Speaker placement behind the screen

We are a small independent movie theater with 100 seats. Our speakers are located behind the screen.  We often get complaints that the dialogue is too low.  Two questions: 1)  What is the optimal height for the speakers?   We've been told that they are too low (currently about 3 ft off the floor).  2)  Can we change the mix so that dialogue is louder without making music, sound effects, etc. louder?  Our head projectionist says no.

Any suggestions for references I can go to?  Thank you!

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When your center speaker is behind the screen like yours is ... you need a special porous screen made to allow the dialog to come through it

THX encoded DVDs actually boost the dialog 3db for this purpose ... it's called an "X" curve if I remember correctly

This 3db boost to the center channel was recorded into the THX certified DVDs so you could place the center speaker behind the special purpose porous screen and the screen still pulled down the sound pressure level (SPL) by 3dbs to balance with the front right and left speakers

The opposite side of the coin is if you play a THX certified DVD disk and place the speaker in front of the screen ...the dialog is to loud and must be dialed  down in the processor which most HT enthusiastic do

Contact "Stewart Film Screens" and talk to someone in support .. they can explain it and help you out but you may have to replace the screen with the proper type for use with a speaker in back of it


Thanks for responding so quickly. Unfortunately, I don't know much about the specs of our sound system.  We do have a porous screen though, so the sound comes through the screen.  We run DCP mostly with an occasional blue ray.  I will contact the group you mentioned and talk to one of their techs. 

If your theater floor slopes upward to the rear, a speaker 3' off the floor will be well below the ears of many of the viewers, which could cause a decrease in volume unless the speaker had an unusually wide vertical dispersion. 
Please give us more info on the room: screen size, seating configuration, source material (blu-ray vs DVD), sound system especially amplification, decoding of sound tracks (Dolby, HD, DTS, etc), height of the seating (front to back), and the exact screen material. Lots of variables. I just had a custom screen made for my room. Expertly done. Acoustically transparent. Gain 1.1  All these things are important. Best of luck. 
It is hard to tell without speaking to the OP, as some one who has worked in motion picture sound I have some thoughts:

Take care of the basics
  • Horns are positioned facing the middle of the audience, not the back wall and ceiling.
  • Measure your speakers at multiple locations and apply corrective EQ as needed.
  • Control resonances to modern standards.
  • Minimize or eliminate noise such as A/C units, outside sounds.
  • Ensure all 3 speakers are operating optimally. Horns and woofers are both producing correct output.
  • Ensure your overall speaker levels are properly calibrated.
Now the next part will seem counter intuitive to audiophiles, and I'm sure there will be uninformed arguments:

  • Some movies such as LoTR are produced with excessive dynamic range. To hear the softest voices requires too high a volume, which you then suffer through far too loud effects.
The solution is to limit the dynamic range. I'm not sure what pro sound processors now use, but investigate and enable any compression that is available to you. If you can't find it via the Dolby/Datasat settings, an audio compressor on the center channel may be what is needed. Available through many recording gear outlets.

The compressor will work to raise the level of the softest sounds, while leaving audible levels alone.

Thanks to everyone who responded.  Getting closer to a solution, and will probably contact a sound tech at the local commercial cinema.