The Type III Ferrichrome / Ferro-chrome Audio Cassette

Sony FeCr 90 Type III audio cassette tape

Most cassette-buying consumers of yesteryear will remember normal tapes (classified Type I), high bias tapes (classified Type II), and to a lesser extent, metal tapes (classified Type IV). These were the three options from which consumers would choose.

And if you look back at the cassette decks from the heyday of analogue home recording, you’ll probably see a reference to each of these three cassette types. Perhaps a physical selector (if it’s a very old deck), but more likely just a series of LED indicators, showing which of the three types the deck has auto-detected, once the cassette is in the machine.

Type I, Type II, and Type IV. No Type III…

But back in the mists of time, there actually was a Type III audio cassette. Living a fairly obscure life for a relatively short period between the mid 1970s and the early 1980s, the ferro-chrome, or ferrichrome tape, was the format that never really made it into the golden era of the compact cassette.

The Type III ferro-chrome pre-dated the Type IV metal cassette, and was a very straightforward attempt to rectify the problems inherent in the two previously existing cassette types (I and II). Type I ferric oxide tapes had poor definition in the higher treble regions. Type II chrome tapes were quite flimsy around the bass regions of the sound spectrum. The concept with the Type III was to combine, on the tape coating, a layer of ferric oxide with a layer of chromium dioxide. Theoretically, this would offer the user the enhanced high frequency definition of chrome, plus the fuller bass of the regular ferric tape. Surely a step forward…

Well, it would have been, and in fact idealistically it was. But there was one glaring problem from the start. Chrome coatings had a high bias (see my Type II chrome article for an explanation of bias), and ferric coatings had a normal bias. Where would the bias be set for optimum performance if the two layers were combined?… That was just it. The bias would always have to be a compromise.

The bias for the Type III cassette was thus set in between normal and high, but nearer to normal. Specialist recording equipment with fully adjustable bias would allow the user to accommodate the ferrichrome cassette, but manufacturers of mass market tape decks now had the dilemma of whether or not to add a Type III bias setting to their machines. Was this new cassette type going to take off? Was it a sufficient improvement over a Type II for people to actually notice the difference? Would the whole of the market adopt the Type III standard, or would it remain the preserve of just a limited number of cassette makers?

Well, whilst some of the market did evaluate the Type III as a cause worth pursuing, for the wider market there was a sort of stalemate. Manufacturers waiting for something to really happen before they threw themselves into the arena, but nothing really happening because too many of them were sitting back and waiting. Had the Type III format been a clear and obvious winner on technical grounds, I’m sure it would have been a different story. But ultimately, the principle was a bit like a cut and shut motor vehicle. Neither one thing nor the other. The fatal compromise on bias must have deterred a lot of techies, but the biggest nail in the coffin for the Type III cassette was probably the sound. Most wouldn’t be able to tell any difference between the Type II and the Type III (especially using typical 1970s consumer equipment), and of those who could, a fair old few actually preferred the Type II. The market never properly adopted the Type III cassette, and when the Type IV metal formula arrived in 1979, ferrichrome was rendered technically pointless as well as technically flawed.

The cassette in the picture is a ninety minute Sony FeCr. The Sony FeCrs were the only Type IIIs I ever bought or used, and I was lucky to find them, lingering around in 1983, well beyond their era. I recorded onto them at normal bias, which is technically incorrect, but the result was fine by me. The sound does have a very obvious brightness, but there’s more thickness in the bass and middle than with a straight chrome tape. To my ear, whilst the treble is strong, it’s not as refined and sophisticated as with pure chrome. The sound definitely isn’t as ‘pretty’, although that could have a lot to do with me being forced to record at the wrong bias setting.

I don’t know how it was in the ’70s, but certainly, picking these cassettes up in the early to mid ’80s it was pretty easy to see why they’d died a death. I actually thought ferro-chrome was new when I found the tapes in a shop in ’83, as I hadn’t seen it before. By that time, people had auto-bias-sensors on their cassette decks, and since the ferro-chrome tapes were ‘notched up’ for normal bias, my deck treated them as such. I thought the reason my deck didn’t have a Type III setting was because ferro-chrome was new. Only later did I discover the story of the Type III cassette and realise that in fact, it was obsolete. But either way, it really was a problem getting a cassette home and finding your recorder couldn’t properly accomodate it. That was the trouble with cassettes. New types needed the approval and acceptance of the whole market in order to survive. The Type III never got that universal acceptance, and accordingly, the concept died.