VOTT Inquiry

I'm the sound engineer at a 1928 vintage theatre in Seattle. We present mostly live entertainment and also have a silent movie series, which utilizes our original Wurlitzer organ. Occasionally we show films w/sound and have recently acquired some vintage Altec speakers from a film projection company. I have a few questions about our VOTT speaker system and was hoping some of you might have some information you could share with me.
We have three double 15" horn loaded bass enclosures, two are loaded with 515C drivers and measure 84" H x 34" W x 39" D and the other is loaded with 515B drivers. The cabinet with the 515B drivers is 1 1/2" narrower in width than the other two. Otherwise, the contruction looks identical. I'm curious as to the history of the two different size cabinets.
The three high frequency drivers are 288Cs that measure 16 ohms, so I assume the diaphrams have been replaced at some point. Each driver is coupled to a 1505 horn.
For crossovers there are two N-500-C and 1 N-500-F. Any comments about the different crossover model numbers?
I use the speakers in an A4 configuration for left, center, and right channels for our films.
Just thought I'd post to the group and see if anyone has any interesting comments about our vintage setup. We are a 3000 seat theatre with a balcony and the coverage is good to about mid balcony with the 1505 horn. For upper balcony I tie the center channel into our PA center cluster.
Thanks for any comments from the group.

Hi there,

I have some info.

The 515B was 15" prior to July 1977 after 16".
The 515C is 16" both are ALLNICO.

Your Enclosures are model 210. Why the 1 1/2 " difference remains a puzzle for now.

http://www.lansingheritage.org/images/altec/plans/1970's-lf-plans/enclosures04.jpg

THE N-500C is 12ohms
THE N-500F is 16 ohms

The N500-C Network should be used with Auto-Transformer model 15067 for Impedance matching.

Since it is a 12 ohm impedance network.

I hope you have the 515B in the middle.

Hi again,

Congratulations sounds like a nice theatre.
Are the projectors in the rear of the balcony .
What model Simplex?

Your screen goes up for theatre plays. Is your screen front or rear stage. Your speakers on casters if your screen is front stage I imagine.

I love those old theatre.Lot's of them around here
some still waiting for restorations.At one time in early 50's we had about 84 of them on one street.

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Hi Mark,
Sounds like you have a beautiful theatre there. To many of these movie palaces and VOT systems in them are meeting the wrecking ball. Are you using the Altec wings on the 210's? With the dual purpose stage they make portability more of a problem but are worth it in better bass performance. You can set them up with a piano type hinge to fold them when moving the speakers.
Convergence answered the cabinet width difference in his first post. The 210A was made 1.5 inches wider to accommadate the 16 inch frame woofer. You have a good system there.

Hi,

I want to apologize for the N500-C Network.
I have 2 sheets and I read the application for 12 ohms.
The answer is 12 and 16 ohms . Yes it's rated for both impedance.When used in the cinema application it is connected for 16 ohms.

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Hi Mark
I have a favor to ask you.

Could you take a picture of the speakers on stage from the balcony with the screen up.

And post it on this forum for posterity

Quote:

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We are a 3000 seat theatre with a balcony and the coverage is good to about mid balcony with the 1505 horn. For upper balcony I tie the center channel into our PA center cluster.

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<font size="2" face="Verdana, Helvetica, sans-serif">Greets!

Dual driver 18 cell horns would solve this problem, though they tend to be pretty scarce/expensive, so stacking dual 1505s is probably more cost efficient.

GM

Hi Gm

Yes but his 288c's measure 16 ohms. He would have to change the 288c's for 8 ohms to stay in match
with Crossover net.

Hello,
Thanks for the quick replies. Hadn't noticed the difference in speaker diameter between the 515B and the 515C. Indeed that would account for the difference in the speaker cabinet width. I do use the 515B for the center channel, only because that would make the left and right a matched pair. I also use some 18" subwoofers in the film setup that is fed from the sub output of the dolby processor.
We have two 35mm projectors in a booth at the top of the balcony. There are also four follow spots in the booth, as well. It is about 160' to the screen. I don't know much about the projection equipment. It is operated by a projectionist we hire for our film series.
I have two sets of wings for the speakers, but I haven't used them because of the time constraints and storage situation. The speakers are stored in a room below the stage and have to be put together the day they are to be used. The speakers are placed on their backs on dollies, the guys helping me moaning and groaning about the size of the bass cabinets, not to mention the 105 lb. 1505 horns! Everything is taken to an elevator, brought up to the stage, horns placed on top with the help of a man lift, amps hooked up,etc. all in a two hour setup period. I then have less than an hour to EQ the systems with pink noise and a computer based real time analyzer, using 1/3 octave EQs. We run the film once, during which time I listen to make adjustments to the left, center, and right channels. As I mentioned in my original post, I split the center channel output into our balcony's center cluster for upper balcony coverage, which requires adding delay time to match the Altec speakers, which are upstage behind the screen. The screen is placed about 10' upstage of the curtain line.
It's a challenging, but fun day for me, as we only use this setup a couple times a year. Before acquiring these old gems, we used a system brought in by the projection company. The horn coverage was narrower and required more used of the house PA system to cover the dead spots. Having the wider coverage of the 1505 has been quite an improvement and keeps the sound "image" true to the movie screen.
Our next use of the VOTT system will be next month for the opening night of the Seattle International Film Festival. We hosted the opening night film last year, which was the first time we'd used the VOTT system in our theatre. The festival organizers commented on how happy they were with the sound quality. I don't think they knew the speakers they were listening to were as old as they are.
Thanks again for the information. I'll keep checking back for further comments.