J. W. Davis & Company D-250AL User Manual - page 5
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The D-250AL is designed to be connected to 8-ohm speakers directly, or to variable impedance speakers that
match the amplifier’s line output voltage of 25V or 70.7V speaker lines.
VI. SPEAKER INSTALLATION
CONNECTING FOR DIRECT 8-OHM OPERATION
Connect 8-ohm speaker(s) to terminals 1 (-) and 2 (+). See page four. To maintain proper phasing, observe
correct polarity. NOTE: This is a bridged output. Do not ground either of these two terminals
.
For 25V output, connect the load to terminals 3 (-) and 4 (+). For 70.7V output, connect the load to terminals 3 (-)
and 5 (+). See page four.
CONNECTING FOR 25V or 70.7V LINE OPERATION
Cable distance should be kept as short as possible to minimize power loss. The chart below can be used as a
general guide showing various wire sizes and the maximum distance related to cable loading that speakers can
be placed from the unit for an approximate -0.5dB loss (-12.5% power). To allow for future expansion and
distributed cable line loss, it is recommended the total system wattage should not exceed 80% of the amplifier’s
rated output. To determine the total system wattage, sum the wattage tap of all speaker(s)/horn(s) used.
USING THE PROPER WIRE SIZE AND LENGTH
70.7V SPEAKER LINE
(FOR 25V LINE DIVIDE ALL 70.7V LENGTHS BY 8)
NOMINAL POWER IN LOAD
LOW IMPEDANCE
SPEAKER LINE
AWG
SIZE
2-WIRE COPPER CABLE LENGTHS FOR SPEAKER LINES AT -0.5dB LOSS IN SPL (12.5% POWER LOSS IN WATTS)
VII. USING HORN SPEAKERS
THE LOW-CUT FILTER
The D-250AL is equipped with a low cut filter that is activated by the LINE OUTPUT switch. When the switch is in
the IN position the 25 and 70.7 volt ouputs will roll-off any frequencies below 120Hz. Low frequencies can damage
horn diaphrams, as well as compression drivers, if no filter is used. NOTE: Some installations may require
additional electronic equipment to protect a total horn, or compression driver type installation.
NOTE: When using the amp’s 25V or 70.7V line operation, the proper tap setting of the impedance matching
transformer determines the individual speaker’s power level. Using these transformers allows the speakers to be
placed at longer distances from the amplifier without significant power loss. The number of speakers for a line-
driven central amplifier system is limited to the power available from the amplifier. The sum of all connected
speakers’ power settings must not exceed 80% of the total power available from the amplifier.
NEW TECHNOLOGY
OLD RELIABILITY
J.W. Davis & Company
• 3030 Canton Street • P.O. Box 710219 • Dallas, Texas 75371-0219
Sales 800-527-5705 • Fax 800-388-9106 • Corp 214-651-7341 • Fax 214-939-0328 • sales@jwd.com • www.jwd.com
-5-
4 OHMS 8 OHMS
16
120
240
480
75
150
300
50
95
190
30
60
120
20
40
75
15
25
50
10
15
30
7.5W
15W
30W
-
-
5,000
-
6,200
3,100
7,600
3,800
1,900
4,800
2,400
1,200
1,500
1,920
960
480
1,200
600
300
60W
100W
125W
2,500
1,500
1,100
1,550
940
750
950
600
450
600
370
290
375
230
180
240
150
110
150
95
-
250W
400W
500W
550
365
275
375
230
185
225
140
110
145
90
-
90
-
-
-
-
-
-
-
-
10
12
14
16
18
20
22
WIRE LENGTHS IN FEET
3,000
750