Sound waves that reflect off of the walls (and other surfaces) of your home theater affect the quality of your listening experience. This is because the reflected sound coming from the walls reaches your ears very shortly after the same sound coming directly from your speakers reaches your ears. You may not even notice the effect of this “comb filtering”, but you are hearing the wall’s negative influence on your room audio (frequency response). These reflections damage imaging and clarity of sound to the listening position. Acoustic “absorption” panels are an excellent tool used to significantly decrease or eliminate these sound issues.
Comb filtering is a specific type of frequency response issue that’s caused when a sound source and its reflections combine in the air. Depending on the difference in arrival time to your ear, some frequencies are boosted and others are reduced.
| Where should Acoustic Panels be placed?|
For the purpose of this FAQ we will only touch briefly on some very rudimentary aspects of acoustic panel placement. Although acoustics is a science, using some of these simple rules and techniques can easily help make a dramatic improvement in any listening environment.
Start by combating “First Reflections” using these steps:
Find the “First Reflection Point” by using a mirror. This is done by sitting in the main listening position of the room facing the front speakers. Have a friend place a hand mirror on the left wall. At speaker height have the friend move the mirror on the wall until you can “SEE” the left speaker’s reflection in the mirror. Mark that spot on the wall with tape. Continue moving the mirror until you see the right speaker. Mark that spot on the wall with tape. Repeat this process for the right wall. You now have your first locations for acoustic panels in your room! If you have a second row of seats repeat this for that listening location and mark the wall.
A really great video from GIK Acoustics
showing this concept can be found here:
Ultimately the spots you marked on the wall should be the location(s) of your acoustic movie posters! In practice you can approximate the location of your acoustic panels and split the difference with one acoustic movie poster to save on the number of panels needed. It’s up to you! For a simple home theater this seems to work just fine.
For a 20’ x 20’ room we usually suggest one or two acoustic movie posters for the back wall and one or two for the back third of the side walls of the room for aesthetics and other reflection points in addition to the first reflection panels. So as a rule, an average room should have between 5 and 12 strategically placed acoustic movie posters or a mix of acoustic movie posters and acoustic panels.
Although the placement, type, and quantity suggestions we have made above are very effective, they should not be considered complete or definitive acoustic treatment of a room. If you’re interested in a more precise sound environment we suggest contacting an acoustic service professional in your area for a consultation.