Pioneer D-23 Operating Instructions Manual page 10

PROTECTIVE CAPACITORS FOR SPEAKERS
If the tweeter, or mid-range speaker, is mistakenly
connected to the power amplifier for low fre­
quency range, or if noise is suddenly generated by
a faulty connection, any large low frequency signal
reaching the tweeter or mid-range speaker may
cause irrepairable damage. To avoid this danger,
it is recommended that protective capacitors be
inserted as shown in Fig. 13. The capacitance of
the capacitor can be determined from Chart 1
once the speaker's impedance and the crossover
frequency (set by D-23) are known. For example,
if the speaker's nominal impedance is 8 ohms, and
the selected crossover frequency is 5kHz, the re­
quired capacitance will be 8J.LF.
Stereo power amplifier
Input
20k
I Ok
7k
Sk
N
4k
I 3k
�
2k
c:
Q)
:J
cr
1 k
Q)
.:: 700
sao
ID
6
400
�
300
u
200
100
70
50
4 6 8 I 0 20 304050701 00
2
Capacitance
MP
Suitable capacitors include
lized mylar), and Oil capacitors.
capacitors (non-polar capacitors) since they have adverse effects
on the quality of sound.
STEREO POWER AMPLIFIERS
Although the use of identical stereo power ampli­
fiers would be ideal, it is also possible to use
amplifiers of different power ratings, depending on
the rated sensitivity of each pair of speakers.
For example, if a 60watt output power amplifier
is used with woofers of 90dB/W sensitivity in the
low frequency region, and the rated sensitivity
of the tweeters being used is 96dB/W, a power
amplifier of 15watts rated output power will be
sufficient. Difference in rated sensitivity is 6dB
(power 1/4; 60W 1/4
x
=
H i g h
mid-ran g e
speaker
Capacitor
Woofer
Fig. 13
Chart1
200300 500 1 000 2000
(J.LF)
MM
(metallized paper), (metal­
Do not use electrolytic
15watts).
LEVEL ADJUSTMENTS
Since the output sound pressure levels in most
ordinary speaker combinations are not the same, it
will be necessary to adjust levels prior to playing.
This entails adjusting the D-23 LEVEL controls
while listening to the sound from the speakers.
The procedure is as follows:
1. Check that all power switches are OFF.
2. Select the most suitable crossover frequencies
and slope characteristics
range.
3. Set the preamplifier controls as follows:
a Turn the TONE control OFF, or the BASS
and TREBLE controls to FLAT.
b Set the MODE selector to L+R (mono out­
puts).
c Turn the BALANCE control fully counter­
clockwise so that sound is heard from the left
channel speakers only.
d Set the VOLUME control to normal listening
level.
4. Check the rated output sound pressure levels of
each speaker from
respective instruction manuals. Commence with
the speaker whose sound pressure level is lowest,
setting the corresponding LEVEL control on the
front panel of the D-23 to the "0" position, and
all other LEVEL controls to"
5. Turn the power ON.
6. Now gradually turn the LEVEL control in the
adjacent frequency range clockwise until there is
a smooth consistency of sound between the two
speakers. Use the level marker to mark this posi­
tion.
NOTE:
Use the rated sound pressure levels of each speaker as a
guide when adjusting levels in this manner.
7. After adjusting levels for all frequency ranges,
re-check the consistency of sound across all
ranges, and mark the positions with the level
markers.
8. Turn the preamplifier BALANCE control clock­
wise so that now the sound is heard in the right
channel speakers only, and repeat the above
procedure.
9. Switch the MODE selector to STEREO, and
check for overall stereo balance.
NOTES:
Change the program source, and repeat the level adjust­
•
ments as a means of checking.
Beginners are advised to compare the same program
•
source with another (or a lready familiar) stereo system.
for each frequency
the specifications in the
oo ".