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M&K CR2401 & CR480

Passive Monitors & Powered Subwoofer
By Hugh Robjohns

M&K CR2401 & CR480Photo: Mike Cameron

Miller & Kreisel have been making domestic and professional loudspeaker systems in America for over 25 years, with a particular interest in satellite/subwoofer combinations. The company also produce a range of specialist audiophile recordings, and Ken Kreisel — the President of the company — is both chief speaker designer and a very experienced recording engineer, so obviously has first-hand knowledge of how musical instruments are supposed to sound.

The first time I encountered M&K speakers was during my SOS July 2001 review of the renowned active MPS2510s and matching MPS5310 subwoofer, and I was extremely impressed with the sound quality and imaging accuracy. I was also taken with the fact that M&K recommend their various speaker systems on the basis of the size of room that they are to be used in, which makes a huge amount of sense, and I'm surprised other manufacturers haven't followed suit.

Although the M&K range of loudspeakers is already pretty extensive, both in the specialist consumer home entertainment market and in the professional range, the designers continue to develop new products. One of the latest additions is the new Creator series, which includes the two units under review here: the CR2401 passive satellite speakers and the partnering CR480 powered subwoofer. This is a physically compact system, but one more than capable of filling a modest-sized room with high-quality sound — and at a very affordable UK price.

It might be worth pointing out that, although the review models were full production units, M&K decided to change the name of the range shortly after supplying them to us. It is for this reason that you can see different model numbers — MP2401 and MP280 respectively — in the photographs.

The CR480 Powered Subwoofer

The subwoofer cabinet is surprisingly compact, measuring just 25.5 x 35 x 28cm (hwd) and weighing 9.5kg. This is an infinite-baffle (sealed-box) design, containing a single eight-inch long-throw driver which is the same as that used in the MPS2810 powered subwoofer — although that model uses two drivers configured as a push-pull pair, instead of a single unit as employed here. The built-in amplifier is an in-house M&K design rated at a very conservative 75W (continuous power), but it is claimed to have a peak capability well in excess of 150W, thanks to a unique circuit design.

The rear panel of the CR480 powered subwoofer — although the model number shown here is MP280, this has now been changed for all new units to CR480. A choice of inputs and setup facilities allows the subwoofer to be used directly in 2.1 systems, or with a bass management controller in more complex surround configurations.The rear panel of the CR480 powered subwoofer — although the model number shown here is MP280, this has now been changed for all new units to CR480. A choice of inputs and setup facilities allows the subwoofer to be used directly in 2.1 systems, or with a bass management controller in more complex surround configurations.Photo: Mike CameronA second powered subwoofer model is also available, called the CR481. This is identical to the CR480 except that its driver is mounted inverted — the idea being that a CR480 and CR481 can be used together, side-by-side, to create a push-pull subwoofer package, very similar to the MPS2810 configuration mentioned above. The advantage of this arrangement is that the CR480/CR481 combination can be installed in small spaces where a larger subwoofer cabinet may not fit.

The front baffle is covered by a curved wire mesh grille to protect the driver, although this can be removed if required — the centre dust cap of the driver carries the M&K logo and the words 'Discover Deep Bass' — nice! The rear panel contains both unbalanced line and speaker input terminals, plus a balanced XLR input, providing a useful degree of flexibility in terms of interconnection. There is also a relatively small vertical heat sink for the amplifier (which obviously needs free air circulation to help cooling), a captive mains lead, and a power switch. The CR480 is intended to be left powered continually.

If used as part of a surround system, the subwoofer would be fed from a dedicated subwoofer output, benefiting from the bass management facilities of the surround controller. This connection could be made either via the balanced line-level XLR input, or via the left channel unbalanced phono socket input — all inputs on the subwoofer are active at all times, and there is no need to select a particular input.

In conventional stereo configurations (as reviewed here), the subwoofer can either accept mono or stereo line inputs via the phono connections (perhaps fed from spare preamp outputs or dedicated subwoofer outputs), or paralleled feeds from the amplifier's speaker terminals — whichever arrangement is easiest to hook up. However, if you're using the loudspeaker connections it is worth remembering that, while the internal electronics incorporate the necessary low-pass filtering for the subwoofer itself, there is no provision for complementary high-pass filtered outputs for the satellite speakers (unlike some subwoofer systems). A lot of systems provide a high-pass filtered feed-through for the satellites to enable them to deliver slightly higher SPLs, once freed from the need to produce low bass, but, if using the loudspeaker connections, the satellites always receive the full-range signal.

Like most subwoofers, the CR480 is equipped with controls to adjust both the turnover point of the low-pass filter and the volume, so that the subwoofer can be matched precisely to the satellite's LF performance, adding the precise degree of low-frequency extension. The filter control can be bypassed (for use with a proper bass-management system) or adjusted between 50Hz and 125Hz. The adjustable filter has a slope of 12dB/octave, and a second filter set to 125Hz (36dB/octave) removes mid-range signals. When used with the CR2401 satellites, the optimum setting is apparently 85Hz — matching the THX specifications — although there is no rear-panel calibration mark for this setting (you have to estimate a point between the 75Hz and 100Hz marks).

The continuously variable volume control is calibrated between -6dB and +9dB in 3dB increments, but actually extends a long way either side of these settings. A toggle switch is provided to invert the polarity of the output, which can often be helpful when optimising the position and turnover-frequency settings of the subwoofer.

In terms of positioning, the handbook recommends placing the CR480 in a corner at the front of the listening room, avoiding corners near doorways or openings. It also suggests a technique which I have found to be very reliable, which is to temporarily place the sub at the listening position, and then listen close to the corners of the room and along the walls (at the height of the subwoofer) to identify the point(s) where the bass is most accurate, extended and tight. The sub can then be placed in this optimum position and you can return to your listening position to fine-tune the level and crossover settings.

CR2401 Satellites

These compact monitors, measuring 330 x 125 x 145mm (hwd), are designed to deliver a similar quality and neutral sound presentation to the company's high-end MPS2510 active system, but in a more affordable package better suited to smaller monitoring environments such as editing suites, home studios and so on.

The CR481 subwoofer has an inverted driver, which allows you to use it with the CR480 as a push-pull pair, especially where space is limited.The CR481 subwoofer has an inverted driver, which allows you to use it with the CR480 as a push-pull pair, especially where space is limited.Photo: Mike CameronLike the subwoofer, these satellites employ infinite-baffle enclosures — so no port resonances to worry about, and an inherently smoother and more extended LF roll-off. At the time of writing, the full specifications of the CR2401 had not been released, so the amount of technical information I can provide is limited. The speakers have a nominal 8Ω impedance, and power handling is suggested to be of the order of 100W — but I had no problems driving them to more than adequate monitoring levels using my reference Bryston 4B 250W/channel amplifier.

The speaker is fitted with two M&K three-inch bass/mid-range drivers, plus a one-inch Vifa soft-dome tweeter, all mounted in a vertical line to minimise the width of the front baffle. These drive units have all been used in other M&K products, so their characteristics are well known to the company. The front baffle edges are all gently rounded to minimise edge diffractions, and with such a narrow baffle, stereo imaging should be very good. Like the subwoofer, a removable curved metal grille is provided to protect the drivers.

The rear panel carries a pair of 4mm binding posts, recessed on a plate at the top of the speaker, and the surprisingly complex crossover is mounted directly behind this on multiple circuit boards. The rear panel is also fitted with a couple of threaded inserts to accept a bracket for wall mounting.

Setting Up

I started listening to the CR2401 satellite speakers on their own, before hooking up the subwoofer. Naturally, the bass response was limited, with a gentle roll-off starting maybe as high as around 100Hz. However, the mid-range clarity was very evident and the high end was detailed without being harsh — if anything, these speakers initially sounded very slightly subdued at the extreme HF, at least compared to my reference PMC IB1s. Stereo imaging presented reasonable width and depth perspectives — as you'd expect with such narrow baffles — but it did not seem to be as precise or stable as some of M&K's more expensive models, or indeed some other popular nearfield monitors. I think this aspect of the system could be classed as adequate, but not exceptional.

Having developed a feel for the capabilities of the satellites by themselves, I hooked up the subwoofer, initially using the speaker connections, simply extending the speaker cables from the rear of each CR2401 down to the subwoofer inputs. The next half hour or so was spent humping the subwoofer around the room, and lying on the floor with my head near the wall, trying to find the best location for the sub. I ended up with a location about 15 inches from the side wall and 20 inches from the back wall, facing into the corner — this being the point where I obtained the smoothest and most controlled bass response at the listening position.

Next I used my Terrasonde Audio Toolbox test set to help establish an initial system calibration with the crossover set to the recommended 85Hz (or as close to that as the lack of calibrations would allow). I started by setting a reference output level on the satellites alone of 79dBSPL (slow response, C-weighting) with a pink noise signal. I then disconnected the satellites and adjusted the subwoofer level control to provide 76dBSPL on the meter — the 3dB lower value in recognition of the reduced bandwidth of the subwoofer output. From this point, I fine-tuned the subwoofer level by ear using familiar music, eventually ending up with the level control set to -6dB (which was a few decibels lower than my initial pink-noise calibration). Clearly, the subwoofer volume is dependent on several factors, not least being the acoustic gain provided by the relative position of the subwoofer to the walls/corner.

Tripole Surround Speaker

M&K CR2401 & CR480Photo: Mike CameronFor surround sound applications, there are two schools of thought regarding the rear-channel speakers. Some prefer to stick with the ITU arrangement of five identical speakers, three in front and two behind, all at the recommended angles and firing sound directly at the listening position. Others prefer more diffuse sound — especially for film use, and typically use dipole or tripole speakers along the sides and rear. To meet these needs M&K have designed a tripole speaker specifically to complement the CR2401 main speakers.

The CR1403 Tripole matches the tonality of the CR2401, and combines a direct-radiator speaker (tweeter and mid-range) with a dipole speaker (sideways firing mid-range units), in the same cabinet. The drivers are all integrated with M&K's unique Phase-focused Crossover. One of the benefits of the tripole concept is a much more consistent spread of sound throughout the room, so that even people sat at the rear of the room can hear reasonable imaging and spatial information.

Listening

With the system now pretty well balanced, I started listening in earnest, and I have to say I was very impressed with the overall sound quality, especially given the UK price of the system — the CR2401s are around a third the cost of the MPS2510s, for example. The integration between sub and satellites was very smooth indeed, thanks in part to the exclusive use of infinite baffle enclosures with inherently gentle roll-off and linear phase characteristics. Having auditioned the system using the simple loudspeaker connections to the subwoofer, I then rewired and recalibrated the system to use a dedicated subwoofer feed from my surround controller, setting the bass management to operate with a crossover at 85Hz again. This seemed to give a slightly faster bass response, but the difference was pretty marginal. The bulk of my listening was done with the system in this configuration.

Like the bigger M&K speakers, these units are able to extract a lot of detail from the recording, and present it in a very natural and proportionate way — the acoustic of the recording environment and the mechanical noises of acoustic instruments were clearly audible, and enabled accurate EQ and mix decisions to be made. The absolute ability of these diminutive speakers is obviously constrained to a degree by the selection and size of drivers, but overall the subjective quality is far greater than first impressions (or cost) would suggest.

There is little to fault on these speakers given their price, although the stereo imaging was perhaps not all it could have been and, as I mentioned earlier, I felt the extreme HF was a little subdued. I tended to want to add a touch more 'air EQ' than perhaps I normally would when mixing acoustic recordings, but I think this is something to which one would quickly acclimatise. The upside was that these speakers were very comfortable to work with over extended periods, with no hint of listening fatigue at all.

Overall, the treble region is crisp and precise without being hard or tiring, the mid-range neutral and detailed, and the low bass is powerful when appropriate, as well as being fairly fast and dynamic on suitable material — although this will depend a great deal on how well the subwoofer has been positioned in the room and aligned with the rest of the system. Indeed, dynamics are conveyed well with no hint of power compression at sensible listening levels, and the system is capable of delivering more than enough SPL for nearfield applications.

In essence, the CR2401 and CR480 together form a three-way monitor (albeit with a common bass section in the configuration employed here), and the system certainly exhibits many of the qualities of a three-way monitor. In particular, the mid-range seems more detailed and less coloured than many two-way designs and, with the relatively low crossover point of 85Hz, the shared bass driver is an acceptable compromise. You could always add a second CR480 to provide a stereo subwoofer system if required! The performance of this M&K system is certainly comparable with two-way systems costing a similar amount, but also offers additional advantages such as a greater bass extension, impressive mid-range clarity, and all the practical conveniences associated with the compact size of the components. The system would make an ideal compact surround monitor setup, and is excellent as a nearfield stereo monitoring system for workstations, edit suites, location recording and the like. It provides good-quality and reliable monitoring, with an impressive price/performance ratio, and has a clear upgrade path to extend and expand the system's capabilities.

Pros

  • Very compact size.
  • Good standard of monitoring.
  • Choice of direct or tripole surround speakers.
  • Flexible subwoofer connections.

Cons

  • No active satellite version.

information

CR2401 passive satellite monitors, £517 per pair; CR480 powered subwoofer, £504.08 each; CR481 powered subwoofer, £tbc; CR1403 passive tripole surround speakers, £420.65 per pair. Prices including VAT.

Stirling Syco +44 (0)20 8963 4790.

+44 (0)20 8963 4799.

sales@stirlingsyco.com

www.stirlingsyco.com

www.mkprofessional.com

Published August 2003