Electricity travels down a wire at about 1/100th the speed of light.
If you made your HDMI cable a couple thousand miles long, you may have an issue.
Just for fun (and sarcasm) let's figure out your delay.
Based on the speed of light, which travels at 983,571,056 feet per second. Divide by 100, then 20/that number...
Your delay, for 20 feet of HDMI cable, is about .0000020334 seconds. Give or take a bit. Call it 2 millionths of a second.
The projector will add far more delay in the video processing itself. Likely 60+ thousandths of a second.
The proper way to deal with any audio delay issues is to use a real A/V receiver and run everything through it. Many A/V receivers include audio delay as one of the built in features of the unit.
[Edited by AV_Integrated on Sep 30, 2015 at 9:10 AM]
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