Best way to get accurate rake angle on speakers

Thanks for all the thoughts so far. I am running DeVore Nines, which have the Tweeter below the midrange. I use one of those chaise lounge, good for your back type chairs, so my ears are generally less than 36" from the ground. The
manual suggests they be tilted even. However, because my chair has my head position lower, I have them tilted forward. I then determine what sounds best by ear.... My main goal here is to then have the tweeters at the same height. As I mentioned, my floor dips, so it makes no sense to measure from the floor up. I was thinking about using the ceiling, but can't figure out what would be most accurate.

I have mentioned using a laser in a previous post. I use a drafting "T" with the short end against the back of the speaker while the long end is pointed toward the listening position. Align the "T" midway between the tweeter and woofer, set the laser on the "T" and adjust the angle of the speaker until the laser is pointed at the same height as your ears.

Some folks assume speakers must always be tilted back, but in many cases the speakers need to be tilted forward to get proper alignment.

Included in proper speaker setup is making sure the left and right speakers are the same distance from the listener. To accomplish this I use a string attached to the back of the listening position. I then extend the string to the front of the left speaker then the right speaker making sure the string makes contact at the same point.

By using this method you should have a tight and well balanced soundstage.

I am using Vandersteen 5A's. In experimenting, after raising the rear of the speakers - maybe 1/8 of an inch or less, the sound went from excellent to jaw dropping unbelievable.

Use your ears to determine speaker orientation that sounds best where you listen from.

If you have good speakers then the dispersion should be such that the presentation is not overly sensitive to rake. I'd suggest to have the tweeters a little above ear level (about a foot) when seated - this means that it will usually still sound good when standing. I prefer speakers level and higher up rather than low but raked as I find a raked setup has a limited sweetspot.