Film-Tech Forum ARCHIVE: Speaker Placement

This is topic Speaker Placement in forum Digital Cinema Forum at Film-Tech Forum ARCHIVE.

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Posted by Carlos Villalpando (Member # 7411) on 02-09-2013, 12:18 PM:

Hi to everyone!
I had this question in my head for a while, so I decided to post it in here.
I don't know if it's in the right forum, but I don't think there's a "sound forum" xD, and since most of the screens are Digital, I thought this one could be the right forum.

I've visited all complexes in the city and I've noticed something:
In some theatres (Cinépolis) the R and L speakers are in a distance were you can notice the sounds coming from the sides of the screen, but not too far to the edges.

In other complex (a local city enterprise) the R&L are so to the sides that you can sometimes mistake them for the surrounds, for example, loud music from a trailer coming way from the sides.

And in other complex you don't even notice them!

So, my question is:
¿How far to the sides of the screen is the ideal spot to put the R and L speakers?

Posted by Marcel Birgelen (Member # 6801) on 02-19-2013, 06:55 PM:

Have a look at the picture here.

That picture represents about the optimal placement for THX certified rooms with three front channels (LF/CF/RF). The big box in the bottom center is obviously the subwoofer.

Even with good equipment, for the end effect, not only the placement of the speakers is important, but also the characteristics of the room and the equalization of the audio system.

What you can also see on that picture is the baffle wall around the speakers. That helps (amongst other things) to smooth the transition between the separate channels, so you cannot pinpoint the exact location of the speakers that easily. Baffle walls are mandatory for THX certified theaters, but are also often applied in theaters without certification.

Posted by Mike Blakesley (Member # 26) on 02-20-2013, 12:10 PM:

In the picture, what is the purpose of the two "indented"-looking areas on each side of the center channel?

Posted by Ian Freer (Member # 1940) on 02-20-2013, 04:11 PM:

quote: Mike Blakesley
In the picture, what is the purpose of the two "indented"-looking areas on each side of the center channel?

It looks like this was originally a 5-screen channel set up but LC and RC have been removed?

Posted by Randy Stankey (Member # 64) on 02-20-2013, 04:36 PM:

Instead of making cutouts in the baffle wall and setting the speakers in the resulting alcoves, the speakers were set in front of the baffle wall and pieces were put around the front of them.

Posted by Jarod Reddig (Member # 6363) on 02-20-2013, 10:57 PM:

Yes I agree with Randy.

Posted by Monte L Fullmer (Member # 2797) on 02-20-2013, 11:42 PM:

If side adjustable maskings are used: the L/R were placed within the FLAT masking tabs.

On unmasked screens, the L/R were place more outward towards the edge of the screen.

Posted by Louis Bornwasser (Member # 3063) on 02-21-2013, 07:10 AM:

The baffle wall has little or no effect much below the crossover frequency. Best effect is 100 Hz or below. Yes, it is important but not exactly for the reason that thx says. Louis

Posted by Sam D. Chavez (Member # 1841) on 02-21-2013, 09:32 AM:

Marcel,

The idea of the THX wall was to pinpoint the channel separation nut blur it. Among many other benefits the wall keeps backstage echos, mostly mid and lower frequencies, from getting though between the speakers and blurring the precise location.

The padding on the front of the wall soaks up the HF bouncing off the back of the screen, for the same purpose; to sharpen the separation, not blur it.

If there are to be sounds located between channels, it's the mixers job to place them there during the mix.

This has been covered a number of times on this forum.