DF (Damping Factor) desirable level really depends on the speaker in question. Some speakers definitely require more than others, some speakers require very little DF. Too much DF can be detrimental to sound quality. There’s no such thing as the more DF the better in every circumstance. Increased DF reflects an increase in NFB and there can be undesirable sonic effects as Atmasphere has eloquently explained in past posts.
Charles
Charles