I have decided to make an experiment to stiffen a woofer's cone with 162g/m2 carbon fibre sheet and transparent laminating epoxy. I will apply them to the backside of the cone. I'm also thinking to apply thin layer of epoxy on the front side of the cone to give it nice high gloss, varnished-like looks. This would also add one layer to the sandwich, which might increase the internal damping of the cone even more.
The cone I'm intending to stiffen is BMS 18S430v2, that has a cone made of mixed carbon fibre, glass fibre and sellulose, and is quite rigid already (but I want more ).
By adding mass to the cone I seek also to lower the woofer's Fs to increase the woofer's linearity playing below-Fs frequencies. I simulated increased cone mass with blue tack, and it seemed to reduce THD <30Hz frequencies, due the fact that a woofer is not so linear below it's Fs than above Fs, and by reducing the Fs the linear zone increases. This will also transfer some of the sensitivity from upper bass to lower bass, which is not so bad since I use the woofer only below 100Hz. I have no real need for 100-200Hz bass sensitivity, so I might as well exchange some to more rigid cone, better sensitivity and somewhat lower THD in the lowest notes.
Has anybody tried carbon fibre with epoxy to stiffen a cone?