Xpression! DPM1

Proactive Powered Monitors

Published in SOS February 1998
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Reviews : Monitors

PAUL WHITE lends a critical ear to Xpression's first ever powered monitor, to test the company's claim of accuracy at a budget price.

In the relatively short time they've been on the market, the two-way Xpression! DPM1 passive monitors have won over a lot of users with their combination of tonal accuracy and low cost. Now the company have built an active version, the Xpression! DPM1 ProActive. These use the same drivers and cabinets as the passive DPM1s, though the bass/mid cone is now deep blue rather than purple, and dual amplifier packs and active crossovers are built into the rear of the cabinet.

Alan Shaw, the MD and chief designer of Xpression! parent company Harbeth, has a history that is closely interwoven with that of the BBC's monitoring systems, and Alan still adheres to their basic design principles. Indeed, Harbeth are the only company licensed to build the BBC-designed LS3/5a, which they still manufacture today, along with the newer LS5/12a.

pros & cons

XPRESSION! DPM1 PROACTIVE £799

pros
Accurate, detailed sound.
Not too heavy to use as a portable reference.
Stable stereo imaging.
Ideal frequency response for use in smaller music studios, broadcast studios, edit suites and MIDI studios. They're also great for general music listening.

cons

More power amp headroom might avoid the slight raggedness that creeps in at very high monitoring levels.

summary

These are extraordinarily good loudspeakers at a bargain price.

Having spoken at length to Alan about his designs, I would say that he's always been obsessed with obtaining the best possible audio reproduction from available loudspeaker technology, and I get the impression that his integrity won't let him market anything he isn't thoroughly happy with. Unlike most manufacturers, who use third-party drivers, Harbeth build their own bass/mid drivers from scratch using some unusual manufacturing techniques researched with the aid of a significant Science and Engineering Research Council grant. As far as I know, the Xpression! bass/mid driver is unique, in that it is built around a high-pressure, injection-moulded, 200mm synthetic-polymer cone that varies in thickness across its diameter to minimise resonances and coloration. This driver, which also features an aluminium voice coil, has a moulded plastic basket rather than a metal chassis, and the cone is supported by a long-throw roll surround. A field-cancelling magnet is fitted to the rear of the driver to enable the monitor to be used close to computer and TV monitors. The 1-inch soft-dome tweeters, which are built by Morel, use ferrofluid cooling and are individually tested and selected.

According to Alan, the aim with the active monitors was to reproduce the filter characteristics of their original crossover, which gives it a relatively gentle slope compared with most other active designs, but the closer coupling between the amplifiers and the drivers yields a much improved damping factor compared with the passive version, and this translates into a tighter, better-controlled sound, particularly at the bass end.

The power amplifiers themselves are actually single-semiconductor devices, rather than being built from discrete components, which keeps both the cost and the weight down, and there's around 75W available for the tweeter, with the same for the bass/mid driver. Anti-thump circuitry keeps the speakers muted until the amplifiers have powered up and stabilised. Very high tolerance components are used in the crossover to ensure close matching, and specially designed custom modelling software was used to evaluate the driver performance in their intended cabinets.

CONSTRUCTION

MDF is used for the basic cabinet construction, but the specialised Nextel textured grey paint finish gives the cabinets more of a moulded plastic appearance. All the cabinet corners are rounded, and the baffle features a raised centre section with machined rebates so that the drivers can be flush mounted. Porting is via a slit-shaped port beneath the bass/mid driver. Each cabinet measures 420 x 255 x 305mm and weighs just 12.6kg.

The crossover point is set at 2.6kHz and is based on Sallen and Key filter topography to produce a critically damped response. Overall, the frequency response extends from 46Hz to 20kHz, flat within +/-3dB, which for nearfield use is about ideal. If the bass response were to go much lower you'd run the risk of getting very misleading bass results in a room with no acoustic treatment, but as it is you can hear the fundamental of the lowest note on a 4-string bass guitar. The speakers are relatively sensitive, so there's plenty of level for their intended nearfield application. A solid-state protection trip is used to protect the tweeter from overload -- though few people have managed to feed in enough HF to get this to come on -- and in the event of this operating, a red warning LED on the tweeter surround lights. An orange LED below the tweeter shows that the mains power is active.

The power amp heatsink covers a fairly large area and has low-profile fins to provide adequate cooling without extending too far from the back of the cabinet. Other than the power switch, the only control on the monitors is a sensitivity pot. The XLR input feeds a balanced input stage, though a transformer option is available for those professionals who need complete electrical isolation. Apparently the tweeter sensitivity can be varied, but the adjustment is internal.

AUDITION TIME

Over the past few years small monitors have become big business, but there are some truly terrible-sounding designs out there, both active and passive. Happily, Harbeth's designs don't fall into this category. When you're mixing, the most important thing is to have accurate mid-range reproduction, because that's where human speech frequencies fall, and you can tell a lot about a pair of speakers by listening to material that is predominantly vocal. Of course, when you select your audition material you have to sort out goo

"Over the past few years small monitors have become big business."
d recordings from those that have been enhanced to death, but given good source material the DPM1 ProActives sound exceptionally smooth and natural for voice reproduction. What's more, they'll expose the flaws in material that isn't as well recorded as it could be, whereas coloured-sounding or flattering speakers may hide these details from you.

When I fed the ProActives with acoustic jazz, pianos were reproduced very naturally and evenly, brass fairly leapt out at me, and detailed cymbal work was revealed in intricate detail, as was any other high-end percussion. Double basses had depth and resonance, but stayed tightly controlled, and though the bass response of any small speaker is necessarily limited I didn't feel I was missing anything. Pop and rock mixes delivered a tight bass drum sound that stayed separate from the bass guitar, while right across the spectrum, the impression I had was of being able to hear into the mix, rather than listening to it from a distance. This degree of clarity allows you to better judge the result of adding subtle effects to vocals and instruments.

Along with all other leading loudspeaker designers, Alan Shaw realises the importance of having a response that's as accurate as possible off-axis as well as on-axis. Attention to detail in this area has resulted in a consistent sound, even when you move quite a long way off-axis, plus a very believable, stable stereo image -- sounds that are supposed to be in the centre stay there, rather than hopping from side to side as you move your head. Localisation of instruments within the stereo field is especially good, and any mixes that have been treated with 3D enhancement algorithms work to their full effect.

So far it's all good news, but is there a downside? Obviously, every loudspeaker is a compromise, and in an ideal world I suppose some users would like a little more available SPL, though I'm only being slightly cynical when I say that anyone regularly monitoring at such levels probably won't be in a position to appreciate the finer points of good monitors anyway.

SUMMARY

Within the boundaries imposed by the laws of physics and the cost restraints of manufacture, the Harbeth DPM1 ProActives are exceptional performers, but what's really surprising is that they are also amongst the cheapest active nearfield monitors available. The frequency response is spot-on for smaller studios or home MIDI systems, the clarity and detail is better than on many monitors two or three times the price, and there's no attempt to flatter the sound -- these are monitors in the true sense of the word. I found that there was plenty of level, though the sound does become slightly ragged when you're approaching the maximum SPL capability of the units, but if you monitor at sensible levels, the sound is as smooth and well integrated as you could wish for. Though they cost more than the passive DPM1s, the performance is noticeably tighter, and of course you don't have to budget for a power amplifier and cabling, so they could actually save you money.

The DPM1 ProActives still haven't replaced the ATC20As on my wish list, but at under a quarter of the price of the ATCs, the ProActive's only real competition is probably the Event 2020 BAS. If you're looking for sub-£1000 active monitors and you don't audition these speakers, your ears may never forgive you!

 information
£849 per pair including VAT.
Xpression! Harbeth Acoustics Ltd, Haywards Heath RH16 1UA.
01444 440955.
01444 440688.
www.harbeth.com

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