In order of narrow to wide differences there are: 1) Ampex, 2) NAB and 3) Euro standard widths. If you use a narrower playback head than the recorded track width, you will experience the "fringing effect" which is a low frequency boost below 100Hz.
And a wider playback head than the recorded track will increase tape hiss from the portion of the tape it's reading that is random magnetization (or worse, unerased material from a wider track format).
-------------------------------- David Bradley - Webmaster - Official Klaatu Home Page, klaatu@xxxxxxxxxx