Octet Matrix Audio Home Theater Speaker User Manual - page 5
Home Theater Speaker Placement
Octet Matrix Audio -2010
Page 5
Subwoofer
Unlike the other speakers in a home theater system, subwoofers can be placed in many different
locations. That’s not to say that subwoofer placement is unimportant, but due to limitations in the way
in which humans determine the direction of low frequency sound sources, we do not require a
centered, clear line of sight placement. Acoustic waves lower than about 140 Hz have wavelengths large
enough to “wrap around” most obstacles in a typical home theater setting and will not be reflected the
way higher frequency acoustic waves are. These large wavelengths also make it difficult for humans to
detect phase and level differences between each ear. Phase and level differences are the primary
indicators the human brain uses to determine the direction of sounds.
Low frequencies are “enhanced” when subwoofers are placed near boundaries such as walls or corners.
While this sounds like a good thing, the frequencies that are reinforced are usually at the higher end of
the subwoofer range which will create boominess rather than low frequency extension. Boominess is
excess bass that is not present in the original recording and is often mistaken for low frequency
extension. If not corrected, this will result in dialog articulation problems and allow a subwoofer’s
location to be identified.
While some subwoofers are designed for a specific boundary placement (instructions or specifications
will tell you if they are), most subwoofers perform best on the floor several feet from the nearest
boundary. The intersection of the floor and wall can be a good location, but it may take longer to find a
location with suitable performance. A corner location can work, but the crossover frequency may have
to be adjusted lower to help reduce the tendency of the corner loading to increase the higher frequency
content of the subwoofer.
A well placed and adjusted subwoofer should provide deep bass that appears to originate from the main
speakers, or surround and/or rear speakers if the low frequency effect originates from the rear.
A fairly simple test will let you know if your subwoofer settings or placement will give up its location:
1) Download the Octet Matrix Audio Subwoofer Setup DVD ISO image in the Tech Center. You will
need to burn this image to a DVD using software designed specifically to burn DVD ISO images.
2) Set up all of your speakers with the subwoofer in the location you have chosen. Run the receiver
system optimizer according to the instructions, or set the speaker levels, time delays, etc.
manually before continuing. Confirm that the receiver is in Dolby Digital surround sound mode
with all additional DSP processing turned off.
3) Put the DVD you burned in step 1 into your DVD or Blu-ray player. Select and listen to the Left
and Right Channel Pink Noise Phase Test tone to confirm that the speakers are in phase and the
image is centered between the main speakers and does not shift or warble.