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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

�

1 k

.::

700

sao

400

�

300

200

100

6 8 I 0

20 304050701 00

Capacitance

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

H i g h

mid-ran g e

speaker

Capacitor

Woofer

Fig. 13

Chart1

200300 500

1 000

2000

(J.LF)

(metallized paper),

(metal

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.

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 ".