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Most Reel to Reel machines for home use utilise 1/4inch wide tape in varying lengths and thicknesses.

Tapes come in varying thicknesses - Standard Play - Long Play etc - as the tape gets thinner more length can be spooled on the same size reel (so more time for Record/Play).

Some tapes have an additional coating on the rear of the tape - this is usually called "Black Coated" or "Blue Coated" etc.
With the extra coating on a same length tape - the reel will appear to be more full than with a non-coated tape.

Coated tapes are useful for long-term storage as, while the tape is stored `spooled`, "loud" musical passages Recorded on a section of the tape may well slightly change the magnetic property of the next section of the tape spooled further on the spool (the slight echo of the "loud" part on top of a quieter passage on the tape is known as `bleed-through`). So to paraphrase - if you intend to keep your recordings stored for a long period of time then a suitably professionally coated tape is to be recommended.

The modified chart below shows a comparison of tape lengths and time / tape speed. The original code is courtesy of Video Interchange in the USA.

Time Chart for Open Reel-to-Reel Analogue Audio Tape   (Approximate)

Reel Diameter Tape Length

One Direction
Mono/Stereo/4 Track Discrete

2 Directions
Mono or Stereo

Two Directions
4 Separate Mono Tracks

Tape Travel across the heads Per Second
1 7/8" - 4.76cm 3 3/4" - 9.53cm 7 1/2" - 19.05cm 15" - 38.10cm 1 7/8" - 4.76cm 3 3/4" - 9.53cm 7 1/2" - 19.05cm 15" - 38.10cm 1 7/8" - 4.76cm 3 3/4" - 9.53cm 7 1/2" - 19.05cm 15" - 38.10cm
3" - 7.62cm 300ft - 9.144m 30 min 15 min 71/2 min 33/4 min 1 hour 30 min 15 min 71/2 min 2 hours 1 hour 30 min 15 min
5" - 12.7cm 600ft - 18.288m 1 hours 30 min 15 min 71/2 min 2 hours 1 hours 30 min 15 min 4 hours 2 hours 1 hour 30 min
5" - 12.7cm 900ft - 27.432m 11/2 hours 45 min 22 min 11 min 3 hours 11/2 hours 45 min 22 min 6 hours 3 hours 11/2 hours 45 min
7" - 17.78cm 1200ft - 36.576m 2 hours 1 hour 30 min 15 min 4 hours 2 hours 1 hour 30 min 8 hours 4 hours 2 hours 30 min
7" - 17.78cm 1800ft - 54.864m 3 hours 11/2 hours 45 min 22 min 6 hours 3 hours 11/2 hours 45 min 12 hours 6 hours 3 hours 11/2 hours
7" - 17.78cm and 101/2" - 26.67cm 2400ft 73.152m 4 hours 2 hours 1 hour 30 min 8 hours 4 hours 2 hours 1 hour 16 hours 8 hours 4 hours 2 hours
101/2" - 26.67cm 3600ft - 109.728m 6 hours 3 hours 11/2 hours 45 min 12 hours 6 hours 3 hours 11/2 hours 24 hours 12 hours 6 hours 3 hours


Early tape and wire machines recorded over the whole width of the tape - Monaural Record/Replay.

When 2 track tape heads were employed - a machine could Record/Replay Mono in one direction (and then Mono Record/Replay again if the tape were turned round and used on the other side). These 2 track (or 1/2 track) machines could also record stereo in one direction only.

2 Track Recording
With the advent of the 4 track head, machines split the tape width into 4 sections for Record/Replay. Thus you can record stereo in one direction on the tape and turn it over to record stereo on the other side. Most 4 track machines also gave you the facility to Record a Mono track in one direction (say on track 1) - then Rewind the tape and Record Mono (again on track 3) in the same direction as the first session. Thus - via the switching you can achieve 2 seperate Mono Recordings in the same direction - and of course Play them back independently. Turn over the tape and ...... same again, but with tracks 2 and 4 - or Record Stereo. Very flexible.
4 Track Stereo Recording
On specialist machines such as the Teac 3340 and 3440 you are able to switch the 4 track machine so that all 4 tracks can be used in one direction - all at once. These machines are known a Symul-Sync machines. Via the comprehensive switching on the machine you are also able to Record one or more tracks at a time while listening to any or all of the others which are being used in Replay mode. This type of operation is also known as 4 channel Discrete. These types of machine are useful for studio/home Multi-Track recording use. 4 Track Recording in one Direction
As the width of the tape is still only 1/4 inch - 4 track machines cannot Record/Replay with the same efficiency as that of a 2 track machine which utilises more of the tape width for each track. The Signal to Noise Ratio of 2 track machines is therefore generally better than that of a 4 track machine.

Thanks again goes to Video Interchange for the use of their (modified) graphics which we cannot better for their usefulness in displaying the tape heads and use of the width of the tape.

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