I would say putting them close to the headers would slow the flow and cool the exhaust quicker (not good) making the exhaust from the mufs>> back cooler and slower causing it to be a deeper sound (longer sound waves)... but it will also cause more backpresure because the gas is moving slower after the muffler than before the muffler causing a backup of gas.
Putting the mufflers closer to the end of the exhaust (not at the tip though) would allow the highspeed / high temp gasses to flow smoother through the exhaust tubing then dump into the muffler then out the exhaust quicker,high speed gas, sound waves , higher pitch.
Sound good?
HEADER>>>>>>>>>MUFFLER> > > > > > > > > > > > > > > > > > > > OVER AXLE> > > > > > > >EXIT
HEADER>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>MUFFLER> > > >OVER AXLE> > > > > > EXIT
The closer the marks the higher the speed of the gas.
Putting the mufflers closer to the end of the exhaust (not at the tip though) would allow the highspeed / high temp gasses to flow smoother through the exhaust tubing then dump into the muffler then out the exhaust quicker,high speed gas, sound waves , higher pitch.
Sound good?
HEADER>>>>>>>>>MUFFLER> > > > > > > > > > > > > > > > > > > > OVER AXLE> > > > > > > >EXIT
HEADER>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>MUFFLER> > > >OVER AXLE> > > > > > EXIT
The closer the marks the higher the speed of the gas.