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» Film-Tech Forum   » Operations   » Film Handlers' Forum   » optical stereo from a Holmes? (Page 1)

 
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Author Topic: optical stereo from a Holmes?
Bruce McGee
Phenomenal Film Handler

Posts: 1776
From: Asheville, NC USA... Nowhere in Particular.
Registered: Aug 1999


 - posted 07-11-1999 12:56 AM      Profile for Bruce McGee   Email Bruce McGee   Send New Private Message       Edit/Delete Post 

When I was in 35 professionally, it was at a drive-in that had 20 year old equipment. That was 1975-1979. Here's the question:
IF I install a pair of solar cells side-by-side in my Holmes so each will see only one stripe of the dual soundtracks will I have a simple stereo sound system?

I have several stereo prints, and trailers. Also I have plenty of time on my hands to experiment.

What do you folks think?

Bruce

Asheville, NC

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Brad Miller
Administrator

Posts: 17589
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99


 - posted 07-11-1999 02:13 PM      Profile for Brad Miller   Author's Homepage   Email Brad Miller       Edit/Delete Post 
"Technically" yes, but fair warning the sound will probably not be too good if you are home constructing it. I can't imagine how that could be mounted in a variety of projectors and actually work properly.

I've never worked with a Holmes, but if you call your local cinema parts supply dealer they might have an actual solar cell and bracket assembly for around $100-150 you could just pop in and then do an A-chain on. Better yet, if you can afford it, go with a reverse scanning LED kit. Although I doubt Kelmar or Component Engineering has gotten to the Holmes projector kits yet.

The $100-150 kit would be well worth your time and frustration in trying to figure out how to home make a stereo pickup.

ASCs number in Dallas is 214/265-9303. Roy Lisenbee is the man to talk to at extension 822. If it's out there, he can order it for you.

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Ken Layton
Phenomenal Film Handler

Posts: 1452
From: Olympia, Wash. USA
Registered: Sep 1999


 - posted 07-11-1999 03:26 PM      Profile for Ken Layton   Email Ken Layton   Send New Private Message       Edit/Delete Post 
The key to it would be getting the solar cell close enough to the film, otherwise you'd get crosstalk. Get a raw stereo Kelmar cell and make a bracket for it. It would be nice if there were a "universal" reverse scan kit we could adapt to a bunch of different machines.

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Bruce McGee
Phenomenal Film Handler

Posts: 1776
From: Asheville, NC USA... Nowhere in Particular.
Registered: Aug 1999


 - posted 07-11-1999 09:42 PM      Profile for Bruce McGee   Email Bruce McGee   Send New Private Message       Edit/Delete Post 
The current cell is mounted in a 4-pin tube socket, and is in the exact position that the old PE cell was. There is nearly 1 3/4" of space between the film sound gate, and the face of the cell. I can remove the cell cover and remove the solar cell from the socket, and put a piece of white paper in there while film is running. I can clearly see the 2 tracks on the paper.

I started wondering about this when I ran my first stereo print on the Holmes. It sounded like I was hearing an out of phase recording. When I adjusted the solar cell position more to the center between the 2 tracks, I noticed how the fidelity changed for the better.

This machine was in pieces when I got it. I found that I could use an 1156 auto lamp, and a 12v DC supply for the exciter. I have run about 30 hours of film on it without blowing a lamp. The DC supply handles the hum in the filament perfectly. The solar cell came from a junked Eiki 16 machine.

I used an SMPTE audio test film that I found on the net to focus the optics. Having good results so far.

There's more than enough room for 2 cells installed side by side. Is the left channel on the sprocket side of the soundtrack?

Is it obvious that I am on a major "restricted" budget? I am the owner of a 250 watt tube power amp that is in Newport News, VA, but I have no way to get it here to western NC except to drive 7 hours. My job requires too much time for a trip...

I appreciate your sharing of knowledge and your help. Now, if I had 2 running Holmes... Just a dream for now.

Bruce McGee

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Greg Mueller
Phenomenal Film Handler

Posts: 1687
From: Port Gamble, WA
Registered: Jun 99


 - posted 07-12-1999 09:27 AM      Profile for Greg Mueller   Author's Homepage   Email Greg Mueller   Send New Private Message       Edit/Delete Post 
I can pretty much assure you that CE will not be producing reverse scan kits for the Holmes. I had a Motiograph sound head on my first setup and I had a Kelmar stereo cell in it. I didn't care much for the mount system they used so I built myself a 3 axis adjustable dovetail mount that I did like. I would imagine that would be possible with the Holmes as well, but I don't think I've ever seen a Holnes so I don't know for sure. I'd get my hands on a Kelmar cell and attack it from that angle.

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Bruce McGee
Phenomenal Film Handler

Posts: 1776
From: Asheville, NC USA... Nowhere in Particular.
Registered: Aug 1999


 - posted 07-12-1999 09:31 AM      Profile for Bruce McGee   Email Bruce McGee   Send New Private Message       Edit/Delete Post 
Any idea what a Kelmar cell might cost, and where to get it?

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Greg Mueller
Phenomenal Film Handler

Posts: 1687
From: Port Gamble, WA
Registered: Jun 99


 - posted 07-12-1999 09:35 AM      Profile for Greg Mueller   Author's Homepage   Email Greg Mueller   Send New Private Message       Edit/Delete Post 
Oh yah, the problem with using 2 seperate cells is getting them close enough together (physically) to read the track in the same place on the film. You can't get them close enough on a horizontal plane that's for sure. The only other way would be vertically and that would mean that you would have to stack them ahead and behind each other in time. That would give all your films the dubbed Italian effect, which might be interesting but not desireable.

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Aaron Sisemore
Flaming Ribs beat Reeses Peanut Butter Cups any day!

Posts: 3061
From: Rockwall TX USA
Registered: Sep 1999


 - posted 07-12-1999 12:22 PM      Profile for Aaron Sisemore   Email Aaron Sisemore   Send New Private Message       Edit/Delete Post 
Bruce:

You can get the solar cell unit ( with a bracket, though as others have said I doubt you'll find one that will drop-in to a Holmes) from any cinema equipment dealer. Another point to consider is that these cells will be going to be positioned close ( within about 1mm) to the film so the cells-in-an-old-phototube-socket trick won't really work (the cells themselves are quite small). You might have to get a different slit lens for your soundhead if yours has a large slit in it. The ones with smaller slit sizes give MUCH better sound quality. You will need a basic set of Dolby test films to get the alignment spot-on as well ( you can 'wing it' for this but I have found that to get it truly right the first time, the test films are necessary. These films are also available from a cinema dealer.) Good Luck!

Aaron



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Ken Layton
Phenomenal Film Handler

Posts: 1452
From: Olympia, Wash. USA
Registered: Sep 1999


 - posted 07-12-1999 01:52 PM      Profile for Ken Layton   Email Ken Layton   Send New Private Message       Edit/Delete Post 
Ask around at the cinema dealers. You don't have to buy a brand new cell, a used one will do. With all the stereo cells being pulled out and replaced with reverse scans, I don't think it would be much of a problem to pick up a used one cheap.

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Brad Miller
Administrator

Posts: 17589
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99


 - posted 07-12-1999 04:20 PM      Profile for Brad Miller   Author's Homepage   Email Brad Miller       Edit/Delete Post 
Ken, what a wonderful idea! Actually, I've got one I pulled out of my JJ when I converted to reverse scanning you are welcome to have Bruce. You will have to take a knife and CAREFULLY cut into the hot glue strip to retrieve the full length of the leads, but the actual cell can be easily removed from the large bracket with an allen wrench.

Send me your mailing address to my private email at Flix@film-tech.com and I will ship you the cell. Hope you can make it work. Be sure and let us know here what you find. There may be someone else out there who will want to do the same thing with another Holmes!


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Bruce McGee
Phenomenal Film Handler

Posts: 1776
From: Asheville, NC USA... Nowhere in Particular.
Registered: Aug 1999


 - posted 07-12-1999 05:03 PM      Profile for Bruce McGee   Email Bruce McGee   Send New Private Message       Edit/Delete Post 
Thanks, Brad, for the offer. I will even attempt to take pictures of the contraption when I get it installed. Our local theater supply is 100 miles away in Charlotte.

A Holmes is not "professional grade" by far, but THIS one is still running after 50 years!

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Bruce McGee
Phenomenal Film Handler

Posts: 1776
From: Asheville, NC USA... Nowhere in Particular.
Registered: Aug 1999


 - posted 07-17-1999 01:54 PM      Profile for Bruce McGee   Email Bruce McGee   Send New Private Message       Edit/Delete Post 
I have received the Solar cell. I have to install it right up against the film at the slit? This may be a major problem as the Holmes doesent have a per-say sound drum like you guys are used to.

I figured out the wiring fast enough. But, I mayhave to go with the twin cells installed inside the old PEC enclosure similar to what I have now.

I would like to thank Brad Miller for sending this cell assembly to me. I will keep thinking about how I can do this using this cell. Right now, all I can come up with is the 2nd cell beside the one I have. I need to ask one more time: Is the left channel on the left side of the soundtrack on the sprocket hole side?

More News to Come, if anybody is still interested...
Bruce McGee

I had a chance to get a Super for good money a few months ago. I should have taken it.

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Brad Miller
Administrator

Posts: 17589
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99


 - posted 07-17-1999 04:35 PM      Profile for Brad Miller   Author's Homepage   Email Brad Miller       Edit/Delete Post 
Right channel is closest to the edge of the film. Left channel is closest to the picture.

I hope you can make that cell work. Did you take it off of the bracket? Good luck.

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Ken Layton
Phenomenal Film Handler

Posts: 1452
From: Olympia, Wash. USA
Registered: Sep 1999


 - posted 07-17-1999 05:03 PM      Profile for Ken Layton   Email Ken Layton   Send New Private Message       Edit/Delete Post 
Bruce:
Have you given thought to using a fiber-optic "Light Pipe"? That way you could put the end of it up against the Holmes' sound gate hole and 'guide' the light right to the surface of the stereo solar cell.
You could probably take a light pipe from and old Bell & Howell 16mm sound drum or see if Dolby can get you one from a Cat 700 reader.

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Gordon McLeod
Film God

Posts: 9390
From: Toronto Ontario Canada
Registered: Jun 99


 - posted 07-19-1999 10:57 AM      Profile for Gordon McLeod   Email Gordon McLeod   Send New Private Message       Edit/Delete Post 
The old Phillips FP20 and FP7 used glass light pipe and there should be some of those still kicking around with the conversions to LED's taking place

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