
Three-way Active Monitors
Sometimes, a dose of old-fashioned good engineering delivers something well worth listening to...
Active Two-way Studio Monitors
Their A7 nearfield monitors received many plaudits, not least in the pages of SOS, but manufacturer Adam thought there was room for improvement.
Active Nearfield Monitors
PMC broke new ground a decade ago with their TB2 monitors, but the competition have been catching up. Does PMCs new activated design nudge them back to the front of the pack?
Secondary Reference Monitors
Avantone have added on-board amplification to their contemporary take on the classic Horrortone secondary monitor, and the result is something quite special...
Two-way Nearfield Active Monitors
India may be a growing force in most industries these days, but few Indian pro-audio companies have made it into Western markets. Can Sonodynes speakers change all that?
The time-domain response of monitors is often sacrificed for level, but this sealed-cabinet design tackles that issue head-on...
Nearfield Monitor Speakers
With digital and analogue inputs, these small speakers from newcomers Infrasonic promise a lot for the money. Can they outperform their budget price tag?
2.1 Monitoring System
If you demand brutal and revealing precision from your monitors, read on...
Active Three-way Monitors
As well as a distinctive design, these huge nearfield monitors offer a frequency and time-domain performance that compares with the best.
Studio Reference Monitors
Adam make the leap to a three-way speaker design that seems to pay dividends in clarity and separation.
JBL have a reputation for clinically precise monitors, but this time theyve come up with something a little smoother...
Coaxially-mounted speakers may seem a bit old-school, but theres nothing wrong with the theory — and a touch of DSP can make them very modern indeed!
DSP Reference Monitors
Built-in DSP extends the flexibility and usefulness of these capable speakers.
Events new owners make some extravagant claims for these new high-end monitors, whose design is said to put quality first. Do they live up to the hype?
Studio Monitors & Subwoofer
Samsons new low-cost nearfields can produce a big sound, but do they measure up for serious mixing? We find out.
Ribbon tweeters can yield a smooth sound, while still capably reproducing transient detail — and the Pro Ribbon range promises to do so for an attractive price.
Active Nearfield Monitors
Focal control everything from design to manufacture in their factory in France — and this approach appears to be paying off.
Active Midfield Monitors
Getting the balance right between the benefits and disadvantages of ported and non-ported speaker designs is a tricky job, and K+H do it better than most with this ported model.