What do you get when you cross Klein + Hummel's pedigree in speaker design with Neumann's decades of industry experience? A very good monitor indeed...
It's hard to believe that I reviewed the Klein + Hummel O300D three-way, nearfield monitors as long ago as October 2004. The O300 range quickly gained a reputation as one of the best nearfield monitors that money could buy — and not that much money in the grand scheme of things, either — thanks to the combination of accuracy and transparency associated with a good three-way design, the precise time-domain performance of a sealed cabinet, and a surprisingly compact and very practical form factor. The only real criticism levelled at the O300 was about its slightly restricted maximum output level, which concerned some heavy rockers, although some were trying to use it as a midfield rather than a nearfield speaker! Personally, I always found the O300 was more than loud enough, and it has remained one of my favourite monitors throughout the last decade.
Since then, the K+H company have been acquired and rebranded by Neumann, but their design philosophy remains completely intact and, if anything, production quality has actually improved. The first monitor released under the new stewardship was the KH120A (reviewed in SOS in April 2012), which was a redesign of the preceding O110 model, and it punched well above its weight. The new KH310A is, similarly, a redesign of the previous O300 model, sharing the same size, aesthetics, layout and underlying design concepts, but with improved technical performance across pretty much every important parameter.
Neumann market the three-way, fully active KH310A towards the project studio, broadcast, post-production and mastering sectors, as a high-quality nearfield monitor suited to small- and medium-sized control rooms. As with the previous model, a version with a digital input is also planned but is not available at the time of writing, and I was equipped with the analogue version for this review.
The speaker's 28-litre cabinet measures 292 x 383 x 253 mm (HxWxD) — identical in height and width to the O300, but 2mm deeper — and it weighs 13kg. The monitors are shipped individually, with stock taken from the warehouse as required in left- or right-handed forms to suit the end user's requirements. There is no 'stereo pair' matching as such because every model is matched accurately to the factory reference. In effect, any two mirror-image speakers can be used as a precise stereo pair, as response deviation between any two randomly selected speakers is less than 0.5dB.
Each speaker is packed individually in a well-padded carton, along with three mains cables (with Euro, UK and US plugs), four sticky feet, a comprehensive operating manual and a quick-start guide. The monitors are labelled as 'left' and 'right' (either can be used as a centre monitor in 5.1 arrays), and normally the tweeter/mid-range drivers are placed on the outside of the monitoring triangle.
Although I used the monitors mainly on conventional floor stands, threaded inserts on the side and back panels allow numerous alternative mounting options, and Neumann have a wide range of optional mounting brackets and adaptors. All three drivers are magnetically shielded, so there's no problem with placing the KH310A on meter bridges near moving-needle meters.
At first glance, the most obvious differences between the old O300 and the new KH310A are that the mid-range driver is seated a little deeper within its chamfered recess — a deliberate move to help guard against accidental damage, since there is no protective front grille — and the surround on the bass driver has unusual indented radial lines, which apparently reduce radial standing waves across the surround material. The illuminated badge (now a white Neumann logo) has also been relocated, and sits between the HF and mid drivers on the edge of the cabinet. A switch on the rear panel allows its brightness to be adjusted when the speaker is active, with settings of 100 percent, 60 percent, 30 percent, or off. It also flashes red when the speaker protection systems are activated, even if the normal power-on illumination is disabled.
However, despite the general similarity in appearances, pretty much everything in the KH310A is new, starting with the cabinet construction, which has been redesigned to reduce structural resonances. The all-new electronics boast lower noise and distortion, and all three drivers are brand new units, designed exclusively for the KH310A from the ground up, entirely in-house and using the latest computer simulation techniques to optimise the magnetic circuits, physical geometry, and so on.
A 25mm 'alloy fabric' dome tweeter sits in an elliptical, mathematically modelled dispersion (MMD) waveguide, while the 75mm mid-range driver has a fabric dome and neodymium magnet (the woofer and tweeter both use ferrite magnets). Both the tweeter and mid-range dome are said to exhibit much better break-up mode behaviour than most similarly sized components from other mainstream manufacturers. The 210mm long-throw woofer uses a composite sandwich cone and an 'extremely linear force factor' (ELFF) design.
There are lots of bewildering marketing terms there, but the important point is that, relative to the old O300 model, the ensemble of new drivers delivers lower harmonic and intermodulation distortion, smoother responses both on and off axis, and improved efficiency, which translates into the much-requested greater output level. The waveguides around the tweeter and mid-range driver not only control directivity, but also act to increase the efficiency and reduce reflective interference from the other drivers.
Confirming its 'full-range' status, the published -3dB frequency response limits are given as 34Hz and 21kHz, and the overall response is very well controlled, remaining within a ±2dB tolerance between 36Hz and 20kHz. Returning to the issue of peak loudness, when measured with unmusical pure sine-wave signals, the new KH310A manages 3.5dB more SPL throughout the mid-range and 3.9dB more below 100Hz compared to the O300. This may not sound much, but with normal music material it is claimed to translate into around 7dB more SPL in typical listening conditions — and that really is quite a lot when 3dB represents a doubling of acoustic power! For the head-bangers who still want more, adding the matching (and enormous) KH810 subwoofer removes some of the LF workload from the KH310A, allowing a further 7dB increase in the maximum output level, while also extending the LF response down to 18Hz.
The KH310A is capable of producing 116dB SPL between 100Hz and 6kHz at one metre (for three-percent distortion), and around 105dB SPL between 50 and 100 Hz. That is pretty loud for a nearfield speaker but, more importantly given that this is supposed to be a reference monitor, when delivering a still generous level of 95dB SPL at one metre the total harmonic distortion remains below 0.5 percent for all frequencies above 85Hz. Now that really is impressive. Neumann quotes the acceptable frequency response tolerance as ±2dB, but typically achieves better than ±1dB.
The electronics chassis built into the rear panel contains four Class-AB integrated power amplifiers, with a high-capacity, switched-mode, universal power supply that operates on any mains supply between 100V and 240V AC. Power consumption at idle is 24W, rising to 300W at maximum output, and a cast aluminium heatsink deals effectively with unwanted heat. The new PSU design has been optimised specifically to maintain the bass transient response and maximise headroom margins. The bass driver is powered by a bridged pair of amps to deliver a nominal 150W (210W peak), while the mid-range and tweeter amps each produce 70W (90W peak). The driver protection circuitry is quite elaborate, with independent thermal limiters for each driver, as well as soft-clipping and excursion-limiting for the woofer.
The input signal is split between the three drivers via fourth-order (24dB/octave) crossover filters centred at 650Hz and 2kHz. There's a sub-sonic filter working below 15Hz to protect the woofer, as well as some protection above 20kHz to avoid ultrasonic intermodulation. The choice of a 2kHz crossover frequency ensures that mid-range dome break-up modes occur well above its working range (and the tweeter breaks up well above 20kHz).
Three rear-panel slide switches provide response-shaping options, starting with a HF shelf EQ which provides +1, 0, -1 or -2 dB above 2kHz. The bass output can be reduced by 0, 2.5, 5 or 7.5 dB at about 50Hz, with the roll-off starting at 150Hz, and the mid-range switch introduces a response dip of 0, 1.5, 3 or 4.5 dB between 50 and 500 Hz (centred at about 180Hz). The handbook provides helpful advice about the most appropriate settings for different speaker locations and situations.
The input sensitivity is set with a slide switch and rotary gain-trim knob. The switch sets the output SPL for a nominal 0dBu input signal, with options of 94, 100, 108 and 114 dB SPL, while the rotary pot allows the level to be attenuated by up to 15dB to provide intermediate output levels. In combination, the total sensitivity adjustment range is 35dB, which is almost twice that of the old O300's 18dB range. Most of my listening was done with the switch set to 94dB SPL and the trim at 0dB, since I found that combination provided ideal compatibility and sensible listening levels with all of my monitor controllers.
The electronically balanced input connection is via an XLR, with a maximum input level of +24dBu and an input impedance of either 10kΩ or 20kΩ, depending on the gain-switch setting. A ground-lift switch that floats pin 1 is provided, in case ground-loop problems are encountered.
I auditioned and worked with the KH310A at different distances in different environments. In a midfield studio setting I was around 2.5 metres away, while in a nearfield desktop arrangement I was around 1.2 metres away. At no point did I ever feel that the speaker was nearing its limits from a volume point of view. There was always plenty more on hand than I ever wanted, but then I was always quite content with the volume that the old O300 could produce, even at 2.5 metres. Nevertheless, the new KH310A gives no hint of strain when driven considerably louder than the old model, and it was quite able to keep up with my reference PMC IB1s with the might of a Bryston 4B behind it.
When sitting quite close to a monitor there is a risk that the outputs from each driver remain separate, rather than integrating properly to form a cohesive whole, and that is obviously more likely with a three-way design than a two-way, because the drivers often end up spaced further apart. However, the neat packaging of the KH310A, combined with the effective waveguides, seems to overcome that issue very well and, even when sat only around 1.2 metres away, the driver outputs gelled nicely into a cohesive and integrated whole. The other issue that often crops up when sitting close to the speakers is that of self-noise. However, the internal amplifiers in the KH310A generate no audible noise at all at any practical listening distance. The published self-noise specification is less than 20dBA at 10cm, and I had to put my ear next to the tweeter to hear any amplifier hiss at all.
When mounted in free space, well away from walls, the KH310A's tonality is absolutely spot-on, with excellent balance between bass, mid and the high-end, although the EQ options provide useful tweakability. When positioned closer to a back wall, the bass-cut options proved very effective in restoring the optimum balance, too.
As with the O300s, on first hearing the KH310A there is a sense of incredulity that such compact speakers can deliver such a big sound. I'm not just talking 'loud' here; the KH310A delivers a remarkably extended and natural bass response with a huge stereo soundstage that is stable over a wide listening area and has real depth. Playing some of my own simple coincident and ORTF recordings produced beautifully lifelike imaging, with natural width and separation between instruments and voices, and real, tangible depth information.
The horizontal dispersion is extremely consistent across the entire frequency range, with around a ±55-degree working angle. The vertical dispersion is less, naturally, but is still very well balanced over about ±40 degrees. What this means, in practice, is that you don't have to sit precisely in a small 'sweet spot' to hear the correct balance or stereo image — you can move around quite a bit without losing quality.
For such a compact cabinet the quantity and quality of bass provided by the KH310A is astonishing, and the relatively gentle roll-off that comes from the sealed-cabinet design means that useful information is perfectly audible down the lowest musical octave. There is no boominess at all, no 'overhang' and no smearing; it's all very precise, fast and natural. Kick drums and bass guitars can be heard as distinctly separate instruments, not one amorphous thump of LF energy, and applying level changes or EQ to just one is clearly audible as such.
Three-way speakers are supposed to provide greater mid-range clarity than two-ways, mainly because each driver has less of the spectrum to worry about, and so can be more linear and accurate, resulting in fewer intermodulation issues. While some of the latest two-way designs are beginning to challenge that view, the clarity and resolution of the mid-range in the KH310A is pretty special. When the words 'mid-range' and 'special' are used in the same sentence, a lot of people will think of the well-known and much-loved ATC mid-range driver, and K+H actually used it in their O500C model. However, it was deemed too expensive for the new KH310A, so the Neumann/K+H designers designed their own 75mm mid-range dome driver, which they describe as being more cost-effective, more sensitive, having lower THD and intermodulation distortion, and better break-up behaviour. That's a very bold claim, but on listening it is very easy to believe; the mid-range is very revealing and very accurate.
The KH310A presents a huge amount of information without being obviously forward or 'shouty'. It is extremely detailed and revealing, but remains unfatiguing, even after many hours of listening. Standard spoken-voice recordings (always a revealing challenge for any speaker) were reproduced with a very natural and lifelike character, and without any obvious colorations or resonances. Everything I listened to — from commercial classical, choral, jazz, rock, R&B and pop, as well as my own recordings and mixes-in-progress — were reproduced with equal accomplishment. Some speakers can sound great on rock, but lifeless on classical, or example, but a true 'monitor' should present the audio information accurately and reliably, regardless of the genre, and the KH310A does exactly that very skilfully. If the recording is poor, the KH310A makes that obvious; if it is good, that is made clear too. And that's precisely what a reference monitor is supposed to do.
The only thing I can find to criticise the KH310A for is that in some situations it could become susceptible to mobile phone interference — hints of 'blippity-blippity-blip' noises — if a mobile phone is placed near the back panel and operating on high power. I live in a very poor reception area, so my phone is constantly operating flat out to reach the nearest mast, and I happened to place my mobile phone on top of a speaker at one point, which is when I became aware of this issue. However, when the phone was more than a metre in front of the monitors there were no problems at all, and this isn't something that concerns me unduly. I've had much worse problems with other speakers occasionally in the past, but it is a fairly rare occurrence these days. I have reported the problem back to the designers and they are looking into it to see if the susceptibility can be reduced further.
After evaluating a second pair of KH310 montiors after this review was published, I'm pleased to report that the mobile phone interference issue appeares to have been resolved. I've not experienced any blippity-blippity-blips at all since swapping the speakers over.
Overall, then, the new KH310A is even better than its forebear. I'd go as far as to state that it easily rates as one of the very best active three-way monitors currently available, as well as one of the most compact. It certainly gets my vote for 'Best New Monitor of the Year'!
In every way, this is a stunningly good reference monitor and one that is genuinely worthy of that title. It also represents excellent value for money, too. For a number of reasons I never quite got around to purchasing a pair of O300s (although I did borrow pairs a few times for specific jobs), but I will buy these KH310As rather than let them go back to Germany — I really couldn't work without them now! .
There aren't many sealed-cabinet monitors on the market, let alone three-way ones. The benefits of sealed cabinets can be obtained with the much cheaper Acoustic Energy AE22, although that is a two-way design. The nearly 60-percent more expensive Unity Audio Boulder is an impressive three-way monitor with a sealed cabinet, building on the success of the two-way Rock. There are plenty of ported three-ways around, including the Quested V3110, Adam S4X and S3X, Focal SM9 and Dynaudio Air 20, but they are all more expensive than the KH310A, and none are as compact.
2.1 Monitor System
This interesting monitor system uses the natural roll-off of the satellite speakers to provide the crossover with the subwoofer.
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