Plastic Coned Hi-Fi Loudspeakers: Brilliant Engineering Solution?

First touted supposedly as an ideal solution against cone break-up inherent in early paper coned hi-fi loudspeakers, do plastic coned loudspeakers offer a brilliant engineering solution?

By: Ringo Bones

Maybe is it because on my first-hand audition of supposedly high-tech Bextrene and Polypropylene (MRP – Mineral-Reinforced Polypropylene) high fidelity loudspeaker cones whose drive units are well enough engineered to give smooth string tone, but on orchestral crescendos suffer from timbral muddle and tonal quack; I mean an overwhelming majority of them – i.e. ones within my price range – display a degree of plastic quack that was apparent with violins, plus a little nasality, just enough to add character when played at sound-levels of a typical violin or a Classically trained singer performing live sans electronic amplification. Fundamentally, the argument in favor of plastic cones over paper cones rests on plastic’s high stiffness in comparison to paper, with the potential avoidance of any unwanted resonance or cone “breakup” in the intended working frequency range. But were plastic coned hi-fi loudspeakers really has more flaws in comparison to the paper coned loudspeakers they are intended to replace?

Use of heavy, well-damped plastic cones that display a great measured performance – frequency response flatness wise – but little else in terms of subjective purity of tone and timbre (i.e. sound quality) came about as a result of a research into loudspeaker cone materials started by the BBC that culminated in the early 1970s. Thus prompting established high fidelity loudspeaker manufacturers of the time to switch from paper cones to plastic cones – i.e. Bextrene and Polypropylene. When other established hi-fi loudspeaker companies with bigger R&D budgets like B&W, KEF, Celestion and Wharfedale equipped themselves with sophisticated research facilities during the early 1970s eventually merely confirmed what the BBC had discovered a few months before, thus taking to plastic cones with enthusiasm. But to the ears – and wallets – of long-time hi-fi enthusiasts, too many top line monitors with plastic coned drivers brewed up in Britain between the early 1970s up to the early 1990s have sounded perplexingly poor in relation to their enormous engineering input for questions not to have been asked.

Fueling me and other hi-fi enthusiasts growing suspicion on the capabilities of plastic coned loudspeakers was back in 1995, when the well-established loudspeaker company called Mission produced the 731 LE whose better performance was largely due to switching from the use of plastic to a doped paper cone on the main driver. Even though there are scores of loudspeaker manufacturers – mainly in Britain – who swear by performance of plastic coned drivers – i.e. Spendor, Rogers, KEF, etc. But more often than not, plastic coned loudspeakers are still viewed by an overwhelming number of veteran hi-fi enthusiasts as something that’s good enough for mainstream pop and rock music, not for music that demands a little more precision and soulful rendition.