History of lead-in and lead-out grooves?

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Bob Dillon
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Re: History of lead-in and lead-out grooves?

Post by Bob Dillon » 17 Jun 2019 18:06

That frequency test record from 1930 is from when electrical pickups had also been in use for a several years. As for the best mechanical reproducer, I don't really know where the ceiling is for their high frequency response. My hunch would be not beyond 4-5,000 kHz.

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Re: History of lead-in and lead-out grooves?

Post by H. callahan » 18 Jun 2019 04:12

I was shocked when seeing the diagram as it indicates that all the improvements new-style-soundboxes do feature cannot extend upper FR limit - as if reduced mass and therefore reduced inertia did not help. I mean basically everything is different with a new-style-soundbox, but upper FR limit is (nearly) the same?

In the video i can hear the sweep comming down at about 0:27, its very low volume but its there. Should be above 5kHz.

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Re: History of lead-in and lead-out grooves?

Post by Bob Dillon » 18 Jun 2019 18:25

The video isn't the best quality, video or audio. I'd like to find a higher-rez one that someone has done lately. It is interesting that he used that sweep record on several different phonos, if you look into his uploads.

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Re: History of lead-in and lead-out grooves?

Post by H. callahan » 20 Jun 2019 06:49

Yes...
...still i wonder what could be the reason for old-style- and new-style-soundboxes having about the same upper FR limit. Maybe the tonearms have too much play or maybe the diaphragms are not stiff enough to reproduce cycles above 5kHz, or maybe the soundboxes vibrate too much to properly read frequencies above 5kHz... it´s really strange.

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Re: History of lead-in and lead-out grooves?

Post by Bob Dillon » 20 Jun 2019 18:17

A crude steel needle in said soundbox is likely going to be an obstacle too. Especially considering the tip wears quickly. Can't trace those fine HF modulations.

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Re: History of lead-in and lead-out grooves?

Post by H. callahan » 21 Jun 2019 02:39

At the end of the record yes, but at the beginning a 10kHz cycle would be 0.0485mm in length - to my calculation - while a not-worn tip is 65μ which should fit very well into a 10kHz cycle, unless i got the units/math wrong.

Also when looking at the diagram one can see that the new-style-soundbox is loosing ground at about 3.7kHz, while the old-style-soundbox is loosing at about 3.5kHz but does come back for a spike at about 4.2kHz - this is totally strange.

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Re: History of lead-in and lead-out grooves?

Post by Bob Dillon » 21 Jun 2019 18:52

I know that some antique phonograph enthusiasts rebuild (or will have rebuilt by a specialist) their reproducers with glass diaphragms, to replace the mica diaphragms that many have. Supposedly they sound better. I wonder if glass would give better HF response too. Glass was not used in phono reproducers originally for the "klutz factor". Too breakable if dropped or handled roughly.

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Re: History of lead-in and lead-out grooves?

Post by H. callahan » 22 Jun 2019 06:58

Glass could be stiffer (depending on thickness) which was good for HF reproduction, but the new-style-soundboxes have a spider to increase stiffness of the aluminium-diaphragm (or it is shaped into a calotte to increase stiffness) - so i´m not sure if its lack of stiffness.
Changing a needle would "be fun" when the diaphragm is made of thin glass...

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Re: History of lead-in and lead-out grooves?

Post by H. callahan » 22 Jun 2019 14:44

.. i have found another reference where it says that a Victor Orthophonic soundbox can have about 70Hz to 5.5kHz. So the diagram seems to be a little conservative on the new-style-soundbox.

Also i have been looking at the tip of an unplayed needle with a strong loupe, at the area where it does contact the groove its diameter is about 0.1mm. The contact area of an unplayed needle should be smaller than that, but as the needle wears very fast that´s pretty tight for frequencies above 5kHz (at the beginning of a record mind you).

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Re: History of lead-in and lead-out grooves?

Post by Bob Dillon » 22 Jun 2019 20:29

H. callahan wrote:
22 Jun 2019 06:58
Glass could be stiffer (depending on thickness) which was good for HF reproduction, but the new-style-soundboxes have a spider to increase stiffness of the aluminium-diaphragm (or it is shaped into a calotte to increase stiffness) - so i´m not sure if its lack of stiffness.
Changing a needle would "be fun" when the diaphragm is made of thin glass...
The spider reproducer is not a new idea. Gianni Bettini designed something like that in the 19th century. It was a cylinder reproducer. The idea behind the spider is to utilize / activate more of the diaphragm area, rather than a single point in the center where the stylus / stylus assembly connects to it. It lateral reproducer it's the "needle bar."

https://www.bing.com/images/search?view ... ajaxhist=0

https://youtu.be/1xcGMLc9_IQ
Here the uploader comments that the diaphragm is thin aluminum. A cite from a book (The Fabulous Phonograph by Roland Gelatt) claims Bettini favored mica. Maybe Bettini used both.

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Re: History of lead-in and lead-out grooves?

Post by H. callahan » 23 Jun 2019 04:49

Hmmm, with adjustable counterweight if i see correct, very nice!

According to some website the center of the diaphragm should be as stiff as possible for better reproduction of HF, which is why a glass diaphragm should improve HF-playback - but i guess a stiffer diaphragm also will create less distortion on medium and low FR due to fewer bending.
The problem i especially see with phonograph-reproducers and spider-diaphragms is that due to the spider the diaphragm is harder to move for the groove, which should result in increased wear. I think a spider diaphragm would be helpful for recording as more of the energy the diaphragm is hit by can be used to cut the groove, but for playback of cylinders a spider might be not ideal for the long term.

I don´t own a metal-diaphragm-soundbox (for shellacs) but judging from youtube-videos i find that a metal diaphragm does add a metally coloration to the sound. Soundboxes with aluminium diaphragms might be more linear, but i find mica to sound "more neutral/natural". Maybe because distortion cannot be heard as good with mica than with aluminium, but i also favour mica.

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Re: History of lead-in and lead-out grooves?

Post by Bob Dillon » 24 Jun 2019 02:31

"The larger diaphragm is also less stiff, potentially causing irregular vibration "patterns" on the diaphragm surface."

http://www.victor-victrola.com/Soundbox%20Article.htm

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Re: History of lead-in and lead-out grooves?

Post by H. callahan » 24 Jun 2019 05:10

Which is why aluminium-diaphragm soundboxes usually feature a spider to increase stiffness.

Strange thing though is that the Victor No. 2 has higher frequency response while having higher dynamic mass at higher frequencies.

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Re: History of lead-in and lead-out grooves?

Post by mvno_subscriber » 26 Jun 2019 09:25

Bob Dillon wrote:
14 Jun 2019 18:09
I wonder if the thread starter is still lurking around. #-o
I'm here. Don't have much wisdom to offer, just absorbing everything :)

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Re: History of lead-in and lead-out grooves?

Post by H. callahan » 27 Jun 2019 04:05

Nice to hear that you´re not annoyed by all this off-topic-stuff.

While reading through the link Bob Dillon provided i found another mention of missing lead-out-grooves, but no explanation why they are missing:

http://www.victor-victrola.com/Records.htm

"Most appropriate early records used on Victors and Victrolas have no lead out groove (the eccentric circle at the end of the record close to the label). That is a good indicator that the record is pre-1925, and will play well on an early phonograph. For the post-1925 Electrola and Orthophonic models, the eccentric lead-out groove will be used to shut-off the machine at the end of the record. "

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