HK Audio PR:O 15XA

HK Audio's PR:O 15XA is an active — or, more correctly, powered — two-way speaker built into a traditional high-quality plywood enclosure and equipped with a 15-inch woofer, augmented by a horn-loaded one-inch HF compression driver. These two drivers are fed from a single 600W (into 4Ω), high-efficiency Class-D amplifier via a passive crossover network. Though it may be used with the company's PR:O 18 Sub A subwoofer, it still manages a very respectable 55Hz to 19kHz response (±3dB) when used alone, and can generate a maximum SPL of 123dB (at one metre). The constant-directivity horn flare provides a 60 x 40-degree coverage, while the electronics pack includes a single-knob Music/Speech tone control and a 35Hz subsonic filter to prevent very low-frequency material from over-stressing the main driver. Further protection is provided by an integral peak limiter, plus an RMS sound limiter that keeps an eye on the average power levels to head off overheating. HF driver protection is provided by means of passive protection circuitry. A common approach is to place a suitable low-voltage light bulb in series with the tweeter, such that excess power causes the filament to heat, consequently increasing the circuit's resistance and reducing the current being fed to the driver.

Trapezoidal in shape, the cabinet is extremely well built and has carrying handles routed into the woodwork. A textured paint finish protects the wood, while the whole front of the cabinet is covered by a metal grille with a thin layer of acoustic foam on top. This looks very elegant, but I'm a little concerned that the foam could get damaged in transit if the speakers are transported without covers. Overall dimensions are (WDH) 470 x 445 x 615mm (18.5 x 17.5 x 24.25 inches), while the weight is a solid, but not unmanageable 22.4kg (or 49.4lbs). At the base of the cabinet is HK's very practical DuoTilt pole mount, which essentially has two pole sockets: one perpendicular to the cabinet as usual, and one placed to tilt the cabinet slightly downwards so you can get more sound onto your audience and less onto the ceiling. There are also three M8 thread-rigging points for more permanent installations.

All the connection points are located on the metal rear panel, with the Gain and Tone controls at the top. Gain is self-explanatory, but the Tone control is interesting, as it is designed to move between music and speech characteristics. At the anti-clockwise or 'Music' end of the spectrum, the mid-range is dipped slightly, while the low end is boosted to give a 'loudness' effect. At the other extreme, the Voice setting boosts the mid-range slightly in the 1.5kHz region, and in the centre of its travel the filter is essentially flat or bypassed.

The input is via an electronically balanced XLR connection, accompanied by a Mic/Line switch that sets the sensitivity so that, where necessary, you can feed a dynamic or battery-powered electret mic directly into the cab without needing a mixer. A Through connection links the input to a second XLR, which may be used to feed an additional speaker cabinet.

Directly above the IEC mains inlet is a power switch and a limiter status LED, which shows green at safe operating levels and flashes red when the limiter comes into play. It is OK for this to flash occasionally, but if it is on all the time you're running at too high a level and the sound quality may suffer. If the LED comes on and stays on when no signal is being passed, it indicates a fault in the speaker system. The speaker link NL4 Speakon connector is at the bottom of the panel.

The back panel of the PR:O 15XA features Gain and Tone controls, an Input XLR/jack combo socket with Mic/Line switch, an XLR Through output, a Power switch, IEC power inlet, and a parallel Speakon output for powering an additional passive, 8Ω, 300W speaker.

We tested the speaker as part of a PA system used at an outdoor event, and here we discovered one small practical problem: there is no clamp to hold the speaker to the pole, and on slightly uneven ground the cabinet kept wanting to swivel round on the pole. This is hardly likely to be a problem at indoor gigs, but at events like this one you might have to resort to gaffer tape to keep things stable.

The other thing we soon discovered is that these speakers can go very loud, but unlike some plastic systems they do so without that annoying, boxy, mid-range coloration some plastic systems exhibit due to cabinet resonances. With the Tone control set right across to Music, I found the sound a bit too scooped for my own taste, but the continuously variable character is useful in that it enables you to dial in anything from a bit of mid-scoop to a hint of mid-boost. This is particularly useful when using simple mixers that may not have very sophisticated mid-range EQ control.

When combining a 15-inch woofer with a one-inch HF driver, the mid-range can often end up being the poor relation, as it sits just outside the comfort zone of both speakers, so they have to work hard to make things join up in the middle. Being hypercritical, the PR:O 15XA does suffer from this slightly, but compared with similar-sized competing systems it actually manages pretty well, and with careful use of the EQ control vocals come over with clarity and presence without sounding harsh. I certainly preferred the sound to most of the powered or active plastic-cabinet systems I've tried, and their performance was particularly impressive in light of the price. Another factor that's often not taken into consideration is what you hear when you're behind the speakers. With plastic cabinets, you're often subjected to a boxy rumble when you're working behind them, but a good ply cabinet like this behaves rather better, making it easier to get a good monitor mix.

Premium-priced wood-box systems, including those made by HK Audio, may well give you a bit more of a hi-fi sound quality, particularly in the mid-range, but I was still very impressed by the performance/price ratio of these speakers, particularly the effortless way in which they handled high-level material. On a practical note, you can probably get a pair of these speakers into the back of a larger hatchback (or a smaller one with the back seats down) and you won't outgrow them easily, as you can add one or more subs when you move to playing larger venues. Definitely worth checking out if you want a quality speaker that is still affordable. 0

HK Audio PR:O 15XA

Powered PA speaker