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MiniDisc and sleeve

Magnified view of a MiniDisc

MiniDisc: logical successor to the cassette tape

As a highly satisfied owner of MiniDisc equipment, I encourage everyone to consider the format as a permanent replacement for cassettes. The MiniDisc is the logical successor to tapes, just as the CD was to vinyl records. It's important to note that the MiniDisc is primarily a recording medium. It was not designed as a replacement for the CD, just the decades-old cassette tape format. Confusion over the MiniDisc's intended purpose plus early technical limitations and high cost made its initial acceptance slow outside of Japan, but things have changed. In late 1997, Sony (inventor of the MiniDisc) lowered its prices and the format is now within the reach of most consumers.

A brief overview of the MiniDisc:

MiniDiscs are a digital recording & playback format much smaller than a CD, yet capable of delivering virtually identical sound quality. Each disc is encased in a protective housing measuring roughly 7cm x 7cm x 5mm thick. The image above is close to the actual size at 800 x 600 resolution on a 14" monitor. In addition to the housing is a plastic sleeve for each disc. Their compact size and durability makes MDs ideal for use outside the home.

A typical MiniDisc stores up to 74 minutes of stereo music and newer MDs can hold 80 minutes. The key to fitting all that information into such a small space is ATRAC (Adaptive TRansform Acoustic Coding). Part of the ATRAC algorithm removes sounds that are masked to the human ear. For example, if a loud drum-strike occurs on top of a much softer one at a specific frequency and volume, the latter can be removed without the human ear noticing. This is done with sounds that are completely masked, like a waterfall drowning out the sound of a nearby stream. Sounds that are partially masked are represented with fewer digital samples since the ear can't hear them in full detail. The ATRAC algorithm is complex, but it works very well and has been refined to near perfection. You can do a crude masking demo at home by clapping loudly at the same time someone else snaps their fingers. Under the right conditions the finger snap will be inaudible.

There is a lot more to ATRAC than just masking, though. It uses other tricks to compress the bulk of the data, but they are beyond the scope of this review. Visit the links at the bottom of this page for in-depth articles.

The term "compression" is often used to describe ATRAC, but it's a misnomer because frequency range and dynamics are left intact. "Perceptual coding" is the accurate term. If it helps aesthetically, just think of MDs as CDs with the hidden clutter removed. Any recording process involves some alteration of the source, so it's not fair to say that masking algorithms violate a universal standard of purity. Some very good science has gone into the MiniDisc and it's almost as remarkable as the invention of the CD. It allows CD quality audio to be stored at roughly a 5:1 ratio to the original digital source by using efficient 20-bit storage and the aforementioned perceptual coding. Good sound quality can even be obtained at a 12:1 ratio with the MP3 (MPEG Audio Layer 3) format. Download an MP3 player and some songs to hear how well perceptual coding works with over twice the data reduction of ATRAC. 160kb MP3 files have very good quality if you can find any. Note that MP3 sound quality is highly dependent on your computer's sound card, the sampling rate and the source material. Most cards add noise to the output and people who make MP3s can be sloppy about it. To get the purest MP3 sound you need an error-free file and a sound card with digital output fed into a good stereo system.

When the MiniDisc first came out in 1992, the ATRAC scheme wasn't quite perfected and some people noticed rough edges (mainly treble) in certain music. But with the latest ATRAC versions the differences are insignificant, especially in the mobile/portable environment where the MiniDisc excels. Critical listening comparisons should be done with decks using ATRAC 4.0 or newer (which were generally built after 1996). Even when you listen on good headphones, you hear no evidence of "missing" music in any frequency range. All the subtle detail and instrument placement remains intact. Don't let anyone tell you that MiniDisc sound quality is less than superb. Bench-test definitions of sonic purity are much different than actual human hearing. ATRAC may improve slightly in years to come, but it's already so good that most people will never notice. Note that the playback decompression algorithm is fixed, so if you buy a player now you aren't missing out on small future recording improvements.

Wariness of acoustic masking among audiophiles is based on theoretical principles that are of minimal value in the real world. You may recall that the CD was criticized as a lossy format when it first appeared, because it "removed" minuscule segments of sound during sampling. Arguments against the MiniDisc are similar in many ways. Most of the skepticism is based on hearsay, technical ignorance, archaic ATRAC versions, audiophile snobbery, overblown fears of piracy or the old pastime of criticizing anything new. But masking technology has actually been around for decades, with Dolby Labs as one of the pioneers. If it sounds basically identical to CDs and much better than the cassettes it was designed to replace, does it really matter that data was removed? Time spent bickering about purity could be better spent enjoying the MiniDisc's superb sound and practical features.

Other Web sites (below) go into great technical detail about ATRAC and the MiniDisc format, but I will list what I consider the best reasons for dumping cassettes and using MDs in your car or portable player:

MiniDisc vs. recordable CD formats:

Some people think re-writable CDs (CD-RW) are an ideal format, but they are ignoring the MiniDisc's compactness, durability, editing features and lower lifetime cost. The same applies to upcoming recordable DVD or any CD-sized format. A big issue with CD-RW is that re-writable CDs, due to their lower reflectivity, cannot be played in most of today's audio CD players (most CD-R record-once discs can). Another problem with CD-RW is that non-jacketed discs pick up scratches in front-loading mobile players. Surface flaws can sometimes interfere with playback and seriously affect the ability to re-record on sensitive discs. CD-sized discs are also more subject to skipping and harder to manipulate, as mentioned above. CD-RW discs cannot be edited at random after the first pass. You can only redo the last track or the entire disc; very primitive compared to the MiniDisc's flexibility.

Yet another drawback is that CD-RW discs are up to five times as expensive as MDs. Recordable DVD is projected to be even more costly. CD-R discs are currently cheaper than MDs but the gap is closing and they have the drawbacks of all larger, non-jacketed formats and no after-the-fact editing features. The cheaper initial cost of CD-Rs is lost the first time you need to re-do a disc and have to trash the whole thing. You also spend more time organizing track lists and re-burning a CD-R than you do editing specific tracks on an MD. These formats can certainly co-exist but I think the MiniDisc is superior in many ways, especially for mobile use.

No technology is perfect and I've found some limitations, but they are trivial compared to the MiniDisc's advantages. I list them here for objectivity's sake.

I hope everyone who reads this will consider a MiniDisc deck and help make the medium less expensive for all of us. It doesn't belong in a rare niche market like DAT (digital audio tape). MDs should be sold wherever cassette tapes are sold, with a reasonable price of about $2 per 74 minute disc. Home decks are already available below $200 and prices should continue to drop as more people are exposed to this amazing format.

The MiniDisc Community Pages (best Web resource) | Usenet newsgroup:

Official Sony MD site | Pictures of MiniDisc gear | 20-20khz test tones | Comments