Is a acoustically transparent movie screen really acoustically transparent

[bebop86]

I am thinking of putting a 14 foot movie screen up which is supposed to be acoustically transparent- I would have to put my 2 channel speakers behind the screen- Does this impact the 2 channel sound in any way or is it really acoustically transparent - thks

 

[JackD201]

If air itself isn't really "transparent" over distance then I doubt any screen would be. That said, a bit of EQ should fix that as far as movies go. Is it a fixed screen?

 

[amirm]

There will be an effect that can be minimized by slanting the speaker and having as much distance as you can between the screen and the speaker (at least a few inches). The issue here is not just loss of high frequencies but the sound bouncing back toward the loudspeaker and creating comb filtering. Slanting/toeing the speaker and having some distance helps a lot.

If you want to hear the effect before committing, as the screen company for a sample. Make sure the sample is over a stretched panel. Sit in your normal seat and have someone slide it in front of the speaker and out. Keep your eyes closed and see if you can tell the difference. The effect varies good bit between screen material. Material that lets maximum amount of audio through, is usually not as good for video since the image will have those holes in it too.

 

[amirm]

Here are some measurements i made for my own screen selection. The speaker is a Revel CS52 and test is with nothing, Revel's own grill, and two types of screen material ("4k" and "2K"). As you see the response variation is quite a bit and not just a straight attenuation of highs due to comb filtering. Do not believe anything screen companies tell you.

 

[DonH50]

Does the "breakpoint" starting around 600 Hz correlate to anything like distance to screen, distance from screen bottom to speaker projection, or anything like that? Just seems interesting that they all "break away" at about the same frequency.

Just curious - Don

 

[amirm]

It is proportional to the distance from the speaker and thickness of the material. Here is a simulation of 3 mm cloth with a distance of 4 inches as an absorber (pink line):

Pretty close match for where the start of the attenuation. The ringing shows why you can't just compensate with a simple tilting of the response.

 

[DonH50]

Makes sense, and the graph illustrates the comb filtering nicely, thanks Amir.

 

[GaryProtein]

Acoustically transparent movie screen is an oxymoron.

 

[DonH50]

Totally off-topic, but I started laughing to myself after reading Gary's post, looking at his avatar, and visualizing a screen in front of that system, no way...