dB Technologies Flexsys F315

The Flexsys range was introduced back in the summer, and two versions are currently available — the F212 and F315, which are both full-range units but designed for slightly different applications. The Flexsys F212 speakers are also used as the mid/top end of the dB Technologies' Gala and Concert systems, which employ their 15D and 18D powered subs, whereas the F315 models are designed to be used as standalone, full-range speakers.

The units supplied for review were a pair of F315 full-range speakers, which — as the model number suggests — are three-way boxes that use one 15-inch low-frequency driver. Each cabinet houses a Digipro power amp module, which incorporates all the necessary signal processing and, in the case of the F315, has two Class-D power output sections rated at 500W each — one to drive the 15-inch woofer and the other to handle mid-range and HF signals. The drivers are described on dB's website only in terms of their nominal sizes and voice coil diameters; the 15-inch woofer has a three-inch voice coil, the horn-loaded mid-range driver is six inches in diameter with a two-inch voice coil, and the compression driver has a 1.5-inch-diameter diaphragm in a one-inch exit housing. The nominal HF coverage pattern (taken from the CD horn dimensions) is a fairly standard 90 x 40 degrees, and the website information says that the horn is rotatable, although I can't see how this could be achieved unless the mid-range horn mounting was rotated as well — and the user manual (supplied with the speakers) agrees with me in saying that this isn't an available option.

There is an abundance of power available from the integrated amplifier section, and the specifications claim a maximum SPL of 131dB with a frequency response of 60Hz to 19kHz at -3dB, extending to 47Hz to 20kHz measured at -10dB. The two amps themselves are equally rated at 500W RMS each for LF and MF/HF, with a sharp 24dB-per-octave active crossover operating at 750Hz, and a passive circuit splitting the MF/HF output path at 2kHz.

For a three-way active design, especially one with such a high output and power rating, the F315 is very compact and lightweight. The whole thing stands less than three feet tall, and is only a couple of inches wider than the 15-inch woofer. In order to achieve effective enclosure volume, the F315 is quite deep at just under 20 inches, and has a pronounced trapezoidal shape with a curved front, which results in a good-looking, easy to handle cabinet. The size and shape of portable full-range speakers are important to 'travelling' users like me, in that they can dictate how (and how often) they will be used — the F315s are not tall enough to be operated standing on the floor with a standing audience, but they are compact and light enough to be used on stands or poles and have good-quality, 36mm metal pole-mount sockets in their bases. Up-to-date design of speaker and amplifier components has enabled the weight to be kept down to a very useful 31kg, which makes the F315 an easy box to transport and deploy, and they seem perfectly happy on stands despite their tall-ish overall shape.

I liked the look of the F315s as soon as I unpacked them — they are all black (call me old-fashioned but I still prefer black for all-round use) and they have a good, strong, convex metal grille covering the entire front of the cabinet, backed internally with black acoustic foam, which offers protection for the driver components and looks absolutely right. There are three large, recessed handles: one on each side for general lifting and carrying, and another on top of the cabinet, which is very handy for shunting the speakers around when they are sitting on the floor or in the back of a van. This top handle is the same size as the side handles, not one of those token handles that can so easily bite your fingers, and is a welcome feature that I have already come to appreciate! There's also a simple recess-type handle set into the bottom panel, which helps when lifting or positioning the cabinet from below or when it's lying on its side. The enclosure is made from 15mm-thick birch ply and is finished in a textured black lacquer. The whole thing gives a comforting impression of solidity, and there are no creaks, cracks or groans when you rock it about or thump it onto a hard surface. The handles and grille are well-secured and neatly fitted, and the only observation I noted about the general finish was that the black paint seems to be quite thin — an accidental scrape against the side of a stage exposed a line of bare plywood. This is easily touched up (one of those instant shoe shine scuff cover things is good in an emergency, I find), but I would want to use transport covers (available as an optional extra) to preserve a neat and tidy appearance in the longer term.

In terms of practical applications, the F315s are designed to be used on their own without the need for additional subwoofers, although, given that they would almost always be positioned some distance (a few feet) from the ground in order to have the horns at a usable height, the low-end performance could be slightly compromised. Personally speaking, I have always used 'full-range' speakers with subs wherever possible, which has always delivered great results. I experimented with the F315s on stands, on top of other (dummy) speakers, on the floor, and with subs, and I liked what I heard in all configurations. Used on their own with the horns just above head height there is actually plenty of bass, and it remains tight and well under control at high volumes — certainly more than enough for small venues or for reinforcement work, where you don't need loads of thumping low end. When I used the F315s coupled to a pair of active subs I could achieve a greater overall level, as all their available power was being used to reproduce frequencies above about 90Hz.

Setting up the F315s is quick and easy — plug in a full-range signal via the rear-panel XLR input, connect to the mains, switch on and you're away. There's a rotary sensitivity control on the control panel that lets you turn the signal level down to nothing (always my favourite starting point) and four LEDs indicate the unit's operating status in terms of ready (ie. on), signal present, mute, and signal limiter. An output XLR is provided for linking to another F315 (this output level is not affected by the input sensitivity setting) and a mode selector switch offers a choice of two preset EQ settings — either flat response or 'processed', which enhances the low frequencies and reduces the HF output somewhat. This works quite well with low-level music playback, or when generally less projection or a mellower sound is needed.

One of the really good things about good-quality, integrated amp/speaker packages like the F315 is that everything possible has already been optimised, and all is properly matched to deliver best performance with a high level of protection. The F315's thermal monitoring allows protection circuits to kick in when the operating temperature exceeds its safe maximum, and output monitoring will detect potentially harmful load variations, as in the case of driver malfunction. The onboard limiter will detect signal overloads, and all the protection functions are completely automatic in that they will allow normal service to be restored as soon as the problem-causing condition goes away. All key parameters are managed by the onboard processor, which looks after the relationship between signal levels, power supply and the output stages so you and I don't have to, and the switched-mode power supply will correct for mains supply variations, which, let's face it, aren't exactly unknown in some venues.

One thing I noticed was the relatively modest heat sink on the rear panel of the F315 — the surface area is reasonably large but the 'fins' are smooth and don't protrude all that far from the panel surface. There is no cooling fan either, and the main reason for this is the use of a full Class-D amp design, which is much more efficient than conventional Class A/B circuits. The Digipro pack uses a high-voltage supply (necessary to achieve the required headroom at high output levels), and the true pulse-width-modulation amp stage — running at 500kHz — uses extremely fast switching components to deliver the very clear, detailed and crisp performance you'd expect from this type of equipment, whilst also achieving more than 90-percent efficiency. The high efficiency is realised because the output stage is switched on (ie. output current flows) only for as long as it needs to be (look up 'duty cycle' in Wikipedia) in order to properly reproduce the audio signal, and the vast majority of the available power goes directly to where it's needed (to the speakers) in the form of audio signal. During the testing I did both at base and at a live gig, the F315s did indeed stay pretty cool, and I like the idea that there's no fan to clog up or burn out.

I took the F315s along to use at an outdoor (town centre) Christmas lights switch-on event, where the main requirement was loud, clean projection and lots of it. The speakers were a breeze to lift out of the van and get into position without needing two people on the job, and I had brought along a couple of 18-inch powered subs to stand them on. From past experience I knew that the mobile trailer stage might get a bit bouncy and I wanted something big and solid to sit the main speakers on, rather than a pair of tripod stands. I had plenty of time to mess about with the F315s, both with and without additional subs, and I tried a few of my favourite test tracks through them at various volume levels right up to what I'd truly call 'very loud'. The output from these speakers is impressive, and although taking any kind of measurement in a street scene would have been a bit pointless, I can say that these speakers were more than equal to this medium-sized outdoor job. The HF and mid-range projection was very good indeed, and the balance was nice and even throughout the audience area. The vocal projection and clarity was the best I had ever achieved at this particular event, and I had the system running at a real thumping town-centre level — for the speeches, announcements and the live bands — without so much as a flicker from the limit LEDs. A good live test, this one, and one that had me seriously considering whether a pair of these F315s would fit very nicely into my inventory

I had been so impressed with the live performance that I went back to do a bit more testing back at base. Over the post-Christmas weekend I had a few little repair jobs to do on my gear, so I took advantage of a quiet, no-one-around kind of Saturday afternoon to set the dBs up outside and give them a proper caning. I left them whacking away for a good 20 minutes with the limit LEDs flashing, with no apparent problems, and I was able to get about 30 metres away from them (very clear and crisp vocals) and walk off to the sides to check the horizontal coverage (nice and wide, as advertised). The more I used them the more I liked them, and their easy portability makes them a clear and present possibility for my 2009 shopping list. 0

dB Technologies Flexsys F315

Active PA speakers