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Blue Sky Big Blue

2.1 Monitor System
Published November 2007
By Hugh Robjohns

The biggest Blues in the Blue Sky Range aim to be the best - and they don't disappoint.

Blue Sky Big BlueMost of the Blue Sky monitoring systems have been reviewed in the pages of SOS over the years. The System One was reviewed in February 2003, the Pro Desk in July 2003, and the Media Desk in January 2005. Now it's the turn of the latest and largest addition to the fleet, the Big Blue: an enormous mid-field, full-range, 2.1 monitor system that has been designed to satisfy the needs of those who need LOUD; we are talking 2KW of amplifier power on tap in the full 2.1 system!

Like the other Blue Sky monitors, the Big Blue system has been designed specifically as a 2.1 monitoring combination, comprising a pair of SAT 12 three-way monitors, and a SUB 15 subwoofer. Also like the other systems, it can be upgraded to a surround monitoring rig, simply by adding the additional rear and centre speakers and Blue Sky's bass management system (and maybe even an extra subwoofer!).

However, whereas all of the other Blue Sky systems are relatively compact, the predominant factor of the Big Blue system is... that it is big! Each SAT 12 monitor measures 381mm (15 inches) wide by 711mm (28 inches) high, and is 432mm (17 inches) deep. Not surprisingly given their bulk, they weigh just under 42kg (92lbs) each, so some assistance is required when unpacking and rigging them — and you'll also need some very sturdy stands. The cabinets are constructed from three-quarter-inch MDF, with one-inch panels front and back, and aren't the most aesthetically pleasing I've ever seen, but they do have a certain industrial, no-nonsense look that will appeal to many.


The SAT 12 'satellite' speaker is a three-way, front-ported design, complete with integral three-channel amplifier and line-level crossover. The amplifier pack mounted in the rear panel provides 200W each to the bass and mid-range driver, plus 100W to the tweeter. The drivers are all fairly familiar: the bass driver, for example, is borrowed from the SUB 12 subwoofer and features the same mica-filled polypropylene 'hemispherical' cone with a long-throw, two-inch, vented motor coil assembly and cast aluminium chassis.

The four-inch mid-range driver is another hemispherical design, this time with an aluminium-alloy cone borrowed from the Media Desk system. The tweeter is the distinctive dual-concentric design with its integral waveguide 'nose', as used on other Blue Sky monitors. All three drivers are 4Ω devices, and the crossover points are set at 300Hz and 3kHz, so the mid-range driver covers the most critical three-octave band by itself. All three drivers are magnetically compensated, to prevent distorting the colorimetry if you happen to place them near those quaint, old-fashioned CRT picture monitors.

The rear panel of the SAT 12 has two analogue balanced input XLRs, the first being labelled as a 'full range' input. The manufacturer claims the system can deliver a frequency response stretching between 45Hz and 30kHz (±3dB) using this input, but the system is really intended to be used with the associated subwoofer, which is catered for with a dedicated '80Hz input' XLR. In this case, the signal is high-pass filtered at 80Hz, with a phase-corrected 12dB/octave response to allow correct matching with the SUB 15. As far as I can see, there is nothing to stop you wiring to both sets of inputs if you wanted, so that you could, in effect, switch the sub in and out by routing the signal via the sub/satellite or straight to the satellites — a facility some might find useful if their monitoring controllers don't already provide the facility to bypass the subwoofer.

You can appreciate the sheer size of the Big Blues from this rear shot, in which you can see the standard XLR connectors at the top.You can appreciate the sheer size of the Big Blues from this rear shot, in which you can see the standard XLR connectors at the top.The front baffle contains a removable panel that carries the tweeter and mid-range units, allowing them to be rotated as a pair relative to the overall cabinet. This makes it possible to use the SAT12 horizontally or vertically without sacrificing imaging precision (making it easy to configure the speaker for use as a horizontal centre channel above or below a screen, for example). Around the perimeter of this sub-baffle is a grid of four slotted, triangular port vents, lined internally with open-cell foam. The manual suggests that the design of these slots helps to reduce cabinet diffraction effects as well, and refers to them as a proprietary "Multi-Aperture Acoustic Diffraction Absorber." The idea is to help maintain a smooth mid- and high-frequency response off-axis, which is something that can be an issue on speakers with wide front baffles. Supportive evidence as to the efficacy of the 'MADA' is the well controlled response between 200Hz and 15kHz, which remains within an impressive ±1.5dB window.

I've already mentioned the two XLR inputs on the rear panel, but I should also mention that each has an adjacent pair of DIP switches that alter the input sensitivity by 10dB. The maximum input level is +12dBu with switches in the 0dB position, and +24dBu with them in the -10dB position (I know that 12+10 isn't 24, but that's what the specifications claim!). In addition to these sensitivity switches, there is also a recessed, rotary level-trim control that attenuates the level up to 12dB from the nominal input level selected on those DIP switches, with markings at 1dB increments.

The SAT 12 is well equipped with room-matching equalisation facilities too, and these are divided into four sections: tweeter, mid-range and woofer levels, plus baffle compensation. Each section is configured with four DIP switches, so that each driver can have its relative level changed by up to 3dB (up or down), in 1dB increments. The baffle compensation section allows the inevitable 'bump' in LF response, caused by mounting the speaker in a baffle wall (half space), to be attenuated by up to 11dB.

The final pair of DIP switches control the bright blue LED on the baffle panel. Normally, this is illuminated when the monitor is powered, but flipping these switches causes the LED to flash briefly when the monitor is first turned on, and then extinguish: my preferred operating mode! A rear-panel LED also illuminates when the speaker is powered and is unaffected by the switch settings for the front-panel LED.

The mains input socket and configuration controls are mounted below the enormous heatsink. The familiar IEC mains inlet is associated with a separate fuse holder, mains voltage selector and rocker-style on-off switch. There are no facilities for remote on-off switching. All of the connectors and controls are contained in a removable panel, with the heatsink mounted towards the top of the speaker's rear panel. Below this are four quarter-inch threaded sockets for bolting the speaker to an Omnimount or Powerdrive wall bracket. Another four sockets are installed in the base of the speaker as well. You'd need a lot of faith in your wall structure and bracket fittings to support these 42kg speakers, but I'm assured it is possible to mount them in this way! I think I'd stick with good old-fashioned steel floor stands and Blu-Tack, myself.

SUB 15: The Lowdown

This bespoke subwoofer — Blue Sky's largest offering to date — is a sealed cabinet design with a massive 15-inch long-throw driver (and in this case long-throw means about 2.5 inches!). The cabinet is built from three-quarter-inch MDF with one-inch baffles, just like the SAT 12s. It measures roughly 21 x 21 x 18 inches, and weighs a hefty 57kg. Like the satellites discussed in the main text of this article, it is very much a two-person lift when unpacking and installing.

Built into the cabinet is no less than 1kW of amplification, and comprehensive bass management facilities for a full stereo (2.1) system. Inputs are provided for left and right stereo channels, plus a dedicated subwoofer input and output. The latter are for daisy-chaining an additional subwoofer onto the basic system, and they avoid the internal low-pass filtering, to prevent double-filtering.

The SUB 15 subwoofer has been designed for use with the SAT 12 monitors in 2.1 and 5.1 surround setups.The SUB 15 subwoofer has been designed for use with the SAT 12 monitors in 2.1 and 5.1 surround setups.

In the default 'Blue Sky' filter mode, the left and right output signals are derived by passing the inputs through 80Hz, 12dB/octave high-pass filters, which are designed to complement the filters built into most Blue Sky satellite monitors (most of which have 12dB/octave 80Hz filters of their own, the combination producing a 24dB/octave slope). At the same time, the low-frequency content from the stereo input is summed and low-pass filtered with a 24dB/octave Linkwitz-Riley 80Hz filter to feed the subwoofer amplifier.

However, the system also allows the filtering to be configured manually, if required, by switching to 'Universal' mode. In this case the high-pass filtered outputs and low-pass signal to the internal amp are all performed at 24dB/octave, but with user-adjustable turnover frequencies for the left and right channels (between 50 and 160Hz).

In both cases, the subwoofer level can be adjusted from a reference sensitivity downwards, with markings at 3dB and 6dB intervals. The subwoofer output polarity can also be inverted with a toggle switch.

The normal bandwidth of the subwoofer is specified as 30-200Hz, but the bottom end can be extended electronically to 20Hz if required — although you'd need a very large and well-treated room to benefit. There is also an auto-power facility that shuts the unit off if there is no input signal for 15 minutes.


I hooked the Big Blue monitors up alongside my own reference PMC IB1s (powered by a Bryston 4B amplifier) and was able to match the levels and switch between them as the auditioning session progressed. Initially, I used the flat response input without the sub, and then swapped inputs and added the sub to the system afterwards.

The first impression of the Big Blues on their own is of a very accurate and smooth response, free of colourations and resonances. They tended to sound a little bass light compared with the PMCs in my room, which is a little surprising given the cabinet sizes, but this tallies with the specifications and frequency response plots published in the excellent manual. The monitors were all placed well out into the room, so there was little, if any, LF reinforcement from boundaries.

Ignoring the bass response aspect for a moment, the clarity and resolution through the mid- and upper bands bordered on the scary. Any sonic imperfections in the source material were revealed starkly and without mercy, which is what a true monitor speaker is supposed to do. Equally, the sublime balances of really high-quality material were revealed in all their intricate glory. Most notably, the neutrality and precision of the sound stage from these Big Blues is quite excellent, allowing you to really hear deep into the most complex of mixes with ease. Similarly, the stereo imaging is very broad and stable, with superb front to back depth on suitable recordings, and a razor-sharp centre image. Simple coincident stereo recordings, for example, are portrayed with lifelike perspectives and scale. To my old BBC-trained ears, the top end was a little forward compared with some traditional British monitor designs, but this was easily addressed with the HF driver level switches.

Dynamics were handled accurately and without any hint of compression, and transients had a real snap to them, even at 'silly' levels. The system clearly has more than enough headroom for most monitoring applications and never sounded strained. Equally, I found it easy and enjoyable to listen to these speakers over extended sessions without any signs of listening fatigue, which in my experience is a reliable sign of a good monitor.

After reconfiguring the inputs for use with the enormous subwoofer, and aligning the system (the manual gives very good, easy-to-follow instructions for aligning the complete system), I repeated my listening tests. This time the bass response easily matched (and could exceed, if required) that of the big PMCs, providing a well-balanced, solid sound. With any satellite-plus-subwoofer system, it is all too easy to unbalance the frequency response, with drastic consequences for monitoring accuracy. However, the Blue Sky alignment instructions (and downloadable test files) make the job quite easy (assuming access to at least a simple SPL meter), and I found that it only took a few minor tweaks to balance things to my personal taste after the main alignment process was completed.

The sub reduces the workload of the SAT 12s considerably, allowing even greater headroom, but doesn't cloud the excellent mid-range in any way that I could hear. It is not uncommon with cheap subwoofers to find that they generate such high levels of distortion that the benefits of extended bass response are negated by reduced resolution through the mid-range — but that is certainly not the case here. I found that the standard 30Hz mode worked best in my room. Switching to the 20Hz mode seemed to cause a lot more structural rattles without any real sonic benefit.

Overall, the Big Blue system impressed me very much. Like the smaller systems, the emphasis is clearly on accuracy and precision with a lot of detail, but, to really let the system deliver its best, proper room acoustic treatment is essential — especially given the very extended LF response when used with the subwoofer. There is no doubt that this is a true professional-standard monitoring speaker system, as the price tag implies, and it would be well-suited to serious mastering, mixing and post-production applications.

The flexibility in configuration and alignment makes the Big Blue system very versatile to install, and the power handling will meet the needs of all but the most seriously deranged head bangers, or the very largest of control rooms. The Big Blues serve admirably as the new flagship Blue Sky monitor, and deserve serious audition for anyone investing in this level of monitoring system.  


There are quite a few monitors at the same kind of price as the full Big Blue 2.1 system. For example, the ADAM S4a and S5a monitors bracket the Big Blue system quite neatly. The highly revered ATC SCM50As are also around the same price point, as is the Dynaudio Air 25/Airbase-1 combination. A slightly less familiar option is the stunning Geithain RL901K ­ unusual looks, but fantastic sound quality ­ or the far more familiar Genelec 1037C or 1038B monitors. Moving away from the active designs, the Earthworks 6.3 is a very impressive monitor, and there would be just enough money in the budget for a decent amp. The same applies to the PMC IB1 or even the IB2, at a push.

Published November 2007