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A&R Arcam One Monitors


At first sight, Arcam is an unusual Christian name for a speaker, but scores approbation once you know it's an abbreviation for 'A&R Cambridge'. But what about 'A&R'? Well, these initials stand for 'Amplification and Recording' - the name a group of erudite students gave to their fledgling business, a decade ago. Originally, they produced embryonic stage and studio equipment, but in time, they became exclusively involved in Hi-Fi, where today they've built a fine reputation by dint of careful design and patient attention to quality control.

The Arcam One is a two-way monitor, with a 200mm Thiele-loaded bass/mid driver and a dome tweeter. So far, all very conventional, but the Arcam One is twice the volume of a near and acknowledged rival, the Celestion SL6. Also, lurking at the back of the cabinet are all the connections needed to gain access to the drivers individually, bypassing the (internal) passive crossovers. Result: the Arcam can be speedily hooked up to an existing bi-amped monitoring system and driven actively.

Drivers/Crossover



Like the SL6, the Arcam One's bass cone is made from cobex to promote good behaviour in the midrange. The ported bottom-end loading has a QB3 alignment, tweaked by listening tests, because designer Anthony Holden doesn't believe you can simply look up Thiele parameters in a set of tables, and leave it at that. "Most UK designers use a B4 alignment without further ado." But this QB3? Well, 'B' is for Butterworth, the name for the family of roll-off curves with the smoothest transition. 'Q' stands for Quasi.

In practice, this indicates that the exact transfer function (the curve shape) is half-way between Butterworth, and one of the alternative functions, like Thompson (T) or Chebyschev (C), while '3' indicates a third order curve - that's one that rolls off at (3x6dB) 18dB per octave. Thus it's rather like the slope on an 18dB/octave crossover, but with one exception: the curve steepens to -24dB/ octave below 40 Hz. This is the effect of the magic letter 'Q' in the alignment, yet without introducing the excessive phase shift of -24dB/octave in the audible region above and about the roll-off point. This tweaking is achieved in part by resistive loading in the vent, which opens onto the back panel. Low bass is omnidirectional when it emerges from a small box (remember our piece on sub-woofers?), so why not? The resistive loading, meanwhile, comprises reticulated foam, the sort used for mic windshields.

The crossover point is at 2.3 kHz. Like the bass/mid unit, the tweeter is made to A&R's own specification by a well known manufacturer. In common with the Electro-Voice Sentry 100A, steps have been taken to prevent diffraction effects (viz. sound bouncing off the adjacent cabinet surface, creating interference parts) and in turn, audible colouration. To this end, the baffle immediately around the tweeter is treated to an area of bituminous panel, on which is laid a U-shaped foam strip, all very like a model of an 18th century landscaped garden!

The crossover PCB is mounted by a pair of unlocked screws, and this would prove to be insufficient if any sort of road use is contemplated. On the other hand, the cabinet's inner surfaces are largely covered with bituminous damping panels, and the crossover card is mounted on one of these, so the mounting is satisfactory in that rattles and resonances won't arise. The PCB tracks are above average width (this spells a low resistance) but not quite commensurate with the hefty 20 amp wires which hook the crossover to the external terminals and the drivers!

Capacitors are a mixture of Nipponese non-polarised electrolytics specially designed for crossover duties (these comprise two polarised capacitors, wired back-to-back, in a single can) on bass, and plastic film types on the top-end. A&R have attempted to brace the electrolytics (which are amongst the most mechanically fragile of components) with some RTV rubber compound, but have been too stingey. Result: the compound has no effect, and is wasted. Notwithstanding this, the same compound has been used to good effect to support the inductors, which is fortunate, because they are wound with heavyweight wire on generous ferrite cones, and therefore weigh a ton! A&R's John Dawson stressed that they're very aware of crossover 'crunch-up' at high levels; this is borne out in that the bass driver inductor is about the same size as the inductor used in a certain 600 watt PA speaker!

For the maintenance engineer, the fact that all connections are soldered will draw a frown, but the crossover terminals are clearly marked T, B, E - I'm sure you can guess what they mean. And like all A&R products, there's a label telling you the serial number, who made the card, and the date of assembly.

Cabinet Construction



Inside, the enclosure is elaborately braced. Designer Anthony Holden used an accelerometer glued to the side of the cabinet to track down vibration in the panels (in poorly designed cabinets, the highly coloured sound from the panels can exceed the output of the drivers themselves!), and determine the most effective means of removing the resonances. Internal reflections, meanwhile, are taken care of with sandwiched layers of acoustic wadding, plastic foam and bituminous panels. These marginally decrease efficiency and alter the predicted tuning of any Thiele enclosure, so reinforcing Anthony's point about actually listening to the results, rather than relying on computation alone.

Drivers are secured with high-tensile hex-head bolts screwed into threaded inserts. This is the correct way to mount drivers - other makers please note! Driver connections are soldered, incidentally - that's fine for consistant sound quality over an extended period, but again, the maintenance engineer frowns...

Positioning



A&R recommend that Arcam Ones are placed about 300-600mm (1 to 2 feet) from the wall you're facing, and at least one metre (3 feet) from the room's corners. In common with any other speaker, they're also best angled inwards - so the two imaginary lines drawn on-axis (ie. in line with the dead centre of the cabinet) cross about six inches in front of your nose. The review examples came replete with a pair of modernist sculptures, (or stands if you prefer) to which the Arcam's were firmly bolted. This prompts an explanation of the role of stands in today's Hi-Fi belief-systems.

Essentially, given that the distance of a speaker from the room boundaries profoundly influences bass-end qualities, and not overlooking the fact that the floor (and ceiling!) are just as much boundaries as the walls, stands provide defined operating conditions, in that to listen on-axis, your own ears (as well as the drivers) will be a healthy distance from the floor. The reality of this can be demonstrated by placing a speaker on the floor, and angling it upwards, so that it's on-axis to your listening position. Contrast this with the speaker raised 0.5m (19") off the floor - and listen to the difference in the bass; the top end certainly won't be any different, provided the tweeter is always on-axis. But there's more to it than that - the nature of the stands themselves can gravely influence the bass sound.

Accordingly, A&R's stands are not, therefore, tinny steel frames, slung together as an afterthought. Rather, they're made from carefully specified wood, and are shaped to avoid unbalancing the Arcam's bass qualities. Now this is based on raw pragmatism, involving listening tests and measurements, yet these stands incorporate styling and finish that few would grimace at - even women with Venus in Capricorn! Consequently, the Arcams offer great kudos if your recording activities take place in tidy, highly domesticated open-plan living rooms.

Trouble is, many readers suffer in a cramped room, where stands are totally out of the question. To do the job properly, you should nonetheless adhere to the essence of a firm, resonant-free mounting. In other words, you should screw the Arcams to the shelf or mounting bracket, using the threaded bushes provided, and also a bituminous damping panel and some thin sheet foam should be sandwiched between the Arcam and the mounting surface. Furthermore, before finalising the positioning, it will repay you to experiment over a period, trading-off any proximity to adjacent, horizontal surfaces (like equipment racks or shelves) by increasing the spacing from the rear wall and room corners to compensate. For these tests, double-sided gaffer tape will serve to keep things deadened in lieu of the big bolt-down. The real wood veneer can certainly withstand such action.

Activation



The Arcam Ones are compatible with bi-amplified systems - those using active crossovers. To achieve this, the internal passive crossover must be bypassed so that the bass/mid and top amps can feed their respective drivers directly. A&R have made this possible without dubious switching arrangements. Switches are out because with up to 17 amps cruising round the monitor chain's output wiring, any switching at full drive levels will cause 'arcing' which will bite away a hefty chunk of the switch mechanism. OK, we could mount a cooker switch on the back panel, but some subtlety is also required - small programme details at low listening levels represent a few microamps of current, and power station-sized switches aren't up to passing such small currents without lousing up the sound, albeit only slightly at higher levels.

A&R's method is to bring the driver and crossover output connections onto binding post-cum-4mm sockets on the back bench. These are strapped with plated brass strips. To "go active" then, all you do is slacken off the terminals and unhook the straps. You're then left with seven empty terminals, four of which are clearly marked, and go to the low and high amps. The other three terminals are white, which symbolises their passive role. But they're not the conventional (passive) input points - with the straps back in place, the single-amp connection goes to a pair of red and black terminals further down the panel, again marked clearly 'Normal (passive) input'. If this sounds complicated, worry not: full, easy-to-read instructions are printed on the panel.

The only reservation I have about this arrangement is the difficulty in clamping the terminals really tight. If this isn't done, they will surely slacken off in time, leading to ail manner of strange, intermittent effects. The complete remedy is to bring in the Heavy Squad, that's Messrs Molegrip and Lever-Wrench! Failing this, tighten as best you can, and make periodic checks for signs of loosening. The good news is that with the straps being removed, active mode operation is relieved of these precautions.

Arcam Sound



Superb bass qualities were immediately apparent even in small, 'difficult' rooms. Hard and soft bass notes weren't transposed or falsified, and the low-end articulation was remarkably tolerant of room dimensions, drive levels and one's proximity. Generally, bass performance of this standard only arises when you pay out £500-plus for Thiele loaded designs of the Electro-Voice or ATC calibre and in this respect, A&R's principle (that of not taking Mr. Thiele's mathematics at face value) has paid off.

Overall, the sound balance is very even, yet slightly forwards; there's a distinct, yet broad, rise about the crossover point. Centred at 2.4 kHz, and only 1dB high, this isn't exactly pleasant on bright programme, yet not fatiguing either, even at very high levels. Listening to records of known origin on a pair of Arcams supports the 'JBL plague-theory', and should teach you the steely, ear-ripping consequences of piling on too much presence at mixdown! On the other hand, you should be careful not to mix too dull if monitoring with these speakers. If in doubt, a switchable parametric EQ set to cut 2.4 kHz with a very low Q setting will give you a check on the Arcam's own (very mild) irregularities.

High frequencies are notoriously hard to assess if nothing much is amiss, so I resorted to an A-B (=alternate) test against a pair of Celestion SL6 speakers. The Arcam's top-end sound is distinctly crisper, and likewise recorded cymbals on the SL6 were airier and drier. It is hard to put contrasting adjectives on the Arcam, and neither make could be judged 'best' - they're just different. Having set up the A-B test, I resolved to compare the Arcam's stereo properties with the SL6. It's a sign of A&R's confidence in their speaker that they raised no objection to this test - some speaker manufacturers would raise their arms in horror. The results are as one might expect - the Arcam exhibits competent and unusually stable, yet conventional, stereo imaging which fills an imaginary isosceles triangle between the speakers, whereas the SL6 open out the sound stage into three dimensions and radically expand the room boundaries, on a decent stereo recording. The Arcam has good detail up-front - and neither speaker is wrong (at least insofar as both are good, yet neither are perfect), so provided you're aware of your monitoring requirements, the Arcam's superlative bass performance can be fairly weighed against the SL6's own set of pros and cons.

Listening Tests



Our main listening tests were done in the nearfield, with the Arcams 4 feet (1.3m) from the ears, and 5 feet (1.6m) apart, using A&R's own SA200 power amp (see review this issue). Integration was excellent, but to assess high level performance, we hooked them up to a Yamaha PC2002, rated at 350 watts per channel. Above 100 watts (peak power metering), the bass takes on a pleasurably 'fat' quality. Above this, the colouration resulting from thermal compression in the midband is less acceptable, and the treble dips out. But this is no bad thing, because it gives us advance warning that the Arcams are being pushed too hard, well before the amp clips. In effect our tests indicated that these speakers can be driven safely at 350 watts, but you wouldn't want to drive them much above 150 watts if clean monitoring is your aim.

To put this all into perspective, sensitivity is below average, at 88dB, but the slightly forwards sound and flat bass response to 65 Hz compensates admirably for this, making them subjectively the equal of some speakers rated 3 or 4dB more sensitive. For, as I've remarked before, sensitivity figures are all averages and it all depends on where you draw the line. By this reckoning, A&R are conservative in their specifications and this may be taken as a good sign. Finally, we found it difficult to make the bass/mid driver cones hit the end stops sharply, even at 150 watts! A super-heavy Augusto Pablo dub recording was duly brought out, but even then, it wasn't easy to 'over-excurse' the bass driver. So here for the first time is a domestic Hi-Fi speaker which won't freak out too easily on raw low frequency bass.

Conclusions



The Arcams scored thumbs up all round, and can be highly recommended for main studio monitoring. In effect, A&R are making their speakers available at two-thirds of the price of competing 'serious' monitors. The latter can naturally score a few points in areas untouched by the Arcam (such as life below 65 Hz or a 25 watt tweeter PHC), but for the most part, a certain (budget) level of monitoring accuracy has been brought into more affordable realms, thanks to A&R Cambridge.

The Arcam One monitors retail at £299.00 inc VAT (per pair). The stands cost £49.90. Available direct from A&R Cambridge, (Contact Details). Or from selected Hi-Fi dealers (list available on request).

A&R Arcam One: Shortform Data

Frequency response: 65 Hz - 20 kHz ± 3dB
Minimum Load Impedance: 6.5 ohms
Sensitivity: 88dB SPL @ 1 watt @ 1 metre
Power Handling (PHC) 100W (350W possible)
Finish: Teak or walnut
Accessories: Acoustically matched stands
EX202 Active Crossover
SA200 Power Amp
Size: 270(W) x 330(D) x 470(H)mm
10½" x 13" x 18½"



Previous Article in this issue

Korg SDD1000 Digital Delay

Next article in this issue

Rane HC6 Headphone Console


Home & Studio Recording - Copyright: Music Maker Publications (UK), Future Publishing.

 

Home & Studio Recording - Feb 1985

Donated & scanned by: Mike Gorman

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Gear in this article:

Monitors/Speakers > A&R > Arcam One

Review by Ben Duncan

Previous article in this issue:

> Korg SDD1000 Digital Delay

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> Rane HC6 Headphone Console


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