What To Do Behind An Acoustically Transparent Screen

When you build a home theater with an acoustically transparent screen the speakers are placed behind the screen. These speakers can be placed in a wall or an alcove behind the screen.

The left and right screen loudspeakers should be spaced laterally so that they form a triangle with a 45 degree angle to the primary seat. This size screen will visually work best with 2:35 to 2:50 aspect ratio screens. Sitting this close to a 16:9 screen may not be comfortable. The screen loudspeakers should point to a location on the center-line of the theater seating at a distance about two-thirds the length of the room. Screen speaker tweeters should be mounted no more than 15 degrees off the viewer ear height. The speaker can be angled toward the viewer to help with this.

Using a wall as either a baffle wall for your box speaker enclosures or in-wall speakers will add a boost of up to 6 db to the lower frequencies. The wall itself will work best if it is very dead acoustically and does not vibrate. This can be done with multiple layers of drywall, MDF and 2×4 construction. Placing the speaker on a shelf will cause fewer problems than in another box. Equalization to compensate for this baffle step in bass response may be required if the speaker is not designed for this purpose. Allowing access behind the wall can help with future maintenance if it is possible. The increase in sound output from this baffle wall will reduce the strain on your speakers and amplifiers. Mason Super W pads can be used to reduce vibrations from your speakers to the wall.

It is important to cover all wall surfaces behind the screen with sound absorptive material to prevent interference from reflections. THX recommends 1 inch thick Black Coated Insul-SHIELD® for this purpose. Sound absorption material should be used behind the wall as well and the speaker hole should be not much larger than the speaker.

When installing masking material for various screen formats be sure the material does not obstruct the sound when in the most restrictive position.

Finally be sure everything is visually non-reflective behind the screen and black if possible to avoid seeing reflections from behind the screen. Black acoustically transparent fabric can be used for this purpose as well, but it will absorb another 1 db of the high frequencies.

W. Jeff Meier

ISF and THX Certified Home Theater Consultant

17 Comments
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SR

Nice article, thanks. Do you think it is beneficial to seal between the wall and the speakers? Like with neoprene or weather stripping?

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Matt Harden

Jeff,

I understand covering everything behind the screen wall with Insulshield; but what about pink insulation in general? Should the cavity behind the wall be filled with insulation?

Thanks!

W. Jeff Meier

You could use other products. I would be careful to be sure it is not visible. Many theaters use too much thick material in them and too few thin products resulting in too many high frequency reflections. The proper distribution depends on the overall content of the theater including flooring and seating.

Edward

Because of room limitations, the only place I can put the subwoofers is in the front where the screen is. Should I also put them behind the screen or should they be at ground level? They are front facing. Any help is appreciated. I can’t find this info anywhere.

W Meier

The best location for phasing subwoofers is somewhere between the front main speakers. A single subwoofer will phase best under the center channel speaker.

Behind a screen you may have more problems with rattles if you do not secure things well and isolate the subwoofer from the structure.

Edward

Thank you. I think I can handle the rattles fairly easily, just needed to know if they could go behind the screen or if they should be at ground level.

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