An acoustically transparent screen is a projector screen that allows you to mount speakers behind the screen to localize the sound with the image in your home theater. These acoustically transparent screens increase a sense of believability and involvement by having perforations or being woven.
This is the type of projector screen used in movie theaters to place the speakers behind the screen for a cleaner look.
You cannot place speakers behind any type of projector screen as sound waves interact with the screen reducing the quality of sound and distorting the image. This is where acoustically transparent projector screens come in.
These screens are made of materials that have “holes” which create a negative space where the sound waves can interact with the screen with little interference.
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Types of acoustically transparent screens
There are 2 types of acoustically transparent screens;
- Perforated projector screens.
- Woven projector screens.
Perforated acoustically transparent screens are made up of PVC/vinyl materials with many tiny perforations (pierced micro-holes). These perforations have diameters equal to or less than 0.3mm which allow sound to travel through the surface with minimal distortion to the image.
For these screens to work great, the least amount of light should pass through the screen which eliminates reflection behind the screen minimizing the double-image effect.
Problems with perforated screens
- This can occur because the holes in perforated screens cover 10 or less percent of the surface which is not enough for the best acoustic transparency. Because of this, some of the sound frequencies bounce off the surface of the screen rather than pass through it which dampens the sound. To partly correct this, you will need to do some adjustments to the audio on the audio processor.
- The moiré effect is a phenomenon where pixelated radial patterns are formed on the screens to line up with the pattern on the screen. This can occur in the perforated projector screen because the holes have a uniform pattern.
Woven transparent screens
Woven projector screen materials are made up of polyester or nylon that have loom weaves similar to those found in textile materials. These screens are precisely woven in a way that leaves tiny spaces between the weaves for sound to pass through.
Woven screens come in a variety of patterns and thickness which makes them more effective in reducing the moiré effect.
Problem with transparent woven screens
- This can be caused by errors in the angles of the screen surface weaves which can lead to the formation of vertical, horizontal, or vertical patterns.
Double imaging/ghosting effect;
- This looks like 2 overlapping images and occurs in woven projector screens due to the reflection of light from the back of the screen after it passes through yarns on the woven surface. When this happens a second image is produced from the back. You can reduce double imaging by adding a black acoustically transparent backing. However, this is going to negatively affect the acoustic performance by 2 or more DBs.
Images with poor color temperature;
- Color temperature is the hue of the projected image but with a poor temperature, the red, green, blue, and yellow hues can appear brighter than they should. Poor color temperature on a woven screen occurs due to clusters of the woven material being slightly larger than intended which makes some pixels brighter than others.
Woven vs perforated projector screens
Perforated screens have better acoustic transparency than woven projector screens but are more susceptible to the moiré effect. These perforated screens, therefore, deliver better sound.
Most perforated screen manufacturers combat the moiré issue by making screens with smaller micro holes. These manufacturers produce acoustically transparent screens that are THX certified and will give you a great image in any home theater setting.
THX-certified perforated screens are expensive but an average perforated screen should produce a pretty good image with a 720p resolution.
Compared to perforated projector screens, high quality woven screens are less expensive but it will take a bit of effort to get rid of the double image.
However, any acoustically transparent screens can have pixelated lines which can be very distracting and reduce the viewing quality. This also applies to entry and mid-level woven screens.
If you want great acoustic transparency and are willing to spend more for a high-quality image, you should go for a perforated screen but if you want a balance of the two without spending as much, then a woven screen will be better.
What is moiré effect on acoustically transparent screens?
As we mentioned earlier moiré effect occurs when pixelated line patterns are formed on the screens. These lines can either be diagonal, horizontal, or vertical depending on the angle of the weaves or the pattern of the perforations.
The projector’s resolution plays a big role in this effect with higher resolutions having more pixelated lines. Higher resolution projectors such as 1080p, 4K, and 8K projectors have more pixels running both vertically and horizontally, therefore, the pattern on the screen is more likely to match with the pixilation.
However, your screen may not always be the problem, your projector can also cause the moiré effect. If you can see the pixelated line pattern at a close distance to the screen, then your projector is causing this problem. But if you cannot see the line from a close distance, then the screen is causing the problem.
How to reduce the moiré effect
You can combat these distracting patterns by using a smooth acoustically transparent screen.
This effect can also be reduced by doing the following;
- Rotating the screen material surface by 180° then flipping it front to back and back to front.
- Adjust the projector’s zoom in or out even if you will have image spillage then move the projector closer or farther accordingly until it fits into the screen.
- Reduce the projection angle and make sure that the projector lens is pointing directly straight to the screen.
This should be able to reduce the moiré effect to some extent if not completely.
How to choose the right acoustically transparent screen
There are several brands of acoustic screens in the market for a home theater owner to choose but there are a few things that you need to consider before shopping;
- Screen size.
- Aspect ratio.
1. Choosing the right screen size
When it comes to choosing the right screen size it is not always about going as big. However, in some instances, having a bigger screen will be better but this will depend on your projector’s resolution and your room’s configuration.
Sometimes having a screen that is too big can reduce the image clarity and this may also the image harder for your viewers to see, especially if your home theater room is small which puts them too close to the screen.
On the other hand, a small projector screen can be frustrating to watch on which forces the viewers to move closer to the screen. For an optimal viewing experience, your seating distance should be twice the height of your acoustically transparent projector screen.
This is why planning the appropriate size for your acoustically transparent screen is important.
Here is how you can choose the right screen size
The size of most projector screens is measured diagonally but, in this case, you will need to know the height and width of the screen to make it easier.
Then you will need to determine the right height for the screen using your seating distance as a guide. As we mentioned above the best distance from the viewers to the screen should be twice the height of the screen as a general rule of thumb.
The width of the screen will then be determined by the aspect ratio. For example, for an aspect ratio of 16:9, the width will need to be 1.77 times wider than the height, or you could take the height multiply it by the 16 and divide the number you get by 9. You can do this for any aspect ratio.
Your projector’s throw ratio will also come into play when you are choosing the widest screen size you can use. To determine the maximum screen size using the throw ratio, divide your projector’s throw distance to the screen by the throw ratio.
For example, if your throw distance (distance from the projector to where the screen will be placed) is 100 inches and the projector has a throw ratio of 1.25, then the screen should be 80 inches wide. You can then use this width to determine the height of your screen using the aspect ratio.
2. The right aspect ratio for your screen
Choosing the right aspect ratio for your screen is pretty straightforward as you need to match the aspect ratio of your projector with the screen.
If your mismatch the aspect ratio, your image will not fit perfectly into the screen which will reduce your viewing experience.
3. The right screen gain
Projector screen gain is the measure of how much light the screen reflects once it is hit by light from a projector.
An acoustically transparent screen with a gain of between 1 and 1.22 should be great if you have a projector with a brightness of about 1500 lumens for a moderately lit room.
Can you put speakers behind your projector screen?
Yes, you can put speakers behind your projector screen when using an acoustically transparent screen that allows sound waves to pass through. These can be either in-wall speakers or any other type of front speakers to give you a more cinema-like experience.
However, if you place the speakers too close to the screen, comb filtering will occur. For minimum sound attenuation and true audio transparency, the speakers need to be at least 12 inches away from the back surface of the acoustically transparent screen.
But like with anything, there always pro and cons to using these screens.
Pros and cons of acoustically transparent screens
- A cleaner home theater set up as you get to hide your speakers for the left, right, and center channel behind the screen.
- You get to save space.
- These screens are of higher quality and therefore more durable than most standard projector screens.
- Problems with the moiré effect.
- Slightly lower image quality in some but not all cases.
- Costlier than standard screens as more work is needed to make them work perfectly.
How to build a DIY acoustically transparent screen
- Determine the right size for your screen depending on the projector you have and your room configuration. Use the method that we talked about earlier in this post.
- Pick a high-quality acoustically transparent material from a local store or online. I would recommend using a woven screen and investing in an acoustically transparent black backliner.
- Buy PVC, Metal, or wood to build the frame for the screen. Wood is easier to work with but metal is more durable but I would recommend using wood for an easier DIY build.
- Build a frame for the screen with the inner dimensions of the frame being the size of the screen.
- Cut the screen material and black backliner using the size of the screen and leave about 5 inches or more on each side for attachment of the material to the frame.
- Stretch the screen material with the backlines are being the rear of the screen to the frame then staple it in, sew it in or glue it to the frame depending on what you are using for the frame.
- Mount the screen to the wall for testing before permanently stapling it to the frame.
- Use a black felt tape or black velvet and place it to the part where the frame is to make the screen more pronounced, add style and depth, and to mark the edges of the screen for when you are setting up the projector.
- Install the acoustically transparent screen to your wall and you are ready to go.
My final thoughts
Using an acoustically transparent screen is a great way to transform your home theater in terms of looks and sound. You may not really need to do this.
But if you want the following, this is something you should consider;
- The flexibility and ability to place you speakers behind your projector screen to get sound that directly comes from the screen.
- An easier speaker installation as you will not have to worry about the aesthetics and everything will be hidden.
- A bigger screen for your home theater without having to worry or where you are going to place your, speakers, without obstructing the projected image.
When done right an acoustically transparent screen is a great home theater addition.