Cassette Tape Speed Calibration

Pogre

Pogre

Audioholic Warlord
My dedication to the casette deck is for the reason of preserving the vinyl of some old blues albums and some rock bands that I cannot find digitally. I know I can buy a USB equipped turntable and do it digitally but I dont want another turntable, even temporarily. With onboard dbx2 , the tapes are as good as the source be it vinyl or CD. Impossible to tell the difference between source and recording.

I calibrated 4 decks in less than hour and they wont need calibration again for a very long time. It was a fun learning exercise. :) Just thought I'd share my experience..... :)
I think it's cool. If I had cassettes and a good player still I'd be all into it too.
 
highfigh

highfigh

Audioholic Overlord
Not an option in my book. ALL have to play the same speed.
The speed is immaterial unless you'll play all tapes on more than one machine; it's the pitch and alignments that are more critical. If you record a tape on one machine and play it on a different one, there's no guarantee that the head alignment, bias & equalization and noise reduction (if used) will be correct on the playback machine. It may be within a useful and 'acceptable' range, but it won't be absolutely correct.
 
highfigh

highfigh

Audioholic Overlord
They certainly have their problems! Reel to Reel has the same problems except many aspects are improved since there is so much more tape to hold the information (both due to wider tape and much faster travel speed. Cassettes pushed the limits and it was a testimony to the enthusiasm and ingenuity directed at HiFi of the day that they actually became a pretty good sounding media within a decade of their introduction into the market. I wish I still had my old Nak to compare my old tapes vs a CD of the same music!

But I will always have a love of the cassette because of how it allowed me to take music into the car (before CDs) without too much concern about the heat of the sun or other damage (since I was recording from LP's and could always make another cassette if worse came to worse). I also used cassettes for my home listening to preserve my LP's and slow the accrual of snap, crackle, pop! The recordings I made and played back on my Nak did not lose much at all to the original and I only broke out the vinyl for special occasions!
The speed of cassette tape severely limited the frequency response- if you look at the spec sheet for ANY tape equipment, it shows the response at various levels and when they showed "20Hz-17KHz ±3dB", it was always at -20dB, never at -0dB VU. At the higher level, most decks would only do about 12KHz and some couldn't even hit that.

Cassettes were for convenience and to allow rewinding, as well as reducing the size of the mechanism in portable and car units. Performance came later.
 
3db

3db

Audioholic Overlord
The speed is immaterial unless you'll play all tapes on more than one machine; it's the pitch and alignments that are more critical. If you record a tape on one machine and play it on a different one, there's no guarantee that the head alignment, bias & equalization and noise reduction (if used) will be correct on the playback machine. It may be within a useful and 'acceptable' range, but it won't be absolutely correct.
I do play cassettes across all 3 systems, one system on each floor and other than the speed that was off, playing cassettes recorded with either DolbyC or dbx sound very much the same across all decks so the head alignment must be very close across all three decks. ;)
 
KEW

KEW

Audioholic Overlord
The speed of cassette tape severely limited the frequency response- if you look at the spec sheet for ANY tape equipment, it shows the response at various levels and when they showed "20Hz-17KHz ±3dB", it was always at -20dB, never at -0dB VU. At the higher level, most decks would only do about 12KHz and some couldn't even hit that.

Cassettes were for convenience and to allow rewinding, as well as reducing the size of the mechanism in portable and car units. Performance came later.
If I read this right, Nakamichi broke that limit!
This is also consistent with the published FR in my 1977 High Fidelity Magazine Test Reports. Teac Abd Tandberg (and everyone else) show the type of response you are suggesting, but Nakamichi shows flat to nearly 20kHz!
 
3db

3db

Audioholic Overlord
The speed of cassette tape severely limited the frequency response- if you look at the spec sheet for ANY tape equipment, it shows the response at various levels and when they showed "20Hz-17KHz ±3dB", it was always at -20dB, never at -0dB VU. At the higher level, most decks would only do about 12KHz and some couldn't even hit that.

Cassettes were for convenience and to allow rewinding, as well as reducing the size of the mechanism in portable and car units. Performance came later.
What do you mean performance came later? In terms of what, how much later? Im asking you to provide context to that statement because its unclear.
 
3db

3db

Audioholic Overlord
If I read this right, Nakamichi broke that limit!
This is also consistent with the published FR in my 1977 High Fidelity Magazine Test Reports. Teac Abd Tandberg (and everyone else) show the type of response you are suggesting, but Nakamichi shows flat to nearly 20kHz!
Even the Nak Dragon specified its frequency response at -20dbw down. I cant think of one deck that specified frequency response at 0dbw.
 
Bucknekked

Bucknekked

Audioholic Field Marshall
I'm pretty sure I still have some old cassettes layin' 'round here somewhere...

Hey, don't they wear out after time? Is there a way to preserve the recording or copy it without losing anything?
yes. there is a lifespan for each and every recording medium. even optical CD's have a lifespan.
none of us is getting any younger or prettier. neither are any of those old cassettes, 8-tracks or reel to reel tapes.
Just like your singing voice doesn't improve with age, neither does theirs.
YMMV, caveat caveat caveat.
 
KEW

KEW

Audioholic Overlord
Even the Nak Dragon specified its frequency response at -20dbw down. I cant think of one deck that specified frequency response at 0dbw.
Did you see the FR in the link that showed it at 0dB?
I don't know that I am right, but like I said High Fidelity's Test Reports show rolloffs near 10kHz for respected brand names, but Nak shows a near linear response at 0dB.

Here is SoundandVision's commentary on the 1982 Nakamichi Dragon (see the statement I made bold):
Overall record-playback response, measured at a -20-dB level, was within ± 1 dB from 20 Hz to beyond 20 kHz with all three tape types, which is truly remarkable cassette-deck performance. Dolby tracking error-the difference in frequency response with and without the noise-reduction system-was within 1.5 dB from 20 Hz to 20 kHz using either Dolby-B or Dolby-C. Even at the 0-dB level, where all cassette tapes run into saturation at the highest frequencies, response did not drop to -6 dB until 13.2 kHz for the ferricobalt SX, 14 kHz for EX-II (ferric), and 18 kHz for ZX (metal). Indeed, though not shown on the graph, with metal tape and Dolby-C, the Dragon 's response at a 0-dB recording level was down only 2 dB at 20,000 Hz!

Naturally, the technology from the top dollar Nak Dragon trickled down over the next five years to where they were still expensive compared to Teechnics, Sony, et al, but not totally prohibitive given the ability to have good FR out of your recorded cassettes.
Obviously, I used metal tape and Dolby C for everything I did.
 
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highfigh

highfigh

Audioholic Overlord
What do you mean performance came later? In terms of what, how much later? Im asking you to provide context to that statement because its unclear.
Cassettes weren't originally used for high quality music recording- they were a cheap way to record on a small cassette, certainly much smaller than an 8 Track. Shoe box and other portable recorders were some of the early devices that could use these tapes but nobody would ever accuse them of being high-fidelity.

 
highfigh

highfigh

Audioholic Overlord
If I read this right, Nakamichi broke that limit!
This is also consistent with the published FR in my 1977 High Fidelity Magazine Test Reports. Teac Abd Tandberg (and everyone else) show the type of response you are suggesting, but Nakamichi shows flat to nearly 20kHz!
At what VU level? That's the important part- some showed the response at -10dB.

The first stereo store I worked for had a couple of Sony sponsored 'Tape Deck Clinic' events, where they brought engineers form Japan to test any brand and model, excluding large commercial units. One of these clinics had a man who went by the name of Kato and if you're familiar with the Sony TC-540, TC-630 and any cassette decks during the '70s and '80s with TC-K model numbers, the K referred to him, according to the reps. He saw the frequency response from one of his models (TC-K55) that was very bad and he asked for a screwdriver, function generator & multimeter. He set it up, tweaked a few things and when he re-tested it, it was flat below 20Hz to about 20KHz @-20dB better than +/-3dB (again, this is the standard test level). This was a deck that we sold for $300.
 
highfigh

highfigh

Audioholic Overlord
Did you see the FR in the link that showed it at 0dB?
I don't know that I am right, but like I said High Fidelity's Test Reports show rolloffs near 10kHz for respected brand names, but Nak shows a near linear response at 0dB.

Here is SoundandVision's commentary on the 1982 Nakamichi Dragon (see the statement I made bold):


Naturally, the technology from the top dollar Nak Dragon trickled down over the next five years to where they were still expensive compared to Technics, Sony, et al, but not totally prohibitive given the ability to have good FR out of your recorded cassettes.
Obviously, I used metal tape and Dolby C for everything I did.
Look at the price in late-1970s- early 1980s dollars and think about how many people saw it as 'affordable'.

I'm not saying cassettes can't or don't sound good, but they do not have the ability to sound as good as the original without the help of noise reduction and tape formulations that are more expensive.
 
highfigh

highfigh

Audioholic Overlord
I do play cassettes across all 3 systems, one system on each floor and other than the speed that was off, playing cassettes recorded with either DolbyC or dbx sound very much the same across all decks so the head alignment must be very close across all three decks. ;)
Head alignment has nothing to do with noise reduction calibration and unless there's a large sound difference, you would never know if the azimuth was different, although more complex sounds may have a cyclic coming and going of the high frequencies if they're really off.
 
3db

3db

Audioholic Overlord
Head alignment has nothing to do with noise reduction calibration and unless there's a large sound difference, you would never know if the azimuth was different, although more complex sounds may have a cyclic coming and going of the high frequencies if they're really off.
Head alignment is critical with NR, especially with dbx. If the head alignment was off, the response would be a mess and may lead to audible pumping effects. If azimuth was off, HF would sound muted.
 
davidscott

davidscott

Audioholic Field Marshall
Agreed.
Alignment issues would exaggerate any response problems when using NR. DBX was supposedly notorious for having these issues. That said I never owned a DBX unit but did own a few different versions of Dolby with my decks.
 
KEW

KEW

Audioholic Overlord
Look at the price in late-1970s- early 1980s dollars and think about how many people saw it as 'affordable'.

I'm not saying cassettes can't or don't sound good, but they do not have the ability to sound as good as the original without the help of noise reduction and tape formulations that are more expensive.
Your original post made it sound like HiFi and cassette could not be used in the same sentence, and I remember doing several source vs recording comparisons in my 20's and hearing a very small difference, but being okay with it as not big enough to feel like I was losing a significant amount of quality. This judgement was with the idea of using my recordings so as to preserve my vinyl and decided that the pervieved loss of fidelity from the Nak (which was not obvious or even persistent) was far preferable to the pops which would inevitably develop on the LP's!
I bought my Nakamichi 581Z new in 1983 and paid $700 for it. It was the cheapest route to Nakamichi's technology and the most expensive component in my system, but it was also my most used source for music. I was far from wealthy, but audio was what I spent any extra money on and I had pegged it for my tax return dollars at least 4 months before I got the returns! I was splitting rental cost for a house with two friends and driving a well used 1976 Toyota "5 Speed" Corolla hatchback that I "lovingly" referred to as LGSB (little gray poop box) to give you an idea of how I could afford a $700 cassette deck in '83
It also had a bias and sensitivity calibration system built into it (I adjusted the screws based on the VU meters which acted as a calibration display) so you could optimize for the specific tape being used before recording.
Here is a link with some basic info:

For the sake of nostalgia (mine was gray)!
1584211485931.jpeg
 
highfigh

highfigh

Audioholic Overlord
Your original post made it sound like HiFi and cassette could not be used in the same sentence, and I remember doing several source vs recording comparisons in my 20's and hearing a very small difference, but being okay with it as not big enough to feel like I was losing a significant amount of quality. This judgement was with the idea of using my recordings so as to preserve my vinyl and decided that the pervieved loss of fidelity from the Nak (which was not obvious or even persistent) was far preferable to the pops which would inevitably develop on the LP's!
I bought my Nakamichi 581Z new in 1983 and paid $700 for it. It was the cheapest route to Nakamichi's technology and the most expensive component in my system, but it was also my most used source for music. I was far from wealthy, but audio was what I spent any extra money on and I had pegged it for my tax return dollars at least 4 months before I got the returns! I was splitting rental cost for a house with two friends and driving a well used 1976 Toyota "5 Speed" Corolla hatchback that I "lovingly" referred to as LGSB (little gray poop box) to give you an idea of how I could afford a $700 cassette deck in '83
It also had a bias and sensitivity calibration system built into it (I adjusted the screws based on the VU meters which acted as a calibration display) so you could optimize for the specific tape being used before recording.
Here is a link with some basic info:

For the sake of nostalgia (mine was gray)!
View attachment 34652
I never said they couldn't be used in the same sentence, but the response is still not the same as the original, unless the original is limited to that of cassette. That said, I have enjoyed many cassette tapes over the years, but never with less noise than some other sources. I will say, though- if a cassette is the first generation after an extremely noise-free recording, the cassette can be eerily quiet. I recorded some friends in a band in '82 with a Sony PCM-F1 digital recorder and dumped it to cassette for them and myself. I hadn't played tapes in years, mainly because my car was stolen with more than half of my cassettes and I just didn't feel like going through the whole ordeal again but in about '98, I needed to rent a car and since I don't like commercial radio, I decided to grab a few tapes. The first one I played was of the band I had recorded and I knew it was playing because I could hear the background in the club (including the terrible acoustics), but there was a sense of spaciousness and a noticeable lack of tape noise. I had to turn it down when the music started because it was too loud. I also have some tapes that were recorded on a Nak deck and they sound excellent, even now.

I always liked the Sony decks with variable bias- they mostly had three heads, so it was easy to set it to be accurate by switching from tape to source in the first minute, or so.
 
3db

3db

Audioholic Overlord
With dbx engaged, neither anyone in my family nor friends could teĺl the difference between a CD and its recording on a Maxell Chrome tape. They might not be identical from a signal analysis but to the human ear they sounded identical. With good calibrated decks, its not unreasonable to expect that cassettes can be made to sound equal to the source.
 

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