Speaker Set Up...Math/Geometry Experts Please Help


Hey guys, I need your help. I am helping a friend of mine set up his speakers and can't figure something out.

His speakers need to be tilted back to time align the drivers. According to the graph supplied from the manufacturer, we need a rake (tilt) of a 1/2 inch. This is measured using a plumb bob hanging from the back of the speaker, (which is perfectly flat). You measure the distance from the string to the back bottom of the speaker. The problem we are having is that even if we let the plumb bob settle, as soon as we try to measure the distance, the string moves just from the air disturbance around the string. We are having trouble getting an exact reading.

My question is: Can you convert the 1/2 inch distance to a degree? I have a really nice digital level that we can put on top of the speaker, start with it perfectly level and zero out the level. My level only reads in degrees, so I need to know how many degrees correspond to 1/2 inch tilt.

I've actually done this a few times in the past and always used the plumb bob method, but with current technology, was hoping to get it perfect.

Maybe this can't be converted? I've tried looking it up online, but Geometry was always my weak subject.

Thanks guys!
128x128mofimadness
I am very impressed with the math-related gymnastics being performed by the student body, but is this hobby really supposed to be this anal?
Lindisfarne - you've been around here a long time and you ask THAT question!? :-)
Even after you tilt the speaker cabinet back, the resulting time-alignment is good for only one listening height, is it not? Does anyone sit exactly the same height the whole time they are listening to music?!
We got these set up over this weekend and they sound really good. It does indeed help being a little anal and following the manufacturer's procedure.

Bdp24...not sure how you listen, but my ears are pretty much the same height when I listen. I might turn my head from side to side at times, but it would look kinda funny if you bob your head up and down :-)

Thanks again guys for all the help.