In 2001 Apple changed the way many of us listen to music by introducing the iPod – not the first portable player to play music files, but the one that took off with the public. It was accompanied by the equally influential iTunes, an application that links to an online store on Apple’s servers in one direction, and to the iPod in the other direction. A few clicks and you can purchase the music you want and be listening to it via your computer.

iPods are all very well, but what about when you want to settle back and listen to music at home? This is also an area of rapid change, as CDs give way to music streaming. There are many approaches, including powered speakers connected to a computer, docked iPods with built-in amplification and speakers, wireless connections based on an Apple AirPort Express or Logitech Squeezebox, or Apple TV if you prefer not to have any other computer running, or music streamed to a games console such as Xbox or PlayStation 3, or custom solutions from Sonos, Linn and others.

It is notable though that most hi-fi and home cinema systems still use amplifiers or receivers connected to passive loudspeakers – except in the case of sub-woofers, which usually have their own built-in amplification.

A passive loudspeaker is one which receives a high-level output from an amplifier. That works pretty well; but there is a problem which the glossy brochures skate over but is well-known to audio engineers. It’s hard to make a single speaker driver that handles the full range of audible frequencies accurately, so high fidelity speakers have two or more drives, one for high frequencies (tweeter) and one or more for the mid-range and low frequencies (woofers). For accurate sound reproduction, the audio signal has to be split, sending the correct frequencies to the appropriate driver. This task is handled by a component called the crossover, and in an passive system it works on a signal that is already amplified. Passive crossovers tend to contribute considerable distortion.

A better approach is to split the signal before it is amplified. The obvious consequence is that you need a separate amplifier for each speaker driver. This is known as an active system, or where the crossover and amplifier is built into the loudspeaker, an active loudspeaker. Active loudspeakers also simplify the audio engineer’s task: since the amplifier is only ever used with a driver that is known in advance, it can optimised for that purpose.

Historically, active systems have been found mainly at the unaffordable end of home hi-fi, and in professional kit designed for monitoring audio in the studio. The pros like them because their low distortion make it easier to hear any flaws in a recording. There are also plenty of powered speakers at the very low end – those little speakers you plug into a computer – though many of these are not really active internally. Most home hi-fi is still based on passive speakers.

Why don’t the hi-fi manufacturers make more active systems at affordable prices, given their well-known benefits? There are a number of reasons. Passive systems sound good enough and are cheaper, since you don’t need as many amplifiers. Passive systems also preserve an upgrade path, since there are more separate boxes.

Still, there may be a gap in the market, and it is one that the British company AVI is determined to fill. The ADM loudspeakers are its solution, introduced as ADM 9 in 2007 and upgraded to ADM 9.1 in 2008 – maybe there will be a 9.2 soon? ADM 9.1s are high quality active loudspeakers that also include a DAC (digital to analog converter) and a pre-amplifier. All you need is a digital source with a standard S/PDIF optical output (also known as TOSLINK) . This means that you no longer need an external amplifier; you can control volume with the AVI remote. AVI are Apple enthusiasts and recommend a Mac Mini running iTunes as the source, accompanied by an AirPort Express if you want to avoid having the Mac wired directly to the speakers.

Mac Mini with ADM 9.1 Active speakers.

Of course you don’t actually have to use a Mac; and personally I favour the server-based Logitech Squeezebox with its multi-room capabilities. The following image shows an ADM 9.1 system actually playing some music. The Squeezebox is wired to a network, though wireless is also common, with the Squeezebox Server running on a PC in another room. An optical cable connects the Squeezebox to the ADM 9.1. The left channel speaker has all the connections and the pre-amplifier, so the other cables you can see are one that connects the right channel at a low level from the left speaker. and power cables for both left and right speakers.

Here is the back panel:

The digital inputs are the same; one has its dust cover removed. The analog input, according to AVI, goes straight to the pre-amp, avoiding any digital processing. You can use this if you prefer an alternative DAC (though there is little reason to do so), or if you have analog music sources. The analog input also lets you integrate the ADM 9.1 with an existing hi-fi setup, if you have multiple sources connected to an existing amplifier.

The supplied remote is a simple affair with volume and input selection, plus some controls for an optional and expensive subwoofer which I have not heard. The existence of the subwoofer is a clue that the ADM 9.1 is not designed for an extended bass response, though whether you need it depends on your preferences and taste in music; they are perfectly usable on their own.

Setup and positioning

The ADM 9.1 comes with remote, TOSLINK cable complete with mini-adaptor suitable for a Mac Mini, co-axial cable to connect right and left speakers, and a few sheets of A4 stapled together which constitute the owner’s instructions. Setup is straightforward, with a couple of caveats.

The first is that you have to have your digital source sorted, whether that is Mac or Squeezebox or something else. The best way to do this is a matter of some debate, and while connecting the ADMs is easy enough, getting the server side organised can be fiddly.

Second, the ADMs sound at their best on stands – AVI recommends “solid stands, typically 60cm in height” – the idea being to place the tweeter at ear level. Avoiding room boundaries is also recommended. The sound is noticeably better if you sit in a sweet spot, central and several metres away. That’s not to say they sound bad elsewhere though. They are never boomy, so even if they end up in sub-optimal positions like bookshelves the sound will not be annoying.

You are likely to need at least three power sockets nearby, one each for the speakers and another for your digital source.

The ADMs do not normally come with a coaxial digital input. I am not sure why, since some people prefer a coaxial connection and it even supports a higher 24-bit/194 kHz resolution, though I am sceptical about whether this would be audibly better than the 24/96 maximum for the optical inputs. An AVI dealer told me optical was safer, since the DAC is electrically isolated from the source. I am sceptical about this as well; I have used coaxial connections on many occasions with no issues. However, you can order them with a coaxial input as a custom option.

The sound

Unfortunately I am not equipped to measure speaker performance so all I can offer is my subjective assessment of the sound. Here then are my observations.

The ADM 9.1s are clear, neutral and surprisingly powerful. They go very loud; I have not tried them at their limit but it is plenty loud enough for most domestic use. In case you are wondering where the heat sink is – it is the back panel, and this does indeed get quite warm in use. The bass is a little light but clean; the treble is never harsh. If want to feel the kick drum with your chest as well as your ears, though, you will need a sub-woofer.

These speakers are probably not for everyone. I have used them for most of my listening over a period of several weeks. In the right circumstances – excellent recording, listener in the right spot – they are superb. Listening to Dylan’s Don’t Think Twice the guitar sounds uncannily real. Listening to Marvin Gaye’s Turn on Some Music from Midnight Love, you can hear the different texture of all the different rhythms but the song still sounds cohesive and the vocals clear. Vladimir Ashkenazy playing Chopin is beautifully conveyed. Female vocals seem to be a particular strong point, whether Kate Bush or Joni Mitchell or Annie Lennox.

So what’s the problem? Well, either the ADMs are exceptionally lean, or most other speakers are artificially lush – possibly both are true. Play classic rock like Deep Purple or Led Zeppelin and they sound far too polite, and not just because of lack of bottom end.

I had an interesting experience listening to Peaceful Easy Feeling by the Eagles. At about 2.27 – 2.50 on the left channel there is some obvious distortion. Thing is though, I’d never noticed it before. At first I thought there might be a fault. However, listening on another system showed that the distortion is there on the source; and listening to an alternate mastering of the same song also showed it, suggesting that the fault is probably on the master tape.

I’ve had similar experiences with other material, hearing flaws that I had not noticed before, and discovering that it was there all along. I guess this is a compliment to the ADMs though it does raise the question of whether this system is just too honest for its own good.

Another thing I noticed is that in comparison to the Naim SBLs that I normally use, the ADMs sounded a little less open, more boxy, though the difference seemed to lessen at higher volumes. I would be interested to know if playing them with the matching sub-woofer would remove this.

Summing up

The theory behind the ADM 9.1s is spot-on. Keep the box count down, use active crossovers. The result is a system that is ideal for the new world of music streaming. It is wrong to think of them as just speakers; since they include DAC, pre- and power amplifiers you really do get everything other than a digital source.

Value for money is therefore better than perhaps it first appears. That said, you can assemble an excellent passive system for the same price, or even a reasonable active system using nearfield monitors from the pro world, so despite AVIs outspoken marketing the value for money is good rather than truly exceptional.

The ADMs will not necessarily impress you greatly on first listen. Of course it depends what you are used to and what your expectations are. The lean sound and lightweight bass means that the merits of the system are only revealed after extended listening.

It seems to me that there are two groups of people who will love this system. One is the person who wants excellent sound with a minimum of fuss and clutter. Just plug in the Mac or Squeezebox and go.

The other is someone who values a clean, uncoloured sound that is never fatiguing. The ADMs are particularly strong for the natural acoustic sounds of classical and folk music.

If you expect your system to add a touch of boogie to your sound, the ADMs are not the right choice.

Just on a practical note, a few things could be better. The ADMs have separate power switches on the back; you will either leave them on all the time, or have to remember to switch both off after every listening session. I am not sure how much power they use when not being driven, but would have thought a standby mode controlled by the remote would be an advantage.

There is no visual indication of what source is selected or whether the system is muted, which can cause confusion.

The supplied documentation is skimpy as well as poorly presented. If you have a question like, what should the settings be on a connected sub-woofer (especially if it is not the rather expensive AVI model), you will find no help here.

I’d like to see a coaxial S/PDIF input on all models, perhaps in addition to the two optical inputs. Aside from anything else, you need an external digital switchbox or preamplifier if you have several sources to connect.

Nevertheless, I congratulate AVI on producing a system that fits so well into into today’s computer-sourced hi-fi era, and which provides a full active system at a reasonable price.

Update – adding a subwoofer

The official AVI subwoofer is rather expensive at £800 but I was intrigued to know by how much adding a sub would improve the sound. I still have not heard the official one, but I tried the ADM 9.1 with the well-regarded BK Electronics XLS200 Mk2. This is a compact sub with a 10” driver and a 275w amplifier – compared to the AVI model which has a 10” driver and a 200w amplifier – and retails for only £302.28. BK Electronics build to order so I had to wait a few weeks, but service is excellent.

My initial results were poor, for a very good reason. The ADM 9.1 has a dedicated subwoofer output, and I presumed that this was pre-filtered to only those frequencies suitable for the sub to reproduce. Therefore I switched the filter on the sub to off. The result was a sound with extended bass, but troubling distortion.

I then realised that the subwoofer output on the ADM is a full-range signal. I switched in the filter on the sub, and set the crossover to 80hz. Now the system started working as designed. The sub “disappears”, in that it does not sound as if a further loudspeaker has been added, only that the ADMs now go deeper than before. The sound is more balanced overall, so that subjectively the entire audio range is improved, even though the sub only operates at the lowest frequencies.

I realise that some listeners are happy with the 9.1s without a sub, but personally I much prefer them with the sub added, even with this cheaper alternative to the AVI offering.

Although the sound has more grunt with the sub, the system remains clean sounding and somewhat tame and polite when it comes to hard rock. Nevertheless, it is a most satisfactory system, and given the relatively modest cost of adding the BK sub I highly recommend it.

Update: The ADM 9. 1 has now been lightly revised as the AVI 9T – the T stands for “tweaked”. AVI is working on a full-range successor to the 9.1, the ADM 40. More details here.

Specifications

Good question. Here’s what AVI quote:

Power amplifiers – High speed, linear, analogue bipolar, 75 watts per channel for the tweeters and 250 watts per channel for the bass drivers. System distortion typically better than 0.002%. 
Crossovers – Active 4th order Linkwitz Riley. 24bB even order filters.
Preamplifier – High quality state of the art analogue preamplifier with two digital and one analogue input. Control is remote and volume settings are remembered for each separate input.
Volume control resolution – 1/2 dB steps 100dB range
DAC – Up to 24/192 with optional coaxial input or 24/96 with preferred Optical S/PDIF. Sample Rate Conversion to remove jitter.
Bass driver – Very high power handling, long excursion 6.5″ paper cone drive unit with 1.5″ voice coil and exceptionally broad bandwidth to enable a phase perfect crossover at 3.4 kHz. Bass extension better than – 6dB @ 60Hz.
Tweeter – 1″ Silk Dome tweeter with -3 dB point of 28 kHz.
System Amplitude response better than + or – 2 dB 100 Hz – 20 kHz.
Max continuous SPL (both driven 1 m 100 hr rating) 108dB with 8dB Threshold.
Analogue input sensitivity – 150 mV

I observe though that a power rating means little without qualification (RMS or Peak); and that “System distortion” is vague too. And how about “Very high power handling” for a spec?

AVI isn’t the first company to give imprecise specifications. Still, this is disappointing from a company that claims to be straight-talking.

Price

The ADM 9.1 loudspeaker are currently £1125.00 delivered within the EU. The matching sub-woofer is £800 delivered within the EU.