TechRadar Verdict
While hardly a universal solution, the R 907 is arguably the more 'chummy' of Jamo's dipole flagships. Its distinctive character is a love-hate thing – and not just due to the dipole design – but if you fall into the 'love' camp, little else will do
Pros
- +
With powerful bass and an open midrange, the R 907 is entirely free from the overhang and honk a big box can sometimes produce…
Cons
- -
…though it's not free of colorations from the drivers themselves. Also, thanks to the size and weight, this isn't a speaker to be shoehorned into smaller rooms
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The idea is simple: take the flagship Jamo R 909 dipole speaker and make it smaller.
The result is the Jamo R 907 – which despite the design criteria is still one of the biggest speaker systems you can buy.
Jamo's latest open-plan loudspeaker arrives nose-to-nose on a pallet, packed in a wooden case you could sub-let.
Moving the speakers out of the box is just about a two-person lift, and they need a huge room to breathe. In other words, although this is a smaller design than the R 909, it's no less uncompromising.
Distinctive design
Its dipole construction places the R 907 into a relatively rare subset of loudspeakers. A dipole design that uses conventional 'cone and dome' drivers makes even electrostatic speakers seem commonplace. The concept's not without its supporters, though; loudspeaker demigod Siegfried Linkwitz (he who effectively rewrote the book on loudspeaker design, as well as being one half of the double act that brought us the Linkwitz-Riley crossover) is a strong advocate of dipoles.
In simple terms, dipole speakers radiate energy (music) to the back and front of the loudspeaker, by having the drive units on a single baffle board, without any cabinetwork behind that baffle. At a stroke, this eliminates any potential cabinet coloration and hysteresis loops from the air pressure inside the cabinet influencing the motion of the loudspeaker drivers.
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Of course, this only works if the baffle is tough enough to stay the course; the sevenlayer MDf-sandwich front baffle board is 43mm thick, glued and shaped under high pressure.
Rigid baffle
The result is a baffle shaped not unlike the hitty part of a whopping great cricket bat, stuck handle-first in the ground.
The baffle's rigidity is reinforced by a double collection of spikes, nuts, spanners and torture implements. If you don't like to see trailing wires and speaker gizzards, the magnetic rear grilles do a fair job of pretending there's a speaker cabinet.
Cabinets do have a distinct bonus when it comes to bass reinforcement, though, because the air moved to the front of the driver has an alarming habit of scooting round the back of the unit, effectively 'short-circuiting' the speaker below around 200hz. This is why hybrid electrostatic systems from the likes of MartinLogan have a dipole panel unit and a bass driver in a subwoofer box.
Decent bass
Jamo's system does without the box, thanks to a significant bass boost engineered into the crossover, overcoming the 'short circuit' and giving the speaker a gentle 6dB/octave roll-off from its 100dB peak at 200hz.
As such, the R 907 gives workable bass down at around 30hz and – as a handy by-product – the 2x 380mm drive units don't need to be made from relatively heavy materials. They're made from a lighter grade of air-dried paper and have vented pole pieces and baskets and sport 50mm voice coils, all of which is claimed to give them a 30hz resonance frequency and a fast, taut bass response.
Midrange is covered by a 150mm magnesium drive unit, developed in tandem with SeAS, which uses a combination pole piece and back plate in place of a conventional ferrite ring. It also has a ventilated voice coil aided by the solid matt-chromed phase plug. This is similar to the unit found in the R 909, but lacks the Stonehenge-like standing stones magnet arrangement around the voice coil.
Top quality components
The R 909 uses ScanSpeak's legendary Revelator tweeter unit, but the Jamo R 907 relies on an enhanced version of the DTT 28mm multi-coated textile dome tweeter. Unlike the other units in the speaker, the tweeter is enclosed in its own double-damped chamber, so isn't technically behaving as a dipole.
Despite being a three-way, four-drive-unit design, the crossover network is surprisingly simple, with crossover points at 250hz and 2.5khz, straightforward 12dB/octave (or second-order) slopes throughout and a low parts count.
What components are in the crossover are quality, though, with clarity cap foil capacitors and air-coil inductors. Of course, we'd expect nothing other than the best given the rest of the design.
Dynamic loudspeaker
Jamo has a clear objective with the R 907 (and the R 909) – to make a speaker with all the benefits of a dynamic loudspeaker, but none of the limits of a box – and it has largely achieved this goal.
Reading over the listening notes for the R 909, the ever so slightly smaller R 907 does make the tweeter closer to ear height when listening. If your normal listening position is slumped in a couch, though, this will sound like a mid-forward design. This is a speaker that demands your attention, both mentally and physically.
The first thing that hits you is the bass. Literally – bass notes reach you with a physical force that's as impressive as it is deep and powerful. The strange thing is, the bass driver doesn't seem to be moving much air in the process.
Put your hand up against the bass driver of a subwoofer pumping out super-deep bass and each beat will feel like a stiff breeze; with the R 907, the air hardly moves at all. This is because of the dipole arrangement and, in sonic terms, it makes bass seem fast, deep and reasonably well controlled.
Lively performance
Then you realise the bass and midrange are unlike anything you've ever heard before. The sound is extremely fast, making recordings seem more 'live' than usual. Listening to My Drug Buddy by evan Dando and Juliana hatfield (a live acoustic recording made in a radio studio in california), one got the uncanny impression of being sat in the studio with them.
The same thing applied to Seasick Steve recordings, where the speaker's output had precisely the same weight and tonality as Steve's cranked-up Roland cube 30 amplifier, and almost the same volume, too. This doesn't just sound like the recording; it sounds like the artist is making the recording in your room.
This is where the Jamo hits its zenith. Like a panel electrostatic speaker, it has no timing lag from the speaker cabinet, making the sound appear more temporally 'there' than that of any conventional model.
It also has the headroom and range of traditional cone-and-dome speaker drivers, so the sound is far larger, louder and more dynamically impressive than with any electrostatic. In other words, this is like a panel speaker for those who want to play Ac/Dc, or Mahler's eighth at a good lick.
Less versatility
The problem with eliminating the cabinet is that it leaves the nature of the loudspeaker drivers fully exposed. Those box colorations can on occasion be more than benign; they can help calm down frisky drivers. In the case of the Jamo R 907, the top end of the loudspeaker can turn shrill.
This makes the model less capable of handling a wide variety of musical (or more accurately, recording) styles; something with a lot of treble energy – such as early Led Zeppelin albums – quickly moves past 'exciting' and into 'scorching'.
This will make the Jamo unpopular with those who plan on using the speakers hanging off the back of some network audio products. It also means the idea of using the R 907 with almost any amp isn't practical; a few hundred well-designed watts will tame the upper midrange.
Strong character
The character of the speakers will ultimately shine through, whatever you hook them to and whatever you play through them. This is considered acceptable with box speakers because there's no way to eliminate the box colorations, but is not accepted with panels. Which is a shame, because if you dismiss this speaker out of hand, you miss out on a model that's like the Quad electrostatic for rockers.
Most of us equate dipole designs with electrostatics, and that means the Jamo R 907 comes as a bit of a shock, in both good and not so good ways. The good part is the discovery that it can knock out military-grade bass, but with that comes the revelation that removing the box does not remove coloration and the character of those drivers shines through. Which makes this model a sort of 'tweener' product, lying somewhere in between the sheer accuracy of an electrostatic panel and the sheer entertainment factor of a bigbox speaker.
If that sounds like 'compromise' to you, then the Jamo R 907 is unlikely to win you over. If it sounds like 'two wrongs making a right', then it just might be that no other speaker on the market will suit you better than this one.