Film-Tech Forum ARCHIVE: Surround speaker placement

This is topic Surround speaker placement in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Michael Brown (Member # 890) on 07-26-2001, 05:22 AM:

The Showcase Cinema I have been visiting has their surround speakers placed quite high up on the walls. This seems to be reducing the amount of surround you actually here. I saw jurassic park 3 here and didnt notice that many surround effect, I saw the film at another theatre and the surrounds were much better. Are their any guidelines as the the height of surround speaker placement.

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Michael Brown
Bradford Student Cinema
www.Bradfordstudentcinema.co.uk
"Do you snorkle?
No, I get nervous when brightly coloured fish stare at me face to face."

Posted by John Pytlak (Member # 331) on 07-26-2001, 09:09 AM:

Here are a few links:
http://www.moviesoundpage.com/msp_home.htm
http://www.thx.com/theatres/index.html
http://www.dolby.com/tech/
http://www.sdds.com/tech/index.html
http://www.jblpro.com/
http://www.hps4000.com/pages/articles_page_.html
http://www.iis.ee.ic.ac.uk/~frank/surp98/report/sl9/dolby.html

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John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Eastman Kodak Company
Research Labs, Building 69, Room 7419
Rochester, New York, 14650-1922 USA
Tel: 716-477-5325 Cell: 716-781-4036 Fax: 716-722-7243
E-Mail: john.pytlak@kodak.com
Web site: http://www.kodak.com/go/motion

Posted by Bill Langfield (Member # 818) on 07-26-2001, 10:17 AM:

Michael,

Surround or A.P is not meant to 'noticed'.
It is intended to blend in.

The theatre that you 'noticed' the surrounds would have had
them set above 85db so you could notice them.

If you are watching a movie, and sudenly realise WOW sound just came out of the speakers on the wall (or brom behind EX) then they are
being over driven.

PS, I always wind up the surrounds. Then the techs come in and
EQ the joint, wind downd the subs, and lower the surrounds.
I like to turn those two UP so people
get some OMPH!!! (Hi John Wilson!!)

Bill.

Regarding my adjustments, it must be noted, that when I started
working at the complex, all of the cinemas had all channels except centre at preamp level turned all the way down.

Posted by Mark Mayfield (Member # 729) on 07-26-2001, 10:48 AM:

There certainly are industry standards, which are followed by most film dub stages. The idea being, if you set up your theatre according to the same standards followed by the dub stages, you will reproduce the same artistic effect intended by the film's creators. Not only speaker type, placement, but also levels, as established primarily by Dolby. If the theatre strays from these standards, then the presentation is not a true representation of the "art" of the film.

In general, I recommend that a typical "wide by wide" dispersion surround speaker array begin about one-third the room's length from the screen, and be placed about 10-12 feet above the floor, following the slope, and spaced from 8-12 feet apart, aimed across the theatre so that on axis is aimed at the farthest seat on the other side. There are MANY variables to these rules of thumb, but in general, they reproduce the dub stage environment.

Levels are typically set at between 82-85 dB. Modern soundtracks often include dramatic surroundeffects that WILL cause localization, but sometimes this is intentional on the part of the filmmaker. Surround is no longer just ambience. Be sure your surround speakers are capable of wide dynamic range and frequency response, because digital soundtracks have chnaged the rules of the surround channels.

Posted by John Pytlak (Member # 331) on 07-26-2001, 12:55 PM:

To give Mark his due, and not leave out EAW, here's a link:

http://www.eaw.com/pages/TechSupport/Install/Installsupport.html

Posted by Gordon McLeod (Member # 33) on 07-26-2001, 01:44 PM:

I usually start 1/4 of the distanc eback from the screen and plot the heigth and spacing from there.
I usually set the digital surrounds dead on spec but set the optical surround level (nice feature on some processors) with the cat 153 surround test film

Posted by Mark Gulbrandsen (Member # 72) on 07-26-2001, 04:10 PM:

Mark,
I am interested in your opinion of the HPS-4000 system in regards to its supposed built in EX decoding ability. One would think that this would screw up the levels and channel balance a bit.
Just doesn't seem possible to me that it would do all this properly. While I canb understand that there can be some decoding going on I wonder if its whats really intended.
MArk @ GTS

Posted by Gordon McLeod (Member # 33) on 07-26-2001, 09:07 PM:

I question the ability for a speaker array to be able to decode EX rear channel with the seperation that the SA10 has. The matrix chip creates about 40db seperation between ajacent channels. If the speaker array was capable of creating a rear effect that strong on ex print (the rear channel is in effect encoded as a equal Ls and Rs mono surround) then a optical or mag film with mono surround would appear to be steared to the rear wall only, unless electronics gets involved.
Physics play to strongly against that claim unless it is possible that it generates perpetual motion as well

Posted by Mark Mayfield (Member # 729) on 07-27-2001, 11:03 AM:

Mark G -
Either you are kidding or you have some info I don't. I've never heard of a speaker being able to do matrix de-coding - maybe you or John Allen can tell me where I can learn about this.

In any case, I am not going antagonize my competition, but it does sound suspect.

Posted by Gordon McLeod (Member # 33) on 07-27-2001, 01:50 PM:

On the MSP page Mr Allen claims that his surround arrays do not require the ex decoder to decode ex effects

Posted by Brad Miller (Member # 2) on 07-29-2001, 08:16 PM:

This is the one claim that I simply do not buy. There is no way that the EX channel can be acoustically derived from the stereo surround channels to the same discreteness and steering as having the electronic circuit. If that were indeed so, then the same could be said for optical sound. I'd like to see a theater run something in Dolby A or SR that does not have a center screen channel and derive it acoustically from the screen left and right speakers and be able to achieve the same amount of separation. Sure the "effect" can be there and I have no doubt that any well designed surround speaker array can give these impressions, but for true separation the matrix circuit MUST be used. Otherwise information that is supposed to come only from the rear wall surrounds is actually coming from every surround speaker. Sort of like running a Pro Logic home reciever in "phantom" mode.

Posted by Gordon McLeod (Member # 33) on 07-29-2001, 08:58 PM:

Especially considering the claims of evenness of coverage of the surround array. The focusing on the rear wall will tend to create a uneven coverage from the sides anyway
But I have always questioned the eveness of those particular speakers anyway

Posted by Mark Gulbrandsen (Member # 72) on 07-30-2001, 12:46 AM:

Mark M.,
John Allen claimed that on the Movie Sound Page web site. Many of us questioned it then. Of course a rear channel in a good surround array can derive something to that effect, but could never properly reproduce what is intended to happen if properly decoded electronically. A number of us were after an experts opinion on this and we all definately consider you an expert in this field. Any further comments and elaboration would be appreciated. Now all I need to see is an article in Box Office describing the new HPS-EX surround array.....phew!
Mark @ GTS

Posted by Phil Connolly (Member # 465) on 07-30-2001, 08:37 AM:

Most Showcase Cinemas in the UK seem to have the surround levels set too low, I think its just they way their techs work.

Its a shame because most sites have decent sound systems and every screen has digital audio, but they are too conservative to make the most of it. This true for the three locations I've visited, Warner Village and Odeon (newer sites) have similar specs but seem to have more in the surrounds and Sub's, witch is better.

My local Showcase (Derby), does have a good presentation standard in all other respects.

I don't know if its the same in the US but former AMC cinema now UCI in the UK, seem to but their surrounds on the Ceiling of the auditoriums, which is horrible. These speakers also have a limited dynamic range which in Derby is most noticable in the DTS screens. In those theaters, I'm glad if the surround level is too low.

Posted by Michael Brown (Member # 890) on 07-30-2001, 08:48 AM:

The UCI in sheffield has the surrounds hidden up in the ceiling.

Posted by John Walsh (Member # 168) on 07-30-2001, 09:22 AM:

The Zeigfeld in New York had theirs in the ceiling when they opened, but later mounted speakers on the side walls for (I think) "Close Encounters."

While that was OK for mono surround, I don't think you get good stereo "imaging" with ceiling speakers. Although, I know many owners didn't want to spoil the "look" of their auditourium with speakers on the walls.

Posted by Gordon McLeod (Member # 33) on 07-31-2001, 09:28 AM:

I feel too many theatres use to few surround speakers for the room size and also do not space them for a even flat coverage. Surround coverage is best met wit the more the better