How well do those 17$ DIY home theater kits on ebay work? are they just a scam?

Its a simple concept of using the plastic enlarger screen from a overhead projector(The thing in school where your teacher would put a piece of paper on to project it). Yes it works, but you will need a TV or a computer screen to create the image. It will provide a bigger image with less clarity and will be hard to see in the daylight. Not bad if you want a really big screen.

How well do those 17$ DIY home theater kits on ebay work? are they just a scam?comedy show

If the kit includes the use of a Fresnel lens to enlarge the viewing area, there are factors be be aware of. Indeed these kits enlarge the viewing area but with a loss of brightness, clarity and sharpness.

The most important factor is the loss of lumen output.

One of the basic laws of physics involving light propagation or transmission, is the inverse square law.

What this law states is, every time you multiply the distance of the projected light source X 2, you must increase the source output X 4.

With this said, if you are using a TV set as your source, take into consideration the throw distance, this is the measurement between the "kit lens" attached to your TV source and the screen or wall it is to be projected on.

To make a long answer short, the anomalies associated with these "big screen" kits basically comes down to the available amount of lumen output. Your TV can not provide sufficient lumen output compared to other sources such as a LCD or DLP projector.

Bottom line, you get what you pay for!

One of my favorite quotes:

"Buy the best first and only cry once!".

To surmise, a standard TV will not allow one to increase its output sufficiently to project at significant distance.

With this in mind, the end result will be a less desirable video program quality that can only be viewed in a very dark environment.