Film-Tech Forum ARCHIVE: 70mm Dolby with CP55 ?

This is topic 70mm Dolby with CP55 ? in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Lionel Fouillen (Member # 1475) on 11-04-2002, 05:06 AM:

Hello,

I have a question about playing 70mm prints with Dolby Stereo magnetic sound using a CP55 processor.

But first, I will introduce myself since I just registered to this forum. I'm not currently working in the cinema exhibition but was always interested in theatres and their equipment, and why I often end up in the booth talking to the projectionist is a mystery - I was however a Super8 filmmaker in my teenage years and used to collect 16mm prints. I was happy to find Film-Tech two weeks ago and will occasionally post a message or reply to some.

In 1989, the "Palace" 9-plex in Liege, Belgium, decided to install 70mm and THX. Screen #9 seated about 600 and was the main house. For move-overs, they also installed 70mm and THX in the smaller Screen #5, seating about 250 (with a nice 40ft screen). I had the opportunity to visit the booths. The bigger one had a CP200 but the smaller one only had a CP55. I've lived with the feeling that "something was missing" when showing 70mm through a CP55.

The equipment was as follows:

1 x CP55
1 x SRA5
1 x Dolby MPU
1 x Dolby power unit
1 x THX 3417
5 x JBL 2-channel amplifier

Since there was no screen masking or curtain (!) it was easy to see the speakers in the THX-compliant baffle, which looked like this:

3 x JBL 4675
1 x JBL 4688 subwoofer
10 x JBL 8330 surround (4 on each side wall and 2 on the rear wall)

So is it a way to outfit the CP55 sothat formats 42/43 are properly reproduced? I had asked the projectionist but he "didn't know".

Thanks,
Lionel

Posted by Steve Guttag (Member # 268) on 11-04-2002, 08:21 AM:

Based on the equipment you described, no they can not properly play back the 70mm magnetic film properly in either format 42 or 43. Chiefly, they are missing the noise reduction channels. The CP-55 only has room for 2 channels of type-A. I suppose with enough cleaver wiring, the SRA-5 with a couple of Cat. 22s installed MIGHT be able to be wired in such a way as to provide th other two channels. A Cat. 441 card would also be needed to provide the magnetic downward expansion for the baby-boom.

With a Panastereo CSP-4600 on the head end instead of the MPU and a full UDA/55 (for Dolby digital) upgrade, it would most certainly be possible to run formats 42 and 43 in either A or SR.

Steve

------------------
"Old projectionists never die, they just changeover!"

Posted by Peter Hall (Member # 695) on 11-04-2002, 11:15 AM:

We've used CP55s with SR and A type 70mm - you need to add bandpass filters for the sub and LsRs (P / Q) - works fine but you need a lot of external wiring / switching. Of course the 55 needs to be modified for stereo surrounds, plus you need to switch the DA20 input or go thru the DA20 and bypass the sub - get a CP65 ! (or a CP200 - another shameless plug - we have one in stock - here

Posted by Peter Hall (Member # 695) on 11-04-2002, 11:21 AM:

HI again -

I was wrong ! (there are three words seldom used on Film Tech !). Our configuration with a 55 and 6 external channels of noise reduction and bandpass filters (we used standard crossovers with the F point modified for 180hz) actually gives you a better reproduction than a CP65. We use the LeRe surruond tracks and sub bass - the 65 ignores the LeRs stereo surround on format 43 and uses the old style "S" output for mono surrounds. Other than that the 55 uses the same B chain cards as the 65 and sounds as good

Posted by Lionel Fouillen (Member # 1475) on 11-05-2002, 02:15 AM:

Thanks for your replies.

I doubt they would have thought of the complex wiring and card mixture you mentioned. They've simply showed too little interest in quality presentation (by several other aspects of their multiplex I didn't mention) for that. Regarding the use of THX, it was installed by Decatron which is a subsidiary of the Kinepolis Group that owns this multiplex, so they must probably do whatever they want with it

Posted by Michael Schaffer (Member # 1204) on 11-05-2002, 04:13 AM:

Why invest to install 70mm and then save the money for the screen masking? Strange attitude.
By the way, Liege is a nice city! My best friend lives in Aachen. When I visit him, we like to go on small expeditions to Belgium which is always fun. People there have over a 1000 different beer sorts and speak really funny French.

Posted by Lionel Fouillen (Member # 1475) on 11-05-2002, 07:00 AM:

Speak funny French? Maybe you heard a few people speaking Walloon which is the regional dialect. I myself cannot understand it

The multiplex I'm talking about was once a large 1800-seat Fox theatre (actually it belonged to a local independent exhibitor who leased it to Fox on a full-time basis). My father often reminds of its former curved 2.55 CinemaScope screen and magnetic sound with nostalgy. It was converted to a 6-screen multiplex in the mid-1970's (with small screens and full mono sound in each auditorium, plus malfunctioning automated changeovers because they installed 2 Cinemeccanica V5 with big 3000ft reels in each booth).

The Kinepolis Group bought it in the early 1980's and added 3 more screens in unused cloakrooms, corridors and lavatories in the late 1980's. For the 70mm, they enlarged the screens and didn't have room anymore on the sides for masking or curtains because of exit doors. The larger house screen sucks: it measures 43ft x 16ft (aspect ratio = 2.68) and both Scope and 70mm images fill the screen. Not only this screen is too small for the 600-seat auditorium but we lose 12% of the Scope image and 18% of the 70mm image! If they had put a screen of appropriate width, they would have obtained the required space on the sides for masking and curtains, and no picture loss!

But all their modern purpose-built multiplexes also have a "no masking - no curtain" policy. Their huge screens extend from wall to wall and from floor to ceiling but I hate when there is no masking. And I appreciate a nice curtain with concealed lighting for the showmanship aspect...

Posted by Michael Schaffer (Member # 1204) on 11-05-2002, 11:26 AM:

Yes, and the wall-to-wall and floor-to-floor concept probably means they blow up and heavily crop the formats to fill the whole wall...
No curtains, maybe, but no screen masking? Can you even get the THX certificate without masking?

Posted by Peter Hall (Member # 695) on 11-05-2002, 12:16 PM:

THX and masking have no relation - however crop does. THX|allow 5% max, but want 3% (a la SMPTE). We favour masking but in it's absence a true floating screen (back lit, rounded corners, factory cut plates) is a lot better than simply fixing standard masking on 4 sides. BTW, has anyone experience with CNC aperture cutters ? Apparently you dial in the RP40 numbers and it does the rest - probably costs a lot more than my 1/4" file !