Suggestions for 'filling the port' of bass reflex

If you want to, "tone it down a little"; Go to a fabric/upholstery shop and get some (loose-not "felt")bonded dacron(http://cgi.ebay.com/Upholstery-Bonded-Dacron-Quilting-Batting-Padding_W0QQitemZ350220762258QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item518ac8bc92&_trksid=p3286.c0.m14&_trkparms=65%3A12%7C66%3A2%7C39%3A1%7C72%3A1205%7C293%3A1%7C294%3A50). You can experiment with different densities, by rolling it tighter/more loosely, and damp the port to your tastes. Most other suggestions will turn your cabinet into an acoustic suspension design, and completely ruin the system designer's alignment. Have you tried lifting them off the floor and/or moving them away from any corners?

I use upholstery foam about 1 inch thick that can be rolled up and placed in the port. It works well.

I used expandable rubber test plugs available from the plumbing department in any hardware store to plug ports in my PSB Stratus Goldi speakers. They happened to be a perfect fit and made an airtight seal. They come in 1-1/2, 2, 3, 4" sizes and if they don't fit for you you can wrap an undersized plug with strips cut from bicycle inner tubes to get close, then turn the wing nuts to expand the plugs to seal the ports. This is a cheap and easy solution unless your ports are on the front and you don't use covers. Talk about low WAF!

I had good results cutting soda straws to the length of the port and then simply packing it full. This reduces turbulence and overload without changing the tuning of the port. Using fabric, wool etc. impede the air movement is not only a gamble, worst case it can damage the speaker.

I've used filter wool refills from a tropical fish pet shop. You can buy large bags of it for a few dollars.