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XIII. PROJECTION AND PROJECTORS
TABLE XXVIII Audio Performance Data of Projectors A to F Inclusive3
Projector
Watts rated output
Watts measured output6
Signal-to-noise ratioc
A
25
19.4
45.7
B
15
13.2
29.7
C
12
11.2
45.6
D
10
— d
38.7
E
10
9.6
46.2
F
10
11.8
19.7
a Data taken from Tables 4 and 5 of Circular C 439 (pages 25 and 37). b At 5% RMS total harmonic distortion of the test sine wave oscillator signal. c This value is for flat response measured without a neutral density filter. d The total harmonic distortion of this machine exceeded 6.4 percent at all poweroutput levels.
destructiveness is very serious despite the machine 's technical excellence otherwise. The test is a simple one, yet despite its simplicity it is of primary importance. Unfortunately, manufacturers do not usually provide data concerning this essential feature of their machines, and the buyer must find out for himself. Users and prospective users of 16-mm sound
TABLE XXIX Flutter Performance of Projectors A to F Inclusive
Amplitude Projector modulation (measured on 2% scale)
Percentage of flutter
Frequency of flutter and aural observation
1.55-1.65
1.55—1.65
0.4
0.3
1.0
1.2
0.6
0.45
c
1.55—1.65
0.25
0.45
0.33
D
1.55-1.65
0.7
1.4
0.85
E
1.55—1.65
0.4
1.2
0.7
F
1.56-1.62
0.45
0.62
0.53
Noticeable flutter by aural observation.. Rather violent fluctuations of various periods on occasion.
Noticeable flutter by aural observation.. Violent fluctuations of various periods on occasion. _
Long period fluctuations of approximately one second.
Noticeable flutter of various periods by aural observation.
Noticeable flutter by aural observation..
Noticeable flutter by aural observation..