| Model "D" |
Series 2-3-4 808 |
Series 5 |
Series 6 |
Series 7 |
Logic 7 |
Studio 8 |
|
| No of Speeds | 2 | 2 | 2 | 3 | 3 | 3 | 3 |
| Speeds | 3.75 & 7.5 |
3.75 & 7.5 15 & 7.5
|
3.75 & 7.5 15 & 7.5
|
7.5 , 3.75 , 1.875 15, 7.5, 3.75 |
7.5 , 3.75 , 1.875 15, 7.5, 3.75 |
7.5 , 3.75 , 1.875 15, 7.5, 3.75 |
15, 7.5, 3.75 |
| Wow & Flutter |
0.2% @ 7.5 |
0.2% @ 7.5 |
0.16% @ 7.5 |
0.16% @ 7.5 |
0.08% @ 7.5 |
0.1% @ 7.5 |
0.08% @ 7.5 |
| Frequency Response
@ 1 7/8 ips |
n/a | n/a | n/a | 50 - 7kHz | n/a | n/a | |
| @ 3 3/4 ips | 50-5kHz | 50 - 6kHz | 50-6kHz | 50-6kHz | 40-14kHz | 40-14kHz | 30-12kHz |
| @ 7 1/2 ips | 50-9kHz | 40-12kHz | 40-12kHz | 40-15kHz | 30-17kHz | 30-17kHz | 30-15kHz |
| @ 15 ips | n/a | 40-15kHz | 40-15kHz | 40-15kHz | 30-20kHz | 30-20kHz | 30-18kHz |
| Cross-talk | n/a | 40dB Stereo | 40dB Stereo | 45dB Stereo | 50dB Stereo | 50dB Stereo | n/a |
| Signal - Noise |
Unwtd >45db Wtd 50dB |
Unwtd >45db Wtd > 50dB |
Unwtd >50db Wtd > 55dB |
Unwtd >50db Wtd > 55dB |
Unwtd > 55db Wtd > 60db |
Unwtd > 60db Wtd > 65db |
Wtd > 59dB @ 7.5ips |
|
Speed Accuracy |
n/a |
Greater than 2% |
Greater than 0.5% |
Greater than 0.5% |
Greater than 1% | Greater than 1% | Greater than 0.1% |
|
SUMMARY OF RESULTS. |
| Wow
& Flutter: On this aspect of mechanical performance you can see the difference that the new smaller capstan made from the series 2,3 & 4 to the Series 5 & 6. Although it only reduced the Wow & Flutter figure from 0.2% to 0.16%, in those days this was a considerable achievement. As we progress up the range, and also in time. We see the gradual improvement of this measure of short term speed stability, brought about by better engineering, in the manufacture of motors, and particularly in the precision lathe work involved in the turning of the capstans idlers, and flywheels. The difference between early Wearite decks and the modern Logic deck is reflected in the very much improved mechanical performance, indicated by the wow & flutter figure of 0.08% |
Frequency
Response: The figures clearly show a steady and quite dramatic improvement in the frequency response from the Series 2 up to and including the Series 7, the Logic shows no further improvement. Many of these performance improvements have resulted from the evolution of recording tape. As manufacturers found ways of making thinner and stronger base materials, reducing the oxide particle size, and increasing the density of tape oxide. These developments gave manufacturers the impetus to improve bias / erase oscillators, and produce record amps capable of more gain with no increase in distortion. Better head design led to increases in maximum record level being possible. Whilst improved tape to head contact and narrower head-gaps gave a wider frequency response. |
Signal
- Noise Ratio: One of the most important quality and performance indicators. An area in which Dolby Labs would play a major role in years to come. In the above table note the dramatic improvement in the un-weighted figures, from the early Series 2 at > 45 dB to the Logic 7 at > 60 dB. When you consider that a difference of 3 dB is a twice as good. This figure will vary dependant on track width, quarter track machines are usually 2-3 dB lower than the equivalent half track model. And half track would be 2-3 dB lower than a full track model. Un-weighted Noise: Means measuring the machine and all its mains hum and amplifier noise. Making no allowance for the actual range we humans hear. Weighted: A measurement that restricts the measured noise to a band of frequencies that human hearing is most sensitive to namely, 200 to 12,000 cps. |