major difference in sound between the original Westminsters and the newer Westminster Royale HE and SE models, especially in the speed of the bass?Hardly what I'd call major... there's a small taming of mid-bass & lower mids region in the newer model vs the (very) old ones. Maybe the upper register is more pronounced in the new ones as well -- can't tell definitively.
Not sure what exactly you're referring to by "speed" of the bass. Bass isn't very "fast" in the first place... upper bass? mid-bass? Cheers