Let's Get Technical
Since the original AE1 with its heroically built latex polymer lined cabinet, we have paid special attention to minimising the sound energy radiated by the loudspeaker cabinet. Later models of the AE1, and other Signature models took this approach a little further by lining the cabinet with steel plates to increase the panel mass which greatly reduces sound transmission.
One popular method of cabinet construction is to follow the principles established by the BBC which was to use thin panels which are then loaded with damping material to reduce resonances. What is often overlooked is that the BBC monitors needed to be portable as they were designed for studios and broadcast vans. Loudspeakers for home use do not need to be portable and so are not constrained by the limitations effecting the BBC engineers, therefore cabinet colouration can be significantly reduced compared to these traditional designs. In his 1988 BBC report ‘On the design of Loudspeakers for Broadcast monitoring’ Mathers discusses the use of constrained layer techniques in cabinet construction noting that ‘it is the most effective means of obtaining a stiff heavily damped sheet’ but adds that there are some technical difficulties in making this approach work effectively.
The Reference Series launched in 2011 had a cabinet built to these constrained layer principles. The engineers at AE were able to develop and sandwich formed by MDF layers and a high loss, high mass damping material along with the correct bonding technique to form a high mass, stiff, well damped panel ideal for use in loudspeaker cabinet construction fulfilling the criteria of low sound transmission, high self-damping to control panel resonances, and high panel stiffness to reduce colouration at low frequencies.
The latest version of this technology is now used in our 500 Series, we call it the Resonance Suppression Composite or RSC for short. It gives our drive units the ultimate stable platform to work from effectively dissipating unwanted sound energy as heat within the damping layer rather than it escaping into the listening environment through the panels or returning to the drive units to interfere with the diaphragm motion.
The original AE1 was famous for pioneering the use of Aluminium Ceramic composites cones, now widely used by many famous manufacturers, Acoustic Energy were one of the pioneers of this technology. We called it ‘pure piston’ technology and our particular implementation was protected by a European Patent. The AE1 was lauded as a breakthrough loudspeaker bringing big speakers sound to a compact monitor, that was not thought possible at the time. Over the last 30 years AE has continued to develop it’s metal cone drive units, and the latest versions can be seen in our AE1 Active loudspeaker as well as our 300 Series range.
For our 500 Series we wanted to break new ground by bringing technology from the rarefied High End of Hi-Fi into much more accessibly packaged and priced products which would once again rewrite the rule book for what is thought possible. The carbon fibre cones we use in the 500 Series woofers allowed us to keep the same incredible stiffness as our aluminium ceramic cones but were only half the mass which allowed us much greater freedom to optimises the rest of the woofer. Using a larger voice coil improved the heat dissipation reducing thermal compression, and the increased BL available from the optimised motor structure allowed us to use an enlarged copper sleeve on the motor pole which significantly reduces non-linear distortion products created by inductance variation with voice coil displacement.
The alu domed tweeter used in our 300 Series and features a highly optimised motor structure with large rear chamber which greatly reduces the reflected rear radiation from re-radiating through the dome and lowers the fundamental resonance of the tweeter well outside the working band. By optimising the dome shape and the suspension, we negate the use of ferrofluid which otherwise colours the sound by damping the dome motion.
The 500 Series gets our latest carbon fibre dome which maintains the stiffness of the aluminium dome and the extra strength allows us to remove the protective grill mesh which we found to very slightly degraded the sound. The carbon dome gives a surprising open, natural sound free of harshness or colouration associated with lesser rigid dome tweeter designs.
Our tweeter designs all feature our Wide Dispersion Technology™ (WDT) waveguide. This has a number of positive effects on the sound output. Essentially a constant directivity horn, it increases the dispersion of the tweeter at high frequencies, removing the so called ‘sweet spot’ and dramatically opening up the soundstage. At frequencies closer to the crossover the dispersion of the tweeter is actually narrowed to better match the midrange woofer which means the sound of the speaker is more consistent with listening angle. A further added benefit is a boost in tweeter sensitivity and commensurate lowering of distortion across the operating band. Each waveguide is developed in tandem with the tweeter through the use of Boundary Element Modelling (BEM) we can accurately predict the far field frequency response of the combined tweeter-waveguide system.
One approach to crossover design is to use super simple first order filters to give the shortest connection between the driver and amplifier, such an approach is non optimal in terms of rejection of out of band output and therefore excess distortion is common. At the other end of the spectrum, through the use of computer modelling highly sophisticated complex crossover can be developed to smooth every wrinkle in the frequency response. At AE our philosophy is to use the minimum number of high quality components required to achieve our targets for integration, stopband rejection and distortion. If a design needs too many components then we go back to the drawing board and alter the woofer, tweeter, or enclosure design to solve the acoustic problem rather than compensate with a high number of low-grade crossover components. We also minimise the use of resistors in our networks and use air core inductors and high grade Polypropelene film capacitors at critical locations to ensure absolute clarity is maintained.
In order to reduce the effects of woofer cone breakup we often use elliptical filter designs to ensure maximum attenuation of break-up modes without having to use high order crossovers with their associated penalties.
Carbon Woofer – Need
AE500 Plate – Need
Carbon Tweeter – Need
Cab Show – Need
500 Series Spike – Need
Crossover – Need (AE3 – on MZ)