Silent to Sound

 

 

SILENT TO SOUND

 

(This was a very long page so I have divided it. Page 1 is an introduction and a look at Specto add-ons,

  page 2 covers the Gem, page 3 the 200B, and some sound-on-disc projectors and page 4 is mainly 8mm.)

 

9.5 sound was introduced only shortly before the war, and the only projectors, the Vox and Super Vox, were made in France. War obviously put a stop to production, so post-war British nine-fivers faced a dearth of projectors. Partly because of this, but also because of your true nine-fiver's terminal obsession with getting stuff on the cheap, sound conversion units reared their fascinating (to the collector) but ugly (to the film-lover) heads. (Good sentence, eh?).

Pathé had in one sense shown the way, with the Vox initially available as the "S", but sound had clearly been envisaged in the original design. Apart from the one-off sound Baby (see under Babies), the main targets for add-on sound units were the Gem and the Specto, but units were made for the 200B  and even the H (see later). The Gem later went on to infamy as the Son (ugh). I know little of 16mm sound add-ons, such as the Ampro, but assume they were mostly pre-war as thereafter war surplus caused second-hand 16mm machines to flood the market.

The problems with adding sound to a silent machine are many. Among them is the sheer speed of operation, 50% faster than envisaged at the design stage. One has to accept this proved no problem with the Gem mechanism.  The Specto, however,already had a mechanism where the claw operated twice per frame, being held back from engaging the film on the second stroke. One would expect wear if not worse. Probably the biggest problem is controlling the speed - a simple electric motor tends to gain speed as it warms up and to vary its speed with variations in load. Together with smoothing the film across the sound reader, this could significantly affect sound quality.

Associated Cine Equipments (ACE) of Erith, Kent, made add-on sound units for Gem and Specto, for both 16mm and 9.5mm, with 12 watts sound output claimed. They were sold either as complete units with projector, in a case, or separately. I have a copy of a 1950 advert. Prices were:-

Gem, complete projector 9.5 £81 12 0 Sound unit only £44 2 0

                                       16 £92 10 0                          £52 10 0

Specto                            9.5 £95 12 0                         £54 10 0

                                      16 £ 99 10 0                         £54 10 0

 

Specto Conversions

The ACE Specto unit was designed for the standard 400ft capacity model; the lower arm remained in place, but folded down against the front of the projector. A unit to take the Educational model was available at a slightly higher price. The unit itself had a 900ft take-up; a top spool extension arm was available for 10s. 6d. I have to say that these prices look stupendously high, considering what average weekly wages must have been. A test Report on the 9.5 unit was published in the October 1959 issue of Amateur Cine World (ACW). Here is the text.

"The outstanding feature of these Sound Units is that no modification to the projector is required - an important point. There can be no doubt that the Specto is a difficult machine to convert as the motor occupies the very place where one would wish to put the soundhead. It is interesting to note, therefore, that Associated Cine Equipments have located their soundhead after the lower sprocket, which means that the film is pulled through the soundhead by the take-up reel.

Tests show that this unconventional procedure works extremely well. The sound is very good, comparing most favourably with that from other 9.5mm machines. Our critical ears detected a small amount of wow, but this would doubtless not be noticed by the average audience. Obviously, it is essential to use reels that are not bent, and take-up belts of the correct type, to maintain smooth film travel.   We tested a 9.5mm standard (100 watt model) Specto projector and Sound Unit. The unit is solidly built from aluminium castings, and the black crackle and plating match the finish of the Specto exactly. The appearance of the complete unit is unified and quite pleasing. (Note that the pictures are my 9.5/16 machine, with the longer arms cannibalised from a 16mm machine. I had to remove the lower arm; with 400 ft capacity, the arm would fold down between the motor and the sound unit - MAS).

The Sound Unit incorporates the complete soundhead and amplifier very neatly. There are no loose "extras." The Specto is simply placed on the platform of the unit. Adjustable locating bars are provided to allow for any small differences in the position of the film path on different Spectos, so that the projector can be accurately lined up with the sound head.

The soundhead

The sound head itself, located on top of the Unit, scans the film on a rotating drum in the customary fashion. The sound drum shaft, mounted in ball races, carries a solid flywheel 4.75 in. diameter and nearly 0.5 in. thick. A roller below the drum provides the necessary drag, and holds the film onto the drum. The film is guided between a flange on one side of the roller, and a flange on the opposite side of the scanning drum. A roller above the drum carries the film round to the take-up reel.

The photocell, a midget type CG-10, is fitted in a very neat plug-in holder. The cell protrudes into the hollow interior of the scanning drum, where it directly picks up the light coming through the sound track - there are no mirrors, etc., to get out of adjustment.

The optical system - the standard projected slit type - has a relatively long focus objective lens, so there is plenty of room between the optical system and the drum for the film to be threaded comfortably and easily. The 4 volt 6 amp exciter lamp is fed from the transformer with raw A.C., but due to the high amperage and high thermal capacity of the thick filament there is negligible mains hum. A neat feature is that the exciter lamp also illuminates the control panel through a plastic window.

Compact amplifier

The very compact amplifier, in which the valves are lying 'on their sides', permits the shallow construction of the part of the base on which the projector stands. Grilles above and below the valves provide ventilation. The valves, all standard International Octal types are; 6J7 first stage, followed by double triode 6SN7 amplifier and inverter respectively, and two 6V6 output valves in push-pull. The rectifier is a 5Z4. The amplifier has an output of approximately 12 watts. We obtained ample volume in a large room with the volume control in about the half way position. From this we should judge that a 250 watt model Specto and the appropriate Sound Unit would give a creditable performance in a small hall.

A socket is provided for a gramophone pick-up to be plugged into the amplifier. The pick-up socket feeds into the second stage of the amplifier. A change-over switch on the control panel permits selection of film or gram. No provision is made for balancing level and tone of the two; the pick-up would normally be balanced externally to the film. The switch for film/gram changeover is definitely a good point for the amateur showman. No tone control is provided on the amplifier, which is set at a pleasing balance for film.

A small but important refinement of the Sound Unit is that the mains are plugged only into the Unit. A plug on the Unit provides current to the Specto. A good feature is that the same three pin plugs and sockets are used on the Unit as on the Specto itself, so the Specto owner's leads will be suitable for the Unit, and the three pins permit proper earthing of the metalwork. Both switches are normally left "on", and the machine operated from the control panel of the sound unit.

The amplifier is automatically switched on when the jack on the loudspeaker lead is plugged into the amplifier. A voltage selector for 200 to 250 volts (on the model we tested) is provided on the amplifier, which, like the usual transformer model Specto, is suitable for A.C. mains only.

The loudspeaker, a 10 inch Wharfedale of 15 ohms impedance, is contained in an attractive leatherette covered wooden case, which also serves to carry the Sound Unit when not in use. The take-up arm is also carried in the case. Some 30 ft. of speaker cable is provided, and is wound around brackets in the speaker case for storage. A well-made carrying case for the Specto projector is available as an extra; this is covered in grey leatherette to match the speaker case. A monitor speaker is available for those who wish to use the machine in a separate room or operating box.

Spool arms

The Specto we used had 400 ft. spool arms with an extension piece supplied by A.C.E. fitted to the top arm to enable it to take 900 ft. reels. A machine with Specto 800/900 ft. arms would not require this. When the Specto is placed on the Sound Unit, the lower (400 ft.) spool arm of the projector is in the folded position. A lower 800/900 ft. type arm would have to be removed before placing the projector on the Sound Unit.

The lower spring belt is replaced by a small rubber belt. It is this which provides a positive drive to a double pulley on the Unit, and from there a spring belt provides the slipping drive to the take-up spindle. A special take-up arm for reels up to 900 ft. capacity is supplied with the unit, and screws to the front of the casting.

For the 16mm Units, a special 1,600 ft. lower spool arm is available. This does not take its drive from the projector, since that would no doubt place undue strain on the motor. Instead, the 1,600 ft. arm has its own induction motor drive and slipping clutch (as distinct from the better known practice of using a series wound motor with a positive to the reel but "electrical" slip). The separate motor, which takes its current from the unit, gives the best quality sound on large reels of 16mm., because it gives a smoother take-up and hence a smoother drive to the film at the soundhead.

To mask off the sound track when sound films are being shown, a simple slide-over gate mask (supplied with the Sound Unit) is fitted to the 9.5mm Specto. The mask fits behind the top screw which holds the front plate of the gate on the Specto, and is moved in or out of position with the finger after taking out the lens. We found that it tended to raise the front plate of the gate slightly, so a little care was needed when threading to slip the film into the gate without its meeting the edge of the front plate. No mask is, of course, needed on 16mm.

A nice feature is that tilting of the machine is provided by the two front feet of the Sound Unit. The Specto seems to maintain sound speed surprisingly well once the motor has been warmed up. Messrs. A.C.E can fit governors, but they do not feel that the extra cost is justified for ordinary usage. Further, they prefer the user to hold to their commendable principle that no modification should be made to the Specto.

Four models

Two models of the Sound Unit take the 9.5mm Standard and the Educational Spectos, while another two take the 16mm machines.

It will be remembered that the 16mm Specto has claws on the inside, whereas S.M.P.E. sound film normally requires the claws to be on the outside. To overcome this the film is run with the perforations "inside", and a reversing prism is supplied to go on to the projector lens. Special sprockets and relieved gate plates are also available. The new Specto "Dual" which has 16mm claws on the outside cannot be used on an A.C.E. 16mm Sound Unit, but is suitable for a 9.5mm Unit. The entire Sound Unit shows evidence of very careful planning, and the construction is extremely good. We should say that certainly it is a most attractive proposition for the Specto owner who wants sound  for home use or in a  (my italics)."  Quite hard to imagine any other option for a Specto owner!

I never had enough pix of the Specto sound unit and most of those were lost in the Great Doftware Disaster of 2015. When I was renewing the Silent-to-Sound page, it was obvious my original pix of the Specto sound unit were inadequate. I have now taken some additional pix. These are mostly of a unit I picked up I know not where, but which some bright spark thought would look good roughly over-painted in best Admiralty Battleship Grey. Wrong! It does however make photography a tad easier - it is hard to get decent pix of all-black things.


Spsd1     Spsd2     Spsd3     Spsd4     Spsd5     Spsd6     Spsd7     Spsd8     Spsd9

First we have a view of the amp. The valve line-up from the left is:
1. VT74/5Z4
2. An anoymous thing made by B&H
3. 6V6GT/G
4. 6SL7GT
5 .6J7/VT91


Pic 2 is from the front of the machine, with the two front plates removed. Note just above the switches bottom left an angle piece which seems to do nothing. It is in fact perspex or simlar and allows light from the exciter lamp to  illuminate the switches and knob on the outside. The exciter incidentally is 4v 24w. Pic 3 is from a different angle, with Pic 4 a close-up from Pic 3. This is to show a feature marked with two red lines in the close-up. The complicated little switch unit is for the speaker output, which is via a standard jack plug, but it has this additional feature. Inserting the jack pushes the two marked strips into contact, which is necessary to complete the mains circuit - with the jack removed, there is no power (except thru to the projector) and so the amp cannot be powered-up unless the speaker is plugged in, a useful safety device for a valve amp. Those old enuff (ie nearly anyone who reads this sort of stuff) will recall the original Vox amp and, I think, the Home Talkie amp, had a simlar arrangement.
Pic 3 also shows the layout of the sound head, which is seen from other angles in Pix 5 and 6. Finally some general views of the machine and a very old pic from the original website.

(Gem next page).