The Pluto Speakers & Amplifier

[Pluto Speakers in situ]

Siegfried Linkwitz's Legendary Loudspeaker Design

[Italian version]

Product name: Pluto Speakers
Manufacturer: Pluto Speakers
Cost: 2,450 UKP. (Currency conversion)

Reviewer: Mike Cox - TNT UK
Reviewed: February, 2015

For 37 years Siegfried Linkwitz worked for Hewlett Packard at Palo Alto and Santa Rosa, California. With a hobby in audio, Siegfried made his name with the "Linkwitz-Riley Crossover" in partnership with Russ Riley.

Since retiring in 1998 Siegfried has continued his interest in audio, publishing a series of loudspeaker designs on his website.

One of the designs is the Pluto, the details can be seen here:- Linkwitz Lab.

The technical description is very detailed, so if you want more information please take a look.

The basic concept is a two way speaker using an active crossover and the very clever use of PVC or ABS plastic pipe to support the drivers. I was going to say provide the cabinet, but it is not really a cabinet as it is not a box in the normal sense.

What Plutospeakers have done is license the design and then repackage it in a far more domestically acceptable finish. What you get are the speakers, speaker cables and an amplifier with active crossover.

The amplifier has three single ended, RCA phono inputs, active crossover and four power amplifier channels all packaged in a superbly finished, brushed aluminium case complete with a similarly finished remote control.

The speaker cables use a four pole Speakon connector at each end that makes the connection very simple and impossible to connect out of phase. The speakers themselves are beautifully finished in a range, of what looks like, pearlescent colours, like a metallic paint on a car. For your 2,500 you get everything but a source and with the 30 day money back guarantee. A good value package by anyone's standards.

[Pluto amplidier]

Please ignore the smudge marks on the amplifier case, using flash on the camera makes these show up very clearly, yet you cannot see them in normal light.

The speakers have a thick anodised aluminium base complete with shallow spiked feet. They seem insensitive to room placement, no port helps here as does the upward firing bass driver. It took no more than 10 minutes to unpack and set-up the Pluto system before I was able to relax with some of my favourite albums. The remote control seems to have a good range, it never failed to work in my 4m x 5m room unlike some others I have used. It is solidly built device, no cheap plastic remote here.

The volume control is activated by the usual up and down buttons and this aspect is the only complaint I have on the functionality. The volume is relay controlled and they make a loud series of clicks each time the volume is changed.

[Pluto Speakers in situ]

When the amp is switched on the volume starts at zero and increments one step at a time until it reaches the last volume position. The produces a long series of annoying clicks, I am sure there must be quieter relays.

With the remote as well as volume you can select from the 3 inputs and blank the display. You can also power on and off, the display shows a single LED dot to indicate the amplifier is in standby mode.

The unique selling point of this set-up are the looks of the speakers, the rather alien looking mid/tweeter staring at you from above the upward firing bass driver. Rather reminiscent of an alien from war of the worlds.

In Use

Whatever you think of the looks, in use the Pluto speakers plus cables and active crossover equipped amplifier will not fail to impress. Using my regular test tracks from the Tallis Scholars singing the Allegri Miserere you get a detailed sound stage with plenty of the recording venue ambience.

The width of the sound is good extending beyond the speakers with the right material although perhaps a little less depth than the best. The height is good extending above the speakers giving a very realistic scale to the sound stage.

Comparing with the best set-up I have heard in my room (Demand Better Audio Envy 3 with 300B SET amplifier) the Plutos sound a bit dry and tonally thin. This is an unfair comparison as the Plutos are half the price and include the amplifier plus speaker cables. In spite of the small size of the Pluto's bass driver (11cm) the bass has good reach whilst remaining clean with minimal bloating.

As I write this review I am listening to Bob Marley and the Wailers album 'Legend' where the electric bass is clear and the tune is easy to hear. Some set-ups can give a one note bass with the rhythm hard to make out.

Turning to my favourite female singer, Ella Fitzgerald, her voice comes across clearly without any obvious colouration. Again, compared to the best in my room, the voice lacks a little of the richness achieved with the Envy 3 and 300B set-up.

Diana Krall is another of my favourites and the 24bit 96kHz rendering of the "All for You" album comes across beautifully with realistic rhythm and timing. Compared to the best the Diana Krall loses some detail and air though the balance is so good you would never know.

The amplifier design features a number of operational amplifiers (six) assuming it follows the original Linkwitz circuit. My recent experience with discrete operational amplifiers from Sparkos Labs & Burson Audio has shown that they can make a significant improvement.

The tone is richer and more detail is available so I wonder how much the Linkwitz design would benefit from the the original OPA 2134 op amps being replace?


If you were to purchase an equivalent setup the shopping list would be long, speakers, probably stands, speaker cables and amplifier. These days it is getting increasingly hard to find a dealer able to put on a good demonstration.

With the 30 day money back guarantee you can audition in the comfort of your own home and know exactly how it will sound. A system in a dealer's demo room never sounds the same when you get it home.

The fit and finish is excellent, much more robust than the usual wood veneer finished MDF box. The benefits of the unsual design are a low colouration sound with little bloat or overhang to the bass.

I love the looks, though I can appreciate the Plutos may not be to everyone's taste. The colour options should enable the Plutos to fit in most domestic situations. In summary, great value for money for an audio replay solution that does it differently.

Facebook logo

© Copyright 2015 Mike Cox - -