Paul White appraises these new speakers, whose unusual appearance is no mere designer's whim but the result of some radical rethinking of speaker cabinet design.

There are as many 'right' ways to design loudspeaker systems as there are speaker designers, but the electromagnetic drive units themselves have changed very little since their inception at the end of the last century. Though there have been departures in both drivers and speaker design — the electrostatic driver being a prime example — most models still employ electromagnetic drivers in rectangular enclosures which are either sealed or ported to extend their bass performance. The engineers at Dawn Audio, acknowledging that driver technology is about as advanced as it's going to get, turned their attention to the cabinet and its influence on the sound.

Box Clever

Speaker boxes might seem like pretty boring things, but they do more than simply provide a place to park the speakers. The air trapped inside the cabinet acts as a resilient cushion for the bass driver's cone, but it also provides a mechanism for sound to be reflected around inside the box, which can cause problems. Any standing waves produced inside the box will impinge on the rear of the bass driver's cone, affecting its performance, particularly the flatness of its frequency response, while the box itself may resonate at certain frequencies.

This resonance and standing wave problem has been tackled by Dawn Audio, firstly by using a different construction technique, and secondly, by using a different box shape to minimise front-to-back internal reflections. The box is not just wood or particle board but a multi-layer sandwich of MDF and glass reinforced plastic (GRP) — the reason being that this form of construction exhibits high self-damping. The outer shell is made from 25mm MDF with Dawn's proprietary sandwich damping system on the inside. The angled front baffle of the cabinet discourages the formation of standing waves and, as a side-benefit, this also provides a naturally converging angle when the speakers are set up with their backs parallel to the rear wall. The cabinets, which are unported, are finished in black textured paint.

The overall size of the cabinets is 620mm x 340mm x 220mm, and though this may seem a little on the large size, it should be remembered that these speakers are capable of performing as a main, full-range monitoring system and not just as nearfields. Their quoted frequency response is from 35Hz to 30kHz, plus or minus 5dB.

Driver Time

Unusually for a studio monitor, the Patrols use drivers with a hi-fi pedigree, and rather than selecting parts from several different manufacturers, all the drivers are made by Peerless, the famous Scandinavian hi-fi component manufacturer. Handling the bass end are two 200mm cone drivers (39 mm voice coils) fitted with synthetic (Polypropylene) cones and roll foam surrounds. These are front mounted and the chassis edges covered by a plastic trim ring, though these were not fitted on the review models.

The mid-range driver is a 100mm, rear-loaded device with a rigid plastic cone; the treble is handled by a 25mm, soft-domed tweeter. All four drivers are fixed in place with a proprietary adhesive/sealant to provide a degree of mechanical decoupling and to ensure a perfect seal around the drivers. All the drivers are fed from a passive crossover operating at 500Hz and 5.3kHz, which keeps the crossover points away from the most vulnerable area of the midrange. Rear-panel connections are made by means of binding posts which can also accept banana plugs.

"The stereo imaging achieved by these speakers is particularly good, with no trace of that hole-in the-middle sometimes found with less considered designs."

Because the drivers have their origins in hi-fi, they seem fairly efficient; the quoted figure is 90dB/watt at 1 metre. Power amplifiers of up to 200W per channel are suitable, though it is possible to use the Patrols with amplifiers as small as 35W if high sound levels are not necessary.

Sound Check

While the frequency response is quoted as 35Hz to 30kHz, these figures are at 5dB down, the roll-off starting at around 75Hz. This approach usually produces a more natural sound than a cabinet that has been tuned for the most dramatic bass, and though the bass retains a warm character, it is reasonably well controlled and the subjective level of different bass notes is consistent. In fact the bass feels reassuringly powerful, but the controlled roll-off at the bottom end should enable the speakers to work well in a variety of rooms without unduly provoking low frequency room problems.

The general sound feels well-balanced across the whole audio spectrum, and because of the soft-dome tweeters, the top end is clean without being harsh. If there is a criticism, it is that the mid-range drivers chosen do exhibit a hint of harshness on some material, though not excessively so. The sound doesn't have the same degree of transparency and integrity which comes with ATC or Genelec monitors, but then the Patrols are not particularly expensive given their power handling and range. For the majority of monitoring applications, they are sufficiently revealing of detail and present a pretty honest balance perspective.

The stereo imaging achieved by these speakers is particularly good, with no trace of that hole-in the-middle sometimes found with less considered designs. Also impressive is the way the sound hangs together off-axis — you can walk almost anywhere in the room and get a good balance.

"The angled front baffle discourages the formation of standing waves and as a side-benefit, this also provides a naturally converging angle..."

Conclusion

No monitor yet built is perfect in every respect, but in the mid-section of the market — where the Patrols are targeted — we have come to expect a certain level of quality. Criticisms are minor, the most significant being the slight mid-range harshness, but the forthcoming new (and heavier) generation of cabinet design may well help in that respect, as well as further tightening the already well-controlled bass end. The review pair were prototypes and were less solidly built than the production models, so the bass may tighten up slightly also.

In a monitoring situation, the ability to present a properly balanced sound is paramount, something which the Patrols do very well, and though not as transparent as some more up-market designs, they are sufficiently revealing to be used with confidence on critical mixes. Also important is the off-axis response, not only because it ensures that everyone in the room hears more or less the same balance, it also minimises colouration problems caused by inaccurate off-axis sounds bouncing from walls and ceilings back to the engineer's monitoring position.

There are surprisingly few monitor loudspeakers in the 'around £1000' category — most cost either much less or significantly more than this figure. The choice is narrowed even further when a full-range design is necessary, and while some models have subjectively more impressive bass responses, the smooth roll-off inherent in this system ensures good monitoring accuracy and is probably more forgiving of acoustically imperfect rooms.

Further Information
Dawn Patrol monitors £1175 per pair including VAT.

Dawn Audio Ltd, (Contact Details).