Your description of the Judy Collins tape is similar to what the Abbey Road folks were up against
with the Beatles tapes. A master like Sgt. Pepper contains master mixes completed over several
weeks. The early albums can contain sections cut at sessions months apart, and mixed to mono masters
at those sessions. All of this made for azimuth variences within single tapes, and hence the details
adjustment notes that had to be followed on the fly while LPs were being cut. I don't think azimuth
fine-tuning was as much a concern back in the day, so I doubt this was done very much in the LP
heyday. I think gross and highly audible azimuth problems were what worried engineers back in the
The azimuth article you said you're working on may be of great interest to ARSC Journal readers.
This is right up the alley of a lot of work being done by ARSC members. I would love to know more
about actual field experiences regarding azimuth and cassettes, keeping in mind that very few of us
have playback decks with easy azimuth adjustment available.
-- Tom Fine
----- Original Message -----
From: "Richard L. Hess" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, September 10, 2014 2:18 PM
Subject: Re: [ARSCLIST] AZIMUTH (was recording "cleanup" plugins and 192/24)
> Hi, Jim,
> I do, too. StereoTool is the best assistant in that regard. In fact, it is the only support
> software I have found useful for azimuth alignment on program. Tones are a different story and a
> scope (generally a software variant--specifically RME DigiCheck) is very useful.
> What have you found to assist in azimuth adjustment and how do you use it?
> The "crutch" remark was meant in context to purposely downgrade the ultimate repro performance by
> intentionally using a two-channel head for a full-track tape to enable azimuth alignment via
> instrumentation tools and then sum the channels.
> It is a tough decision to decide whether to go with the full-track head and risk being out of
> azimuth because there is no accurate instrumentation or use the sub-optimum two-track playback to
> get better azimuth but suffer from the losses created by mis-matching between repro channels and
> other effects. I found that especially with the early full-track tapes, the sound was richer with
> a full-track head than with a summed NAB stereo head, even though azimuth was easier to adjust
> with the NAB stereo head.
> Other people I know and I have been able to obtain pleasing and presumably accurate results with
> full-track play heads.
> Anyway, with a mono signal, what software tools help you align azimuth on program?
> As an aside, when Judy Collins's #3 album was being remastered, the project was done and Alan
> Silverman checked the mono sum and found that the azimuth was off despite the fact he had aligned
> to the tones at the head of the tape. It was somewhat common practice to record a series of tones
> at once and then splice them into the individual album tapes. He went back and started over. I had
> given Alan a good CD-R copy of a pristine vinyl copy I had found and he indicated that was not
> what he thought the album sounded like, so I'm happy to say he pretty much matched the LP sound.
> This was about a dozen years ago.
> On 2014-09-10 12:49 PM, Jim Sam wrote:
>> I use software to help me align azimuth on cassette transfers all the
>> time in conjunction with my ears. You can call it a "crutch" or you
>> can call it being thorough and professional.
>> Consider that you could theoretically calibrate a reel machine by ear,
>> too, but I wouldn't hire anyone that didn't use a voltmeter or DAW
>> On Wed, Sep 10, 2014 at 9:01 AM, Richard L. Hess
>> <[log in to unmask]> wrote:
>>> I probably should clarify...
>>> Think of the azimuth error situation as a right triangle.
>>> The "perfect" azimuth is one leg that is vertical. The actual recorded
>>> azimuth is the hypotenuse. The azimuth error is the leg which is horizontal.
>>> The length of the horizontal leg of the triangle can be translated into the
>>> time delay and the phase shift between the two channels.
>>> When the two channels are summed, even small errors which CAN be equalized
>>> out, grow into huge errors and cannot be recovered, so the re-timing between
>>> stereo channels prior to summing will produce far better results than not
>>> using it and summing the two channels will reduce the noise taken from
>>> either channel.
>>> For high-quality music work, using a full-track head is superior, but for
>>> oral history production work (especially from cassettes) there is merit to
>>> summing the two tracks, especially because mono cassette machines are hard
>>> to find and few (if any) were made with the quality of the top stereo
>>> Here is an example using a cassette:
>>> 15 arc minutes (1/4 of a degree) azimuth error.
>>> Single channel -3 dB point ~ 9 000 Hz
>>> Summed channels -3 dB point ~ 3 400 Hz
>>> Single channel -6 dB point ~ 12 000 Hz
>>> Summed channels -6 dB point ~ 4 600 Hz
>>> Sliding the second channel in time to be in alignment with the first
>>> provides a huge improvement in the high-frequency response.
>>> I contend that, if desired, losses of up to approximately 6 dB can be
>>> equalized out as long as there is no additional boost and a rolloff after
>>> the - 6 dB point (to avoid increasing noise).
>>> On 2014-09-10 10:25 AM, Richard L. Hess wrote:
>>>> Hi, Andrew and Tom,
>>>> I am (very) slowly working towards a paper on azimuth.
>>>> The full-track mono tape is, of course, the hardest to play from an
>>>> azimuth perspective (of the common formats)--I hate to think about the
>>>> 1-inch two-track!
>>>> Transport guidance is a huge issue and I have found that the Studer A80
>>>> is magical in that regard--and the Studer A810, not so much. The Sony
>>>> APR-5000 is between the two.
>>>> For those of us who have taught ourselves how to adjust azimuth by ear
>>>> (sort of the same thing as focusing a camera lens in many ways), we do
>>>> not need crutches, but I have come to realize that using a two-track
>>>> head for "factory workers" might be beneficial.
>>>> For one project I proposed (but we chose not to implement) a wide/narrow
>>>> head for full track mono. We batted around a few different
>>>> configurations--including a long discussion with Greg Orton. I was
>>>> thinking of something like 0.120 and 0.04. The nice thing is even if
>>>> things go south, you still have a good percentage of the highs on the
>>>> 0.04 track, albeit noisy.
>>>> With that said, for oral history cassettes, I use, in addition to manual
>>>> azimuth adjustment, the azimuth compensation feature of
>>>> www.stereotool.com. This allows excellent channel summing for improved
>>>> noise, assuming both channels were recorded.
>>>> There is a similar feature in iZotope RX Advanced.
>>> Richard L. Hess email: [log in to unmask]
>>> Aurora, Ontario, Canada 647 479 2800
>>> Quality tape transfers -- even from hard-to-play tapes.
> Richard L. Hess email: [log in to unmask]
> Aurora, Ontario, Canada 647 479 2800
> Quality tape transfers -- even from hard-to-play tapes.