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Author Topic: The "Door" on Sound Heads Dean Kollet Jedi Master Film Handler Posts: 591 From: Florida State University Registered: Jul 2003 posted 01-12-2005 12:30 PM                     I was wondering what the reason if for the door on soundheads, more specifically the Simplex 5-Star. I've run shows with it open and closed in both Analog and Digital (basement reader) and I didn't notice a difference. The rest of the projector and film path is opened, why would they close this? I'm guessing it's some weird engineering theory, but I guess my question if why?  |  IP: Logged Michael Schaffer "Where is the Boardwalk Hotel?" Posts: 4143 From: Boston, MA Registered: Apr 2002 posted 01-12-2005 12:37 PM                        It is indeed a very weird engineering theory behind that: to keep as much dust and dirt out as possible. Most older projectors had closed film compartments as well, not a bad idea as such. In the olden days, fire safety probably played a role too.  |  IP: Logged Mike Blakesley Film God Posts: 12767 From: Forsyth, Montana Registered: Jun 99 posted 01-12-2005 12:37 PM                        - Keep dust out - Make it look nice Plus in the old days of flammable film, there were probably fire prevention issues.  |  IP: Logged Chris Hipp Phenomenal Film Handler Posts: 1462 From: Mesquite, Tx (east of Dallas) Registered: Jul 2003 posted 01-12-2005 01:51 PM                     It could alos be to help keep out extraneous light. Run a loop through it someday and shine a flashlight and see what it sounds like. Of course a properly designed booth will not have lighting in front of the port window while the movie is running anyway so it doesnt really help.  |  IP: Logged Thomas Procyk Phenomenal Film Handler Posts: 1842 From: Royal Palm Beach, FL, USA Registered: Feb 2002 posted 01-12-2005 02:05 PM                     But the door on the Simplex 5-Star has a clear plexiglass "window" on it. So if its job is to contain fire, it fails, and if its job is to keep light out, it fails. I close all the "doors" whether on the projector head or soundhead, just because it looks nice and I always have that feeling that exposed moving parts are better when contained. Hate to have someone with long hair or a "required" tie sweeping around the machine... =TMP=  |  IP: Logged Randy Stankey Film God Posts: 6539 From: Erie, Pennsylvania Registered: Jun 99 posted 01-12-2005 02:17 PM                     Some older model projector heads like Century, Simplex, et. al. have doors too. Since you can mount an older sound head onto a newer model projector, it would make sense that the sound head has a door. Keeping the door shut on the sound head keeps out a lot of stray light. Now that we have red light/electronic readers that's not so much of an issue. However, when solar cells were in use, a fluorescent light shining on the sound head could REALLY mess up the sound! Open the door on an older (solar cell) sound head and flick a cigarette lighter in front of the cell, if you want to try a test. You'll hear a loud, "POP!!" in the speakers! Most people who use electronic red readers and have never seen a solar cell would never consider problems like that. I guess it's one of those things you don't think about unless you've had to deal it before.  |  IP: Logged Stephen Furley Film God Posts: 3059 From: Coulsdon, Croydon, England Registered: May 2002 posted 01-12-2005 02:52 PM                     quote: Thomas Procyk But the door on the Simplex 5-Star has a clear plexiglass "window" on it. So if its job is to contain fire, it fails, and if its job is to keep light out, it fails. I don't know what a 5-star sound head is, but if it's got a plexiglass, or similar, window in it then either it's something fairly modern, i.e. post nitrate (ok, it could still be about 50 years old!), or the original glass has been replaced. Given that few soundheads from the nitrate era are still in use today, I would guess that it's a modernised version of an old design, and thick, wired glass was no longer considered necessary.  |  IP: Logged John Hegel Expert Film Handler Posts: 166 From: Lake Mills, Iowa Registered: Sep 2000 posted 01-12-2005 04:11 PM                        On really old equipment, before solar cells, could it have helped with the tubes that were used for audio pick-up? The tube pick-up that I found in our theater has huge optical area. I'm thinking it had to have been 1x3".  |  IP: Logged Stephen Furley Film God Posts: 3059 From: Coulsdon, Croydon, England Registered: May 2002 posted 01-12-2005 04:37 PM                     quote: John Hegel On really old equipment, before solar cells, could it have helped with the tubes that were used for audio pick-up? Yes, and the old glass photocells were in use not that long ago. Quite a few places still had them until they converted to Dolby Stereo, and I seem to remember that Scott Norwood was asking recently about converting a pair of universal bases to read cyan tracks. I assume that these machines still have them.  |  IP: Logged Leo Enticknap Film God Posts: 7474 From: Loma Linda, CA Registered: Jul 2000 posted 01-12-2005 05:15 PM                        The most widespread fire prevention device on projector operating sides was the combination of an enclosed spool magazine and film cutting device where the film was pulled into or out of it. The cutters were so that if film in the feed spool ignited, the fire wouldn't then spread to the take-up magazine (and vice-versa). Remember, you cannot prevent or arrest a nitrate fire by removing the oxygen supply (i.e. housing film in an airtight enclosure), because the combustion process generates its own oxygen. So whatever the reason was for enclosing projector mechs and soundheads, it wasn't nitrate fire safety. My guess would be noise suppression and/or keeping dust out. There are some mechanisms, e.g. the GK-19, which have safety magazines but the rest of the mechanism open. Some earlier spool magazines were airtight (or very nearly so), and if the film within caught fire, the rapidly expanding combustion gases would usually cause them to explode. That's why, from the late '20s onwards, you started to see spool magazines with tapered lips facing away from the operator's side, to allow a film fire to burn itself out in a controlled way and with the smoke and flames directed away from the projectionist. Of course if this did happen you wouldn't want to stay around - one or two deep breaths of those nitric acid fumes and your lungs would be like you'd smoked 80 a day all your life - but it did buy you the time needed to get safely clear.  |  IP: Logged Ken Layton Phenomenal Film Handler Posts: 1452 From: Olympia, Wash. USA Registered: Sep 1999 posted 01-12-2005 05:26 PM                     I believe at one time the door was required for Underwriter's Laboratories approval.  |  IP: Logged Mike Blakesley Film God Posts: 12767 From: Forsyth, Montana Registered: Jun 99 posted 01-12-2005 05:43 PM                        quote: Stephen Furley I don't know what a 5-star sound head is, but if it's got a plexiglass, or similar, window in it then either it's something fairly modern, i.e. post nitrate (ok, it could still be about 50 years old!), or the original glass has been replaced. We have a 5-star, purchased new in 1980. It came with a plexiglass window in the door (as did the Simplex projector). I always figured that the door was an old design, but the plexiglass was a newfangled post-nitrate feature.  |  IP: Logged Dean Kollet Jedi Master Film Handler Posts: 591 From: Florida State University Registered: Jul 2003 posted 01-12-2005 06:04 PM                     So besides fire prevention for Nitrate films, the really isn't a reason for it. I've seen booths running 5-Stars without the door attached and they all seemed fine. I'm guessing it just evolved into an asthetic thing then.  |  IP: Logged Chris Trainor Expert Film Handler Posts: 161 From: Greenville, RI, USA Registered: Jun 99 posted 01-12-2005 06:49 PM                        The door wasn't really to prevent nitrate fires, but to prevent the fire inside from getting outside. Little bits of burning film could've easilly fallen out of the projector onto the floor, etc if there wern't any doors. Also back in those days the operators were in the booth while the film was running, so it kept burning pieces of non-extinguishable film from landing on them too. --Chris  |  IP: Logged Bruce Hansen Jedi Master Film Handler Posts: 847 From: Stone Mountain, GA, USA Registered: Dec 1999 posted 01-12-2005 06:52 PM                     BTW: the LED readers still use solar cells to convert the light into an electrical siginal.  |  IP: Logged

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