By HOWARD A. ROBERSON
In September 1984, we published a "Cassette Test Update" covering 12 formulations; this, in turn, was an update of the September 1983 review of 77 cassettes. The fact that this present article covers 49 new and updated products illustrates the continuing improvement made by ail manufacturers. Included here are 20 Type I tapes, 23 Type IIs, and six Type IVs. There are three formulations from BASF, six from Denon, three from Fuji, eight from Maxell, four from Memtek Products (Memorex), five from PDMagnetics, three from RAKS, four from Scotch, five from Sony, five from TDK, and three from Triad. I may have missed some improved tapes, at least since our previous coverage, but I have relied on the manufacturers' announcements and responses to queries.
(Editor's Note: As we were fact-checking this article prior to sending it for typesetting, we were told by a PDMagnetics technical ser vices representative that the firm had ceased operations in the United States. Since goodly stocks will remain on dealer shelves and the firm will continue to do business in Canada, we felt the most reasonable course was to include the data Mr. Roberson had taken. -E.P.)
BASF emphasizes that their LH Maxima I and Chromdioxid Extra II are the IEC Standard Reference Tapes for Types I and II, respectively. The company's new Type II tape is Chromdioxid Maxima II. The names sound impressive, albeit a little complicated. The boxes and tapes show abbreviations: LH-MI, CR-EII, and CR-MII--much easier to handle. All formulations have new shells and packaging.
Denon's tape line is new, with the exception of DX-1, which remains in the line. The "HD" in each of the new formulations stands for "high density." In their literature, Denon emphasizes the "over-sized window, the higher-grade pressure-pad spring, the trans parent H-shaped slip sheets and the DB (dynamic balance) hubs." Denon's best tape for high (Type II) bias is HD8, which uses New High Technoroum--a mixture of cobalt-coated ferrite and metal.
Fuji has improved their FR-II with new, fine-grain Beridox magnetic particles, applied with advanced coating technology for greater density and uniformity. The FR tapes' cassette mechanism has been improved with honey comb slip sheets, a loop-prevention guide, a tension stabilizer guide, and other features. Fuji's GT-I and GT-II cassette tapes are close, magnetically, to their FR-I and FR-II counterparts. The GT shells and mechanisms, how ever, are made to operate at higher temperatures and under conditions of vibration such as exist in car tape-player service.
Maxell made general improvements across the line and made changes to the line, as well. LN is gone, replaced by UR. UDS-1 and UDS-II are new products specifically targeted for distribution through chain stores and other mass merchandisers. UD drops out of the line, with UDS-I in a sense its replacement. UDXL-I and UDXL-Il, in case you haven't noticed, are simplified to XLI and XLII, respectively. XLI-S and XLII-S remain in the line. Experience with the particles used in these cassettes supported the technology used for the coating on UDS-II. A new ferri-crystal magnetic particle was developed for UDS-I.
Memtek Products has updated the Memorex MRX I and HBII formulations, but two new additions to the line are of greater interest. HBXII is a high-remanence formula designed to provide higher MOLs (maximum output levels), greater sensitivity, and increased frequency response compared to standard high-bias tape. The new CDXII is a late addition to the still-limited category of metal-particle cassettes for Type II bias. Memtek wants the "CD" in the name to emphasize the tape's ability to record wide dynamic ranges, such as on Compact Discs and digitally mastered LPs.
PDMagnetics has updated most of the formulations in both its standard and HG (high-grade) lines. The improvements include new shell designs for better tape visibility and better mechanical performance. As a fair percentage of our readers may know, PDMagnetics is a joint venture be tween Philips (whence cometh the "P") in the Netherlands and DuPont (providing the "D") in the United States.
RAKS has not been represented in any of our previous surveys, and it appeared worthwhile to include their three formulations. The RAKS tapes are products of Turkey, and the sup plied literature did not provide much information.
Scotch has made improvements across the entire line, including new packaging. I had never tested Scotch's CX formulation before, so a report was considered to be in order at this time.
Sony calls its line of newly designed audio cassettes "high tech," and they're not just using buzzwords. Bias noise levels are reduced with the use of new Super Crystal Gamma ultrafine magnetic particles, which are said to be distributed more evenly and densely, with an improved binding system for stronger adhesion. The improved Su per Protection (SP) II mechanism, parallel-ribbed liners, and stepped hubs all help to ensure more even tape winding. The shells now have a wide-window design for greatly improved viewing. The line consists of HF and HF-S Type Is, UCX and UCX-S Type IIs, and the Type IV Metal-ES.
TDK has improved the D and AD Type Is, as well as the SA, SA-X and HX-S Type IIs. The D formulation has been updated to bring a new level of premium performance to "value-conscious consumers." The improved AD combines ultrafine Linear Ferric Oxide particles with a better binding process, improving both the distribution and orientation of the particles. TDK has resisted the name-changing strategy used by some others. They have, how ever, made further improvements in their SA formulation and have changed their Laboratory Standard cassette mechanism to reduce mechanical resonance during recording and play back. SA-X offers high sensitivity with low noise, claimed to be "lowest in its category." Because my first report on HX-S (September 1984) used early, limited-production samples, I decided to do a complete re-check to verify the conclusions made at that time.
Test Methods
Each manufacturer supplied three samples of each formulation evaluated. I examined the packaging and un wrapped the samples, noting any tab instructions. Every sample was fast-wound once in each direction before any other tests.
I used a Nakamichi 582 deck for the great majority of these record/play back tests. I also used a Nakamichi CR-7A and Aiwa and Akai recorders for some follow-up tests.
Bias and sensitivity figures for all tapes tested were measured with reference to the standard IEC Type I, Type II, and Type IV reference tapes. Bias was measured at an internal point in the deck, using a Heath SM-5238 audio voltmeter in its dB mode and re cording the meter's dB output on a calibrated stripchart recorder for easy reading to 0.1 dB. Sensitivity was calibrated using the 582's built-in 400-Hz tone and setting a Fluke 8050A true rms meter, in dB mode, to read "0.00" during playback of the IEC reference tape. Relative sensitivities for all other tapes were then read directly from the meter.
Bias was set using pink noise, band-limited to 20 Hz to 20 kHz, as the source, with adjustment made for the best response at 20 dB below Dolby level. The record-head alignment was always trimmed before the bias adjustment to ensure the absence of skew effects. Because the bias could be set to make all of the -20 dB responses nearly alike, no plots were made at this level nor was there any effort to mea sure the minor differences in the-3 dB points. Swept-sinusoid plots and -3 dB checks were made at Dolby level, however, as this data was indicative of high-frequency saturation limits.
In a change from previous tests, the maximum 3% distortion points are out put levels, referred to Dolby level (200 nWb/m at 400 Hz). The Fluke 8050A was set to read "0.00" dB for playback of a Dolby-level calibration tape, and all maximum output level figures were then read from the 8050A's display.
The MOL figures for 100, 400, and 1,000 Hz show the signal levels at which third-harmonic distortion reached the standard 3% level. The MOL figures for higher frequencies show the signal levels at which twin-tone IM (TT1M) distortion reached 3%.
For this test, I used tone pairs of 2.0 and 2.5 kHz for the 2-kHz MOL data, 5 and 6 kHz for the 5-kHz data, 7 and 8 kHz for the 7-kHz data (not shown in Table I but used in plotting the figures for all formulations), and 10 and 11 kHz for the 10-kHz MOL data.
The signal-to-noise ratio was referenced to the signal level that produced 3°A, distortion at 400 Hz, measured with IEC A weighting. (For those who wish to compare these results with figures obtained with CCIR/ARM weighting, subtracting 2.6 from the dBA figure will provide a fairly accurate conversion.) A 3-kHz tone was recorded and played back to assess flutter. I should point out that these results are just general indications: The deck which one uses has a considerable effect on the measured figure for any tape. Even relative rankings may shift when the same tapes are measured on a different cassette deck, especially if those rankings are close to begin with. The same 3-kHz tone was also used to test for dropouts and to determine the degree of level stability at this moderately high frequency.
I measured modulation noise differently this time than I have in the past. Formerly, I used a simple 1-kHz notch filter to remove the recorded high-level tone, measuring the distortion products (and noise) remaining. However, the "notch" of such a filter is not perfectly square-sided, but tapers enough to filter out some of the distortion products, too. This time, to minimize the notching needed, I recorded the high level tone on both channels, reversed the polarity on one channel in play back, and trimmed levels and head alignment until the test signals from the two channels (when mixed together) nulled each other out as far as possible. I then used a filter to notch out only the residual tone left after nulling. This method works because the 1-kHz test tone is coherent and correlated channel-to-channel, but the modulation noise is not. Therefore, summing the two channels, with one out of phase, cancels the tone, while the noise power from the two signals adds; with a little level compensation, the method works out just fine.
Use Tests
The first tests involved removing the external plastic wrapping and then fast-winding the samples in each direction. I had been frustrated in the past when trying to get a cassette's wrapper off. Even after using the pull tab, it is often a struggle. I have found that by purposely pulling the tab toward the other end of the box and then, perhaps, toward the "short" end at the last moment, I can remove most wraps very easily. So, how well did this work on these samples?
BASF: Removal of the wrap was easy with the across-the-box pull. A couple of the boxes hung up a little when opening. All samples wound smoothly.
Denon: These tapes have a little curved arrow on the wrap, giving the essential clue for easy removal. I liked the high-quality boxes. All winds were smooth.
Fuji: Wrap removal was easy with the across-the-box pull. I liked the GT-I and GT-II shells with their tactile clues on A and B sides. Not only are these good for users of car players, but blind people will also find them helpful. All winds were smooth.
Maxell: There is a diagonal arrow at the tab, but I found it was better to pull straight for a short distance before going diagonally. All of the Samples wound smoothly.
Memorex: The pull tab was not very obvious, but it worked very well with the swooping pull. The new Memorex boxes are not as well sealed against dust as the previous ones, but the cassettes can still be inserted either way for storage. All samples wound smoothly.
PDMagnetics: The packages opened easily with an across-the-box pull (which I prefer). Some boxes hung up very slightly when opened or closed, but general quality was high. All samples were smooth and quiet in winding.
RAKS: Most samples opened easily with the tab. Several of the boxes were rather grabby on opening. Most of the cassettes made little squeals or burbles during fast winding.
Scotch: All samples opened easily even CX, where the pull tab is closer to the center of the box. All cassettes wound smoothly.
Sony: The wrapper for each of this company's formulations has an obvious pull tab; right next to the tab is the instruction to "Pull Diagonally." This was the best combination for wrap removal I found in the collection. Some of the samples were notably quieter in winding than the average.
TDK: In general, removing the wrap was very easy. As a group, the TDK samples were the quietest during fast winding.
Triad: All samples opened easily with the tab, and all were quiet during the fast winding. The triangular window is different, but it limited the visibility of the tape packs between the hubs.
Measurements
TABLE I--MEASURED DATA
Table I lists the results of the evaluation of the 49 formulations, using the Nakamichi 582 deck. The arrangement is different from most of our surveys in the past, although it is quite similar to the Table in our September 1984 re port. I remind all readers that the present tests are based upon tests of maxi mum output level for 3% distortion rather than maximum recording level for that distortion point. Please also note that the 2-kHz data is now obtained from TTIM rather than HDL3 tests. I have also provided plots showing frequency response at 0-dB output level (solid line) and MOL for 3% distortion (dashed line) for each tape formulation. Note that distortion at the 0-dB level is less than 3% wherever the solid curve is below the dashed one, and more than 3% wherever the dashed curve falls below the solid one. Therefore, the MOL curve will probably be of more help in understanding the limits on record/playback levels for each tape.
The brief comments on each of the tapes are arranged alphabetically by brand within tape type. Most of these tapes showed little or no skew, had consistent bias requirements and sensitivity, had quite good 3-kHz output-level stability, and showed average flutter. I have therefore not mentioned these areas unless something was poor--or especially good.
TYPE I TAPES
--------------TYPE I
For all tape types, high MOLs are a fundamental requirement for high performance. Since most of the Type I tapes have about the same absolute noise level, the higher a tape's 400-Hz MOL, the higher its signal-to-noise ratio. Type I tapes show neither high MOLs at 10 kHz nor really extended response at 0 dB, but they are generally better than Type II tapes in these regards. The basic reason for this is not an innate superiority of Type I tape but a difference in equalization: The smaller high-frequency boost used in recording Type I tapes causes less saturation. At the same time, however, the difference between Type I and Type II playback equalization is the main reason why Type I tapes have generally lower S/N ratios than Type IIs. Nevertheless, the best-performing Type I tapes, with 400-Hz MOLs of +6 dB or more, have S/N ratios that are a match for many Type II tapes.
BASF LH Maxima I (LH-MI): An above-average tape, with good MOLs, low noise and extended response at 0 dB. In fact, it had the widest response of any Type I tape tested here.
Denon DX3: This is an above-average tape, with good MOLs, fairly low noise and extended response at 0 dB. Bias requirements and sensitivity were very consistent.
Denon DX4: Because this formulation's measurements were so very close to those for DX3, I rechecked some tests. I got the same results-but no matter, this is an above-average tape for the same reasons as given for DX3.
Fuji GT-I: This is a slightly above-aver age tape. The MOLs were fairly good, but the response at 0 dB was not particularly impressive. Bias requirements were very consistent. As stated earlier, the shell design is excellent for easy use when the user isn't able to see the cassette.
Maxell UR: This LN replacement gets a somewhat above-average rating for its combination of fairly good MOLs and high-end response close to 10 kHz. Flutter was lower than average.
Maxell UDS-l: This is a good addition to the tapes available-one of the better Type I formulations. MOLs were high across the entire band, noise was low, and 0-dB response was quite well extended. Bias requirements and sensitivity were very consistent, and flutter was slightly lower than average.
Maxell XLI: This is one of the best Type Is, offering high MOLs, low noise, and fairly well-extended response. Bias requirements and sensitivity were both very consistent. Flutter was lower than average.
Maxell XLI-S: Overall, this is one of the best Type I tapes. It had high MOLs and low noise, but some areas were not a match for XLI. Bias requirements were very consistent, but sensitivity had a 0.6-dB spread among the two sides of the three samples. The 3-kHz output stability was very good, and flutter was lower than average.
Memorex MRX I: This formulation had good MOLs for the lower frequencies, but less so for the higher ones. The 0-dB response was about average, which corresponds to the results obtained for high-frequency MOLs. The bias requirements were very consistent, and the flutter was lower than average. Overall, this is an above-aver age tape.
PDMagnetics FERRO: This is an aver age Type I tape in all respects.
PDMagnetics Tri-Oxide FERRO HG: Compared to FERRO, the higher MOLs overall, the lower noise and the more-extended response get this tape a slightly above-average rating, aided by consistent bias requirements and lower-than-average flutter.
RAKS High Dynamic: This is a lower-than-average tape; in fact, it measured the poorest of the lot. MOLs were very low, the modulation noise was high, and the response was the least ex tended of the Type Is. Bias requirements and sensitivity were not consistent, and dirt deposits from two of the three samples confused the taking of data. In addition, flutter was poorer than average.
RAKS High Dynamic I: Overall, this was a slightly better performer than the other RAKS Type I, but it showed other problems. Dropout performance was poor enough to be audible, and one sample jammed in record mode.
Scotch CX: Overall, this is a formulation of average performance in most respects. Bias requirements were very consistent, and dropout performance was better than average. Flutter was noticeably better than the average one of the best in this regard.
Scotch XSI: In most areas, XSI seemed a lot like CX during the testing, and the general results were also average. Dropout performance was better than average, as was the flutter.
Sony HF: This is a below-average Type I tape, with rather low MOLs, high noise, and restricted response at 0 dB. Flutter was lower than average.
Sony HF-S: This is definitely one of the better Type I tapes. MOLs were good across the band, noise was low, and response was good at 0 dB. Bias requirements and sensitivity were very consistent. The flutter was slightly better than average.
TDK D: Overall, this formulation fits into the group of average-performing tapes. Bias requirements and sensitivity were very consistent.
TDK AD: A good combination of high MOLs, low noise, and a fairly well-ex tended response. Bias requirements were completely consistent, and flutter was slightly better than average. Add it all up: This is one of the better/best Type I tapes.
Triad FX: This is definitely one of the better Type I tapes, with good MOLs across the band, low noise, good response and high consistency in all respects. The flutter was lower than average.
TYPE II TAPES
---------TYPE II
Different criteria must be applied when evaluating Type II tapes. The basic need for a high-quality recording medium remains, of course, but a few differences from Type I tapes appear.
For example, most Type II tapes have low MOLs at the higher frequencies, but they usually have higher signal-to noise ratios than Type I formulations. A good part of this is the result of record and playback with Type II (70-µS) equalization. The record-EQ difference also affects 0-dB response at the higher frequencies, where Type I tapes beat most of the Type IIs. (If the same EQ were used for both Type I and Type II tapes, the performance of the two groups would be more similar, and some Type II tapes would then show better high-frequency MOL than Type I tapes.) Take particular note of the results for Denon HD8, Memorex HBXII and CDXII, TDK HX-S, and Triad EM-X.
These tapes stand as worthy competitors to the Type IV metal-particle tapes, at least in some areas of measurement, and generally demonstrate superior performance. Excepting HBXII, incidentally, all these tapes are metal-particle formulations, and they could be the best choice for tape decks that don't perform particularly well with Type IV tapes.
BASF Chromdioxid Extra II (CR-E II): The MOLs were lower than most of the other tapes in this report, and the signal/noise ratio and 0-dB response were average. Bias requirements were completely consistent from sample to sample. The 3-kHz output-level stability was better than the average Type II. Overall, about average.
BASF Chromdioxid Maxima II (CR-MII): The low-frequency MOLs were quite good, but the high-frequency ones were on the low side. The signal-to noise ratio of 63.0 dBA was one of the very best for all Type IIs and Type IVs. The 0-dB response rolled off at 7.3 kHz, quite obvious in the plot. Bias requirements and sensitivity were very consistent. The 3-kHz output-level stability was excellent, and the dropout check showed good smoothness even at the fast scan rate. The flutter was lower than average. Overall, this is one of the better Type II tapes; for recording material which does not have considerable high-frequency content, it is one of the best.
Denon HD6: The MOLs were mostly on the low side, and other results were average. Bias requirements were completely consistent, and flutter was slightly better than average. In toto, somewhat below average.
Denon HD7: The increase in MOLs over HD6, and other improvements, were desirable differences. Bias requirements and sensitivity were completely consistent. The fast scan for dropouts was quite smooth-one of the better performances. Flutter was better than average. Overall, a good, average Type II tape.
Denon HD8: This is one of the metal-particle Type II tapes, and it evidenced quite high MOLs across the band and a 0-dB response that was much more extended than most Type IIs. Do note that the signal/noise ratio was actually lower than average. If noise reduction is used, however, this may have little significance. Bias requirements were completely consistent, and the 3-kHz output-level stability was better than average. Adding it all up, this is one of the better-to-best Type II tapes.
Fuji FR-Il: This formulation showed good MOLs and reasonable 0-dB response. Bias needs were very consistent. The 3-kHz output was smooth and stable, one of the best for all tape types. Flutter was low, also one of the best. Definitely one of the better Type II tapes.
Fuji GT-II: Although the manufacturer targets this tape for the car market, its high MOLs, low noise and good 0-dB response make it good for any use. Bias requirements were very consistent. The 3-kHz output was stable and smooth-the best overall for all tapes tested. Flutter was better than average. One of the best Type IIs.
Maxell UDS-Il: With so-so MOLs along with a mediocre signal-to-noise ratio, this is a below-average tape. Consistent bias needs were a plus.
Maxell XLII: The MOLs were quite good, the very consistent bias and sensitivity were nice, the 3-kHz output-level stability was excellent, and flutter was better than average. This is a better-than-average Type II.
Maxell XLII-S: I expected this tape to outperform XLII but was puzzled to see that, overall, it did not. Its S/N and its MOLs (at frequencies below 5 kHz) were the only areas in which it outperformed XLII. Overall, this is one of the better Type II formulations, but it would perform best when recording material that didn't have very much high-frequency energy.
Memorex HBII: The MOLs were just average overall, but the 0-dB response was impressive: In fact, it was the best for the nonmetal-particle Type IIs. Bias needs were very consistent. Flutter was slightly lower than average. The sum total makes for a better-than-aver age Type II tape.
Memorex HBXII: The high MOLs, the good 0-dB response, and the low noise make an impressive combination. Bias requirements were very consistent. The 3-kHz output-level stability was better than most, and the flutter was one of the lowest. HBXII is one of the better-to-best Type II tapes.
Memorex CDXII: This is Memtek Products' entry into the Type II metal-particle derby. (They have dropped their Type IV formulation.) The MOLs were very high for a Type II, the noise was fairly low, and the 0-dB response was well extended. The flutter was notice-ably better than average. This is one of the best Type II tapes, and it is a match for some of the Type IVs.
PDMagnetics 500 Crolyn: The MOLs were on the low side across the band, and the 0-dB response was quite restricted. Bias needs were completely consistent, but this is a below-average Type II formulation.
PDMagnetics 500 Crolyn HG: This tape's designation indicates better performance than its stablemate, but alas, the tests don't show it. The S/N ratio was slightly better than that for 500 Crolyn, but the modulation noise was considerably poorer. With MOLs and 0-dB response on the poor side, this is a below-average tape.
RAKS High Dynamic II: With the lowest MOLs, the lowest S/N ratio and one of the poorer 0-dB responses, this is the poorest Type II in this report.
Scotch XSII: This tape had average MOLs overall, and the 0-dB response was rather limited. Bias needs and sensitivity were very consistent. The 3-kHz output-level stability was one of the better ones, considering all tape types, and the flutter was lower than average. This is an average Type II formulation.
Sony UCX: The MOLs were generally high, and the 0-dB response was better than average. Bias and sensitivity were very consistent. Flutter was much lower than average--one of the best. UCX is one of the better Type IIs.
Sony UCX-S: I had expected to get somewhat higher MOLs with this formulation than with UCX; instead, I got slightly lower figures. Nonetheless, UCX-S is also one of the better Type IIs. Bias needs were very consistent, the 3-kHz output level was very stable, and there was nothing to see in the dropout check-one of the best tapes in this respect.
TDK SA: Fairly good MOLs, a reason able 0-dB response, and excellent out put-level stability make SA one of the better Type II tapes.
TDK SA-X: This is nominally one of the "hot" tapes, recommended by its maker for challenging applications. Formerly, such tapes had very high MOLs at higher frequencies, but most manufacturers have changed their formulations to yield lower noise instead. Typical of such tapes, SA-X actually had average high-frequency MOLs. It did have the best signal-to-noise ratio of all Type IIs tested (albeit just barely), a figure exceeded by just one Type IV formulation. It is one of the better tapes for recording material with limited high-frequency energy.
TDK HX-S: The fact that this tape had the highest MOLs across the band, and the most extended 0-dB ,response, makes this the best-performing tape of all Type IIs. It is even a match for some Type IVs. The formulation evidenced very consistent bias needs and sensitivity. The 3-kHz output-level stability was one of the best for all tapes, and the scan for dropouts was one of the smoothest.
Triad EM-X: This recent addition to the metal-particle Type IIs had average low-frequency MOLs, but the high-frequency MOLs were impressive. The 0-dB response was well extended, matching the other similar-formulation Type IIs. Overall, one of the better Type IIs.
TYPE IV TAPES
--------TYPE IV
The better metal-particle Type IV tapes still stand as the best performers, primarily because of their very high MOLs and reduced high-frequency saturation, gaining greater response extension at 0 dB. It has also been generally true that the metal-particle tapes are relatively noisy, and the net result of this is that the signal/noise ratios for Type IV tapes have been little or no better than some of the Type IIs. However, I found a refreshing exception to this tendency, as the comments below reveal.
Denon HDM: This is an average metal-particle tape which offers high MOLs, low noise, and very good 0-dB response. Bias and sensitivity were very consistent, and the output level was very stable. Flutter was lower than average.
Maxell MX: The MOLs were very high, the S/N ratio was high, and the 0-dB response was very good-what else does one need? Well, MX does have very consistent bias needs and sensitivity, smooth 3-kHz output with high speed scan, and lower flutter than average. One of the best Type IVs.
PDMagnetics 1100 Metal HG: This is a typical metal-particle tape with very good MOLs, a very good S/N ratio, and a well-extended 0-dB response. Bias needs were very consistent, and the 3-kHz output-level stability was one of the best for all tapes. Flutter was better than average.
Scotch XSMIV: The MOLs were the lowest for this group of Type IV tapes, and the formulation was matched or surpassed by two of the Type II metal-particle tapes in a number of respects. Bias requirements and sensitivity were very consistent. This is a very good tape, but the Type IV competition is tough.
Sony Metal-ES: This tape had the highest MOLs of the group, produced the highest S/N ratio by over 3 dB, and matched the widest 0-dB response. Bias needs were very consistent. Sony Metal-ES had the highest performance of all 49 tapes tested.
Triad MG-X: This is a typical metal-particle tape, showing high MOLs across the band and an extended 0-dB response. The samples were very consistent in most respects, but there was a regular ±0.2 dB sensitivity change every 0.5 S. Flutter was higher than average.
Further Checks
While checking the 3-kHz output-level stability during playback, several formulations showed noticeable level variations that came and went for no apparent reason. The variations were almost always greater in the right channel than they were in the left, and a short rewind was associated with higher variations. These conditions, were noted with the Nakamichi 582 test deck, but when the same tapes were given the same basic test on an Aiwa AD-M700 and an Akai GX-R99, the level variations were very much smaller even nonexistent, in some cases. My tentative conclusion is that there was some sort of interaction between the particular tapes and their shells and the tape handling of the Nakamichi 582.
I don't know the exact mechanism involved here, but I do suggest to recordists that there may be subtle sonic effects that relate to particular deck/ tape combinations. The variations were usually less than 1.0 dB total and occurred over a period of 2.5 to 3.0 S, so noticing any effects while playing music would be difficult.
Although I run all my tests on C-90 cassettes, I wondered how well other lengths match C-90s for bias and sensitivity. If other lengths are used, what will happen? Another facet of the same question is this: If the deck is set up with C-60s, then how well does it per form with C-90s? This is particularly pertinent when seeking the best Dolby NR tracking.
To test this, I used a variety of old and new formulations of Type I, Type II, and Type IV tape from Fuji, Maxell, PDMagnetics, RAKS, Scotch, and TDK-in as many lengths as I had available. For Types I and II, there was very close agreement among C-90s, C-60s and C-46s in each formulation. (I did not have C-46s for half of the brands tested.) The Maxell LN and UD C-120s, however, required noticeably more bias, particularly the LN tapes.
Most of the Type I and II formulations showed agreement in sensitivity among all lengths. The exceptions were that the C-60 version of UDXLI was 1.7 dB less sensitive than the C 90, and the RAKS High Dynamic C-60 was 1.4 dB more sensitive than its C 90 version.
Each Type IV had its own story. The Fuji FR Metal C-60 required 0.7 dB less bias than the C-90 and had 0.5 dB more sensitivity than its longer counter part. The average figures for the Maxell MX C-60 matched the C-90 results, but there was some spread in both bias and sensitivity of the samples checked. With some older samples of TDK MA, the C-60s required less bias and were less sensitive, but with newer tapes, the C-60s required more bias and were somewhat more sensitive.
With MA-R tapes, the C-60s and C-90s matched closely enough in both bias and sensitivity, but they produced different figures than those obtained for the MA formulation.
With recent Type I and II tapes, the bias requirements and sensitivity for most lengths agree pretty well. You would have only minimal problems in interchanging C-90, C-60, and C-46 versions of a given tape. The use of a C-120, however, could introduce some noise-reduction tracking problems, to say nothing about tape saturation and transport problems.
The discrepancies are larger for the relatively few Type IV tapes. The consistency from batch to batch, let alone from length to length, that is so common in Type I and Type II tapes is not yet shared by metal-particle Type IV cassettes. (I haven't seen enough Type II metal-particle tapes to comment on them.) However, the differences in bias needs that show up in my tests with a Nakamichi 582 might not show up on the many cassette decks, especially inexpensive ones, which lack the headroom or bias capacity to take full advantage of Type IV tapes' capabilities.
To give an idea of how wide a range of bias and sensitivity variations one might encounter, I combined the bias and sensitivity data for the 49 formulations reported here with earlier data on 36 other tapes. The results are presented in Figs. 1 and 2; these show the number of formulations with which particular bias and sensitivity values occur. For these figures, I divided bias requirements and sensitivities into ranges 0.2 dB wide and 0.5 dB apart (center-to-center). Hence the "0.0" bar includes all tapes falling within a range of ±0.2 dB, the "+ 1.0" bar includes tapes that have values of 0.8 to 1.2 dB, and so on.
Note that the most common bias-requirement values, for all three tape types, was just about 0.0 dB, the IEC Standard, but that tapes meeting the IEC Standard for bias were least common among the Type IV formulations.
There was less agreement with the IEC Standards for sensitivity-especially among Type II tapes (where the most common value was + 1.0 dB) and Type IVs (where it was-0.5 dB). The high-sensitivity Type II tapes are the "hot" ones referred to earlier, such as TDK SA-X and the new metal-particle Type IIs.
If you switch tape formulations with out readjusting bias or record sensitivity, you can minimize possible Dolby-tracking problems by choosing a tape whose requirements are close to those of your original tape. Your new tape should therefore be one whose sensitivity is within 1.0 dB, and whose bias requirement is within 0.5 dB, of your original tape. (Bias affects tracking be that requires more bias, but doesn't get it, will have a boosted high-frequency response.) The following list shows some combinations whose bias requirements and sensitivity meet the above criteria; note that the bias groupings do not correspond exactly to those of Fig. 1.
Fig. 1--Bias requirements for 85 tape formulations.
Fig. 2--Sensitivity of 85 tape formulations.
Type I: Among lower bias tapes, Konica ML, Memorex dB, and Realistic Supertape Gold have reasonably well-matched requirements. Medium-low bias: Maxell UR, Memorex MRX-I, PDMagnetics FERRO, and Scotch CX and XSI. Slightly low bias: Denon DX1 and Maxell UDS-I. Tapes requiring nominal IEC-zero bias fall into three sensitivity groups: Fuji GT-I, Loran Nor mal, PDMagnetics Tri-Oxide FERRO HG, and TDK D; Fuji ER, JVC DA3, Magnex Studio 1, Nakamichi EXII, and Sony HF-S; and Maxell XLI and TDK AD-X. For somewhat high bias, there are also three groups: BASF LH-MI, Fuji DR, and Konica GM-I; BASF LH MI, Konica GM-I, and Yamaha NR; and Denon DX-4 and Maxell XLI-S. Finally, for high bias: BASF LH-MI. Denon DX-3, TDK AD, Triad F-X, and Yamaha NR-X. As this listing shows, BASF LH-MI fits in well with a number of other tapes; it's a possible choice in three combinations. On the other hand, some Type I tapes are not listed at all, because their combinations of bias and sensitivity match no other Type I formulations.
Type II: Low bias: Konica GM-II, Nakamichi SX, and Yamaha CR. For nominal zero bias, again three groups: JVC DA7, Maxell XLII and UDS-II, Memorex HBXII, and TDK SA; Denon HD7, Fuji FR-II, Memorex HBII, and Realistic Supertape Hi-Bias (which match especially well among themselves); and the group of Nakamichi SX-II, Sony UCX, and Yamaha CR-X. I picked out two groups for somewhat high bias: Fuji GT-II, Maxell UDS-II, Scotch XSII, and TDK SA; and Denon HD8, Maxell XLII S, Sony UCX-S, TDK SA-X, Triad EM-X, and Yamaha CR-X. The high-bias combinations are: BASF CR-MII and Loran High Bias, and Memorex CDXII and TDK HX-S. Denon HD8 and Maxell XLII-S are possible additions to the last pair of tapes.
Type IV: For low bias: BASF Metal IV, Konica Metal, Magnex Studio 4, Scotch XSMIV, and TDK MA-R. I picked two groups close to IEC-zero bias: JVC ME, Magnex Studio 4, and Nakamichi ZX are in one group; Maxell MX, PDMagnetics 1100 Metal, and Realistic Supertape Metal are in the other.
For somewhat high bias there are also two groups: Fuji FR Metal, Triad MG-X, and Yamaha MR; and Sony Metal-ES and TDK MA. For high Type IV bias, there are just two tapes: Denon HDM and Triad MG-X. Note that the bias and sensitivity combinations of the Magnex and Triad formulations allow them to be used with either of two adjacent groups.
All of these groupings should be considered as general guidelines for use when interchanging tapes without making bias or sensitivity adjustments.
Users who do make such adjustments can interchange tapes more freely, without consulting these guides. In any case, the user should always listen carefully to assess the sonic effects when changing tape formulations.
Measuring Modulation Noise
Although the test for measuring modulation noise was described and the results were listed, additional comment is in order. There is no common measuring practice, and no standards for the band-limiting or notch filters, so there is no way to ensure that different testers will get comparable results.
Quite a few people believe that modulation noise should be measured at something like 10 kHz, but others say this should be called "scrape flutter." I'm hoping to find alternative ways of configuring my cancellation/filtering , setup for more assurance of stable, reliable data. With the increasing avail ability of source material having very wide dynamic ranges, such as Compact Discs, cassette recordings with Dolby C or dbx NR will be more revealing of modulation noise if it occurs. In general, with normal use, dbx NR helps to prevent modulation noise, which is directly related to the recorded level on the tape. Perhaps the improved and improving cassette formulations will ensure that modulation noise will not be a problem, but I will be keeping my eyes and ears open.
Present and Future Formats
Formulations of all types have improved continuously. Even in the last few years, there have been significant changes, such as metal-particle Type IV tapes and, more recently, their Type II counterparts. Shells have also improved, providing better visibility, greater resistance to heat, greater reliability, and lower skew. But we are constrained by the analog format, are we not? Actually, relatively few people are as restricted as they think they are:
Many of them would greatly improve the sound of their tapes if they paid more attention to getting the best tape/ deck match, followed better recording practices, and used higher quality sources. (Retiring their old decks for improved units might help, too.) There is much that can be done with the tools at hand, and the convenience and low cost of the many varieties of cassette recorders/players will continue to have great appeal for many years to come.
We will see digital audio tape (DAT) in one or two formats, and it is likely that we'll be seeing prototype record able Compact Discs in the next year.
Because the technology of the DAT medium is very sophisticated, it is logical to expect that initial prices will be high for both the tape and the recorder(s). The portable Compact Disc players indicate the possibilities as far as sophistication in a small package is concerned. The actual selling price of deck-type DAT recorder/players, and the cost of DATs, will determine how much of the large analog cassette--for mat market shifts to digital. In the meantime, enjoy all of the marvelous things there are to record, play and listen to.
(Audio magazine, Jun. 1986; by Howard A. Roberson)
Also see:
Cassette Test Update: 12 Formulations (Sept. 1984)
58 Cassettes Tested (Sept. 1978)
Performance of High Energy in Magnetic Materials in Audio Cassette Recording Tapes (Sept. 1978)
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