I recently bought a DIY Sovereign/Olympus cabinet with 136A woofers and PR15 passive radiators, and have been informed that the correct radiator for the 136A is the PR15C.
http://www.audioheritage.org/vbullet...-have-I-bought

So, does anyone know the difference in mass between the PR15 and PR15C?
I'd like to make the PR15 into a quasi-PR15C (if the C-version is actually the heaviest, of course).