We have recently started shipping our newest product, the M100 Floorstanding Speaker, which is the first model of ours to come with port plugs. A port plug, as its name suggests, is simply something that will plug one of the loudspeaker ports, keeping air from moving in and out of the cabinet.
There are a number of reasons why you might want to use these, and they are going to be offered on the website as an accessory, so I'll also cover where you might want to use these other than for the model M100.
When you place a loudspeaker in a room, if it has to be close to anything called a room boundary (back walls, side walls), you get something called boundary reinforcement happening. Boundary reinforcement will tend to accentuate the mid-bass frequencies. In a speaker like the M100 that has very good low frequency extension and output capabilities, you can easily end up with 'too much of a good thing' in those environments. And if you're in a small listening room or environment, you can find that because everything is closer to the boundaries that you'll also get that midbass accentuation, which can be too much of a good thing and can actually make things sound really slow and congested.
For this reason, we've supplied port plugs with the M100. We suggest that you set up and listen to the speaker as-is without any of the plugs in place for a week or two, and then add one plug at a time (in the M100 we suggest adding them in the bottom three rear ports), and every time you add a plug, listen for a few days again, and listen for how the bass character changes. This is something that is very room dependent and also dependent on your personal listening tastes. Some people may like that bass accentuation. There's no right or wrong answer as to whether you should use the port plugs, but they are there as an option if you find the speaker has too much mid-bass.
Now I mentioned earlier that we're going to be offering these port plugs on the website, and there are a couple of other situations where you may want to look at using them. If you purchase one of our bookshelf models like the M22, M3 or M2, they all have rear ports. If you plan on mounting the speakers on our Full Metal Bracket, up on a wall, again now it's sitting next to a boundary, so it has that same reinforcement. In that case, you might want to try using the port plugs to plug those rear ports. It might give you smoother bass response.
Also, if you're going to be putting a bookshelf speaker on a bookshelf or in a cabinet of some sort, you get the same sort of boundary gain in the mid-bass frequencies. That's another case where you might want to look at buying a couple of port plugs and trying them out. It just might give you a smoother and more linear sound quality.