PMC Prophecy7 Speakers in Black (Ex-Display)
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PMC Prophecy7 – These are our demo Phrophecy7 speakers in Black in excellent condition, please call for more information and price.
Prophecy7
Once thought to be the preserve of larger speakers, prophecy7’s performance and specification set new standards in its class. Mounted within an innovative waveguide, unique to prophecy, the dedicated mid-range driver in this cutting-edge three-way design ensures precise vocal reproduction and thrilling instrumental textures, all delivered with remarkable transparency. What’s more, it enhances overall sound quality by allowing the bass unit and tweeter to focus on their specific frequency ranges, all controlled by a sophisticated hand-built crossover, tuned and honed for ideal driver integration.
Complementing this superlative mid-range and and treble is our custom bass driver, with the latest Advanced Transmission Line, augmented by the revolutionary LaminairX airflow technology, ensuring this still-compact three-way is both refined and massively powerful.
Over a decade since PMC’s engineers introduced F1 aerodynamic principles to the audio realm with Laminair, the advent of the prophecy series sees the latest iteration, the patent-protected LaminairX, working in tandem with ATL.
How does transmission line work?
A transmission line places the drive unit at the end of a long, highly damped tunnel which absorbs all the unwanted mid and high frequency energy that is radiated from the rear of the driver, but allows the lowest frequencies to exit the line in-phase with the frontal radiation from the drive unit, greatly enhancing its bass performance. The transmission line is effective over a wide bandwidth of around two octaves centred on the main resonant frequency of the line, and over this region it controls the motion of the drive unit, massively lowering distortion and raising the maximum possible output level. The resonant frequency of the transmission line is defined by the acoustic length of the line, and is the frequency at which one quarter of a wavelength is equal to the acoustic length of the transmission line.
Transmission line speaker design requires the balancing of many complex parameters and variables, from drive unit parameters, to line length, area, taper and profile, foam placement, thickness and specification etc. All of these parameters affect each other in complex ways, meaning that they must all be considered and optimised together in order to achieve an ideal result. The cost and difficulty involved in successfully achieving this is why PMC are one of so few companies to successfully develop transmission line speakers.
What makes ATL advanced?
Transmission line speakers are not a new concept, and have been around since the 1930s, although they were first popularised by Bailey in the 1960s. However, early transmission line speakers were prohibitively large and unwieldy, and suffered from a myriad of issues such as uncontrolled resonances, poor drive unit/transmission line coupling, unoptimized placement of drive unit/vents etc.
PMC has expended an enormous amount of time and money to research and develop the concepts behind transmission line speakers in order to bring out the full potential of these designs. Our first major development was in the specification of the absorbent foam we use to line our cabinets. This has given us exactly the right combination of mid and high frequency absorption, together with the control of low frequency resonances and the ability to alter the apparent acoustic length of the cabinet by effectively slowing the speed of sound as it passes through the foam. We have also developed the use of resonant absorbing chambers within the cabinet to allow us to further control specific unwanted resonant frequencies, reducing distortion and increasing the linearity of our speakers …
… More recently, we developed the laminair vent, which acts to smooth out the air flowing from the end of the transmission line by dividing it into multiple channels with a larger hydraulic diameter, resulting in massively reduced turbulence within the airflow. The result of this is that we can now play cleaner, louder bass with no unwanted ‘chuffing’ noise.
A significant amount of R&D effort is put into the drive unit design for each new speaker product/line. Because the parameters of the transmission line effect the behaviour of the drive unit and vice-versa, it is vital the cabinet and drive unit are developed in tandem in order to give the best possible performance from the final product. Transmission line cabinets also perform better with a very different set of drive unit parameters than would be common in most sealed and ported speaker designs. In order to achieve this, every single drive unit used in a PMC product is custom designed by PMC, with many being fully built in-house.
Deeper bass from a smaller cabinet
Across the frequencies where the transmission line is active, the air inside the line actually stiffens and couples to the back of the drive unit cone (this is how the cone motion is controlled by the transmission line). When this happens, the apparent moving mass of the cone is significantly increased, thereby lowering the effective resonant frequency of the drive unit. The effect of this is that the speaker can now produce significantly deeper bass, with greater headroom and less distortion than would be possible from that same drive unit in a sealed or ported cabinet.
Because the transmission line is so well damped with acoustic foam in order to absorb the unwanted mid and high frequencies radiated into the cabinet, the quality of the bass produced by a transmission line speaker is also incredibly accurate and well damped, with greatly improved time-domain characteristics than is seen in most simple ported speakers.
Acoustically absorbent chambers
Whilst we make use of highly specified acoustic foams to absorb unwanted resonances and rear-radiation within our ATL speaker cabinets, sometimes we will find that there is a particular resonant frequency that would require an excessive amount of foam to completely damp, leading to an overly dry bass response from the loudspeaker. In these cases, we can make use of resonance absorbing chambers within the cabinet to target specific frequencies that we want to control. These chambers can be precisely tuned to specific frequencies, and can effectively remove these unwanted frequencies from the output of the ATL, leading to a completely clean, uncoloured sound from the loudspeaker.
Lower Distortion
Whilst we make use of highly specified acoustic foams to absorb unwanted resonances and rear-radiation within our ATL speaker cabinets, sometimes we will find that there is a particular resonant frequency that would require an excessive amount of foam to completely damp, leading to an overly dry bass response from the loudspeaker. In these cases, we can make use of resonance absorbing chambers within the cabinet to target specific frequencies that we want to control. These chambers can be precisely tuned to specific frequencies, and can effectively remove these unwanted frequencies from the output of the ATL, leading to a completely clean, uncoloured sound from the loudspeaker.
Laminair – smoothing the air flow
PMC’s Laminair™ aerodynamic vent takes audio performance to the next level, by applying ATL aerodynamic principles from high-performance engineering used from F1 to Le Mans and creating an even smoother, laminar air flow at the exit from the transmission line.
ATL designs involve air moving at high speeds and under pressure.Reducing turbulence and drag at the ATL vent reduces resistance, increases efficiency, eliminates air noise and provides bass with supreme timing and the widest possible dynamic range.The combination of ATL and Laminair takes audio quality to unparalleled new heights:
- Faster, cleaner bass and higher definition sound throughout
- Turbulence is eliminated, increasing the efficiency of the ATL
- Removes air noise — only the music remains
- Higher maximum output and bass with supreme timing and dynamics
Advanced cabinet construction
Structural integrity and accuracy are the most crucial elements when making any loudspeaker enclosure, and with PMC’s holistic design approach every element has been considered to enhance performance. Forming both the cabinet and housing the sophisticated ATL™(Advanced Transmission Line) are precision machined panels of highly specified HDF material, some as much as 40mm thick. With the consumer veneered models, they are prepared both inside and out with veneer that guarantees their stability and long life.
The accuracy of the joints, together with modern bonding agents creates one homogeneous, flawless structure that acts as the ideal, inert platform for the drive units to deliver pure, uncoloured audio.
Laminair X
Over a decade since PMC’s engineers introduced F1 aerodynamic principles to the audio realm with Laminair, the advent of the prophecy series sees the latest iteration, the new LaminairX, working in tandem with ATL. Rarely does anything enter the audio realm with such a profound effect on sound quality and the sheer enjoyment of music: LaminairX unlocks the full potential of PMC’s ATL technology. The improvements both revolutionary technically and above all obvious to the listener. ATL™ designs involve air moving at high speeds with complex fluid dynamics, and introducing the precision machined ultimate aerodynamic control of LaminairX negates turbulence and drag, which in turn reduces resistance, reduces harmonic distortion by up to 3dB, eliminates air noise and provides bass with superlative timing and an unparalleled dynamic range.
In addition, the weight of the all-metal new LaminairX device, isolated from the main enclosure via a layer of sustainable pure cork, both stabilises and ‘anchors’ the speaker for even better control.
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