Film-Tech Forum ARCHIVE: How to upgrade a mono sound system?

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Posted by Michael Trotochaud (Member # 1513) on 08-18-2003, 12:33 AM:

At the moment, I am running a Holmes 8 with a mono solar cell. I would like to upgrade my sound system to at the very least, stereo. What advise do people have as to the best way to do this? I had also read somewhere that I might be able to take a stereo signal from the film and run it through a home surround sound system (like the one for a tv) and this would produce surround sound. Is that a correct statement?

As always, you know more than me, so that means your advice is sought and appreciated.

Mike

Posted by Michael Schaffer (Member # 1204) on 08-18-2003, 04:37 AM:

You need a stereo solar cell. Running the 2 channels through a home surround system is not advisable. While the 2:4 channel decoding is the same, those decoders do not apply Dolby SR noise reduction. Also, it makes little sense since those home systems do not have an adjustable optical preamplifier. You need that to keep the sound fresh. The exciter lamp darkens as it ages, the optical preamplifier allows you to make adjustments for this.

Posted by John Anastasio (Member # 607) on 08-18-2003, 09:32 AM:

You can install a stereo cell in a Holmes, but it's a bit tricky, since you're dealing with a sound gate instead of a drum. Since the cell sits back so far, it's difficult to get good seperation unless you install a small optical baffle between the two cells to keep the signals apart. Yes, it's true that you won't get the full benefit of an SR track using just a home amplifier, but it is a cheap way to get started for home use with a Holmes. Another thing to remember is that the slit lens on a Holmes will not provide you with the proper high frequency response.

Posted by Ken Layton (Member # 133) on 08-18-2003, 09:46 AM:

Changing the slit lens to a narrower slit would help for better high frequency response. The original was a 1 mil. A modern Simplex style T-1 will fit the Holmes.

Posted by Edward Jurich (Member # 1787) on 08-18-2003, 09:50 AM:

Here's a link to a page which has my stereo conversion for my Holmes. I'm not completely done yet but it might be some help.
http://www.angelfire.com/film/shutterblade/holmes/holmes.html
I've added a vertical divider to the old cell cover but it's not enough for complete seperation. I'm thinking of mounting the pickup (in this case photo-transistors) on the sound gate. By the way, those photo-transistors sound great.

Posted by Bruce Hansen (Member # 281) on 08-18-2003, 06:00 PM:

I have a Holmes, and I drilled and tapped two holes on the square bracket on the back of the sound gate. I then made a small piece of plexaglass with two slots that could slide on the screws I installed on the bracket on the back of the sound gate. This allowes side to side alignment, for proper L /R centering. I mounted two small solar cells on the plex, side by side, very close to each other.

Posted by Michael Trotochaud (Member # 1513) on 08-18-2003, 11:39 PM:

I guess that my next question will be, where can I get a stereo solar cell and a Simplex style T-1 slit lens?

Mike

Posted by Ken Layton (Member # 133) on 08-19-2003, 01:47 AM:

Any theater equipment dealer can get you those. Since your in Seattle, call McRae Theatre Equipment at 206-285-8393 and tell 'em I sent you.

Posted by Michael Trotochaud (Member # 1513) on 08-19-2003, 06:19 PM:

With all of this talk of the industry converting over to a cyan track, should I take the money that I was planning on putting towards doing this upgrade and possibly make the machine cyan compatible?

Mike