Thirteen tapes were tested for print-through. They are ranked in descending order of signal-to-print ratio (high numbers are better).
Manufacturer Tape S/P in dB Zonal 675 59 Zonal 818 59 Quantegy 478 58 BASF 468 57 Maxell UD50-60(N) 57 Quantegy 480 57 BASF 911 56 3M 908 56 Quantegy 479* 54 3M 986 54 Quantegy 406 53 Quantegy 408 53 Quantegy 456 51
* Quantegy 479 is a 1-mil version of 480. 3M 908 and 986 have been discontinued.
Procedure: All tests were done at 15 ips because print-through is worse at the higher speed. Print-through is maximum in a mid-range band of frequencies. Each tape was tested with bursts of pink noise first, to determine the approximate maximum of the print-through band for that tape. That maximum frequency was used for the reported test (all between 800 - 1.6 KHz). A few minutes of 300 ms tone bursts at eight-second intervals were recorded on each sample tape. The reel was stored tails out for twelve hours. The reels were played backwards without rewinding and the maximum print-through reported.
The top six tapes in the print-through ranking were selected for further tests.
Tapes are ranked in descending order of signal-to-noise ratio (high numbers are better). All tapes were overbiased 5 dB at 10 KHz, 7.5 ips. S/N was measured at 7.5 ips from a 1 KHz tone at +4 modulometer with the limiter off, to the noise level with pot down, measured A-weighted to simulate the audibility of low-level noise.
Lev (0 Mod) Manufacturer Tape nWb/m THD+N % S/N dBA 3M 986 510 .50 72.2 Quantegy 480 510 .48 71.6 Quantegy 478 510 .45 71.4 BASF 468 510 .57 70.1 Zonal 818 510 .43 69.3 Maxell UD 50-60 (N) 445 .38 69.1
Note about bias: 986, 480, and 818 seem to reach minimum distortion around 6 dB overbias at 10 KHz. I think biasing this high loses too much high-frequency headroom. It also increases low-frequency modulation noise (while reducing high-frequency modulation noise). I've compromised on 5 dB overbias for all tapes. The saturation level at 7.5 ips for a 10K tone with a 5 dB overbias is about -3 dB modulometer for all these tapes. This is two or three dB lower than what you could get with 908, but years of experience with 986 has shown that this HF saturation point is no problem. Where more high-frequency headroom is needed (cymbal-intense music, sound effects) the 15 ips NAB setting should be used.
Modulation noise is hiss and rumble generated only in the presence of signal. It's like distortion, but it makes random fuzz around the tones rather than harmonics. The audible effect is subtle. Low frequency modulation seems related to irregularity of the coating thickness, and high frequency modulation noise to the surface smoothness of the coating. Low frequency modulation noise was measured in the 100 Hz 1/3 octave band stimulated by a 40 Hz tone at -15dB modulation. High frequency modulation noise was measured in the 4 KHz 1/3 octave band stimulated by a 10 KHz tone at -15 dB. Tapes are ranked by low frequency modulation noise. The scale is arbitrary-- lower numbers are better.
Manufacturer Tape HF Mod N dB LF Mod N dB Quantegy 480 50 47 BASF 468 51 49 3M 986 45 50 Quantegy 478 48 53 Maxell UD 50-60 (N) 49 53-56 (klunks) Zonal 818 51 56-60 (klunks)
Note that the ranking is not the same in the high and low frequencies. 480 is 3 dB quieter than 986 in the low frequencies, but has 5 dB more noise in the high frequencies.
Shedding is tested by putting a piece of adhesive tape on the face of the erase head, and running a tape for 15 minutes. The tape is peeled off, stuck on paper, and covered with another piece of tape for preservation. The six reels used for testing were tested for shedding after all the other tests.
478 and 480 are at the most desirable part of the envelope. Since 478 has 6 dB more low frequency modulation noise than 480, the choice is easy. 986 users changing to 480 lose a tiny bit of S/N but gain a significant improvement in print-through.This series of tests applies only to the sample reels submitted by the manufacturers, and says nothing about the manufacturers' ability to deliver consistent quality.