 A.R.T. (Accelerated Ribbon Technology) is the showcase of the company A.D.A.M. Based on the original works of Dr. Oskar Heil, who invented his "Air Motion Transformer" back in 1972, new electroacoustic transducers have been developed that are based on improved layouts and new materials. The membrane consists of a lamella like folded diaphragm whose single folds move according to the alternate current, thus squeezing air in and out. All other loudspeaker drive units, whether they are voice coil driven, electrostatics, piezos or magnetostatics, act like a piston, moving air in a 1:1 ratio. This is undesirable, as the specific weight of air is much lower than that of the driving mechanics. Speaking in terms of electrical Engineering one could say there is a bad match between source and load. The A.R.T. principle achieves a 4:1 velocity transformation between driving diaphragm and driven air, i. e. the air moves in and out four times faster than the folds itself are moving. Besides the transformation advantage the construction of the membrane in single stripes avoids the typical break up of stiff domes or cones at higher frequencies and the resultant dynamic limiting. Another factor in dynamics is diaphragm area. What you see is what you get. The cone area you can see is always the acoustically active area of the loudspeaker - this is true for practically all other drive units. By folding the A.R.T. diaphragm into the third dimension as seen from the listener's position a much larger folio can be used. A factor of more than 2.5 can be seen between the sound generating area and the acoustically effective area of the diaphragm. Thus a smaller movement is needed for a given sound pressure level, and thus the distortions are smaller. )
That much for the theory. Practice shows, that there is much reason in those claims and those are not just empty words. The A.R.T. plays with a sound, that can be described as extremely fast and transparent, but having some trace of sweetness in the sub consciousness, without over brightening. In some way the speaker emulates the assets of electrostatics, meaning the lack of granularity, cleanness. In this it is quite similar to the speaker with the beryllium membrane (just as I herd in the JMLab-a Electra 1007 Be speakers), because there is no tension to be heard in this all, what is sometimes the sin of electrostatics. And when we compare the A.D.A.M. driver to the ribbon transducer, then, at least at comparable price level – in my opinion – A.R.T. sounds in a more palpable, a bit more substantial way. A ribbon, a good ribbon, can sound in an incredibly expanded, at the top frequencies, way, there is so much detail in the sound, so many co-sounds, that are not easy to achieve by other means. Anyway, A.R.T. is one of my favorite transducers. SOUND )
The tested some time ago speakers HM2 are the bigger brothers of the now tested HM1. We will find the same solutions in both of them, the same tweeter, HexaCone diaphragms from Eton on midrange and bass, and the only difference is the diameter of the latter and thus the size of the cabinet. The HM1 are incredibly sleek. Small, with good proportions, look much better than the HM2, which was a bit “heavy”. The sound was superb, and the company probably came to the conclusion, that there applications that need a smaller speaker. And probably the understanding, where the HM1 will prove itself, is the key to success. On one hand we have the same mastery of the treble and upper midrange, on the other we get a much smaller bass. And the difference in the price is not so big. I don’t know the company politics on that, but I have two theories. In the first one, the speakers are to find their place in small studios, near the sound director, where there is no place for a bigger loudspeaker. That’s the studio. The second tells, that the speakers will prove themselves ideally, where there is no… place for the HM2, in small systems, designer systems, (the speakers look terrific with the Arcam Solo and the Denon CX-3 system(we tested the SACD player DCD-CX3). They will be also fine in places there is need to place them close to the wall, and even – I tested that – on the shelves (the other name for such speakers “bookshelf” came not from nowhere). So let us state from the very beginning what we announced earlier: the speakers do not play with lower bass, and its mid range is also somewhat thinned. However, this is not audible that much, as the HM1 have a splendid harmonic structure, perfectly keep the phase relations of the signal, and due to that they show how the bass sounds. If you would attend a rehearsal of a band with a bass or contrabass player, then you would notice, that during the listening on the stage there is no low bass to be heard, as it mostly just hums, but higher bass and midrange – and even treble. For the bass to be reproduced correctly, its harmonic structure must be kept, that reaches extremely high. The same trick is when we add a supertweeter – the first thing that improves is not the treble, but the bass – it reaches lower, is tighter, and similar. Many reviewers confirm that, regardless of the country and title they work for. Anyway – the HM1 do not go very low, but do not sound thin or bright – far from that. )
Track number 2 from the Chet Baker and Art Pepper disc The Route (Pacific Jazz/EMI, CDP 7 92931 2, CD) is described in the booklet as stereo – mono should be the tracks 9-11. It turns out that this is a mistake, because track #2 named “The Route” is also a mono track. However sometimes, if there is something wrong with phasing in the speakers it sounds a bit like stereo – the treble is a bit to one side, the midrange to the other. The A.D.A.M. Played this perfectly – exactly mono, with a very good reproduction of the characteristic of the recording and mastering – not too good, a bit damped. There are not many sounds in the treble range on the disc, and there is not much happening above 12kHz. If the upper midrange is a bit underlined then the disc sounds in a bit livelier way, a bit more modern. But actually it does not need that kind of “help”, despite being recorded without the edges of the frequency ranges, it has splendid integration and coherence. Brightening on one hand betters the tonal balance, but destroys other assets. Here it was clear why speakers from this company are used in studio's around the world – the tonal balance was reproduced ideally, and the dynamics was superb. Different than in typical studio speakers where the tonal balance is extremely towards the treble, the HM1 sound in a perfectly balanced, slightly sweet, on the extreme top range, way. Despite the speakers being small, due to those assets they were able to show the true size of the saxophone, as well as the weight of the trumpet. The latter instrument, due to the very precise drawing, drawn with a very thin line and strong lead, was very believable in its timbre and attack. And although I mentioned that already I wish to repeat, that the treble is phenomenal – maybe it does not have that precise attack of the SEAS in the Dobermann from Harpii Acoustics, I use, but it had probably a slightly better saturation – and this is really quite a praise. For recommendation, I will cite the fact, that in parallel with the speakers I listened to the same material on my reference headphone system - AKG K701 connected to the Leben CS-300 and heard almost the same treble and upper midrange, something, that speakers rarely achieve in any kind of room. )
At that occasion I found out an element that slightly changes the timbre of those speakers, namely a slight upping of upper bass. The effect is not very evident, but even at a distance of 1 meter from the wall still noticeable. This is understandable, that the constructors wanted to emphasize a little on this frequency range, to equalize the treble, but in the HM2 such kind of tricks was not necessary, because bass sounded there in a natural way. HM1 playing it a bit stronger do not fully fit in the description of pleasant sound. When in the player rotated the disc Deadwings Porcupine Tree (Lava Records, 93437, CD) it was known, that this is a modern multitrack disc, mastered just like it is common nowadays, slightly hard, and with a strong beat on the upper midrange. This is not the refinement of older recordings, like King Crimson, but “the world advanced” and we cannot do anything about that. Here the bass line was very clear, but in the upper range slightly harder, what was heard as if the midrange in the upper range would also be stronger. The effect was not unpleasant due to the treble, but it is worth to remember that the speakers will show what is on the disc, and if we play normal discs the we should think about a warmer amplifier like the Primare I21 or I30. If I had to summarize the sound of those speakers, I would say it is based on the midrange – strong and dense and seemingly – warm. The voices are superbly led, have a good definition, and although they are not brought to the front like in the more expensive speakers of this company, they are stably anchored on the stage. The latter is not very big, and it does not have such a precise instrument localization like the Dobermann or the Marcus. Larger planes are rather shown than singular happenings, the instruments are developed on the stage more legato than staccato. Absolutely brilliant sound the archival recordings, like from the Maria Callas boxed edition Live (EMI Classic, 31466, 8CD), because the intrinsic coherence of those recordings is kept, their musical sense. The only words of caution can be said about the HM1 remembering their bigger brothers HM2. The larger speakers sound better, and do not cost much more. Due to the more unconstrained reproduction of the bass their midrange is better articulated, and the bass more even. But if we search for refined, small monitors and we do want to keep them out of sight, then I warmly recommend the listening to the A.D.A.M. HM1. DESCRIPTION )
The HM1 from the company A.D.A.M. is the smaller brother from the tested in the march issue (No35) „HIGH Fidelity OnLine” model HM2. On the outside it seems identical, except the dimensions of course – this is a two way bookshelf speaker, ventilated with two, mounted in the front, bass-reflex outlets. Shortly we can say that the HM1 are really nice, their proportions predestine them to smaller rooms and for placing them near the wall. The enclosure is made from thick MDF and is varnished with a abrasion resistant silver varnish, and the top corners, those near the tweeter, are cut. The drivers are another story. On top we have the completely ingenious transducer A.R.T. (Accelerated Ribbon Technology), and on the bass and mids we have an equally interesting speaker from Eton with HexaCone diaphragm and 127mm diameter. The way of work of the first one we already learned, the second one is characterized by the fact, that its diaphragm is made from cells in the shape of a honeycomb, to make it extremely rigid. The solid spider is cast, and the (shielded) magnet is large. The connecting cables are of the thick braided kind, soldered and not connected with connectors. The cross-over is not located atop of the terminals, but on the back plate, behind the tweeter. Despite the small enclosure, the cross-over is quite big, it almost encompasses the whole back plate, and this mostly due to the very large, nicely looking polypropylene capacitors (MKP) and significantly large coils – one air type and one core type, with a powder core. Also the resistors look nice, because with the exception of a the plastic one, those are the non-inductive resistors with a 5% tolerance. There is a larger amount of those than usual, because a simple regulator of the amount of the treble is made using those – on the plastic element, serving as the mounting point for the cable terminals (not gold plated, two pairs, looking exactly like those used by KEF Audio) we have a three position switch I-0-II with the corresponding settings of -1.5dB/0dB/+1.5dB, that we can use to set the amount of the treble. The speakers do not have a grille, but due to that fact nothing is spoiling the looks of the front baffle. Let us also mention, that the pairs of terminals are connected together by nice looking cramps made from copper braid.
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