Why were the RPM speeds of records chosen

[bileaflet_valve]

At the National Museum of Scotland, Chambers Street, Edinburgh, THIS was on show when I visited in 2012.

Les.

[G6Tanuki]

Fascinating! I wonder what the film-speed was?

I know that during WWII there were various highly creative things done by US companies to capture sound (both audible and ultrasonic) on 35mm film running at *very* high speeds to get good frequency-response. This was used (along with strobe lamps) to investigate destructive mechanical resonances in certain rapidly rotating mechanical assemblies, which were also being filmed at hundreds of frames per second so they could be played back slowly after the thing-under-test had disintegrated.

[Synchrodyne]

Fascinating indeed!

The Cell-o-Phone is also shown at Rmorg; http://www.radiomuseum.org/r/british...und_proje.html. The version shown there was said to use 4 mm film.

Searching Google Books (which often finds stuff that a regular Google search misses) brings up literature references for both “Cell-o-Phone” and “Ozaphone”.

I have attached a couple of snips from the Google Books search.

Cheers,

[Synchrodyne]

Relating this to gramophone record rotational speeds, one might observe that the introduction of the 33⅓ rev/min LP record was a relatively large stepup (along several vectors) from the regular 78 rev/min record, and one that effectively pushed aside other contenders, such as Cell-o-Phone, that otherwise might have been adopted as offering improvements over the regular records.

Although the LP rotational speed was determined by existing practice, overall the LP parameters seem to have well chosen. Effectively it went largely unchallenged until the musicassette arrived, and then it coexisted as a higher quality medium until it was displaced by the CD. So 33⅓ rev/min might have been something of a “Goldilocks” number. Somewhat slower and the upper frequency range would have been curtailed, and somewhat faster and playing time would have been reduced to the point where its utility could have been compromised. One wonders if the CBS folk were mindful of the potential competitors to the disc when it embarked upon the LP development program. As Radio Wrangler has said in another thread, any technology history does better if it covers what was not done (or to extend that a bit, done on the margins) as well as what was done.

Cheers,

[dave walsh]

This is such a profound and clear comment [when you think about it] coupled with the Radio Wrangler observation, that it has the "ring " of credibility even if it wasn't thought through in absolute terms. Saw that RW post but can't locate it just now!
Dave W

[Synchrodyne]

RW’s comment was in the “FET Questions” thread, post #71, see: https://www.vintage-radio.net/forum/...t=98398&page=4. It was: “In any historic study of what was done in some branch of technology, it is equally interesting to consider what was *not* done.”

Long ago I learned that when it comes to writing – or speaking for that matter – if you come across a good or useful turn of phrase or expression, then steal shamelessly and integrate it into your own work. This one is very useful in and of itself, and perhaps also useful when, as it were, one is asking the court’s indulgence to pursue a line whose relevance to the matter in question is not immediately clear, but will eventually emerge.

Regarding the comment in my immediately previous posting, this was simply one of those thoughts that more-or-less fell out of a clear blue sky, and just after I had closed the preceding post. Its resultant credibility is thus probably greater than the sum of its parts, but I won’t argue with the perception.

Re optical recording, I am not sure where one might look for a detailed historical accounting. As I recall, the original “Audio Cyclopedia” by Tremaine – which I haven’t seen for maybe 40 years – had a fairly long section on optical recording, but whether it covered the audio-only formats that came and went as well as movie formats I do not recall.

Cheers,

[emeritus]

I just came across a brief summary of early sound recording in the context of wireless in my copy of "History of Radio Telegraphy and Telephony" by G.G. Blake [Chapman & Hall Ltd., 1928]. This book (saved from the recycle bin during a departmental library clearout when I was at Marconi's) does not normally go into great detail about its topics, but does provide documentary sources. The author wished to "..bring into prominence almost forgotten schemes and devices, in the hope that new ideas may spring therefrom. " (I was intrigued by the non-vacuum thermionic valve, but that's a bit OT for this thread).

The pages mentioning sound recorders using film and magnetic media, and the relevant pages giving the sources, are attached. The earliest recorder mentioned using photographic film is the "Photographophone", dating from 1901.

[Synchrodyne]

So photographic sound recording has a long history! It would be interesting to ascertain the performance capability of the Cell-o-phone equipment, given that it dates back to the 78 rev/min record era, when overall expectations were lower. In that regard, there is an interesting article about audio quality and the perception thereof in the immediate post-WWII period in Popular Electronics for 1970 September, p.29ff, available at: http://tinyurl.com/PE197009. In particular this refers to work done by Olson of RCA.

As the LP was, I think, developed after Olson’s work, the highest attainable audio quality (and probably somewhat future-proofed against expected (and unexpected) equipment developments) was likely a goal as well as extended playing time and a quieter background. If so, that might help explain the huge upward step in performance and so the longevity of the medium. Otherwise, had longer playing time and a quieter background been the sole drivers, then a more modest increase in overall performance might have been seen as being acceptable. Of course, the longevity of the LP was in part due to the fact that a technically effective and economic way was found to accommodate stereo when it [the LP] was around a decade old. In contrast, the performance capability of open-reel tape, at least in the domestic environment, was ramped up in a series of smaller steps that did eventually allow the use of lower speed (e.g. 9.5 cm/s in place of 19 cm/s). The improvement process for machines used in a domestic environment, in terms of fundamental rather than individually realized performance, may not have reached a plateau until Dolby B noise reduction was introduce in the early 1970s. (Although I once saw the comment that adding Dolby B to the Revox A77 was rather like gilding the lily.) Noise reduction systems were proposed for LPs, but did not catch on. Forward/backward compatibility or lack thereof might have been a partial reason, but lack of desperate need was surely a factor.

Cheers,

[Synchrodyne]

Another optical recording system was the RCA Photophone, see: http://tinyurl.com/RCA-Photophone

I’d say that enough early work was done on standalone optical audio recording that had it had the potential to compete with gramophone discs as a domestic recorded sound medium, then a suitable format (or perhaps competing formats) would very likely have emerged as more than a “fringe” item.

Returning to gramophone record angular velocities, as it were, there was an interesting article, including detailed analysis, from EMI in Wireless World for 1951 July, available here: http://tinyurl.com/WW-195106-EMI; and here: http://tinyurl.com/WW-195106, p.227ff.

I shall not attempt a précis of the article. Rather its title “Gramophone Turntable Speeds” and its subtitle “What is the Best Speed for Microgroove Recording” confirm its direct relevance here.

(By the way, I recommend the second link to WW 195106, as it points to the whole magazine (sans advertising sections), which includes other interesting items, including articles on the Wrotham VHF slot aerial (which design became something of a BBC “trademark”); the Daventry Third Programme MF transmitter and radiator (which became the standard textbook example of an MF antifading radiator); and a nice treatment of FM sidebands by “Cathode Ray”.)

Cheers,

[dave walsh]

Further to this discussion and having just watched the SOUND OF SONG again on BBC4, I noticed they used a sequence involving a 33 1/3 disc being played to synchronise with a film recording. I realise that there may be conflicting views on this but just within the area of record speed evolution alone, this program is worth viewing. See the relevant thread and I-Player
Dave