NAD T750 Manual Del Usuario página 13

For best results, the Surround loudspeakers should not beam the
sound directly at the listener. One way of achieving this is to use
'dipole' Surround speakers which aim the sound down the walls
rather than directly into the room. An alternative is to use standard
small loudspeakers for Surrounds, but not to point them directly
at the listening position. It is always worth experimenting with
various Surround speaker positions to see which works best in
your room.
With the recent advent in digital technology, various new surround
systems have emerged. Best known are Dolby Digital and DTS,
both are sometimes referred to as 5.1 formats (5 independent,
full range channels and 1 "Effects channel" for bass). The Dolby
Digital and/or DTS formats can be found on some Laser Discs and
DVDs, for instance.
Using the NAD T750's Ext. 5.1Ch. input, the decoded, analogue
audio Dolby Digital or DTS can be directly connected. Already
there are DVD players available with integrated Dolby Digital
decoder, which will connect directly to the T750.
SPEAKER PLACEMENT
Placement of the speakers in a Dolby Pro Logic surround system
plays an important role in the performance of the system.
FRONT SPEAKERS
The front speakers should be placed with the left and right
speakers evenly spaced either side of the TV screen. The centre
speaker should be placed underneath or above the TV monitor so
that dialogue is localised close to the TV image.
SURROUND SPEAKERS
The surround speakers are used to create a diffuse room-filling
atmospheres rather than pinpoint sound effects. Surround
speakers should be wall or shelf mounted fairly high up either on
the side walls, rear wall or in the rear corners. Speakers can be
mounted facing sideways or upwards to increase the diffusing
effect by bouncing the sound off the walls and ceiling before it
reaches the listener.
SUB-WOOFER
The very low frequency sounds produced by the sub-woofer are
difficult to localise so the Sub-woofer can be placed virtually
anywhere in the room. Placing Sub-woofers against walls or in
corners will increase the amount of bass produced in the room.
WHY HAVE A CENTRE SPEAKER?
The Dolby Pro Logic decoder produces three separate outputs for
the Front signals - left, centre and right. On most soundtracks, the
sound effects and music are spread across all three front channels
but the dialogue is mainly fed to the centre channel only.
Using a separate centre channel speaker will allow the dialogue to
cut through even the biggest sound effects and musical scores.
Having the sound spread across three front speakers also stabilises
the stereo image, making the usable listening area much bigger.
If you are using the T750 with only two front speakers, setting the
Centre mode (No. 17) to PHANTOM will place the centre
information on both the left and right speakers. This creates the
impression of a centre channel sound source.
For best results, you should consider using a centre speaker.
Ideally it should be the same type as the left and right speakers,
although there are now many new speakers, such as the NAD
808CC, which are specifically designed as centre channel add-ons
for existing stereo systems.
All manuals and user guides at all-guides.com
NOTE: Ensure that any speaker that is to be used near a TV or
monitor is of the magnetically shielded type (see loudspeaker's
instruction manual). It is not normally possible to modify an
unshielded speaker to work very close to a TV or monitor.
WHY HAVE A SUB-WOOFER?
Many film soundtracks rely heavily on very low frequency sound
effects which are difficult for normal hi-fi speakers to reproduce.
To faithfully reproduce these low frequencies you can use a
specially designed low frequency loudspeaker with its own built-
in amplifier. Because it is difficult to hear which direction very low
frequencies are coming from, you only normally need one sub-
woofer and this can be placed virtually anywhere in the room. The
Sub-Woofer output of the T750 is designed specifically to drive a
sub-woofer system.
SPEAKER PHASE
In a home theatre system it is important that the three front
speakers are all in phase compared to each other. Incorrect phase
will produce a poor stereo image and an apparent lack of bass. If
you are using speakers all from one manufacturer and power
amplifiers all from one manufacturer then to ensure correct
phasing of the system, just make sure that all the red (+)
connectors on the power amplifier speaker outputs are connected
to the red (+) connector on the loudspeaker.
If you are using a mix of amplifiers or speakers from different
manufacturers, or using amplifiers in 'bridge' mode, then it is
possible that the phase can be internally reversed in the some of
the amplifiers or speakers, so you must check for correct phase
by listening.
To check phase by listening, set the T750 to Dolby Pro Logic and
FM Mute/Mode OFF and select a FM radio station. This will give
you the same sound on all three front speakers. Disconnect the
surround speakers and the right front speaker. A stable sound
image should be heard as though it comes from a single point
between the centre and left front speakers. If the signal sounds
diffuse and not as though it is coming from a single point in space,
reverse the connections to the centre loudspeaker. The signal
should now appear to come from a single point between the left
and centre speakers.
Reconnect the right front speaker and disconnect the left front
speaker and repeat the procedure for the right and centre front
speakers, changing the connection only on the right front speaker
if the phase needs correction.
Surrounds will normally be in phase with each other if they have
been correctly connected.
There is no absolute rule regarding the relative phase between the
front speakers and the surround speaker pair or the Sub-Woofer
(if used). Connecting these using the red (+) connector from the
amplifier to the red (+) connector on the speakers should
produce correct results. But in some rooms reversing the
connections may produce a noticeable increase in bass response
or an improvement in overall stereo imagery, so you may wish to
experiment with reversing the connections on both the surrounds
or reversing the connections to the sub-woofer.
GB
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