Jason Kennedy gets to grips with the Pluto Ultimate loudspeaker system.
This is one of the more unusual speaker systems I’ve encountered, and I’m not just talking about its appearance, IMHO it makes a refreshing change from veneered boxes. It’s also different because it’s a three box active system that was designed by Seigfried Linkwitz of Linkwitz-Reily crossover fame, a design that has been used by loudspeaker manufacturers far and wide for as long as I can remember. The thinking behind the shape is clearly innovative and combats two of the issues that undermine the majority of box shaped speakers. By putting the tweeter in a housing that’s only slightly larger than its dome you remove all sources of diffraction in one fell swoop. By eliminating the hard edges that cause higher frequencies to radiate in an unnatural way (when they hit them), the speaker should be able to deliver very even dispersion. This matters because it affects the way that the soundstage is projected and how the speaker interacts with the room, it’s a fundamental aspect of loudspeaker design that is compromised by a flat baffle. You can see a similar approach in Bowers & Wilkins 800 series speakers and a number of other high end designs.
The trade off, and there is pretty well always one in audio, is that the drive unit’s output is not reflected by a baffle so it has to pump out more energy to achieve the same sound pressure levels as a box design. The solution that Linkwitz has come up with for Pluto is active operation. This system comes in three boxes; two speakers and one amplifier plus its own dedicated speaker cables. These attractively braided cables have four cores marked H and W for high (frequency) and woofer, this is because the crossover and the power amps are in the control box. It’s not something you see very often but Linn does it with Kiko, the smallest of its systems. It means you can have the control that active operation gives without the drawbacks of having an amplifier in the resonant environment of a loudspeaker cabinet.
The second benefit of the Pluto design is that it houses the woofer or mid/bass unit at the top of a tube, firing upwards. The tube shape is inherently very stiff and its vertical orientation means that extraneous energy can be absorbed in the plinth. The potential drawback is that the rearward output of the driver has to be heavily damped in order to minimise standing waves in the tube, and the volume is not very large, the tube is 78cm high and 10cm in diameter, as they say over there, you do the math. The top of the tube flares out to to accommodate the drive unit which like the tweeter is an aluminium unit. This driver likewise is devoid of a flat surround so should have excellent dispersion albeit upwards rather than toward the listener, this will also undermine its efficiency which is probably why there are 150 watts specced for this part of the system.
The amplifier has four marked inputs and two pairs of RCA phonos that are devoid of labelling, it turns out that they can be employed to bypass the onboard amplifiers should you wish to upgrade this aspect of the system. The only catch is that they are not internally connected, so some soldering skills will be required, and some instructions for that matter. If you are a keen DIYer you could always go the whole hog and build some Plutos at home, Siegfried Linkwitz’s own site is chock full of useful info. You would be very hard pressed to achieve the finish that the Chinese company behind this speaker has done, the speakers in particular are beautifully executed with gold plated feet and terminals plus a great powder coated finish on the aluminium used in its construction.
Setting these speakers up is interesting, their presentation changes more than most depending on how close to the walls they are and the imaging doesn’t really gel until they’re about two or three feet from the rear wall. You get more bass power further back but that is not what the Pluto is about, in fact they strike me as being better suited to 2.1 operation. The bass is not very extended by box standards, it’s clean but lacks power. This can be a tolerable compromise if everything else is strong enough to distract you and they do one thing really well, that is imaging. You’ve heard the term holographic bandied about, well this speaker pretty much does it. And it does it as well as models costing significantly more. The absence of a vibrating box around the drivers really pays off with a soundstage that’s as big as the room will allow but not overblown. Live tracks like Nils Lofgren’s Keith Don’t Go sound spectacular, the atmosphere of the venue crackles and the voice and guitar sound extraordinarily present. This result was not achieved without some tweaking however, primarily with the speaker cable. By replacing the supplied cable with some relatively affordable DNM Stereo made for a significant increase in clarity and pace, you could hear a lot more. The supplied cable allows them to image well but they are more capable than that.
The weakness of the system is that it can struggle with complex rhythms, when a big band starts playing dense material things can get congested. The other limitation is dynamics, it’s not possible to get the energy levels that you can with a conventional speaker and amp pairing of similar price. The rhythmic limitation is only obvious with certain material but the dynamic one is harder to ignore.
The Pluto Ultimate is an intriguing loudspeaker and remarkably good value in material terms, you can’t buy many active speakers for this money and none that come with a separate amplifier and cabling. It is also superbly put together and well featured, if you are after first rate imaging it looks like excellent value, just don’t forget to upgrade the cables at the earliest opportunity.
You will have the chance to hear these for yourself at The HiFi Show at Scalford Hall, on the 2nd of March, in room 73 on the ground floor!
Power: woofer 150 watts, tweeter 50 watts
Tweeter: 43mm inverted aluminium dome
Woofer: 133mm aluminium cone
Equalized woofer and tweeter response,
Crossover at 1000 Hz, LR4 (24 dB/oct)
Volume control: 64-step relay attenuator
IR remote control
Outside dimensions: Footprint 30 x 20cm, Height 108cm
Weight: loudspeaker 20 kg, amplier10 kg
£2,495 (special offer at time of writing, normally £2,995)
Discuss Jason’s review here