There are other examples of stereo recordings that can make adjusting 
azimuth difficult using the summing method. IMHO, the best is to use a 
scope that shows a Lissajous waveform. When using test tones, I will 
align azimuth using the waveform viewed on a dual trace O-scope.

Cheers!

CB

Corey Bailey Audio Engineering
www.baileyzone.net

On 10/21/2020 5:40 PM, Mickey Clark wrote:
> Tim-Thanks for the info. Very interesting. -Mickey
>
> -----Original Message----- From: Tim Gillett Sent: Wednesday, October 
> 21, 2020 4:54 PM To: [log in to unmask] Subject: Re: [ARSCLIST] 
> Delayed Channels on Cassette Tapes
> Hi Mickey, I didnt mention summing to mono because I wanted to get
> across the basic idea first.
> Also, there can be problems adjusting azimuth in mono on certain
> stereo recordings. Say a musical piece has a strings backing which was
> initially recorded as a mono track but in mixing to give a fake stereo
> effect the producer has slightly delayed say the left side of the
> strings re the right. It sounds OK in stereo but summed to mono the
> strings now partially cancel out, sounding distant and indistinct. If
> we adjust azimuth for the clearest string sound, we  now have the
> wrong azimuth for other sources such as the important centralised
> vocal.  In that case the vocal is the azimuth reference. The strings
> are still out of phase but that's how they were meant to sound.
> Less common is a stereo tape recorded with a head with gap scatter.
> One head gap is slightly behind the other in time. I have some high
> speed duplicated music cassettes with this issue. Correct azimuth
> summed to mono resulted in incorrect azimuth (lost highs) in stereo.
> So  I adjusted azimuth only stereo and for maximum clarity. Then to
> correct the time differential I moved the delayed track slightly
> forward to match the other. I did this in the DAW, realigning the high
> frequencies in the waveforms by eye.
> Cheers Tim.
> ----- Original Message -----
> From: "Association for Recorded Sound Discussion List"
> <[log in to unmask]>
> To:<[log in to unmask]>
> Cc:
> Sent:Wed, 21 Oct 2020 15:12:02 -0700
> Subject:Re: [ARSCLIST] Delayed Channels on Cassette Tapes
>
> Chris-Another tool is to combine the tracks while listening.Making it
> mono. The azimuth setting is most easily fine-tuned that way--Mickey
>
> -----Original Message----- From: Tim Gillett
> Sent: Wednesday, October 21, 2020 2:47 PM
> To: [log in to unmask]
> Subject: Re: [ARSCLIST] Delayed Channels on Cassette Tapes
>
> Hi Chris,
>
> I'm not sure if you know that cassettes are notorious for azimuth
> misalignment on playback. Experts in tape digitization align the
> tape replay head to the recorded patterns on each tape being played.
> It involves carefully adjusting the azimuth screw on the machine's
> playback head while listening. We aim to extract the brightest,
> clearest sound off the tape. After this has been done, an Azimuth
> Corrector tool might be also used to fine tune the small remaining
> misalignments, especially dynamically changing misalignments which
> occur too quickly to be corrected by adjusting the head's azimuth
> screw.
>
> An Azimuth Corrector is generally not very good on a true stereo
> recording as it can struggle to distinguish between intended and
> unintended inter channel delays.
>
> Cheers Tim.
>
> ----- Original Message -----
> From: "Association for Recorded Sound Discussion List"
> <[log in to unmask]>
> To:<[log in to unmask]>
> Cc:
> Sent:Wed, 21 Oct 2020 13:34:11 +0100
> Subject:[ARSCLIST] Delayed Channels on Cassette Tapes
>
> We are digitising some cassette tapes using Audacity.. A batch of
> them
> are stereo, however they have exaggerated separation of the channels
> (perhaps they need normalisation?), and one channel is a microsecond
> behind the other. We don't actually need stereo, amd have tried to
> merge the channels into mono. But this sounds dreadful - the speech
> part sounds OK, but the music is very 'echo-ie).
>
> Another batch have delays from one channel to the other measuring in
> seconds. How can we time-shift one channel to match the other one?
>
> Thanks - Chris B.
>
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