The Quick Verdict
Get the BenQ LK830ST 4K Short Throw Laser Projector. It lists at $2,499 against $4,899 for the LK936ST, so it's $2,400 less at list. It throws a much wider image from the same spot, and BenQ states it can fill square and 4:3 screens. Input lag is identical, and both have a golf mode. The LK936ST is worth the extra money if you want the mounting slack of a zoom lens and published lens shift, or the higher listed brightness. For most sim bays, the LK830ST is the better buy.
What They Have in Common
Both are 3840x2160, 16:9-native laser projectors with a 20,000-hour rated light source life. Both list 16.7 ms of input lag at 1080p 60Hz, and BenQ names a golf picture mode on each. BenQ doesn't say how either one produces its 4K. It also publishes no warranty term for either model.
Where They Differ
Throw ratio and image size
Image width = throw distance ÷ throw ratio. The LK830ST has a single throw ratio of 0.496:1. From 10 ft back, that gives a 20.2 ft wide image (10 ft ÷ 0.496). The LK936ST has a zoom range of 0.81–0.89:1. From the same 10 ft, it gives 11.2 ft to 12.3 ft wide (10 ft ÷ 0.89 to 10 ft ÷ 0.81).
Turn it around for a 10 ft wide image. The LK830ST sits 5.0 ft from the screen (10 ft × 0.496), while the LK936ST sits 8.1 ft–8.9 ft from the screen (10 ft × 0.81 to 10 ft × 0.89). That gap is the difference between hanging the projector close to the screen and hanging it noticeably further back in the bay. Both count as short-throw by the numbers. The LK830ST simply needs far less distance for the same width. Before choosing, measure the distance from where the lens will hang to the screen.
Screen shapes
BenQ states the LK830ST can run 1:1, 4:3, 5:4, 16:9 and 16:10. Square and 4:3 impact screens are both on that list. For the LK936ST, BenQ lists no selectable aspect modes at all. That doesn't mean it's locked to 16:9. It means BenQ doesn't say. If your screen is square or 4:3, only the LK830ST has that in writing.
Brightness, lag and golf mode
The LK830ST lists 4,000 lumens and the LK936ST lists 5,100. BenQ doesn't name a measurement standard for either, but they're the same maker's figures. As listed, the LK936ST is 1,100 lumens higher. I can't tell you whether either is enough for your bay, because I haven't seen them running. Lag is 16.7 ms on both, so there's no gap. Both have a golf mode.
Mounting slack, size and the rest
The LK936ST has 1.1x optical zoom and published lens shift of vertical -60%+60% and horizontal -23%+23%. It also has 3D keystone at ±40 degrees vertical, horizontal and rotation. The LK830ST has 1x optical zoom, so it has one throw ratio. BenQ doesn't publish a lens shift figure for it. Its keystone is 2D, with auto vertical and horizontal correction at ±30 degrees. If you need flexibility in where the projector hangs, the LK936ST gives you more documented room to adjust.
The LK830ST weighs 7.93 lbs and measures 10.99 x 4.74 x 9.03 in. The LK936ST weighs 15.4 lbs and measures 16.4 x 6.5 x 13.8 in, so the LK830ST is 7.47 lbs lighter. The LK830ST is listed as a 2025 release and the LK936ST as a 2021 release.
Who Should Buy Which
Get the BenQ LK830ST if:
- Your impact screen is square or 4:3 and you want a projector whose maker states those modes.
- You want the lens close to the screen. It needs 5.0 ft for a 10 ft wide image.
- You'd rather keep $2,400 at list and still get the same input lag and a golf mode.
- You're mounting overhead and want the lighter, smaller unit to deal with.
Get the BenQ LK936ST if:
- The projector has to sit further back. It gives 11.2 ft to 12.3 ft wide from 10 ft, rather than 20.2 ft.
- You want zoom and published lens shift so the mount position doesn't have to be exact.
- You want the higher listed brightness figure, 5,100 lumens against 4,000.
- You need 3D keystone with rotation correction.
The Bottom Line
It seems like the LK830ST lines up better with how sim bays get built. It needs less distance for a wide image, BenQ states it can fill square and 4:3 screens, and it lists $2,400 lower. The LK936ST earns its price only if mounting further back, zoom and lens shift, or the extra 1,100 listed lumens matter to your build. Measure from the lens position to the screen, then run the formula with the figures above.