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Neumann KH80 DSP

Active Monitors
Published May 2018
By Hugh Robjohns

The newest member of Neumann’s celebrated KH family of monitors might be the smallest, but it’s also the most technologically advanced.

Neumann KH80 DSPNeumann’s development over the last decade or so of a range of high-quality studio monitor speakers — the KH range — has produced a comprehensive line-up of three monitors and three subwoofers. I reviewed the compact two-way KH120A monitor along with the KH810 subwoofer in April 2012; the sealed-cabinet three-way KH310 in October 2013; and the largest model in the range, another three-way, the KH420 in September 2015. In my humble opinion these are all superb monitor speakers that are not only genuinely worthy of that title, but which also punch well above their retail prices in terms of sound quality and engineering finesse.

Last year a fourth model was added to the range, the new KH80, which is easily the smallest KH monitor to date. Its seven-litre composite-polycarbonate ported cabinet measures just 233mm tall, 154mm wide and 194mm deep and weighs 3.4kg, so this new model is clearly intended for desktop applications as well as installations in outside-broadcast trucks and similar environments where space is at a high premium but sound quality is still paramount. Flexible mounting arrangements are catered for with a pair of M6 threaded inserts on the back panel, coupled with a wide range of optional mounting accessories.

At first glance the KH80’s design looks identical to that of the KH120, albeit scaled down a little, with its two-way format comprising a new long-throw 100mm (four-inch) woofer and the same 25mm ‘alloy-fabric’ dome tweeter as used in the larger models. Neumann have always employed sophisticated modelling techniques to help develop their drivers and cabinets, but they have taken this to new heights in designing the KH80, particularly in optimising the new bass/mid driver’s motor and suspension for maximum linear excursion with minimum non-linear distortion characteristics.

Digital Innards

As I’ve already intimated, the KH80 shares all the familial traits — the anthracite grey-painted and smoothly rounded cabinets (a white version is also available), the triangular ports either side of the bass/mid unit, the moulded waveguide around the tweeter, the illuminated Neumann diamond badge, and the rear-panel sensitivity control and configuration switches. But, while the external design looks comfortably traditional, there are important new talents buried within: this is the most technically sophisticated Neumann monitor yet and (as you might have already guessed from the model’s title) the first to incorporate digital signal processing.

The KH80 DSP combines a 100mm woofer with the same 25mm dome tweeter as that used in the larger KH-series monitors.The KH80 DSP combines a 100mm woofer with the same 25mm dome tweeter as that used in the larger KH-series monitors.Developed in-house, Neumann’s DSP system handles all the expected functions like the (FIR) crossover filters, driver protection, and lip-sync or ‘time of flight’ delay (up to 70ms is available). But it also goes much further as it is used during the factory quality-control tests to correct any frequency response errors (due to component and manufacturing tolerances) and some non-linear driver distortions, too. The result is an exceptionally accurate frequency response and incredible consistency and matching between production units. Putting some numbers on it, the published frequency response charts are flat within ±0.6dB across the entire working range, and any two speakers are matched within 0.25dB of each other — which is just astonishing!

However, the DSP is capable of even more than these core functions, as it is also able to take care of in-room acoustic correction using eight bands of parametric (IIR) EQ, controlled through a promised software app called Neumann.Control — although at the time of writing this is somewhat delayed and still under development. Its release is expected later this year (but Neumann said that last year too...).

Nevertheless, even without the promised control app the KH80 is a very strong performer on its own merits. Despite its diminutive size the specifications state the -6dB frequency response limits are 53Hz — which is only 5Hz higher than the larger KH120 — and 22kHz (this latter figure is essentially determined by the use of a 48kHz sample rate in the DSP processing). So the low-end extension is pretty impressive for a box this small, and the power handling isn’t bad either, with the maximum in-room mid-range SPL given as 108dB (100Hz-6kHz). It should be said that the bass/mid driver is (inevitably) the limiting factor here, with a maximum SPL closer to 92dB SPL — although that is still very impressive for a four-inch bass driver, and certainly more than enough for nearfield listening applications. (And for those with a liking for flapping trousers there is always the option of adding one of the KH system’s subwoofers to take on some of the heavy-lifting duties and increase the maximum SPL capability accordingly.)

Newly developed in-house, the KH80’s two Class-D amplifiers are rated at 120 and 70 W for the bass and treble drivers, respectively. However, these figures are achieved at 10 percent THD, and perhaps more representative figures are 90W for the bass and 50W treble, for 0.1 percent THD — again, more than enough for nearfield applications. Integral driver protection includes independent soft clipping for the bass/mid driver and tweeter, plus peak, thermal and mechanical excursion limiting. Importantly for a nearfield speaker, the self-noise is below 20dBA at 10cm, and that translates to around 0dBA — the threshold of hearing — at one metre, so at normal nearfield listening distances there is no audible hiss whatsoever.

The DSP handles both infrasonic and crossover filtering using linear-phase algorithms in an FIR (finite impulse response) digital filter. The infrasonic filter has a 12dB/octave slope, while the crossover splits the signal at 1.8kHz with eighth-order (48dB/oct) slopes. Eighth-order slopes would be impractical in an analogue crossover for reasons of cost and unwanted phase rotation so, for comparison, the KH120 (and most active analogue speakers, actually) uses fourth-order slopes. However, the use of digital FIR filtering neatly avoids both of these issues, as the complexity of the filter has no cost implications, and linear-phase filters can be designed with a perfect phase response — but the advantage is much better control and matching through the crossover region, and lower distortion overall.

A minor downside of linear-phase filtering, though, is a small processing delay, and the KH80 imposes a (practically negligible) system latency of 2ms. Should that be deemed a problem, there is an alternative filter mode which uses a minimum-phase (ie. analogue-like) filter approach to reduce the latency to just 0.65ms. FIR filter latency is obviously dependent on the DSP sample rate and I mentioned earlier that the KH80 operates with a 48kHz sample rate, which is unusual; most DSP-based monitor speakers I’ve come across operate at 96kHz, partly to minimise latency.

Connecting & Configuring

Sensibly, the KH80 employs a universal switch-mode mains power supply which accepts 100-240 V AC, and there is an isolator switch on the back panel, although access to that wouldn’t normally be needed as the speaker has an auto-standby feature. At full throttle the KH80 consumes up to 180W, but that falls to just 9W when idling, and less than 0.3W when in auto-standby mode. These figures are for a 230V supply and fall to 8W at idle and just 0.05W in standby for a 100V mains supply.

Unusually, these monitors do not require a mains safety earth connection as they are Class II, or ‘double-insulated’. What that means in practice is that the mains input socket (which faces downwards for a very neat cable entry) is a two-pole ‘C8’ or figure-8 type rather than the ubiquitous three-pole C14 IEC type. The major benefit of being a Class-II device is that there is absolutely no chance of suffering ground-loop hums (or buzzes) when connecting these monitors to a computer interface, even if using unbalanced connections — and that may well be a very welcome feature for many! However, the potential downside is the possibility of having no ground reference in the audio system at all (eg. if using a laptop with a bus-powered interface), and that can reduce the effectiveness of the equipment’s RF screening to result in nasty buzzes due to external interference. This wouldn’t be a common scenario, but I have helped a number of people in the last year or two to resolve nasty buzzes which they thought were due to ground-loop problems in systems but which turned out not to have a ground at all, so it’s something to bear in mind.

The combi XLR/jack connector can accept either balanced or unbalanced inputs, and because the KH80 DSP is a Class-II (double-insulated) device, there is no chance of generating any ground-loop hum even when feeding the speaker from an unbalanced source.The combi XLR/jack connector can accept either balanced or unbalanced inputs, and because the KH80 DSP is a Class-II (double-insulated) device, there is no chance of generating any ground-loop hum even when feeding the speaker from an unbalanced source.Despite the extensive use of DSP inside the monitor speaker, the KH80 is only provided with an analogue audio input via a combi XLR. This accepts either an XLR or TRS plug for a balanced (or unbalanced) line-level connection. A standard RG45 network port is also provided for configuration and remote control purposes via the anticipated Neumann.Control app.

Rear-panel user controls are much like the other KH monitors. A rotary input sensitivity trimmer provides up to 15dB of attenuation and works in conjunction with a four-position slide-switch to set the nominal SPL (measured at one metre) for a 0dBu input signal to either 114, 108, 100 or 94 dB SPL. A second four-way slide-switch introduces a low-mid EQ cut (centred at 280Hz, with 0, 1.5, 3 or 4.5 dB attenuation), and this is intended to compensate for the acoustic effect of placement on a desktop or console. A third slide-switch configures the auto-standby modes and selects either local or network control.

The factory default configuration switches the KH80 into auto-standby mode after 90 minutes with no input, waking up again within five seconds when an input signal is detected — but the Neumann.Control software allows the standby delay time to be adjusted. It also allows the brightness of the illuminated Neumann logo on the front panel to be adjusted, and the colour of the logo indicates the current status, glowing red when booting up or if the protection systems are activated, pink (Neumann prefers the term rosé) for network control operations, and white for normal use.

Auditioning

To audition the KH80 I rigged the monitors on top of the KH310s, which I routinely use in my office-cum-studio room, connected to the secondary monitor outputs of my Crookwood M1 console. When I first fired the monitors up I had to double-check what I was listening to because at my normal low-ish listening levels the sound character and resolution was remarkably close between the two models, and the KH80’s bass is far more powerful and extended than I was expecting. Impressively, the bass is very tight and well-controlled, but also remarkably detailed and revealing with no boominess and negligible overhang or time-domain blurring. A very impressive start!

A number of rear-panel controls allow you to tailor the monitor’s frequency response (for desk-placement compensation), sensitivity and standby behaviour.A number of rear-panel controls allow you to tailor the monitor’s frequency response (for desk-placement compensation), sensitivity and standby behaviour.With extended listening I gradually came to the opinion that the KH80s have a slightly more forward mid-range character than the KH310s, but when I discussed this with the boffins at Neumann it was suggested that this is probably a psychoacoustic side-effect of the linear-phase crossover filters, and that the perceived effect was because I was able to listen further into the mix. In fact the KH80 has the flattest and most neutral response of any Neumann monitor to date!

Inevitably, the KH80s can’t compete with the KH310s for low-end extension and power at more elevated listening levels, but for normal nearfield listening they did a remarkably good job, and the differences were a lot more subtle than I expected. I realise I’m repeating myself here, but bass quality is not something that is normally associated with a very small monitor speaker, yet the KH80’s bass performance gives very little away to the KH120 and really is quite astonishing. The very low levels of harmonic coloration help it to deliver a very informative low end, which makes mixing decisions very straightforward and reliable. As with the KH120, I suspect most users working in small rooms really won’t feel the need for a subwoofer.

Stereo imaging and depth is extremely precise, and arguably had the edge over the KH310s, and while that might be expected given the KH80’s narrow front baffle Neumann suggested this is another benefit of the linear-phase crossover design. The practical upshot, though, is that voices are projected in front of the listener with an almost 3D-like stability and presence, and I almost felt like I could reach out and hold individual sources.

The fact is that the clarity and resolution of this new baby monitor is startling given its size and cost, and I’d say the KH80 performs and sounds like a substantially more expensive — and physically larger — monitor than it actually is. Neumann’s monitors all punch well above their price, but the KH80 genuinely sets a new benchmark at this price. In all seriousness, it wouldn’t be hard to spend twice as much on alternative manufacturers’ monitors and still not match the level of performance delivered by the KH80. And that’s before the full power and room-correction capabilities of its internal DSP is harnessed through the keenly awaited Neumann.Control app.  

Alternatives

The most obvious direct competitor is the Genelec 8320 SAM monitor, which also has a four-inch mid/bass driver and internal DSP room-correction capability, and is priced very similarly.

Published May 2018