Well, your not that much of a beginner to recognize the room's effect on the system. There are a few good books on this subject that can answer far more than anyone can in a post. One is Robert Harleys "Complete Guide to High End Audio" and the other (if you want to really get in depth) is Master Handbook of Acoustics.
Some of the issues are pretty easy to solve. The windows behind the speaker. The rear wall--because the couch will be very close to the rear wall you will need some absorber/difuser or you will hear that reflection and it will definitely muddy the sound--drapes are a good idea, heavy fabric that will absorb the sound. Sidewalls: I would also recommend first order reflections have either an absorber or diffuser. Floor: If it isn't carpeted I would recommend buying an area rug. This will take care of most high and mid frequency issues. That's pretty easy. Also, since you mentioned that this will be a family room--and let's face it, Sonex has never been in any Home and Garden magazine--you can build a frame for the Sonex and cover it with a lightly woven cotten or other fabric. You will get near the same results sonically and usually MUCH better results from your spouse.
Bass frequencies need to be addressed as well, but they are much harder to deal with. I don't know what speakers you are using, but based on your room dimensions (I don't know the ceiling height either), you are going to have some bass issues to deal with. You can buy computer programs that will tell you where the problems lie--but I recommend just measuring the actual results and then tackling the problem (if there is one). Get a Radioshack SPL and the corrections for it (it's not linear), but if you do a search on the forums you can find the correction. Use a test CD that will give you warble tones from 20Hz to 500Hz (higher is fine). Then plot the SPL at the listening position. If your problems aren't too bad (no more than +6dB at any frequency below 80Hz) you can probably make a good correction with bass traps or other similar devices. It's difficult to make large bass corrections with only acoustic treatment. Assuming you need bass treatments you have a couple of options. You can buy bass traps and ASC or others will help you based on the plot and the room as to what you need. If you like to experiment you can make your own bass trap with a frame about 3 feet high and large enough to fit newspaper in it (it has to be open on the sides). Fill it with newspaper and cover it with WAF certified fabric (see Better Homes and Gardens). You can start with 2 in the corners behind each speaker. Moving them will change the attenuation. Also the amount of newspaper will change the amount of absorption.
Good luck--happy listening.
Some of the issues are pretty easy to solve. The windows behind the speaker. The rear wall--because the couch will be very close to the rear wall you will need some absorber/difuser or you will hear that reflection and it will definitely muddy the sound--drapes are a good idea, heavy fabric that will absorb the sound. Sidewalls: I would also recommend first order reflections have either an absorber or diffuser. Floor: If it isn't carpeted I would recommend buying an area rug. This will take care of most high and mid frequency issues. That's pretty easy. Also, since you mentioned that this will be a family room--and let's face it, Sonex has never been in any Home and Garden magazine--you can build a frame for the Sonex and cover it with a lightly woven cotten or other fabric. You will get near the same results sonically and usually MUCH better results from your spouse.
Bass frequencies need to be addressed as well, but they are much harder to deal with. I don't know what speakers you are using, but based on your room dimensions (I don't know the ceiling height either), you are going to have some bass issues to deal with. You can buy computer programs that will tell you where the problems lie--but I recommend just measuring the actual results and then tackling the problem (if there is one). Get a Radioshack SPL and the corrections for it (it's not linear), but if you do a search on the forums you can find the correction. Use a test CD that will give you warble tones from 20Hz to 500Hz (higher is fine). Then plot the SPL at the listening position. If your problems aren't too bad (no more than +6dB at any frequency below 80Hz) you can probably make a good correction with bass traps or other similar devices. It's difficult to make large bass corrections with only acoustic treatment. Assuming you need bass treatments you have a couple of options. You can buy bass traps and ASC or others will help you based on the plot and the room as to what you need. If you like to experiment you can make your own bass trap with a frame about 3 feet high and large enough to fit newspaper in it (it has to be open on the sides). Fill it with newspaper and cover it with WAF certified fabric (see Better Homes and Gardens). You can start with 2 in the corners behind each speaker. Moving them will change the attenuation. Also the amount of newspaper will change the amount of absorption.
Good luck--happy listening.