Enhance 35mm optical mono sound?

[Emiel de Jong]

Our former main technician reminded me of the previous weave and flutter on the Philips soundheads which was original. I do not feel like reliving that part of history.

If you actually had flutter with those older type (DP70 original) soundheads that's quite an accomplishment. They had to be adjusted really wrong then.

[Jerry G. Axelsson]

Emiel, I used these Philips Symphony soundheads on other 35mm projectors as well when I thought it over. They gave us some headache in the 90:s when Polyester prints arrived.
The amount of adjustments which can be made are limited. Besides having a good spring for the pressure roller on the sound-drum (with proper tension), what kind of mechanical adjustments are you referring to to address flutter?

[Emiel de Jong]

I am not aware of a Philips soundhead called "Symphony"? Were they marketed that way maybe? But we are talking about the same type of soundhead: exactly like the one in the DP70, but then in a stand-alone version for 35mm projectors, right? You're right there is not really much to be adjusted mechanically. I am just very, very amazed flutter could be an issue with these. What problems occurred with them when polyester arrived?

[Marcel Birgelen]

There is a small difference in thickness between polyester and acetate films, many polyester films being a bit thinner. But still, film thickness has always varied a bit between medium and labs, so I don't really think that's the issue.

[Jerry G. Axelsson]

The main issues with our Philips symphony was weave with Polyester film. The soundtrack sounded like it had a constant speed variations up and down. It did not matter if you moved the pressure-roller closer to the flywheel or increased the pressure with the spring. The bearing for the flywheel and the pressure-roller seemed fine from memory. It was 25 years ago. Here is an ad for the soundhead. The type I used earlier is close to this in layout.

[Jerry G. Axelsson]

My friend Ronald Rosbeek showed me this screenshot to illustrate the difference between three type of light sources.

First exciterlamp, second red light, third white LED.

I am not quite shure what these measurements stood for?

From what I remember he wanted to illustrate how inefficient an exciterlamp was although it had a wide working spectrum. Red light is only efficient on a very narrow wavelength. White LED (whatever "white LED" stood for, I am not shure as Steve pointed out) has a wider wavelength spectrum where it counts to read different types of soundtracks.

[Emiel de Jong]

Nice "Symfoni" advertisement! But Philips definitely didn't use that name in general for this type of soundhead. The soundhead in the advertisement is the first version: there is a roller on a very light spring directly after the sound drum. Very soon they eliminated this roller because the film, without any tension applied to it, itself acted nicely as a buffer for the movement introduced to it by intermittent sprocket and hold back sprocket teeth. Still, I know this type of soundhead very well, and I am curious about flutter, or polyester-related problems: I never encountered them.
Very interesting graphs too: unfortunately I cannot read the numbers: could you upload it in a sharper version? I tend to read something different in them though: that also this specific white led lacks the infrared you need so much. While clearly the exciterlamp feels more and more comfortable going in that region...

[Sam Chavez]

The shortcomings on the slit were on DP70 but that was more a function of the exciter lamp and image rod issues. Original design FP20's and DP75's had like 6dB drop off of light at the ends. The other problem I found on the DP70 was the occasional bad lens, as in poor HF response. Barely to 2K. Found this years ago with CP100 cinema processes. If you tried to compensate with slit loss it would break out into ringing. not knowing at the time what the lenses were capable of, took some trial and error to determine the issue. The newer lenses used by Kinoton and others for modern readers were fine. It was just a matter of establishing magnification to match reverse scan solar cells.

[Steve Guttag]

What that bottom graph shows is how poor a white LED would be at soundhead reader duty. The area of interest is at the far right (infrared)...where the incandescent has an abundance but the white LED is almost no better than the red LED. It's not that it won't work. It's that it won't work as well.

[Sam Chavez]

The soundhead shown looks like the soundhead used by the earlier Philips FP5 thru 56. It was functionally the same as the soundhead used in a DP70 but in a different casting. I saw a lot of these in Brazil and Argentina. Sold quite a few red reader reader kits for those.

[Emiel de Jong]

Indeed this was the soundhead for the FP5-FP56 series, built from the late 1930's till the late 1950's. Here are some leaflets from 1939 and 1950 of the soundhead type 3837; and a leaflet from 1949 of the type 3838. In the 3838 you can see the same parts used in the built-in soundhead of the FP3 projector and how it would evolve in the soundhead of the FP20. My guess the 3838 was made to have a cheaper option available.

type3837year1939.JPG


type3837year1950.JPG
type3838year1949.JPG

[Emiel de Jong]

And then, when the soundhead discussion seemed to get up steam and interesting points were made regarding light sources, it was Silent all over again ;-)

[Helmut Maripuu]

Try contacting the Film Institute in Stockholm, https://www.filminstitutet.se/sv/om-...ografsalonger/ Sweden which has 6 recently renovated Kinoton projectors. Maybe they know where there are spare parts.
Postal address Box 271 26, 102 52 Stockholm registrator@filminstitutet.se 08-665 11 00 (vx)

[Jerry G. Axelsson]

Helmut, I work at the Swedish Film institute and we have no parts for sale concerning this matter. This is more a discussion about custom builds or modification of standard products to improve their performance.

[Brad Miller]

Jerry, so 3 pages into this and I finally had a chance to read through the discussion. You may have already done this, but if you haven't you really should do this first before taking other steps.

Look in this CP650 installation manual on pdf page #68:
http://www.film-tech.com/warehouse/w...585&category=2

There it describes the Mono EQ adjustment. Since you are running reverse scan red light readers, the odds are that you need to adjust this more towards the LF to achieve a mono sound that isn't too harsh or thin. Have you tried this?