Why Cassette Tapes Aren’t Magnetically Shielded?

Given their propensity to go dull whenever they are accidentally placed near magnetic objects – even magnetic screwdrivers - why aren’t cassette tapes provided with inherent magnetic shielding?

By: Ringo Bones

Unlike your Barclay-Crocker prerecorded Open Reel tapes that came in mu-metal cans as standard, prerecorded cassette tapes back in the 1980s and even well into the 21^st Century doesn’t come with protection against erasure when accidentally placed against a strong magnet like refrigerator magnets and electric guitar pickups and electric bass guitar pickups. And if you Google search cassette tapes that are magnetically shielded, you are directed into Google’s lists of invented patents stating that the tiny nickel plated piece of steel behind the pressure pad functions as a “magnetic shield” for the cassette tape. Given that this concern was largely ignored by the leading cassette tape manufacturers during the format’s lifetime, is it even possible to magnetically shield cassette tapes against erasure and loss of high frequencies when accidentally placed closed to magnetic screwdrivers, fridge magnets, and electric guitar and electric bass guitar pickups?

Back in 1979, the world’s leading cassette tape manufacturer TDK released their MA-R series of cassettes and they were the top of the line of the company’s Type –IV metal particle cassettes. The tape formulation used is based on TDK’s patented Finavix particle. It’s very heavy and its metal shell construction – later revealed to be an aluminum-zinc alloy – has the potential to be made with an actual mu-metal alloy capable of actually provide magnetic shielding for the cassette housing instead of just a vibration reduction measure. Sadly, given that these were top of the line in the TDK’s range of cassettes, they were also very expensive. From the 1980s through to the 1990s, TDK’s MA-R series of metal particle cassette often carry a retail price of around a dollar and a half to two dollars less than a price of a compact disc - which for all intents and purposes just too high a price to pay for a blank cassette tape. This largely explains why I totally abandoned prerecorded cassette tapes in the mid 1990s when the “relatively affordable” Marantz CD-63 Ken Ishiwata Signature model entered the market.