Producing Masked Wolf’s Astronaut in the Ocean
Issue 72
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26 July 2006

HK LUCAS_Impact_System

Self-powered three-way speaker systems might be springing up like mushrooms, but German manufacturing can still offer something extra.

Text: Trevor Cronin

The name HK Audio may not be familiar to many Australians in the market for a speaker system, but the company’s founders, brothers Hans and Lothar Stamer have been producing loudspeaker cabinets in southwestern Germany since 1979. The HK brand is popular in Europe and supplies a wide range of speaker systems, from large line array stadium PAs to small self-operated rigs. AT readers may be more familiar with another arm of the Stamer brothers business – Hughes & Kettner stage amplifiers. These units are some of the best sounding amps around, as witnessed at hundreds of gigs that I’ve mixed with Melbourne rock chicks, The Spazzys.

The HK ‘LUCAS (Lightweight Ultra Compact Active System) Impact’ is an easily transported three-way self-powered speaker system that is configured as a three-component rig: a mono bass speaker, that contains three channels of power amplification and two light-weight satellite mid/high speakers.


Myself, and good friends Ed Richards and David Field (who both know a thing or two about speaker systems), went to town on the system with a screwdriver recently (before we’d even listened to it) to check out the sum of its parts.

The mid/high enclosure of the HK LUCAS Impact is manufactured from MDF and contains a one-inch B&C DE12-8 high frequency driver, mounted on a 60° x 40° CD horn. For mid frequencies, an eight-inch Sica neodymium driver is front-loaded on the ported cabinet. Both of these drivers are high quality units hailing from two well-respected Italian speaker manufacturers. A generous amount of Dacron damping material is used inside the cabinet, where we also find a high quality passive crossover network that works at 2.2kHz/12dB/octave. Input is via an industry-standard Speakon NL 4 connector.

HK’s attention to detail to prevent the foam-covered grille from rattling is impressive. The ‘MonoTilt’ pole mount hardware underneath the cabinet is unique, angling the speaker box downwards –10° with no evident wobbling or unintentional turning, which is good for typical pub venues, although I’m not quite sure how you would use this rig in a small theatre with vertically raked seating.

The bass bin is a front-loaded ported enclosure containing a single 15-inch speaker. Mounted on top of the enclosure is the control surface for the system (which glows orange when switched on and looks quite impressive). Inside we find three Class-D digital power amps that are highly efficient, light and powerful, and which are themselves managed by even more digital circuit trickery – the ‘DDO controller’ – that is custom designed to drive the system using 24-bit/48k conversion with internal signal processing of 56 bits.

This controller has a host of features including: multi-band limiting and companding (comp-ressing and exp-anding). For the tech savvy, this is a PCM compression technique, where analogue signal values are rounded on a non-linear scale. The data is compressed before DSP effects and then expanded at the D/A end using the same non-linear scale. Companding reduces the noise and crosstalk. Another function is the integrated subsonic filter that cuts out unwanted low tones.

Next there is system EQ using four presets via Up/Down buttons:

0 = Mute (a little cryptic to have a system mute as an EQ patch!).

1 = Speech: emphasis upon vocal range.

2 = Live: used for live band performance.

3 = Live 2: also used during live performance, but offering softer and deeper bass and slightly less midrange compared to the Live 1 setup.

4 = DJ 1: designed for program material.

5 = DJ 2: like DJ 1 but tonally optimised for MP3 sources to improve the sound.

A flashing display indicates that the controller has muted the input. This mute function is actually a noise gate triggered by the input signal level. There are limiter LEDs for the high and low amps to show you when things are being pushed too hard. Level is controlled by gain knobs for high, low and balance control (left and right pan). Finally there is a ground lift button that separates the signal and chassis ground in the event of hum.


On first glance, we all voiced a few concerns about the susceptibility of the LUCAS Impact system to damage from a spilled drink or something dropped on top that could break off the control knobs. Moreover, it would be quite easy for any unauthorised person to tamper with the controls, but I guess it would be fairly easy to fashion a protective cover – perhaps this should be considered by HK in the future.

Down the back of the unit are fan vents (on the side and back of the housing) and a selection of connectors. Signal input is via left/right combination XLR/1/4-inch jack connectors and there are parallel outputs for routing to other systems. A pair of Speakon connectors feed signal to the satellite boxes.

Power input is via a standard IEC connector with a nifty mains cable tab clamp, which prevents the power cable from being pulled out accidentally – a nice touch. All enclosures are finished in a hard-wearing, textured satin black coating, so all in all, lots of attention to finer details present on this unit.
Transporting the system is quick and easy: tilt the subwoofer on to its casters and place the satellites on top with the foam-rubber grille side facing down, then wheel away. Lifting the gear into a car or up stairs is also fairly easy due to the system’s low weight.


During tests, Ed, David and myself immediately noticed the high fidelity of the system – it produced a clear full-range sound (and it was comforting to know that we’d put it all back together correctly!). Running the system to full volume – that is, with the red protection LEDs just starting to flash – we measured the low end to be 112dB SPL @ one metre and the mid/high unit @ 108dB.

We ran a variety of pop rock and dance music off CD first to test the system. The preset EQs worked well; we especially liked the sound of the system running preset No. 2. Secondly we checked out the rig with a Shure SM58. It produced a crystal clear and loud vocal sound without a hint of feedback, even at a high level.

The system produces quite a large sound, that belies its compact size and light weight. We also (somewhat unusually) ran the system as nearfield monitors in the recording studio with very satisfactory results, the speakers produce a great sound throughout their volume range.

We compared the system with some other speakers and it confirmed our first impression: the HK rig is a well designed, well engineered, very professional collection of equipment, with a little German quirkiness thrown in at no extra cost.


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Producing Masked Wolf’s Astronaut in the Ocean
Issue 72