JBL Synthesis SDP-45 4K - Manual (Page 23)

Basic Operation
JBL SYNTHESIS SDP-45
- 23 -
SPEAKER PLACEMENT GUIDE
[THE FOLLOWING SECTION IS REPRINTED FROM THE CEA/CEDIA GUIDELINES AS WRITTEN BY DR. FLOYD TOOLE AND REPRINTED WITH DR. TOOLE’S PER MISION]
The horizontal loudspeaker layout is defined from the perspective of
the prime listening location . In the example in Figure 1, the prime
listening location is in the center of the seating area; this is obviously not
a requirement. If there is to be only one pair of surround loudspeakers,
as in a 5.1-channel system, they should be placed within the angular
range ±110º to ±120º. If there are four surround loudspeakers, as in a
7.1-channel system shown here, the side loudspeakers can be placed
symmetrically within the angular range spanning ±60º to about ±100º,
and the rear loudspeakers within the angular range spanning
approximately ±135º to ±150º. A 6.1-channel system could obviously
have a single center-rear loudspeaker, but it is recommended that the
signal be split between two rear loudspeakers. Note that, in some
rooms, the rear loudspeakers cannot be, or need not be, on the rear wall
– it is the angles that matter. Given the flexibility in surround speaker
placement, in a small room with two rows there is a benefit to placing
monopole or bipole side loudspeakers in positions that are equidistant
from each row. This yields a simplified sound level calibration which
does not bias one row over another.
If it is necessary to use additional surround loudspeakers for large
audience areas and/or in large rooms, those added loudspeakers should
be spaced by equal angles within the angular range shown in Figure 1.
Finally, the prime listening location, and as many other listeners as
possible, should be placed on the center line of the seating array,
preferably half way between the side surround loudspeakers. From the
perspective of perceived envelopment, these are the best seats in the
house. They are also the best seats in the house to avoid hearing
steering artifacts in upmix algorithms
– the unintended momentary bursts
of sound in surround loudspeakers. In the past, some designers have
avoided this location because they believed that there were low-
frequency acoustic nulls at that location. This is true if only a single
subwoofer is used. However, if two or more are used in the manners
prescribed in the Subwoofer section later in this document, these nulls
are eliminated, and several listeners are exposed to better and more
uniform bass.
Loudspeaker elevations or height: The front three loudspeakers
should be mounted with tweeters at, or close to, ear level. A vertical
discrepancy between center and side channels of about 2 ft (60 cm) is
acceptable across the width of a large screen. The ventriloquism effect
often deals with even greater directional errors than this when all of the
on-screen sounds emanate from the center channel. Surround
loudspeakers should be elevated about 2 ft (60 cm) above ear level, this
being a compromise between the requirements for multichannel music
(all loudspeakers at ear level) and movies (surround loudspeakers
elevated). Be careful to ensure that listeners have line-of-sight contact
with the tweeters of the three front loudspeakers. This may require
staged multilevel seating, which has the additional advantage of allowing
one listener in each row to be on the center line of the room
–staggered
seating is not required. Elevating the surround loudspeakers allows
them to be heard by all listeners in each row. In very narrow rooms, high
wall locations will help avoid localization of the side loudspeakers by
those listeners on the edges of the audience area.
Figure 1 –
A simple diagram showing the angular ranges within which loudspeakers
should be located relative to the prime listening location. The locations of
the front loudspeakers follow guidance at www.dolby.com. The angular
range for surround loudspeakers is the recommendation in ITU-R
BS.775-2 (2006)©. From CEA/CEDIA-CEB22.