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We have similar problems setting azimuth with Cinemascope tracks, which
used left, center, and right microphones that were spaced several feet
apart.  Comparing interchannel phase won't work.

Another instance where using program phase to set azimuth falls apart is
with copies.  If the azimuth was off on the reproducer when the copy was
made, then using phase to set the playback azimuth of the copy will result
in incorrect azimuth.

Ellis

On Mon, Dec 5, 2016 at 1:33 PM, Marcos Sueiro Bal <[log in to unmask]> wrote:

> This all makes sense! Thank you Chester and Richard
>
> Marcos Sueiro Bal
> Senior Archivist, New York Public Radio
> 646 829 4063
>
> -----Original Message-----
> From: Association for Recorded Sound Discussion List [mailto:
> [log in to unmask]] On Behalf Of John Chester
> Sent: Monday, December 05, 2016 1:48 PM
> To: [log in to unmask]
> Subject: Re: [ARSCLIST] Setting azimuth from program - a caution
>
> On 12/5/16 12:56 PM, Marcos Sueiro Bal wrote:
>
> > Could varispeed ameliorate that issue?
>
> No, this is a wavelength problem, not a speed problem.  When the
> wavelength of the recorded bias signal is equal to the gap length, the head
> has no output, regardless of speed.  If you have this problem, your only
> option is to use a head with a different gap length.
>
> Slower playback speed = bias playing back at lower frequency, which means
> it's more likely to survive its passage through the bandwidth-limited
> playback electronics and any filters which would normally prevent bias from
> appearing in the repro output.  Also, bias frequencies between 90 and 180
> kHz will now be within the bandwidth of an A/D converter running at 192k
> sample rate.  But if the head has no output at the bias wavelength, slower
> speed won't help.
>
> -- John Chester
>
> >
> > Marcos Sueiro Bal
> > Senior Archivist, New York Public Radio
> > 646 829 4063
> >
> > -----Original Message-----
> > From: Association for Recorded Sound Discussion List
> > [mailto:[log in to unmask]] On Behalf Of Richard L. Hess
> > Sent: Monday, December 05, 2016 12:11 PM
> > To: [log in to unmask]
> > Subject: Re: [ARSCLIST] Setting azimuth from program - a caution
> >
> > Indeed! That is a good trick, but you might have to use 1/4 speed and
> sometimes the bias wavelength was designed to fit in the head gap null,
> which makes it more difficult to reproduce on a machine with repro heads
> that have the same gap length as the design machine.
> >
> > Cheers,
> >
> > Richard
> >
> >
> >
> >
> >
> > A trick I learned from Danny Sbardella is to adjust azimuth for maximum
> output of  the bias tone played at half speed.
> >
> > Cheers,
> >
> > Marcos
> >
>



-- 
Ellis
[log in to unmask]
818-846-5525