Acoustical tactics for the 2nd
You cannot eliminate room
modes. But room modes are manageable. Begin the
management process by designing or selecting a room with
dimensions that produce a more even distribution of room
modes. The following ratios from the 'Master Handbook of
Acoustics' will assist.
1 : 1.26 :
1 : 1.28 : 1.54
Ratio / George Cardas
Do not panic if you cannot
accommodate these ratios. The ratios are guidelines
that minimize the issue. Potential distorting modes
still exist with any ratio.
you are of the curious nature -- draft a mode analysis of
the proposed room to expose any potential room mode
issues. Locate modes below 300Hz. Analyze
their spacing. Identify coincidences and isolated
modes spaced more than 20Hz. For the less curious
skip to the next paragraph.
F1/F3 Floor Plan Sketch
Create a sketch of the room mode peak and null
points of F1 through F3 on the proposed
points equal the length and width divided by an even
this floor plan sketch to manage/select speaker and
Mounkes Speaker Listener Placement
I had to pick one practical audio application from the
Handbook -- this is it.
late friend Steve Mounkes taught me this simple
speaker/listener placement method many moons ago.
This method, plus a dose of room treatment, delivers
substantial audio improvement.
Divide the room width by values 3, 5, 7, & 9.
Measure, and mark the results along the
width of the room from the left corner, then the
Next, divide the room length by the same values.
Mark these points along the room length
from the front left and right corners.
Observe the on-floor coordinates established by the width
and length points.
While avoiding the peak and null coordinates on the F1/F3
sketch, select a pair of practical coordinates for the
stereo left and right speakers.
Then place the listening position in an equilateral
triangle with the two speakers.
Surround sound locations
multi-channel surround sound system is a circular
configuration that introduces additional speakers onto the
radius is the distance from the listening positions to the
front stereo left/right speaker locations.
Center channel speaker
Place the center speaker on the radius mid-point between
the front left and right speaker positions.
Rear speaker placement
5.1 -- Place the
rear speakers of a 5.1 surround sound arrangement at 110°
left and right of the front center speaker.
6.1 -- Place
another rear speaker at 180° of the front center speaker.
7.1 -- Place two rear
speakers; one 150° left, and the second 150°right, of the
front center speaker.
listening position of the equilateral triangle is the
ideal seating location. However, additional seating
is probably desirable.
Therefore, select additional-comfortable-positions that
avoid room mode peak and null points.
Finally, while evading peak and null points, select the
placement of the subwoofer.
the subwoofer is placed sufficiently away from the room
boundary but less than 1/4 of the dimension, it will
minimize stimulating modes F1 through F4.
Please refer to Chapter Six, page 5, for detailed
troublesome distorting room modes persist, absorb them
with the placement of a broad bandwidth bass trap in the
corner nearest each speaker.
the final analysis, subjectively fine-tune all speaker and
listener positions with the organic sound meter that is
attached to your head.
is still the most sensitive listening device available.
Additional note for the 2nd Region:
Consider experimenting with multiple subwoofers placed in
Multiple subwoofers may create a more even distribution of
the low-frequency sound.