Excerpted from *Audio Technology*

Audiophiles often face a dilemma when choosing speakers: they desire a compact form factor that’s easy to integrate into their homes, yet they also crave the low-frequency throughput of larger speakers. Speaker manufacturers understand this contradiction and actively research ways to improve low-frequency efficiency without compromising speaker size. Of course, a more compromise for enhancing bass is to add an air vent to the cabinet, a design known as bass reflex. Behind the vent is a resonant channel. When the driver emits sound, the out-of-phase sound waves from the back of the driver resonate through this channel. This resonance superimposes with the sound waves from the front of the driver, thereby increasing the sound pressure level and extension of the low frequencies.

The Masterful ATL Technology

In 1990, Peter Thomas and Adrian Loader successfully refined transmission line technology to create the classic BB5 monitor speaker. The following year, they officially founded PMC and designed the LB1, then the world’s smallest transmission line speaker, at the request of the BBC, officially ushering in the era of lightweight transmission line speakers. More than thirty years later, PMC has reached a level of mastery in the application of transmission line technology, even developing a patented proprietary technology: ATL (Advanced Transmission Line). The Prohecy 7 floorstanding speaker, which we are reviewing today, is a perfect example of PMC’s further miniaturization of ATL speakers.

Concealed 1.91m Transmission Line

While the Prohecy 7 utilizes the manufacturer’s ATL Advanced Transmission Line bass-loaded technology, its design is simple and elegant, boasting an ultra-narrow 165mm body. Its slender and elongated shape should easily blend into most home environments. Don’t be fooled by the slender profile of the Prophecy 7; its 965mm tall cabinet houses a 1.91m long ATL transmission line and a 40Hz low-frequency response.

Introducing F1 Racing Airflow Technology

Oliver, well-versed in aerodynamics, understood the benefits of ATL technology, but also knew that low-frequency sound waves still generate turbulence as they leave the ATL outlet. This not only reduces overall efficiency but also creates noise interference, a problem faced by many bass-reflex speakers. In 2016, Oliver created a novel laminar flow inlet under the name “Laminair,” incorporating aerodynamic principles from F1 racing. The ATL transmission line’s exhaust outlet was transformed into vertical guide fins, similar to F1 car spoilers, allowing airflow to be evenly distributed across multiple narrow channels, reducing turbulence and wind noise, resulting in purer low-frequency performance, faster airflow, and significantly improved dynamic contrast. From then on, ATL became inextricably linked with Laminair, becoming a hallmark of PMC speakers.

n-compass technology: The Prohecy7, powered by both ATL and LaminairX technologies, already possesses sufficient capacity to deliver powerful sound within a compact enclosure, meeting the needs of small to medium-sized listening environments. However, PMC further enhances it with another noteworthy new technology, “n-compass,” improving the clarity and dispersion of mid-to-high frequency sounds. The Prohecy7’s tweeter and midrange drivers are surrounded by a one-piece, shallow horn-shaped diffuser and a “Waveguide” waveguide grille, together forming PMC’s n-compass composite waveguide system.

This listening test used a Lumin T3X as the source. For the amplifiers, I tested a PrimaLuna EVO 100 tube preamp and power amplifier set and a Gryphon Audio Diablo 333 integrated amplifier. I liked both. The EVO 100’s elegant lines infused the prophecy7 with a warm musicality, full of human warmth, while the Diablo 333’s powerful dynamics highlighted the prophecy7’s exceptional control over airflow, delivering a truly visceral bass response. Faced with the most difficult choice, I focused on the prophecy7’s airflow control, so this listening test used the Diablo 333 as the primary pairing.

The explosive power pierced the drumheads. The first track was BIS’s *ORFF: Carmina Burana (Chamber Version)*, performed by the Kroumata Percussion Ensemble, a choral version primarily featuring piano and percussion. Kroumata’s playing is renowned for its powerful and aggressive style. The first piece, “O Fortuna,” showcases the exhilarating power of the drums on the Prophecy 7. The low frequencies are smooth and fast, seamlessly transitioning into the mid-low range, clearly outlining the shape and texture of the bass drum. The Prophecy 7’s low-frequency roll-off is natural and unhurried, without any excessive airflow that could cause a “swelling” effect. Even at high sound pressure levels, it clearly presents the position of the piano and the scale of the choir. The explosive power of the drumheads is exhilarating to listen to. The advantages of the Laminair X are evident. …