Court Acoustics SN70

Speaker design has come a long way since the ‘70s. Is there still room on the market (and in your studio!) for an old-school main monitor?

I first came across Stephen Court’s eponymous company, Court Acoustics, in the mid-1970s within the pages of the ‘industry’s monthly bible’, the long-defunct Studio Sound magazine. Court monitoring systems were often mentioned in articles about the professional studios where I hoped to work one day, in my teenage daydreams. However, to those with less grey hair than me, the name might be rather more familiar in the context of the very useful SoundCheck and SoundCheck2 test CDs, which Stephen Court produced with Alan Parsons.

In a career that started at Advision Studios and its subsidiary, Feldon Audio, in the 1960s, followed by a stint as a BBC sound recordist, Court’s interests always included loudspeakers, and he gained experience in PA speaker design, mostly using JBL drivers, for companies like IES, TFA-Electrosound and Tasco. This turned into an independent business in 1973 when he founded Court Acoustics, and initially most of his work centred around designing control room monitoring systems for the likes of EMI Abbey Road, Trident Studios, CTS, Decca and countless more leading recording studios.

These professional studio monitoring systems set a very high standard at the time, and were held in very high regard not least by the bands recording in the studios. Consequently, Court was asked to develop high-quality and high-powered stage PA systems that the bands could take on tour. To put things in context, this was at a time when the typical approach to live sound on stage was to amplify the vocals through a stack of WEM guitar speakers, and the Who’s entire backline and PA system could be transported in the back of a small van!

The live-sound industry, as we know it today, really began back then in the mid-‘70s, and within a few years bands like Emerson, Lake & Palmer were touring with 36 tons of sound and staging equipment! Stephen Court’s innovative PA speaker system designs were quite instrumental in setting the standards at the time, and were frequently chosen by the big acts of the day, including 10cc, Pink Floyd, Slade, Queen, Roxy Music and many more.

Over the last 40 years Court Acoustics have continued designing and supplying high-quality PA systems for bands, clubs, theatres, cinemas, concert halls and stadiums — most recently in the form of the Black Box II system — but no more control room monitors. However, around 10 years ago Stephen and his wife decided to retire to Devon where they ended up taking over the Wharf Arts Centre in Tavistock, on the edge of Dartmoor. This facility incorporates a multi-purpose 200-seat auditorium for cinema, theatre and live music (with capacity for 400, standing), and became what Stephen described as a ‘sandbox’ where he could experiment and develop his ideas. Not surprisingly, the auditorium has subsequently been equipped with a massive Court Black Box II PA system incorporating an octet of 15-inch bass drivers on each side and, as I found out first-hand, it is capable of moving significant amounts of air!

Holding Court

In a large room upstairs, Stephen Court has spent the best part of a decade developing his ultimate studio monitor, the SN70. This is a large, three-way, bi-amped midfield monitor intended for studio applications and, like the PA speakers, it is being hand-built to order a few miles down the road in Plymouth in the UK.

The design inspiration came unashamedly from the 1970s — a period that Court considers the most creative era for popular music on both sides of the Atlantic — and it builds upon a revered classic monitor of that period, JBL’s Jubal L65 system, which was designed by Walter Dick and Ed May, two of the world’s leading speaker designers. In 1974 the JBL L65 monitors cost around $6000, which was a very considerable sum back then!

However, although the underlying concept of the SN70 follows similar design approaches and goals to the classic JBL product, Court’s implementation is a significantly larger system, mainly because the JBL’s 12-inch bass driver and five-inch mid-range driver have been replaced with a 15-inch woofer and eight-inch mid-range unit, improving the LF extension and power handling considerably. A direct consequence, though, is that the cabinet has also expanded from the roughly 85-litre volume of the L65 up to around 185 litres (6.5 cubic feet) in the SN70.

This substantial cabinet is reflex-ported and constructed from 24mm and 18mm MDF panels, heavily reinforced internally with hefty kiln-dried wooden bracing. The overall dimensions are 520 x 860 x 420 mm (WHD), and each box weighs 43kg. The review model cabinets featured a tough metalised paint finish with a removable grille, and the Court company badge across one corner. Beneath the grille three drivers are arranged in a vertical line, with a pair of large circular port vents just above the bass driver on both sides, and a rotary control adjacent to the tweeter to adjust its sensitivity.

The American-sourced 15-inch bass driver features a cast chassis and a long-throw roll-surround, with a ‘poly-fibre’ cone that combines fibreglass and resin to create an ultra-stiff piston. This 4Ω drive unit is rated at 400W and is wired directly to a Neutrik Speakon connector on the rear panel, allowing it to be powered directly from its own amplifier. An active crossover defines the working bandwidth, which spans 23 to 100 Hz (see below), and this arrangement reduces intermodulation distortion and affords greater control over the bass driver.

Mid-range is delivered by a Danish eight-inch driver, again with a cast chassis and a relatively shallow polished-fibre cone. Rated at 150W this mid-range unit is mounted in its own sealed 12mm MDF sub-enclosure, keeping it acoustically isolated from the main cabinet volume, which only loads the 15-inch bass driver.

A German-made compression driver handles the high end, and this features a two-inch aluminium ring radiator powered by an edge-wound ribbon-wire voice coil rated at 50W. The tweeter’s housing forms its own sealed enclosure, and the diaphragm is ‘slot loaded’, which means it speaks into a form of short and narrow horn designed to provide 140 degrees of horizontal dispersion, but only 40 degrees in the vertical plane. Controlling the dispersion in this way is beneficial in minimising the amount of high frequencies splashing off console surfaces and ceilings. The tweeter can be rotated to allow the cabinet to be mounted horizontally, if required.

The mid-range driver and tweeter are integrated through an internal passive crossover constructed with hand-wound coils and carefully matched polyester capacitors, achieving just 0.5dB of insertion loss. Power handling isn’t a problem as it is rated at 500W, and the crossover is tuned to 4.5kHz with 18dB/octave slopes. As mentioned above, the tweeter sensitivity is adjustable over a small range from the front panel to suit room acoustics and personal preferences. In effect, these two drive units form a complete two-way passive monitor with a sealed cabinet, built with an over-sized baffle, and the input to the passive crossover is wired to another Neutrik Speakon connector on the rear panel where it presents an 8Ω load.

Powering Up

Overall, the complete SN70’s acoustic sensitivity is specified as 96dB for 1W at one metre, and the frequency response as 20Hz-20kHz ±5dB, or 30Hz-15kHz ±3dB. A serious set of power amplifiers is required to allow the SN70 to give its best, of course, and when suitably powered it is capable of delivering 112dB SPL at three metres (note that most speakers’ maximum SPL specifications are given at just one metre).

Although any suitable amplifier and active crossover could be employed in theory, Court worked closely with amplifier specialist MC2 (another manufacturer based in Devon, albeit on the opposite side of the county) to develop a custom-built four-channel amplifier with integral active crossover specifically to partner the SN70. The robustly engineered TL-450 system provides two 375W channels for the low end, and two 215W channels for the mid-range and tweeter — all using traditional Class-A/B bipolar circuitry supported by switch-mode power supplies. The built-in Linkwitz-Riley crossovers split the input signals between the bass and the mid/HF amps at 100Hz, with 24dB/octave slopes. Two runs of suitably heavy-duty cabling connect the two amps for each channel to the two Speakon connectors on each speaker cabinet.

The matching amplifier is made by MC2 audio, and it allows for separate adjustment of the bass and mid/top outputs.

Listening In

Given the size and weight of the SN70s, I opted to audition them at Court’s listening room at the Wharf premises — a large upstairs room with a vaulted ceiling. The monitors were initially mounted on low stands (of about 12 inches in height), although we later tried them positioned directly on the floor as well. The MC2 power amplifier was located at the listening position along with a laptop as a source of test material. My auditioning included a number of musical tracks provided by Stephen, as well as an extensive and eclectic collection of my own test material with which I’m very familiar, of course.

My first impression was of just how loud, powerful, clean and solid this monitoring system can be — I felt slightly sorry for the members of the public partaking of their lunch in the Wharf café immediately below the listening room! With the amplifier immediately in front of me, though, I was able to back the levels off to a volume I was more comfortable with for my extended listening. Having individual level controls for the LF and mid/HF amps is useful in allowing the tonal balance between bass and everything else to be fine-tuned to suit the room, speaker installation and personal preferences.

With a 15-inch bass driver the SN70 really moves some air when required, and this creates a very solid low end which sounds effortlessly powerful and natural. It delivers a weight and scale that few ‘monitors’ manage, even many so-called full-range monitors, and the bass extends right down to around 20Hz without any reduction in sensitivity or power. Perhaps more surprisingly, the bass is also extremely tight and well controlled — there’s no hint of bass overhang or under-damped port resonances, or of mid-range-masking harmonic coloration, and I found was able to separate the sonic details of kick drums and bass instruments in a mix without difficulty.

After the sheer scale and impact of the low end, the next most impressive aspect of this monitor is the presentation of dynamics and transients. The slot-loaded ring-radiator presents transient attacks in a way which few conventional dome or ribbon tweeters can ever match. Snare drums and other percussive sounds are presented with amazing power and speed, yet retain all the clarity and detail required of a true monitor. On well recorded material, instrument dynamics are delivered in an effortless way as well, without any inclination towards driver compression or harshness, even when listening at silly levels. Not only does the amp have power to spare, but the drivers can all take it completely in their stride.

For me, the most critical aspect of any monitor is the mid-range, since this is where most of the important musical information resides. Poor resolution here makes mixing a very difficult task, simply because it becomes so hard to hear what’s going on and the effect of any signal processing being applied. With a large eight-inch mid-range driver, and a relatively high crossover at 4.5kHz, I wasn’t sure how well the SN70 would cope, but in fact it delivers a very fine performance with superb clarity and resolution. On a number of carefully selected commercial tracks on my auditioning CD I was easily and instantly able to detect a variety of recording and production ‘flaws’, indicating the very revealing and accurate nature of these monitors. In fact, as my listening continued I kept finding myself wanting to correct some tonal balance or other issue in the recordings — even the most minor issue was exposed clearly, but not in a harsh or obstructive way. On some vintage recordings, for example, the tape hiss (and occasional mild dropouts) was made very audible, and judging the appropriate level of de-noising would be very easy as a result, but it was never obtrusive in a way that distracted from the music, and still very easy to listen through the noise to analyse the low-level elements.

Despite the broad front baffle, stereo imaging proved very stable and well defined, with a wide sweet spot and a good sense of depth and spaciousness from appropriate recordings. I didn’t notice any significant comb-filtering issues while moving up and down in front of the monitors at the listening position either, and the ability to balance the tweeter sensitivity against the mid-range using the front-panel control, and then dial in the appropriate level of bass from the woofer with the amplifier volume controls makes compensating for room positioning fairly straightforward.

Conclusions

Court suggested that the hallmark of his loudspeaker designs is the combination of powerful bass, an open mid-range and exceptionally clean high-frequency transients, balanced to deliver the classic ‘British Sound’ established in the ‘70s. I can’t disagree with any of that, but what I will offer is that the natural sound of the ring-radiator HF unit used in the SN70 is somewhat ‘harder’ in character than the more familiar dome tweeters employed in most modern monitor systems. This is not a bad thing as such, and it undoubtedly contributes to the superb transient speed and detail, but it may be something that takes a little time to acclimatise to for some.

The SN70 is a pretty large and expensive monitor, so this is not a product likely to find its way into many home studios. However, in a larger studio control room, or in a professional mastering suite, the SN70 would make a superb full-range monitoring system with the bandwidth and dynamics to reveal exactly what is going on in a mix, and the resolution to appreciate easily any processing needed and applied. The tonal balance and transparency is maintained at moderate listening levels, but this powerful system is capable of flapping the trouser legs of the most enthusiastic rockers quite effortlessly. The SN70 demonstrates there is still a role for old-school engineering, and Stephen Court’s 40 years of experience really show in this unique monitor loudspeaker.