Speaker distance

The best way?  Put your speaker stands on casters.  Otherwise it's too difficult to experiment, even if your speakers are 77 lbs. each like mine.  You'll find the threaded diameter of speaker stand feet or  spikes is 8mm, so you need a threaded stem caster size of M8.  There are self-leveling casters so after you find the right position you can raise the caster wheel so the caster rests on a solid foot.  It may raise the height of the speaker an inch or two but finding the right location for the speaker is more important.  Good caster wheels will damp vibrations on a hard floor.  

@eisen0169 

Making them movable while experimenting is a great idea. Although, I would recommend furniture sliders...like from Amazon. They are cheap, easy and very temporary. You ultimately want them on spikes (with or without the dimpled coins) or even better something like Townshend Podiums. 

@curiousjim your description is so accurate, I feel like I am in the room. Move over!

Ok - it seems there are a lot of opinions.  Looks like I gotta put it together and experiment.  

Have to use casters, not furniture sliders because speakers are on carpet.  However, carpet is commercial grade and pad is dense thinner rubber also commercial grade.  This is called the "double stick system", meaning the underlayment rubber is glued to the subfloor and the carpet on top is glued to the underlayment.  Basically, this makes a soundproof and vibrationproof surface.  Plus, it's older "curvilinear" carpet, i.e. sculpted, which makes even casters more difficult to roll.  When I change flooring to hard surface I will use self-leveling casters.  As an alternative to the Townshend Podiums, I have first generation anti-vibration plates from this company in Poland.  They are really heavy; overkill for me actually:  https://tewoaudio.pl/