I'm trying to fabricate the box design that is available at polk.com but with a few changes to fit my car perfectly. It's a 2.1 cubic ft single bandpass for the MM120. The modifications I have made to it place it's height at about 12.5" internal height. With the .75" of mdf on top there would be about a quarter inch of space between the bottom and the 13" vents... is this too little? I've been doing a bit of research on the matter and have found that sometimes people put the ports on the outside. Would this be a possibility? I'm planning on the front and back of the box being plexiglass and I'm wondering what size plexiglass would be safe to go with. I'm using 3/4" mdf on everything else. And finally I'm curious if the MM124 would work in this box the same as the MM120
Since you are planning to use plexiglas for the front and rear panels, I would suggest not having the port protruding out of the enclosure. The "plan B' option would be to change the port length. If you use two 4 inch ports that are 10 inches in length then this will raise the tuning frequency by only 5 Hertz. There will be a slight increase in upper bass frequency output also. The original tuning frquency is 57 Hertz and the new tuning frequency will be 63 Hertz. I have attached response graphs below to show you the differences. Now keep in mind that these are "out of car" response graphs.
Greetings to all of you audio officianodos out there. I am looking for a mint SME 3012 Series II init's original box. Please pass on any word of one. Thanks, Ken