Reviewers' ChoiceIn the audio industry, build quality isn’t just synonymous with how well a piece of equipment is assembled, nor is it a measure of how expensive the materials are which constitute the end product. A product’s build quality stems from its innate scientific fundamentals and resulting design, into which are incorporated quality materials and refined assembly processes, to produce a component of high quality and high performance. Build quality is something British speaker manufacturer Monitor Audio takes very seriously, as evidenced by the many successful products they’ve produced since their founding, in 1972.

In 2007, Monitor Audio broke new ground with their Platinum series -- a premium line of six models led by the critically acclaimed PL300 tower speaker ($11,000 USD per pair, discontinued). In 2016, Monitor released the all-new Platinum II line, whose seven models include an all-new flagship, the PL500 II ($28,995/pair). Unfortunately, the size of room this seven-driver, 6’-tall goliath needs to perform optimally disqualified me from reviewing it -- but the model directly below the PL500 II, the Platinum PL300 II ($14,495/pair), seemed a perfect fit for my 21’L x 12’W space. I jumped at the opportunity.

Monitor Audio PL300 II

Engineering quality

At first glance, the PL300 II looks very much like the PL300: Both stand 45.6”H x 16.1”W x 18.5”D with their feet and spikes attached, both are three-way, twin-ported, four-driver tower speakers, and both have leather-clad baffles and are available in the same finishes: Santos Rosewood or Ebony real-wood veneers, or Piano Black, all finished with 11 layers of hand-polished piano lacquer. But the PL300 weighed only 96.4 pounds; the PL300 II tips the scales at 120 pounds. Look a bit closer, and you’ll see that almost everything else is different, too. The front baffle, clad in luxurious Inglestone leather, is no longer concealed behind a one-piece aluminum grille, but is meticulously shaped around the drivers, each of which has its own independently attached, acoustically transparent grille, removable with a magnetic key. The drivers are heavily revised “II” versions of two of Monitor’s Rigid Diaphragm Technology (RDT) drivers -- a 4” RDT II midrange and two 8” RDT II woofers -- as well as an all-new, Micro Pleated Diaphragm (MPD) tweeter.

Monitor’s redesigns of the RDT drivers used in all of the Platinum II models focused on lowering distortion, improving linearity, refining driver sensitivity, and increasing overall power handling. To accomplish these tasks, Monitor’s technical director, Dean Hartley, and his team of engineers scrutinized every facet of the original RDTs, beginning with the Rigid Diaphragm Technology itself. RDT is a sandwich structure originally made from two ultra-thin, low-mass layers of Monitor’s ceramic-coated aluminum/magnesium (C-CAM) alloy bonded to a honeycomb core of Nomex, a flame-resistant meta-aramid developed half a century ago by DuPont. The latest iteration, RDT II, comprises skins of different materials: C-CAM for the front, and woven carbon-fiber for the back. According to Monitor, the differing mechanical properties of the two skins mean that the entire assembly can function better at higher frequencies. The profile of the skins was also revised, to reduce the deformation stresses imposed on the Nomex core and thus maximize the diaphragm’s rigidity. Many different types of bonding were tried to ensure that the finished diaphragm had a superior balance of adhesion and mass. Monitor claims that the RDT II diaphragms, which are barely 2mm thick, not only reduce distortion by over 8dB above 300Hz, they also represent a 60% reduction in harmonic energy, improve damping, reduce mass by 3%, and, overall, produce less distortion than any other driver-cone technology the company has created.

Monitor Audio PL300 II

With the diaphragm construction and geometry refined, Hartley and his team turned their focus to the RDT drivers’ suspensions, voice coils, thermal dissipation, and breathing. To capitalize on the new diaphragms’ greater linearity, they tried to reduce the energy reflected back into the cones by the transition from cone to surround. These efforts resulted in new surrounds of synthetic rubber that are bonded to the cones with a unique adhesive designed to aid in mechanically matching the impedance of the entire assembly. Monitor states that the combination of these improvements further reduced distortion by 6dB from 1 to 4kHz. Propelling the new bass and midrange assemblies are all-new, underhung, edge-wound voice coils outfitted with copper shorting rings to further minimize nonlinear distortion. Each driver is also equipped with a new, patented Monitor Audio technology called Dynamic Coupling Filtering (DCF): a tuned ring of cast nylon that decouples the cone from the voice coil at higher frequencies. The idea is that this ring will act as a solid part up to a specific crossover frequency (500Hz for the woofers, 3.4kHz for the midrange), and, above that frequency, as a damped spring to reduce the transmission of energy between voice coil and cone. Monitor maintains that DCF provides a compound attenuation of 18dB/octave above the specified crossover frequency, further isolating the output between the tweeter, midrange, and woofers. DCF also plays a role in cooling the voice coil by providing venting around it to reduce the power compression and back pressure created by air trapped behind the diaphragm and inside the magnet system.

Dean Hartley used a few other nifty technologies to reduce the buildup of heat in the drivers, such as coating all of the magnets, formers, and voice coils in the bass and midrange drivers, using an anodizing process that turns them almost black in color. The die-cast aluminum basket and steel top plate were also refined, to more efficiently dissipate heat from the voice coil. Finally, the edge-wound, single-layer voice coils of the woofers and midrange were designed to give each turn a thermal path to the outside of the voice coil or toward the coil former. Both the adhesive and the number of turns in each coil were then minimized to eliminate hot spots and maintain consistent temperatures throughout the assembly.

Monitor Audio PL300 II

Dual inverted spider assemblies, designed specifically for the 8” woofers used in the PL300 II and PL500 II and the PLC350 II center speaker, were also developed using extensive finite-element analysis. Their new architecture not only bolsters the suspension system, it reduces second-order distortion by using the system’s own symmetry to cancel out each other’s nonlinearities. In the PL300 II, both woofers “breathe” within the cabinet, which in turn breathes through two revised ports based on Monitor’s HiVe II technology. As in the original PL300, the midrange driver is housed in its own Tapered Line Enclosure (TLE), to isolate it from the rest of the speaker’s interior. The TLE, cast from Monitor’s Anti-Resonance Composite (ARC), a thermoset polymer, and filled with mineral damping to reduce internal standing waves, has been refined in the PL300 II to better complement the new midrange driver. The woofers and midrange are affixed to the cabinet with bolt-through construction designed to ensure uniformly consistent clamping of each driver without the use of mounting rings.

As if all this weren’t enough, the PL300 II has a brand-new MPD tweeter claimed to provide superior transient response, better damping, flatter impedance, and improved diaphragm and magnetic geometries over the ribbon tweeter in the PL300, as well as being more sensitive and able to handle higher levels of power. Fundamentally, the new tweeter is an adaptation of Dr. Oskar Heil’s Air Motion Transducer (AMT), but differs in having shorter rolls, and more of them, to increase its surface area. Monitor says that this approach eliminates the -3dB nulls at 28 and 40kHz inherent in standard AMT tweeters, and simultaneously increases the driver’s sensitivity to 94dB/W, and extends its uniform output to beyond 100kHz. Its greater surface area also means that the MPD needs to travel only about one-eighth as far as a conventional tweeter’s dome to produce the same amount of output -- when attenuated to the PL300 II’s overall efficiency of 90dB, the MPD’s power handling is more than doubled.

Monitor Audio PL300 II

Internal wiring of silver-plated, oxygen-free copper (OFC) connects all of the PL300 II’s new drivers to a brand-new crossover network. This network uses air-core inductors in the midrange and tweeter sections, and laminated steel-core inductors in the bass section -- Monitor says that this ensures both low resistance and, where needed, high levels of damping. Custom-made capacitors of metalized polypropylene are individually selected to ensure variations in tolerances of less than 1%, while aluminum-clad attenuation resistors maximize heat dissipation and power handling. The crossovers in all Platinum II speakers are fed signals through innovative, rhodium-plated terminals milled from solid copper and capable of accepting spades, 4mm banana plugs, or bare wires. These new terminals were not only a pleasure to use, but exuded quality and ingenuity, the latter evinced by a slip ring inside the terminal body to ensure that spades or bare wires won’t turn as the connector is tightened.

The cabinets of all Platinum II speakers, too, are decidedly different from their Platinum counterparts, and are among the most beautiful examples of craftsmanship in the high end. The front baffles, which range in thickness from 10 to 20mm, are, like the midrange driver’s TLE enclosure, made from Monitor’s Anti-Resonance Composite (ARC). The cabinet’s rear and side panels comprise a single piece of laminate: seven layers of 3mm-thick MDF formed in an RF wood-bending machine and, simultaneously, bonded using a unique high-strength epoxy that cures stronger than the MDF panels themselves. The result is a dense, one-piece structure that’s far more rigid than three separate panels could be.

Monitor Audio PL300 II

The interior of the PL300 has also been significantly redesigned for the II, with additional bracing to form a more compartmentalized, more rigid enclosure. Furthermore, all interior cabinet walls have been coated with coal-tar mastic, aka bitumastic, to provide another layer of mass damping to help absorb any residual energy. Supporting the 120 pounds of each PL300 II is a newly designed plinth, finished in gloss black with a black-anodized surround, and two support options: for carpets, bullet spikes of high-tensile, chrome-plated steel; or, for scratch-sensitive floors, black-anodized pucks of a high-grade alloy, with rubber pads.

Dancing with the Devil

After removing the Platinum II PL300 IIs from their substantial, braced, double-boxed packaging, the angel perched on my right shoulder demanded that I stop to take a good look at their gorgeous finish. The flow, stain, and polish of the Ebony veneer were flawless, and the baffles’ Inglestone leather, so supple and expertly applied, was a pleasure to touch as I began positioning the speakers.

Kimber Kable KS-6063 speaker cables tied the PL300 IIs to my Simaudio Moon Evolution W-7M monoblocks, while Clarus Crimson interconnects linked my Simaudio Moon Evolution P-8 preamp, Wadia di322 DAC, and Dell Ultrabook computer. Power was drained from my wall in true Griswold fashion by a Torus AVP20 power conditioner and distributed by Cardas Clear Beyond power cords.

Monitor Audio PL300 II

The wiring done, I began dialing things in using a laser. I typically align speakers so that their tweeter axes cross about 2’ behind my head. With the Monitors, this provided decent first results: the bass was deep and powerful, with easily enough body to energize my room; the midrange was rich and focused, yet fell just short of holographic; and the top end was smooth and refined, though lacking in sparkle and attack. Over the following weeks, as the PL300 IIs broke in, I tweaked their positions so often that I began to feel as if I were dancing with them. Eventually, everything clicked: the PL300 IIs performed best when each speaker was a little more than 2’ from its sidewall, 5’ from the front wall, just over 9’ from my listening seat, and toed in about 13°.

Let the good times roll

With everything set up, connected, broken in, and optimally positioned, the devil who squats on my left shoulder began calling the shots. The PL300 IIs sounded remarkably good at low to normal listening levels, but were absolute demons when played loud -- and man, could they go loud: 117dBA. Stan Lynch’s drums start off Stevie Nicks and Tom Petty’s collaboration on Petty’s “Stop Draggin’ My Heart Around,” from Nicks’s Bella Donna (16-bit/44.1kHz FLAC, Atco/Modern), and through the Monitors they had tremendous impact. Then, with Ron Blair’s bass, the PL300 IIs put forth serious foot-tappin’ slam, begging to be turned way up. I failed to find any volume limits for Hartley’s new drivers -- and trust me, I tried. Each kick of the drum sounded crisp, punchy, and obvious in its accuracy, and likewise Blair’s bass -- though I noticed that, beyond a certain point of indulgence, bass notes became more bloated than controlled. However, as this was more the PL300 IIs bullying my volume-shy room into submission than any fault of the speakers, I can’t really ding them for that.

Listening at civilized yet still spirited SPLs, I reveled in the PL300 IIs’ emotive bottom end. Both the kick of the drums and the rhythmic drive of Blair’s bass were as distinctive and well defined as they were fun. The image of Nicks’s voice appeared dead center on the stage with fulsome solidity, and was defined in space with enough image specificity to easily hear the space between her and Petty as they sang from either side of the mike. Petty’s electric-guitar notes were expertly resolved, clear in their intended intensity, and locked into their positions onstage, with a warmth of tone that I can’t really appreciate through my reference Rockport Technologies Atria speakers. The PL300 IIs also did a commendable job delineating Benmont Tench’s keyboards, a task often muddled by less-resolving speakers.

Monitor Audio PL300 II

Listening to “I’ll Be Your Lover, Too,” from Van Morrison’s His Band and the Street Choir (24/192 FLAC, Warner Bros.), I was again treated to a vast, precisely illustrated soundstage. Morrison was positioned center stage, sounding larger than life, with his acoustic guitar to the right, complemented by John Platania’s acoustic guitar to the left. If “Stop Draggin’ My Heart Around” revealed the PL300 II’s character, it was with this Morrison track that I began to realize the speaker’s competencies. As I played it over and over, I consistently appreciated the levels of refinement and control with which it reproduced the sound of every instrument. Morrison’s and Platania’s guitar notes possessed bite and tonal color and expressed emotion, yet without any sort of aggression. The image of Morrison’s voice was particularly holographic, supplemented by massive dynamic attacks, and a naturalness and scale that greatly contributed to the realism of what I heard. I very much enjoyed listening to this and other Morrison tracks through the PL300 IIs with the lights down, glass of wine in hand. It was easy to get lost in the feelings his music evoked in me through the Monitors -- and that, in itself, speaks volumes about the transparency of this speaker.

I was similarly moved when listening to the title track of Chantal Kreviazuk’s In This Life, in which she’s accompanied by Bradley Thachuk conducting a chamber ensemble of players from the Niagara Symphony Orchestra (16/44.1 FLAC, Pheromone). Recorded live in summer 2011 at the Jackson-Triggs Theatre Stage, in Niagara, Ontario, this album’s hauntingly realistic sound puts me smack in the middle of the concert, especially when my gear is up to the task. The PL300 IIs not only “disappeared” from my room, they seemed to push the walls out a few feet and placed Kreviazuk and her grand piano just left of center stage -- precisely where they should be. Even my ceiling seemed to disappear -- I was treated to an illusion of space that I usually experience only with speakers more in line, performance-wise, with my Rockport Atrias. I set out to listen only to “In This Life” and take a few notes, but that didn’t happen. I laid my computer aside, dimmed the lights again, and listened to the entire album.

Monitor Audio PL300 II

Having seen Kreviazuk in concert at least eight times, I’m quite familiar with how she sounds in a live setting, and throughout all of In This Life the PL300 IIs nailed the liveliness in her voice and created the illusion of my being a member of the audience. From track 1, “Surrounded,” the sound of Kreviazuk’s piano had bite, warmth, and delicacy, yet was consistently chock-full of harmonic dynamism when that was called for -- an aspect, I’ve learned, of her playing. Later, in a cover of Randy Newman’s “Feels Like Home,” as Kreviazuk exercises her vocal power in the choruses, the PL300 IIs did nothing to limit the intent behind her efforts. I was pleasantly surprised at how cleanly, dynamically, and naturally the Monitors portrayed this singer -- these passages can sound a bit shouty at higher volumes through other speakers, particularly my Rockports.

Listening to “In This Life” through the PL300 IIs immediately reminded me of the first time I saw Kreviazuk in concert. The venue was a small bar that seated maybe 50 people, and I sat in the third row, only about 12’ from her piano. As she struck each key, I remember how powerful her piano sounded, yet how her voice dominated as she effortlessly sang lyric after lyric. I heard this same visceral realism and coherence when I listened to “In This Life” through the Monitors -- the nature of the recording and the commanding yet refined character of the PL300 IIs worked together to bring back to life my memories of that first concert. Kreviazuk’s piano notes oozed tonal color with, again and again, effortlessly conveyed weight and impact when those were called for. The decay of each note clearly originated from the same place on the soundstage, yet quickly began to float in the room, only to be eclipsed by the attack and decay of the next note, and then the next. The Monitors’ reproduction of this recording was so alive that I was presented with a delicious dilemma: Should I focus on Kreviazuk, or continue to try to dissect the sound of her piano? But either way, the PL300 IIs themselves were nowhere to be heard.


Consistently throughout my time with them, the Platinum II PL300 IIs had one shortcoming, though it took me a while -- and side-by-side comparisons with my Rockport Atrias ($25,500/pair, discontinued) through a few different amplifiers -- to define it. In short, the PL300 IIs could use a hint more top-end sparkle. They easily reproduced such nuances as string detail, air around objects, precision of imaging, and, in general, bite; missing was that one step further, that last iota of inner detail. For example, the shimmer of brass in Stevie Nicks’s recording of “Stop Draggin’ My Heart Around” was easy to hear, but it was a smidgen more elusive through the Monitors than through my Rockports. The echo behind Van Morrison’s voice in “I’ll Be Your Lover, Too” was clearly audible through the PL300 IIs, but it sounded a shade darker and thus not as easy to hear as it is through the Rockports. Likewise, when I focused on the strings of Morrison’s or Platania’s acoustic guitar, the bite and the texture were there, but the decays didn’t last as long through the PL300 IIs.

Monitor Audio PL300 II

Still, it was all too easy to forget that the Monitor PL300 II costs only $14,495/pair -- it performed at levels achieved by speakers costing far more. The PL300 II’s subtly “polite” sound actually enhanced their reproduction of Chantal Kreviazuk’s In This Life, erasing any hint of aggression in her voice at loud volumes -- I preferred listening to this album more through the Monitors than through the Rockports. There was also an appreciable difference in how the two speakers reproduced bass notes. The Monitors consistently provided more slam, kick, and energy in the lower octaves, particularly at lower volumes. They also sounded able to go quite a bit lower than their specified low-end limit of 28Hz, and instilled in me more confidence when played at higher volumes in a home-theater environment. By comparison, the Rockport Atrias’ bottom end was subtler, more articulate, and better defined, and more accurately communicated such details as textures, the vibrations of strings, and changes in pitch.

Summing up

I had to split hairs to find problems in Monitor Audio’s Platinum II PL300 II, particularly at their price of $14,495/pair. The speaker’s fit and finish are exquisite, its build quality is exemplary, and the science behind its design and development is as beyond reproach as its sound. If I could afford to buy a $14,495 pair of speakers and keep my Rockport Atrias, the PL300 II would be my choice seven days a week and twice on Sunday. I don’t have that kind of money lying around, so I’ll have to sadly, grudgingly send the PL300 IIs back to Monitor. But not before awarding them a Reviewers’ Choice award.

. . . Aron Garrecht

Associated Equipment

  • Speakers -- Rockport Technologies Atria
  • Subwoofers -- JL Audio Fathom f112 (2)
  • Amplifiers -- Rotel RMB-1585 (five-channel), Simaudio Moon Evolution W-7M (monoblocks)
  • Preamplifiers -- Anthem AVM 60, Simaudio Moon Evolution P-8
  • Sources -- Oppo Digital BDP-103 universal BD player, Dell E7440 Ultrabook laptop computer running Windows 10, JRiver Media Center 20
  • Digital-to-analog converter -- Wadia Digital di322
  • Cables -- Clarus Crimson S/PDIF, USB, and interconnect; Kimber Kable Select KS-6063 speaker; Cardas Clear Blue Beyond power cords
  • Power conditioner -- Torus Power AVR2 20A

Monitor Audio Platinum II PL300 II Loudspeakers
Price: $14,495 USD per pair.
Warranty: Five years parts and labor.

Monitor Audio Ltd.
24 Brook Road
Rayleigh, Essex SS6 7XL
England, UK
Phone: +44 1268-740580
Fax: +44 1268-740589


North American distributor:
Kevro International
902 McKay Road #4
Pickering, Ontario L1W 3X8
Phone: (800) 667-6065, (905) 428-2800
Fax: (905) 428-0004