Speakers; Speaker Selection; Speaker Wire Selection; Polarity And Phasing - Rotel RKB-650 Owner's Manual

RKB-650 Six Channel Power Amplifier

Speakers

The RKB-650 has three groups of speaker
connectors, one for each pair of amplifier
channels.

Speaker Selection

The nominal impedance of the loudspeaker(s)
connected to the RKB-650 should be a mini-
mum of 4 ohms. When driving multiple pairs
of speakers connected in parallel, the effective
impedance the amplifier sees is cut in half.
For example, when driving two pair of 8 ohm
speakers, the amplifier sees a 4 ohm load.
When driving multiple speakers in parallel,
select speakers with a nominal impedance
of 8 ohms or higher.

Speaker Wire Selection

Use insulated two-conductor stranded wire to
connect the RKB-650 to the speakers. The size
and quality of the wire can have an audible
effect on the performance of the system. Stan-
dard speaker wire will work, but can result
in lower output or diminished bass response,
particularly over longer distances. In general,
heavier wire will improve the sound. For best
performance, you may want to consider spe-
cial high-quality speaker cables. Your autho-
rized Rotel dealer can help in the selection of
appropriate cables for your system.

Polarity and Phasing

The polarity or positive/negative orientation
of the connections for every speaker and am-
plifier connection must be consistent so all the
speakers will be in phase. If the polarity of
one connection is mistakenly reversed, bass
output will be very weak and stereo imaging
degraded. All speaker wire is marked so you
can identify the two conductors. There may be
ribs or a stripe on the insulation of one conduc-
tor. The wire may have clear insulation with
different color conductors (copper and silver).
There may be polarity indications printed on
the insulation. Identify the positive and nega-
tive conductors and be consistent with every
speaker and amplifier connection.

Speaker Connections

See Figure 2
The RKB-650 has two pair of color coded con-
nections for each group of amplifier channels,
one for the left speaker, the other for the right
speaker. Labels above the connectors show the
proper connections for connecting speakers.
These speaker connectors accept bare wire,
connector lugs, or "banana" type connectors
(except in the European Community countries
where their use is not permitted).
Route the wires from the RKB-650 to the
speakers. Give yourself enough slack so you
can move the components enough to allow
access to the speaker connectors.
If you are using banana plugs, connect them
to the wires and then plug into the backs of
the speaker connectors. The collars of the
speaker connectors should be screwed in all
the way (clockwise).
If you are using terminal lugs, connect them
to the wires. If you are attaching bare wires
directly to the speaker connectors, separate the
wire conductors and strip back the insulation
from the end of each conductor. Be careful
not to cut into the wire strands. Unscrew (turn
counterclockwise) the speaker connector col-
lar. Place the connector lug around the shaft,
or insert the bundled wire into the hole in the
shaft. Turn the collars clockwise to clamp the
connector lug or wire firmly in place.
: Be sure there are no loose wire strands
NOTE
that could touch adjacent wires or connec-
tors.
For each group of channels, connect the left
speaker to the pair of speaker connectors la-
beled LEFT. Connect the right speaker to the
speaker connectors labeled RIGHT. Follow the
labels printed above the connectors, Make
sure that the positive terminal of the speaker
is connected to the + terminal on the ampli-
fier. Make sure that the negative terminal of
the speaker is connected to the – terminal of
the amplifier.
10

Troubleshooting

Most difficulties in audio systems are the result
of poor or wrong connections, or improper
control settings. If you encounter problems,
isolate the area of the difficulty, check the
control settings, determine the cause of the
fault and make the necessary changes. If you
are unable to get sound from the RKB-650,
refer to the suggestions for the following
conditions:
Front Panel Power Indicator Is
Not Lit
No main power to the RKB-650. Check AC
power connections at the amplifier and the
AC outlet. Check the front panel power switch.
Make sure that it is set to the ON position.
If using signal sensing auto power-on, make
sure that a signal is present at the inputs. If
using 12V trigger power-on, make sure that
a trigger signal is present at rear panel 12V
TRIG IN connector.

No Sound

If the amp is getting AC power, but is produc-
ing no sound, check the PROTECTION INDI-
CATORS on the front panel. If lit, see below. If
not, check all of your connections and control
settings on associated components.

Protection Indicator Is Lit

The front panel PROTECTION INDICATORS
light when the RKB-650 protection circuits have
shut off the amplifier. Typically, this occurs only
when the ventilation openings are blocked,
when there is faulty speaker wiring, or after
a period of extreme use. Turn off the system
and wait for the amp to cool. Then push the
front panel power switch in and out to reset
the protection devices. If the problem is not
corrected or reoccurs, there is a problem with
the system or the amplifier itself.