Jamo Reference 909 Speakers (WOW!!)

And as I tried hard to find an answer, I could think of nothing that wouldn’t point, somehow or other, back at its dipole bass. The essence of the R909 cannot lie, for instance, in being a planar speaker with all the well-known advantages related to such designs (fewer side-wall reflections, no cabinet-induced resonances etc.). For even though the R909 is a planar speaker, so are all the full-range electrostatics and magnetostatics.

Full-range dynamic dipole speakers are not from another world. The concept is well known and much explored by DIYers here in Finland for instance. In fact Risto Niska, one of my audiophile colleagues, was fed up with the singing of the boxes and their phase nonlinearities so he built himself such a dipole ten years ago and has been happy ever since. No wonder then that when I first showed him pictures of this Jamo, he shrugged them off: “Nothing special!”

I myself have used folded and open-backed baffles of different sorts to house dynamic wide-band units. These differ from the R909 only in being much larger and not using any filter network to correct the frequency response. Commercial models are not that common, though. There’s the Linkwitz Orion of course, with Siegfried Linkwitz being the long-time spokesman for full-range dynamic dipole loudspeakers. Perfect 8 has a model called The Force but even they recommend a subwoofer for the bottom octave. BD-Design’s Quasar MkII DIY is similar to the Jamo R909 and the Acoustic Plan Veena is yet another one. Legacy Audio’s Whisper and the Gradient Revolution are famous for their dipole bass but their midrange drivers are in a cabinet. (Gradient further manufactures dipole subwoofers for Quad 57s and 63s.) Now Jamo, under the supervision of Henrik Green Mortensen, has gone after the idea full hog, nine long years after building up the gumption to do so.

What unites all of the above speakers is their designers’ conviction that for the most pure and articulated bass, one should never use a box whether sealed or ported. In fact, it’s possible to read the R909’s White Paper to imply that getting rid of a box with all the adverse effects that come along with it was the main goal of its design – “to deliver an exceptionally memorable listening experience” the real goal by extension.

Issues to be considered in this context are, however, more conventional in nature, mainly having to do with the quality of the drivers and the way in which they are made to cooperate. These are important questions but not unique. The majority of serious speaker designers and manufacturers today seek development of their speakers through advanced driver technology. In Jamo’s case, this is even more understandable given that the drivers meant for conventional box speakers cannot as such be fitted into a box-less dipole speaker, most especially the woofers. Custom units were called for.

As a consequence, the white paper claims, the HF region of the 909 has “an incredibly smooth, linear, dynamic and incredibly transparent sound”. I quote the white paper here verbatim because throughout this review I want to take its sentences as reflecting truth, not mere marketing mumbo-jumbo. That is, I’m going to have a serious dialogue with this material. I think this speaker deserves it.

I also pushed the tweeter with Teleman’s Flute Fantasias, Purcell’s Sonatas and various period music to further test its mettle. All these records contain sounds that can be challenging to tweeters. The flute or recorder for example produces low-level whistling sounds that should be audible but never become unpleasant sibilants. Unpleasant sibilants weren’t a problem of the R909. The fact that the speaker’s response extends fairly low helps here too as the subjective aggressiveness of certain HF sounds is partially a function of overall tonal balance.

Due to this character, the speaker can also take to sounding somewhat brassy and coarse. This happens when no lower midrange frequencies are present, when the instruments in question have a nasty, aggressive timbre and — this is important because it very much pertains to the 909 — no artificial reverberations are provided by the room. But note, harsh and nasty is exactly how a speaker should sound under those conditions. A pure and flat lower midrange may not appear to be a big achievement but only after having heard a truly clean lower midrange does one become aware that this property is by no means ubiquitous even in otherwise competent speakers. If this quality of the midrange is what Jamo means by “precise” then I cannot but agree wholeheartedly. If they refer to something else altogether, then I’m out of the loop.

The basics of this design, as you recall, are its dipole bass. The dipole bass means that the woofers are radiating the sound freely in both directions, forward and backward. From a bird’s eye view, the radiation pattern looks like a figure eight. Many things are to be considered in this connection but the by far most urgent problem inherent to all dipolar designs — whether dynamic, electrostatic or other — is how to overcome the weak bass performance due to acoustic short-circuiting. That is, how to prevent the out-of-phase wave forms from canceling each other.

Jamo’s tactic has been to choose woofers that are efficient enough and sport a sufficiently low self resonance. Twin 15-inchers per side equate to the air displacement potential of six 8-inchers or >100dB/1m @ 200Hz according to Jamo. Next, the top end of the woofer spectrum around 250Hz has been low-pass filtered at 12dB/octave to couple with the midrange while leaving the lowest frequencies untouched. This takes care of dipole correction and allows the response to reach the 25-30Hz range with sufficient output.

Much has been made of a dipole’s rear radiation – how it makes the sound too big and spacious, how it obscures image specificity and so on. The sound reflecting off the back wall can be controlled and the reflections tamed by trying different angles as per Jamo’s suggestions. My listening notes do not contain complaints about soundstage and imaging but that may be because I’m accustomed to such a big and relaxed sound from my PHY open baffles above. The sound images weren’t sharp-edged in the audiophile sense nor were they unintelligible or diffuse. These things are largely a matter of taste. Open-backed baffle speakers can be critical of incident angle, so it’s always worthwhile to experiment.

I asked Jamo about amplification and got a list of brands that probably would work well with their R909: “Mark Levinson, McIntosh, Krell, Holfi, Accuphase – the bigger the better. No digital amps, thank you.” I used my 200wpc MidFi Sony and equally powerful Plinius 9200 integrated. Just for curiosity, I tried my 10wpc 6V6 amp too and was amazed by how well the tubes did on these 86 – 88dB panels. In the end, I did switch back to the transistors not only because I felt that the valve advantages in the midrange were not sufficient to offset the lack of control in bass, but because throughout listening to the R909, I got this impression that its sound policy operates on a macro rather than micro level. Discrete differences in the tone color between various amps aren’t a matter of life and death with this speaker. The sound is not transparent in that sense.

When listening to good dipole bass, one begins to question whether one has ever really heard proper bass before. Thousands of audiophiles (me included) have probably used the Mission Impossible sound track to impress visitors with. How many of them have heard the bass as it was recorded? If you have doubts, try the 909. If the truth hurts, you can always resort to the common reaction. I can assure you that once you experience quality dipole bass, it’s hard to go back to boxed bass regardless of whether one otherwise likes dipoles or not.

Too much bass? I’m sure people who mainly listen to studio productions with electric bass guitar in the main role or in which electronic devices produce unnaturally low bass — and who are audiophiles enough — could argue that the R909’s low-to-mid bass is plentiful or something to that effect. But let’s be careful. Once again, dipole bass is unlike boxed bass: even when excessive, its appearance is not what we would normally expect from a box speaker. When listening to music, the R909 does not force the listener to focus on its bass in a way many box speakers do. When the low bass of R909 gushes forth — and it does with Chris Jones for example — one cannot criticize it by normal standards. My favorite test for the nature of the bass is Vivaldi’s sonata for cello and basso continuo. Poor bass reproduction here resembles cheap headphones. While the R909 did add extra growl to the cello and basses, it wasn’t excessive in the least.

Another potential source for midrange colorations is the baffle itself. Jamo’s baffle is well prepared for such threats. It’s 1.7in/43mm thick, made of seven layers of MDF board and attached to a 60lb/26kg cast-iron base. A solid double 5x60mm stainless steel brace with a special damper keeps the baffle connected to the base. Each 909 weighs almost 70kg each. I didn’t hear any acoustic energy around the speakers that I would associate with resonating baffles.

Jamo concludes: “It is a speaker that produces a sound quality which can be described as being firm, accurate but with sublime attack, precision and dynamics. Significantly, it also benefits from the absolute absence of unwanted coloration and reverberation.” I sign most of that to varying degrees, with a huge Yes going to sublime attacks and dynamics. Note how the word ‘music’ isn’t mentioned anywhere. It would be too hasty a judgment that music means nothing to Jamo but I think leaving the word out of this picture tells us about Jamo’s preference to offer to music lovers a platform that will play back any music they happen to like.

Of course each of us has his or her own favorites. My favorites — the sort of chamber and contemporary music that is light in sound but heavy in substance — worked fine over the Jamos, albeit sans the special treatment my personal reference system provides. But it didn’t fail either and that’s a good sign. In addition, the Jamos’ strong and authoritative sound made me feel like playing some unlikely personal choices such as certain choral and orchestral works I enjoy far too infrequently (Rachmaninov’s Piano Concertos sounded majestic).

There’s one aspect of the sound that I think would deserve more attention than I’m able or competent to give here. That’s how the sound of the R909’s dipole bass (or that of any other dynamic dipole speaker for that matter) translates to music. HiFi literature is filled with many deserving descriptions of how dipole bass sounds in comparison to its boxed competitors yet I haven’t seen much written on what that all means in terms of music. It’s not proper to state that dipole bass sounds great if there’s no musical counterpart to that greatness.