JBL PRX515

I like powered speakers. I've used them for years because they are quick and convenient to set up, you don't have to carry speaker leads, and, as all the signal processing and protection is built in, you can just plug and play and not worry about very much. Trouble is, all this stuff weighs rather a lot, and recently I've all but stopped using some of my powered cabs on smaller events because they are just too heavy and clunky to move around. Passive cabs weigh less, therefore are easy to handle, but then there's all the power amps and so on. So in an ideal world, I want a powered speaker that has all the good points without the weight.

The JBL PRX515 is part of a range consisting of four full-range models and one subwoofer. The range includes two-way designs with a choice of 12-inch, 15-inch and dual 15-inch LF drivers, a three-way model with a horn-mounted mid section, and a single 18-inch sub. All the speakers are powered by Crown-designed amplifiers, and incorporate all the necessary signal processing and protection circuitry to ensure efficient and reliable operation.

The PRX515 is, as the name suggests, a classic two-way, 15-inch bass reflex plus horn design, which is pretty much the standard for full-range stand-alone speakers. The power rating of the 515 is given as 500W continuous (1000W peak), with power being derived from two independent amps crossed over at 1.6kHz. The HF amplifier delivers 100W and the LF amplifier is rated at 400W, but of more importance is the actual sound pressure produced, which the manual tells us is 133dB peak using a pink noise input, measured 1m in front of the baffle, by muting the speaker then releasing the mute under full power conditions to achieve maximum SPL.

The drivers are, as you'd expect, JBL's own products, and presumably designed for this and similar applications, rather than being sold as separate components. The compression driver is a 2408H, which has a 1.5-inch polymer diaphragm and a neodymium magnet assembly. The 15-inch LF driver is a 265F model, and is interesting for two reasons: it too has a neodymium magnet (therefore, very light weight) and it uses JBL's Differential Drive system. The Differential Drive technology uses two voice coils with opposite polarity operating in two magnetic gaps, and — as I understand it — results in an increased surface area for the voice coil winding (to better dissipate heat and reduce power compression), reduction in the overall inductance (less variation in impedance) and better linearity within the 'motor' structure. These drivers really are astonishingly light — I removed an 18-inch (neodymium, Differential Drive) driver from one of my JBL SRX718 subs the other week, and I had to go around annoying people by getting them to guess the weight before picking it up. No surprise, then, that by using these new-generation neodymium drivers and Class-D power amps, the weight of the PRX515 is a mere 26kg (that's more than 5dB max. SPL per kilo!)

The rear panel carries input and output connectors, a rotary level control and switches for selecting sensitivity and EQ settings, as well as signal present and overload indicators.

The PRX515 cabinet is of trapezoidal shape and made from 18mm plywood. The finish is something JBL call DuraFlex, which is very hard to the touch — as these speakers were brand new, I didn't try to scratch them, but I think it's the same as on my SRX units, and that's a superb and very tough coating. The top and bottom panels are completely covered by thick moulded 'caps' made of polypropylene, which have nice rounded edges and corners, and look as if they will offer a substantial amount of protection in addition to looking good. The bottom cap incorporates a moulded-in pole socket, which has a flared surround, making it easy to locate a pole or stand when you can't see what you're doing. The closest I physically get to any of my speakers is when I load, carry and rig them, and so the handles are an important part of road-going gear. The PRX515 is excellently equipped in this respect with strong, properly recessed handles, which have a rubber grip bar and plenty of room for your knuckles inside the housing.

The front baffle is entirely covered by a steel mesh grille backed by black acoustic foam. This arrangement offers great protection against anything entering the cabinet or coming into contact with the drivers, and will protect from a certain amount of moisture (for example, light showers when working in the great British outdoors). At the bottom of the grille is a badge displaying both JBL and Crown logos; when the system is switched on, this badge is illuminated and is what my nephews would describe as 'way cool'. The whole thing has a purposeful, understated look to it, which I like very much, and I would be happy to put these speakers into a fashion show or a metal gig, as they'd look right just about anywhere.

The rear panel hosts the amplifier module and control panel. All you can see of the amp is a vertically-finned heat sink that has an unusual design, using very smooth, shallow grooves you could hardly call 'fins' in the usual sense, and which are a great idea because they aren't susceptible to damage and don't bite chunks out of your arm when you carry the speakers. The control panel is neatly laid out, and contains input and output connectors (both balanced XLR, but the input is one of those combi-jack types that will accept standard jacks too), a rotary level control, and switches for selecting sensitivity and EQ settings. The input sensitivity can be set to mic or line so that the speaker(s) can be used with a direct mic input for, say, announcements at an event, or a low-level source (such as an instrument or domestic CD player) can be used and still achieve a high output from the speaker. The other switch is used to apply an EQ pre-shape, which boosts frequencies at the lower and higher parts of the range — useful at very low output levels. The rotary level control acts like a normal trim control for line level signals, with the nominal +4dB marked around the 12 o'clock position. And for microphone level signals, it is used just like a normal volume control; when turned all the way anti-clockwise, the input signal is completely muted.

Despite all the clever processing that goes on internally, there are only two indicators on the panel, and these show that there is a signal present (green) and when an overload condition causes the protection circuits to kick in (red). Apart from the mains connector and power switch, that's all there is, folks — except to say that there is absolutely no 'thump' at switch on (or off), although you may hear a quiet click as the output relay connects. There is no way of switching the front panel logo illumination off, so for a theatre production where this might be a visual distraction, you'd have to deploy a piece of black tape.

When it came to firing up the PRX515s for real, I thought I'd begin with a couple of favourite CDs that I normally use for running up and testing my own gear. The sound quality and characteristics of any system are a question of personal taste, and I can tell you that these speakers are very much to mine. My initial reaction was that there's a lot of smooth depth there, with no hardness or boxiness apparent. The top end is clear and bright, as you'd expect from this format, and there's a clarity and upfront character about the mid-range, which certainly isn't always the case with a 15 + horn setup. In the open air, the overall balance stayed pretty even for quite a few metres in front of the cabinets, with a gradual drop-off in the lower range as the distance increased.

The HF projects very well indeed, and the 70 x 70-degree dispersion pattern should mean that two units could be used side by side with a decent splay angle. As for output level, the PRX515 is, well, very loud indeed. It sounds as if it goes up to at least 11 and then some, and when driven very hard, the dynamics are still there. Used with dedicated subs to handle the low end, the PRX515s could be driven even harder in a narrower band, and that would be one loud rig for the size. As there are no neighbours at the test site, when I tried running the pair of 515s at full output (just below limiting) for about 20 minutes, I chickened out before they did.

When I lent the speakers to a friend's band for a more challenging test, they were an instant hit. As I had arrived early and set them up, they were initially impressed with the sound clarity and even more impressed with the power delivered from such a compact pair of cabs, but thought that the increased weight (mixed gender/age band, you know) would be a problem and not worth the extra performance. This was before they got their hands on the 515s and discovered that they were noticeably lighter than their existing 12-inch speakers. If I were a salesperson, I'd relish the prospect of selling these because they excel in every department. They look the business, they sound great and they're light enough even for the over-50s dodgy-back brigade like myself! 0

JBL PRX515

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