The 38% rule
There are two movable variables - the sitting
position, and the subwoofer position. For a small home, sometimes
neither is variable.
I had read up on this before, and understand
that sitting in a null zone was negative, but I had a lot of
limitations. Nevertheless, I decided to give it a try and just move my
main listening position a few feet forward, and try to get to the front
The result was rather satisfying actually. My subs remained
as they were before, and I didn't even re-do the Audyssey, but suddenly
the bass response from my mains, the centre and also the general rumble
and thump went up a notch.
So do consider squeezing that seat forward back and forward a tad...
THE 38 PERCENT RULE
The placement method used here is based on the "38 percent
rule" which theorizes that the best listening position is 38 percent into the length
of the room, when measured from either the front or rear wall. This offers the best
compromise of peaks versus nulls for any given room size. For 2-channel listening you'll
get the flattest low frequency response by sitting 38 percent of the way back from the
front wall. However, this is not practical in many home theaters, especially those with
large screens, because that puts you too close to the screen. Fortunately, you can get the
same benefit by sitting 38 percent of the room length when measured from the rear wall.
Please understand that 38% is one theoretical best location
to begin measurements, but it may not end up the best place to sit due to other factors -
wall properties, speaker location, speaker type, furnishings in the room, and a host of
other conditions that can affect frequency response. The only way to know which
location really is most flat is to measure the low frequency response at high resolution
using software such as ETF, FuzzMeasure, or Room EQ Wizard.
Once you know the ideal listening position from the front or rear
wall, the next step is to place the loudspeakers. The speakers and listening position
should be at the points of an equilateral triangle, as shown in Figures 1 and 2. Note that
the theoretical point of the triangle is just behind your head, with the axis lines
grazing your ears.
If you have the ETF program or RealTraps Test Tone CD, or another way to
accurately measure your room's low frequency response, you can experiment with different
speaker distances by sliding both speakers along each axis while you measure the response.
Otherwise, put them along the axis at a distance that is convenient and makes sense for
the size and layout of your room. Too often people obsess over minute details that matter
only a little, while ignoring ergonomic concerns that matter much more. Top
I have no financial interest or other interests in any of the items / events I write about.