Floor Loudspeaker Reviews

An ancient connection: Monitor Audio began in 1972 when John Bartlett, founder of the innovative retail chain Audio T, introduced me to Mike Beeny, manager of an Audio T branch near Cambridge, and Mo Iqbal, a local electronics wizard. Mike suggested that Mo and I join him to start a loudspeaker company. Monitor was a fashionable hi-fi term, and I suggested we name it Monitor Audio Ltd. Each director put £300 into the company account. It was registered as a PLC at an address in Teversham, Cambridgeshire. We rented an upper floor office in a warehouse close to Mo's home, since Mo worked all hours. There was additional workspace in his huge double garage. Mike directed sales, Mo was responsible for production management and accounts, and I took the position of technical director for research and development. I also helped supervise production. Lorna Parker was our office secretary.

After launching a handful of increasingly viable designs, we reached a then-astonishing turnover of £1 million in our first year and enjoyed a very successful showing at the Paris Festival du Son. But by this point, I was close to an overwork-related breakdown and reluctantly resigned. Mike had already resigned due to ill health, so it was logical that Mo should take over the company. I continued to contribute, designing several Monitor Audio loudspeakers while writing a book on loudspeaker design, which was published in 1976 (footnote 1).

Now celebrating its official 50th anniversary, Monitor Audio fields a wide range of loudspeaker systems in many key market areas but remains strong in hi-fi separates, where it began. As for me, I haven't been involved with the company for some 50 years.

In the April 2010 Stereophile, Robert Deutsch reviewed the floorstanding Monitor Audio PL200, part of Monitor Audio's flagship Platinum series, which sold for the quite serious sum of $8000/pair (footnote 2). Due to the technologies employed, the PL200 could be viewed as a forerunner of the speaker under review, even though it was larger and more costly. Similarities to the Gold 300 include a pleated-foil tweeter, a deep, anodized-alloy-skinned-Nomex honeycomb-composite-cone midrange, and similarly configured approximately 6" woofers. Robert liked the PL200 a lot.

Fourteen years after RD's PL200 review, the new, sixth-generation Monitor Audio Gold 300 boasts a more competitive list price of $5600/ pair, yet much of that PL200-derived technology remains in place, now further refined.

The Monitor Audio Gold 300 6G
The Gold 300 6G is a slim, tall, floorstanding MDF pillar planted firmly on a visually arresting, oversized outrigger platform constructed of steel and aluminum alloy, with generously dimensioned floor coupling/locking hardware for a large and stable footprint. Connections are made via four biwire/biamp–capable binding posts/sockets with highly polished link straps for single wiring (footnote 3). Each speaker comes with a trio of grilles, one to cover the midrange and treble drivers and one each for the bass units. Their use is optional. They are retained magnetically and are readily detached. Experience and measurements suggest that they should be removed for serious listening. My review samples were finished on all surfaces in a superb "piano" gloss black. Other options include Macassar Wood Veneer and Satin White.

The review loudspeakers were kindly delivered and installed by Michael Hedges, Monitor Audio's chief engineer. I quizzed him about engineering details: Which does he consider most important for sound quality? He confirmed (see my measurements in a sidebar) that the grilles were largely cosmetic and that sound quality improves when they are left off. I removed them for the duration of the audition. He also noted that all the drivers are designed in-house from the ground up and follow a long tradition of using deeply anodized, low-hysteresis aluminum alloy–faced composite diaphragms, which are expected to display purely pistonic behavior. In conventional cones, excess hysteretic (imperfectly elastic) bending can blur musical detail.

This latest Gold 300 6G comes equipped with two 6" (155mm frame; 120mm diaphragm) bass drivers. The low-frequency drivers are improved compared with the outgoing 5G models in both power capacity and distortion, while the desired pure-piston behavior is extended to higher frequencies.

For this three-way configuration, the compact, wide directivity 3" (71mm) midrange driver employs Monitor's CDT and C-CAM technologies, which are based on a single-piece aluminum cone, with anodized top and bottom layers on a solid aluminum core. The suspension is designed to be regressive: mildly nonlinear with respect to excursion, which reduces distortion at higher powers. Voice coil cooling has been improved by better ventilation through the magnet system.

High frequencies are handled by a refined, pleated-diaphragm (Heil-derivative) planar tweeter with an extended ultrasonic frequency range tailored for smooth rolloff and low phase error. The midrange and treble units are integrated into a decorative, strong die-cast alloy chassis. Inside the cabinet, a steel black box encloses this unit, keeping magnetic fields in and out. The close proximity of the midrange and treble units improves the acoustic integration of their outputs. The 6" diameter bass units, in addition to the aforementioned pistonic behavior in their working range, benefit from longer voice coils for increased power headroom. This development is combined with revised antireflection chassis and improved suspension geometry.

Supporting the notably clean front panel appearance is the use of concealed drive-unit fixings, a technique established by Monitor Audio many years ago. The drivers are designed for concealed, single-point fixing via a long bolt that extends through to the back of the enclosure, clamping the drivers (via a gasket) under tension to the front panel. Four such bolts are visible on the back of the Gold 300, one for each bass driver and two for the midrange-treble module. Monitor Audio provides instructions for how to set the bolts' tension, advising that it be checked after shipment, following dramatic temperature change, and after extended use; see the sidebar. This method neatly conceals the front panel driver frame detailing while facilitating easy servicing. It also has other advantages, as we shall see.

Manufactured at an exclusive Monitor Audio facility in China, Monitor's trained personnel build and test each product, with on-line supervision from the UK. Monitor uses well-tested technologies developed by them with a policy of continual improvement using advanced analysis methods such as COMSOL Multiphysics CAD modeling. Their development facilities include an anechoic chamber and cabinet-prototyping capabilities.

In this three-way system, the crossover network uses select custom-made polypropylene capacitors. Air-core and cored inductors are deployed as appropriate to the task and frequency band. Largely built of select MDF, critical sections of the enclosure are doubled in thickness, with multiple bracing divisions for panel-resonance control.

A knuckle-rap test was painful, so solid, inert, and unyielding was the enclosure.

A die-cast fascia plate provides a solid foundation for the new-gen "Heil derivative" micro-pleated ribbon tweeter designed by Monitor Audio and its partnering compact midrange driver. The tweeter output is claimed to extend to beyond 60kHz. Its essentially square aspect ratio offers relatively constant directivity compared, say, with an equivalent ribbon transducer with an extended aspect ratio. The unified driver plate may be mounted higher up on the front baffle, resulting in improved diffraction and directivity when mounted on the enclosure—all seemingly small steps that sum to significantly improved performance.

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Footnote 1: High Performance Loudspeakers is now in its seventh edition. See John Atkinson's review.

Footnote 2: Monitor Audio's core loudspeaker offerings are classified as Bronze, Silver, Gold, or Platinum, in order of increasing quality and price. Later, RD also liked the Platinum-series PL300 II, which he reviewed six years later. John Atkinson favorably reviewed the most recent (3G) Platinum 300 late last year; they sell for $17,900/pair and reside in Class A of Stereophile's Recommended Components.

Footnote 3: I have found some such highly polished "chrome" straps used by other brands to have above-average contact resistance, so I checked and found that these parts are highly conductive. Nevertheless, they must still be fully tightened for reliable connection of both operating sections.