Experimenting with the port plugs on the M100’s I noticed that placement, audio content and amp settings all have an impact on my results. That said the best results was only 1 port plug, first bottom rear port, although minimal I would compare this as fine tuning the amount the bass coming from the 3 woofers, just adjusting the bass knob on the amp changes the sound in a different way, so the plugs was the better option and did a good job, sound now is perfecto !!!.