There are significant differences in the magnetic performance characteristics of tape manufactured for different purposes.
The magnetic particles in the oxide coating are needle-shaped as a result of careful milling.  During the manufacturing process, the needles are oriented by an external magnetic field while the oxide slurry is still liquid.  On tape intended for video recording, the particles are oriented for maximum rententivity when recorded and played back by heads travelling in a helical scanning pattern.  This is a different orientation than that imposed in magnetic tape designed for optimal performance on analog audio tape recorders.  As a result, attempting to record analog audio signals longitudinally on media designed for analog video recording in a helical scanning pattern will likely result is less than optimal results.

Mark Hood
Project Audio Engineer
Sound Directions
IU Archives of Traditional Music

On 12/8/10 6:20 PM, "James Snyder" <[log in to unmask]> wrote:

>I know this has been discussed before but has anyone actually tried
>to use Betacm SP tapes as audio tapes on pro reel to reel machines
>(Sony apr, Ampex atr, etc)? I know it's a metal tape but can one of
>these machines be adjusted to use this tape? At 15ips it should
>sound good if the machine can be aligned to it, no?
>Shai

1. My first question is 'why would you want to?'  You can still buy
1/2" tape for audio.

2. Your going to take the time to unspool the tape from the small hub
tape reels onto an audio tape reel?  That strikes me as labor
intensive and prone to damage the tape.

3. Videotape is not audiotape.  One of the reasons the tape is put
into cassettes is that it is much thinner and more fragile than
audiotape.  Thinness allows long tape lengths to fit in small
cassettes.  It also allows the tape path to be maintained much more
precisely.

4. Metal videotape is designed for much different frequency
characteristcs than audiotape.  Audiotape is formulated for audio
frequencies + a bias frquency (for analog) or a digital signal with
bias for digital.  Videotape is designed for a minimum of 13.5 MHz of
frequency response from SPINNING HEADS travelling at 1500 ips+
diagonally across the tape.  The two are VERY different types of
recordings.

I imagine it could work, but I don't imagine it would sound as good
as you think it would, and would be more trouble than its worth.

James