We then listened to selections from a few CDs. The sound was so good that I had difficulty maintaining the requisite\u00a0Stereophile\u00a0reviewer’s poker face. However, Sheldon Ginn knew the reviewing protocol well enough not to ask what I thought of the sound, and the Kevro team departed. I continued listening for a while, tweaking the speaker positions a bit. Then my wife and I went out for lunch, leaving Monitor Audio’s\u00a0Bringing Sound to Life: System De-Tox Disk\u00a0(CD) playing on repeat.“How do you like the speakers?” she asked. A reviewer’s spouse is allowed to ask such questions.“It’s too soon to say. Right now, I’d say they sound\u00a0really\u00a0good. But I’ll have to do much more listening. I’ll also have to think about how they compare with the Wilson Sabrinas, which I liked a lot.”“You poor boy.”“Yes,” I said with a heavy sigh. “It’s a dirty job. But somebody has to do it.”DesignApart from having three grilles for its four drivers rather than a single grille covering all, the Platinum PL300 II looks identical to the model it replaces, the Platinum PL300. Both have pair-matched veneers of natural wood (Santos Rosewood on the review samples), hand-coated with 11 layers of clear-gloss lacquer and polished to reveal the luster in the grain, with the front baffle covered in Inglestone leather. The speakers are simply gorgeous, with a quality of finish easily up to that of fine furniture.The changes from the original PL300 are on the inside, and involve almost every aspect of the speaker’s functioning. The first indication of these is the weight: the PL300 II weighs 120.0 lbs, compared to 96.4 lbs for the Series I. Sheldon Ginn told me that the greater weight of the PL300 II is attributable mostly to its drivers (magnets, etc.). The price of the PL300 was $11,000\/pair, compared to almost $15,000\/pair for the PL300 II. If you’re the sort of person who judges the values of audio components on the basis of cost per pound, the PL300 II is just a bit more expensive than the PL300. But that, of course, is saying nothing about either model’s technology or sound quality.At the top of the PL300 II’s cabinet is what represents the greatest change: the tweeter. The Series I had a ribbon tweeter, whereas the Series II uses, for the first time in a Monitor Audio product, a version of the Heil Air Motion Transformer (AMT), a kind of folded ribbon used in various forms by a number of manufacturers. According to a\u00a0Monitor Audio white paper\u00a0on the design of the Platinum II series, AMT tweeters typically have a null in their frequency response at 40kHz, with a \u20133dB point at about 28kHz. Research by Monitor engineers found that this null could be eliminated by reducing the roll height of the diaphragm and increasing the number of rolls, the result being what they call a Micro Pleated Diaphragm (MPD). According to the white paper, the elimination of the null allows the MPD to produce uniform output to over 100kHz. Compared to dome tweeters, or the ribbon tweeter used in the Platinum I models, the MPD has a much greater surface area that requires less excursion to produce a given output, resulting in higher sensitivity and higher power handling.Other improvements claimed for the MPD tweeter are flatter impedance, better damping, superior transient response, lower distortion, and “a clean sonic character free of any harmonic artefacts.”Monitor’s Rigid Diaphragm Technology (RDT) midrange and bass drive-units, used originally in the Platinum Is, have undergone substantial development, and are now designated RDTII. As with the MPD tweeter, a high priority was the reduction of harmonic distortion. The specific technical improvements are too numerous to describe in detail here; suffice it to say that distortion above 300Hz is said to have been reduced by 8dB, which represents a 60% reduction in the energy of harmonic components. The 4″ RDTII midrange driver has uniform output to over 6kHz\u2014more than an octave above the frequency (3.4kHz) at which this driver hands off to the tweeter. The crossover’s midrange and tweeter sections use air-core inductors to minimize distortion and component interaction, with custom-made, 1%-tolerance, metalized polypropylene capacitors selected, by means of extensive listening tests, for best sound quality.Monitor’s technical director, Dean Hartley, is particularly proud of the company’s new, patented Dynamic Coupling Filter (DCF), a nylon ring that fits between the voice-coil and the cone. The DCF acts as a solid part up to the crossover frequency, but above that frequency it acts as a damped spring, effectively adding a mechanical first-order filter to complement the electrical network, to result in a compound attenuation of 18dB\/octave.Nor have the PL300 II’s mechanical components been neglected. Improvements thereto include: 1) the curved, multilayered cabinet, cast in Monitor’s Anti-Resonant Composite (ARC), a thermo-set polymer loaded with minerals; 2) new internal bracing for structural integrity; 3) long bolts tightened to a specific torque to secure the drivers to the cabinet; 4) Bitumastic internal damping; 5) Tapered Line Exposure (TLE), a tapered, parabolic enclosure for the midrange drivers, also cast in ARC; 6) the second generation of Monitor’s Hi-Velocity Vent technology, which accelerates the flow of air through the speaker’s ports while reducing turbulence; and 7) rhodium-plated copper speaker terminals.In discussing the design of the Platinum II models, Dean Hartley\u2014who has been with Monitor for 18 years\u2014said that the design has benefited greatly from the use of computer modeling, which, he says, “can take you . . . maybe 95% of the way there.” The development of the Platinum IIs began in 2014, and, in addition to computer modeling, involved building a lot of prototypes. “We still use our ears!”TweaksI began listening to the Platinum PL300 IIs with my\u00a0McIntosh Laboratory MC275LE, a tubed power amplifier with separate output terminals for connecting loudspeakers with impedances of 4, 8, or 16 ohms. In my review of the Wilson Sabrina, I found that while the Sabrina is specified as having a nominal impedance of 4 ohms, I preferred the sound through the Mac’s 8 ohm terminals. The PL300 II is also specced at 4 ohms, and I thought that it, too, might sound better through the MC275LE’s 8 ohm terminals. But not this time. The sound through the 4 ohm terminals was more coherent, with, apparently, better integration between the drivers.The PL300 II’s two rear-firing ports load only the bass drivers; the midrange-and-tweeter module has its own sealed cabinet-within-a-cabinet. When I first talked with Sheldon Ginn about reviewing one of the Platinum II models, he gave me a choice: the PL200 II or the PL300 II. I’d reviewed the PL200\u00a0six years before, which might have made the PL200 II the obvious choice, but I was interested in what Monitor could do with a speaker a step higher in size and price\u2014a price about the same as that of Wilson’s Sabrina, which I’d just reviewed. Ginn said that the original PL300 had a bass response that tended to overload rooms as small as mine (16′ long by 14′ wide by 7.5′ high), and that considerable effort had been made to ensure that the PL300 II would provide a more neutral bass response in a wider range of environments, including the small rooms that are common in the UK (and in my house). He thought it would be a good match.As soon we set up the speakers, and before any serious attempts at optimizing the speaker positions, it was obvious that bass overload was not going to be a problem. Nonetheless, each PL300 II comes with two port bungs\u2014foam inserts that effectively turn this ported design into a sealed box, reducing the possibility of bass boom. I thought I’d better give them a try.I listened to the speakers first with the ports open, then with both ports plugged, and, finally, with only the bottom port plugged. The sound with both ports plugged was too lean. With only the bottom port plugged, the difference was more subtle, but after going back and forth, single bottom port plugged and then unplugged, and listening to music with considerable low- and midbass content, I decided that I preferred the sound with both ports open. Later listening with Theta Digital’s high-powered, solid-state\u00a0Prometheus\u00a0monoblock amplifiers\u2014which provide better control over bass response\u2014didn’t change this conclusion.The original PL200 and PL300 each had a single metal grille that covered the entire front of the speaker; these were magnetically attached, which made it easy to compare the effects of the grilles on the sound. (Like most speakers I’ve reviewed, the PL200 sounded better without its grille.) However, the PL300 II has separate grilles for the tweeter-midrange module and each woofer, and they’re attached differently; installing or removing them requires a special tool (provided). The owner’s manual provides no instructions in the use of this tool, and even Sheldon Ginn had trouble figuring out how to use it. (Hint: think\u00a0can opener.)A white paper on the Platinum II series states that the grilles were designed to be acoustically transparent: the sound should be the same, whether they’re on or off. That’s pretty much what I found. In fact, if anything, I had a slight preference for the sound with the grilles. When I asked Dean Hartley about what might account for this preference, he told me that while the design aim was for the grilles to be acoustically transparent, the speakers were voiced with the grilles on, so one might expect them to sound better that way. So that’s how I did all of my critical listening.The PL300 II comes with a plinth that allows leveling (a spirit level is included), and a set of spikes that the manual recommends using on carpeted, not wooden or hard floors. My listening room has a wooden floor, so I first listened to the speakers without spikes. (The speakers have integral rubber pads.) However, I’ve reviewed a number of speakers that sounded better in this room with spikes, and felt I should try them with the PL300 IIs.Whenever I try a tweak, I go back and forth several times, trying to determine a) whether the tweak makes an audible difference, and, if so, b) whether the difference is a positive one (better, more natural sound, higher resolution, etc.). Comparing the sound of any floorstanding speaker with or without spikes is not that easy: you have to be very careful not to shift the speakers’ positions in any other way. Sheldon and Jeff Ginn (they’re brothers) made another house call, and we compared the PL300 IIs’ sound with and without the spikes. There was a difference, but it was marginal, and required swapping the spikes in and out several times before I could get a handle on it. In the end, we decided that the bass was a bit tighter with the spikes, but it was a close thing. If you owned these speakers, and were concerned about spikes causing damage to a wooden floor, I would suggest using the speakers without spikes and just not worrying about it.The owner’s manual suggests running-in the speakers with 50\u201370 hours of playing Monitor’s\u00a0System De-Tox Disk, and notes that, “like fine wine, the performance will improve with age.” I’m a believer in break-in\u2014I’ve reviewed speakers for which it had an obvious positive effect\u2014but in the case of the PL300 II, any improvements were minimal. I was later told that my review samples had already gotten 50 hours of break-in at the factory.ListeningThe original Platinum PL200, listed in Class A of our “Recommended Components,” was one of my favorites of the speakers I’ve reviewed. I first heard its successor, the PL200 II, at the 2016 Consumer Electronics Show, where it impressed me as representing a significant improvement over the already excellent original. My expectations for the Platinum PL300 II were high.However, my experiences with the PL 200 and PL 200 II didn’t prepare me for the sound of the PL300 II. Right out of the box, the PL300 II had an utterly natural sound that drew me into the music.The sound heard from a loudspeaker can be thought of as having two components: the music the speaker is supposed to reproduce\u2014ie, the recording\u2014and the characteristic sound of the speaker itself, which is a function of the speaker’s mechanical and electronic components. The ideal speaker, of course, would have no sound of its own; every sound made by the speaker would be a precisely accurate reproduction of a sound originally contained on the recording. The ideal speaker doesn’t exist\u2014or if it does, I haven’t heard it\u2014but speakers vary in the extent to which the sound they produce is their own, as opposed to a faithful reproduction of the recording, with nothing added and nothing taken away.The first speaker I heard that impressed me with its lack of “speaker sound” was the original\u00a0Quad ESL. Compared to the Quad, with its planar electrostatic drivers, speakers with conventional woofers and tweeters in a box sounded like . . . well, speakers. Of course, the Quad had its disadvantages\u2014it wouldn’t play loud or go low\u2014so some people combined it with a subwoofer, to extend the bass and, with a suitable external crossover, increase its dynamic capability. But this had a cost: it brought back some of the “speaker sound” the Quad hadn’t had to begin with\u2014and the ESL still couldn’t play\u00a0that\u00a0loud.The decades that have passed since the introduction of the ESL-57 have seen many advances in drive-units, based on a variety of technologies. As speaker designers have become more aware of the importance of controlling cabinet resonances and spurious resonances within the drivers themselves, speakers have come to have less “speaker sound.” The PL300 II is an outstanding example of this trend; it had less “speaker sound” than any loudspeaker I’ve reviewed.My favorite musical instrument is the human voice, and I find that vocal recordings are particularly revealing of “speaker sound.” With the PL300 II\u2014again, more than with any other speaker I’ve reviewed\u2014the sounds I heard from vocal recordings were overwhelmingly those made by the singer, not the resonances of the speaker reproducing the voices. The\u00a0Wilson Sabrina, while undoubtedly excellent, and a speaker that I greatly enjoyed listening to, sounded more like a speaker. In the PL300 II, Monitor Audio has managed to reduce distortion and nonmusical resonances to a degree that made it easier to imagine that I was listening to live singers.This was apparent not only when I played audiophile recordings, but also when listening to recordings that can make no such claim. One of the latter was a recently purchased set of early recordings by Fritz Wunderlich,\u00a0A Life\u2014A Legend\u00a0(10 mono CDs, Intense Media LC 12281). The accompanying documentation is minimal, but I figured that, at $21 for the set, I could take a chance. I’d first listened to this recording through the Sabrinas and found that, though the singing throughout was glorious, the sound had more of an edge than I hear from other, more expensive Wunderlich recordings. By then I’d concluded that the Sabrinas were very fine speakers, so I assumed that any audible deficiencies must be intrinsic to the recording\u2014that, basically, I’d gotten what I’d paid for.The Sabrinas were gone by the time the PL300 IIs arrived, so I wasn’t able to do direct A\/B comparisons. But listening to the Wunderlich set through the PL300 IIs, my persistent impression was that, while not of audiophile quality, the sound of these recordings was better than I’d thought: not as harsh, with smoother highs. Wunderlich was known for the unique quality of his voice, which combined sweetness and strength; through the PL300 IIs, I could hear these qualities even in mono recordings from the 1950s.This ability of the PL300 II to allow recordings to be heard with their best foot forward was not accomplished by glossing over details. The sound was highly detailed: playing familiar recordings, I repeatedly heard things I hadn’t before been aware of. A very specific test I use for detail is the cymbal at 57 seconds into Ana Caram’s “Viola Fora de Moda,” included on the\u00a0Jazz Sampler & Audiophile Test Compact Disc\u00a0(CD, Chesky JD37). Through the PL300 IIs, the onset of the cymbal transient, its decay, and the placement of the instrument on the soundstage were as good as I’ve heard, sounding just . . . natural. The PL300 II also responded appropriately to changes in my system, neither glossing over them nor presenting them in an unforgiving way. Late in my auditioning of the Monitors, PS Audio released Torreys, the latest iteration of their DirectStream DAC operating system. I try to avoid making any changes in my system during the critical listening for a review, so I waited to download and install Torreys until my evaluation of the PL300 II’s sound had solidified. When I did, the PL300 II let me clearly hear the changes wrought by the new OS.In any play, musical, or opera, the success of the production depends not only on the individual performances but on how they work together as an ensemble. Similarly, each component part of a loudspeaker must not only be excellent on its own, but work together with the rest to produce a successful whole. This, I believe, Monitor has achieved in the Platinum PL300 II. The speaker’s sound was exceptionally coherent, approaching in this respect that of a single-driver speaker like the\u00a0Fujitsu Ten Eclipse TD 712z, but without the Fujitsu’s limitations in dynamics and bass.Continuing the ensemble simile: Just as, in an effective theatrical ensemble, there may still be an individual “star” performance, so might be the case for one of a loudspeaker’s component parts. Considering only the PL300 II’s drivers, the star was the tweeter. The contribution of the PL300 II’s tweeter was subtle: it presented high frequencies in a way that precisely mimicked the sound of musical instruments and voices, particularly the overtones. Depending, of course, on the recording itself, the treble range was smooth and extended, with a natural quality that neither emphasized nor diminished this part of the audioband. And, in true ensemble fashion, the contribution of the tweeter blended well with the midrange.In my review of the Platinum PL200, I described its sound as being slightly on the bright side; indeed, in writing of his measurements of the PL200, John Atkinson noted that “the ribbon tweeter looks as if it is a couple of dB too high in level.”\u00a0Stereophile\u00a0writers don’t get to see John’s measurements until after a review has been submitted, but I would bet that his graphs don’t show a similar emphasis for the PL300 II’s tweeter. The sound\u2014again, depending on the recording\u2014was ultraclean throughout the audioband, supporting Monitor’s claim of reduced harmonic distortion.“Ensemble player” also aptly describes the PL300 II’s twin 8″ woofers. With both ports open\u2014again, my preferred configuration\u2014the bass was extended and powerful, and blended well with the rest of the range. The synthesizer note at the beginning of “Temple Caves,” from Mickey Hart’s\u00a0Planet Drum\u00a0(CD, Rykodisc RCD 10206), was there, with no evidence of doubling, at a level that bordered on uncomfortable. The bass was tighter and more powerful with the Theta Prometheuses than with the McIntosh MC275LE, but the difference was evident mostly when I made direct comparisons.According to Monitor’s Dean Hartley, one of the design goals for the PL300 II was that it “stay composed” when playing loud music. In evaluating a speaker, I sometimes play music at levels higher than I would play just for enjoyment, and when I did, the PL300 II did indeed “stay composed.” To push the PL300 II to well above my normal listening level, I used a recording that for me is a guilty pleasure: A la Carte Brass & Percussion’s\u00a0Boogeyin’! Swamprock, Salsa & ‘Trane\u00a0, with guest singer Chuck Brown (CD, Wildchild! 02452). This CD begs to be played loud. I first tried “Papa Was a Rolling Stone” at my normal “high” level, which I think most people would find loud enough, then increased the level two notches on the CAT preamp: an increase of 3dB. The sound itself through the PL300 IIs was merely louder, not distorted. (For this test, I used the\u00a0Theta Prometheus\u00a0monoblocks.) My AudioTools sound-pressure-level app measured 100dB on peaks (C weighting, Fast Response, Internal mic1 high range, iPhone 6 held at ear level). This is not the sort of calibrated measurement that JA makes and discusses in his Measurements sidebars, but it gives you an idea of what I was hearing. I wouldn’t want to listen at this level for a prolonged period, but it’s good to know that the Platinum PL300 IIs are up to it. (Larger rooms than mine would place greater demands on the speakers’ loudness capability.)The PL300 IIs’ depth of soundstage and precision of imaging within the soundstage were apparent the first time I heard them, and continued to impress. To quantify the effect of spatial depth, I like to use the “Depth of Image: Acoustic Clicker” tests (tracks 34\u201342) on\u00a0The Best of Chesky Jazz and More Audiophile Tests, Volume 2\u00a0(CD, Chesky JD68). I’ve used these tracks, which record a clicker at distances from the microphone ranging from 5′ to 80′, many times. With most speakers, the difference in the sound of the clicker from 60′ and 70′ away becomes iffy, and 80′ sounds pretty much the same as 70′. Through the PL300 IIs, I was, first of all, surprised by how well the sound of David Chesky’s voice defined the space of the recording venue as he announced each distance. And when it came to discriminating among the clicker’s sounds at the farthest differences, through the PL300 IIs I was able to distinguish not only 60′ from 70′ away, but also 70′ from 80′. This is outstanding performance.