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Filterlab
20-02-2008, 08:42
Forwarded to me by Ashley, this is Sound on Sound's (http://www.soundonsound.com/) review of the AVI ADM9 speakers with accompanying subwoofer:

AVI ADM9s and Sub

There are few companies who's products successfully straddle both the hi-world and the professional studio market, though when it comes to monitors the UK has more than its share with names like ATC, PMC and AVI. Perhaps having three initials for a name is the secret?

AVI's new two-way ADM9s are the company's first small active speakers, though they have produced powered monitors before (passive crossovers with an integral amplifier pack) and they have a history of building exceedingly good amplifiers that rival esoteric products for a much more realistic price. The ADM9s are ported models in very solidy built but otherwise conventional cabinets using a six inch woofer and a one inch soft dome tweeter. The long excursion bass driver is powered by a 1.5 voice coil, with ventilation through the pole piece to the area beneath the spider while the well damped paper composite cone is fitted with a soft dustcap. The driver is specified to operate well above the crossover frequency used here. The soft fabric dome tweeter is fitted with a phase correcting front plate and is designed for high power handling with an amplitude response extending beyond 30 kHz.

The ADM9s have a very respectable frequency response as they stand going from below 60Hz to in excess of 20kHz, but for serious full range studio monitoring they are best teamed with the ADM9-specific subwoofer. For maximum flexibility in both hi-fi (in the true sense of the word) and studio monitoring environments, the speakers offer a choice of two digital input options as well as the more familiar analogue, and to maintain optimum resolution, there's a remote controlled digitally controlled analogue gain attenuator that works in a series of 0.5dB steps to adjust the signal level after conversion. This is far preferable to a digital attenuator that loses resolution as the gain is reduced.

The included remote controller can also be used to select between the analogue and digital inputs where the level at power-off is remembered on power-on. For pro audio applications there's a version with a 24-bit (up to 96kHz) optical Toslink S/PDIF input using the same Wolfson DAC/clock chips as as the respected Benchmark converters while those who want to use a computer as a music server in a domestic environment can choose a 16-bit (Burr Brown) USB option for direct connection to their Mac or PC. For those who prefer a hard-wired S/PDIF port, low cost third-party optical to coaxial adaptors are easily available.

The ADM9s are quite compact measuring 300 x 200 x 250 mm where the left speaker houses the electronics for the remote controlled dual input preamplifier (one analogue and one Digital) and the digital converter. A single cable connects this to the other 'slave' speaker where AVI have opted for heavy duty unbalanced phono analogue connections throughout as the hi-fi fraternity have a strong distrust of balanced circuitry. High quality phono connectors can also provide a more reliable metal-to-metal contact than jacks or XLRs providing they aren't plugged and unplugged to often.

I know that many speaker designers take advantage of using active circuitry to build in extra filtering in an attempt to further flatten out the response curve in effect compensating for shortcomings in the driver or cabinet design. This approach, however, introduces phase errors that can diminish the stereo imaging and lead to a coloured sound. There is no drive unit compensation or bass boost used in the ADM9s which nevertheless still manage a sensibly flat response. AVI's designer, Martin Grindrod has opted for a steep 4th order crossover with no additional filtering other than at the sub-bass end and has designed his own high performance drivers (built for them by a specialist loudspeaker company) which the company is now using instead of the Vifa and Scanspeak drivers they've tended to use in the past. His take on equalising speakers is that the phase problems caused by extra equalisation are rather more audible than small frequency response humps and bumps.

Martin also argues that a steep crossover is desirable because all tweeters are audible well below the crossover point (as are woofers audible above the crossover point), not just because of phase problems where their range overlaps with the woofer, but also because they distort quite audibly at lower frequencies. Using an active crossover allows the use of a steeper slope, which in turn means less energy reaching the tweeter below the crossover frequency. Furthermore, the amplifiers no longer have to drive the more complex load of a typical passive crossover. This design uses low distortion, high voltage amplifiers that offer generous amounts of headroom and a frequency response of 65Hz to 25kHz +/1 2dB and minus - 6dB at about 55 to 60Hz.

In this design the bass/mid amplifier is rated at the equivalent of 250 watts (500 Watts max)while the soft dome tweeter has its own 100 Watt amplifier so there's bags of headroom to accommodate short duration peaks. The low frequency amplifier bandwidth is -3 dB at 7 and 70Hz while the and the high frequency Amplifier is -3dB at 70Hz and 70kHz. Martin is also a fastidious designer and pays just as much attention to important areas such as power supplies and DAC layout as he does to the speakers themselves. He also claims that his amplifiers have some 20dB better distortion figures than their Class D equivalents. There's no real novelty or departure from the norm in these designs, just adherence to sound engineering practice. The generous power supplies used good old-fashioned transformers rather than switch mode circuitry but the circuit design and layout is up-to-the-minute with extensive use of surface mount components.

Active speakers tend to control the low end better than passive designs as the direct coupling of the amplifier to the speakers (rather than via a passive crossover) improves the damping factor. Sometimes, however, this can be counterproductive in marketing terms as it limits the tendency of the bass driver cone to continue moving once the signal has ended (often called overhang), which can make the bass end seem less impressive, even though it is in fact more accurate. In a system such as this one where the cabinet is correctly damped rather than designed to 'honk' at the same frequency as a kick drum, the initial perception of insufficient bass end may be even more pronounced, though the experienced listener will recognise that it sounds smoother and more natural than a 'hyped' design. Where a greater depth of low end is necessary, the matching sub extends the low frequency response of the ADM9s which used on their own manage a respectable 60Hz to in excess of 20 Hz (-6dB). The typical operating SPL (based on 100 Hour continuous operation using RS426A Program Noise) is rated at 108dB at one metre per pair of speaker which leaves a further 8dB in hand to accommodate instantaneous peaks.


Most studio system include a 2-way crossover in the sub to roll off the low end feeding the main speakers but AVI have discovered that for music applications, adding a sub to turn a 2-way active system into a 3-way active system doesn't really work very well as the high crossover point (typically 80 to 120Hz) places the crossover region at the lower end of the critical vocal range and in a properly designed 3-way system is more likely to be at 200 to 300Hz. Clearly this wouldn't work with a separate sub as the crossover point has to be kept low to prevent the sub being identified as a separate source of sound. Instead they provide the sub with it's own switchable high-cut filter which might typically be set to 40 or 50Hz so that it takes over where the main speaker naturally roll off. This doesn't increase the maximum SPL of the main speakers as it does in some other systems but it does produce a smoother low end.


The Sub comprises a single heavy duty, front facing 10 inch driver in a 35 litre sealed cabinet measuring just 340 x 430 x 360 mm and this is driven by a 220 watt power amplifier based on AVI's existing V2 design. The connections and the adjustable low-pass Linkwitz Riley filter switch are on the rear panel where you'll find a number of switched frequency options covering the 20 to 100Hz range in 10Hz steps. When the sub crossover is set to 60Hz, the low frequency limit is (-6dB) is a little below 30Hz. There's a variable Line In level control and phase switch. The sub takes its feed from two phono connectors on the left hand speaker but there's an extra set of inputs with their own level control for connection as an LFE speaker in a home theatre system. An addition rotary switch selects the source as LFE, Line or a mix of the two in both normal and phase invert modes.

Performance
The AVI ADM9As come across as extremely neutral sounding but probably lack the low end extension for serious monitoring unless you add the sub, which fills out those low octaves in a very natural and seamless way going right down to 30Hz or so. Playing back some well recorded acoustic instruments show how accurate these speakers really are where everything seems properly focussed with astonishingly good stereo imaging. Centrally panned sounds are firmly nailed to an imaginary point between the speakers while stereo and panned sounds are spread out clearly in a wide panorama that seems wider than the physical spacing of the speakers themselves. Those used to less sophisticated monitors may at first feel the ADM9A system lacks punch at the low end or assertiveness at the top end but that's only because the majority of studio monitors tend to hype these areas while the ADM9s tell it like it is. Once you've worked with them for a little while you come to appreciate their smoothness and honesty, whether for mixing pop music, acoustic ensembles or even classical music.

As a compact, high quality monitoring system, the AVI ADM9As plus the sub turn in a very impressive performance at a very realistic price. The system is easy to set up, includes really first rate converters for anyone who has a spare S/PDIF output to feed them and the remote analogue volume control (which works on both the analogue and digital inputs) is a real bonus if you don't have a separate monitor controller. Available in plain black or a choice of real wood veneers' these speakers fit in well both in the studio and home theatre systems and genuinely bring high fidelity to studio monitoring.

Steve Toy
20-02-2008, 12:29
I think this looks like a very tempting proposition for someone starting pretty much from scratch with a system.

Filterlab
20-02-2008, 12:37
Indeed, and in fact those moving from a 17.5k system looking for an improvement if you read AVI's website. I think they'll sell truckloads, as long as audiophiles can change their way of thinking that computers can't do music. Of course, for non-audiophiles looking to get into high quality sound, chances are they're already using their computer as an audio source so this is a natural way to go. :)

I'm currently looking into the AVI Labs V2 power amp as it happens.

Marco
20-02-2008, 20:57
I think they'll sell truckloads, as long as audiophiles can change their way of thinking that computers can't do music.


You're right, Rob, but that's quite a big challenge as many so-called 'audiophiles' have years of deeply ingrained prejudices to deal with. The other problem is that the computer route isn't willy-waver friendly. Unfortunately, for many, hi-fi is not about music it's about collecting audio jewellery...

Marco.

Filterlab
20-02-2008, 21:02
Unfortunately, for many, hi-fi is not about music it's about collecting audio jewellery...

Marco.

Tell me about it, I live in Surrey remember and it's all about the biggest TV and the most speakers round here, even if the speakers are rubbish sounding.

Shame as it undermines hi-fi, but hi-fi will always be around for the more discerning folk like us.