Re: Need more head room, long, narrow room
I would down tilt the speakers by what I thought was appropriate to the room size, ceiling height, audience location, seated vs standing, speaker characteristics, security/stability of the speaker on the stand, and a whole raft of other reasons. The fundamental idea remains increase the direct sound on the audience and reduce the reflected sound. I also want to consider where the front of the audience is.
Your 40 m example is a little extreme for covering on a SOS gig. If you have the horn just above ear height and want any level at all at the back of the audience, the front of the audience is going to be ear searingly loud. Increasing the height and adding down tilt moves the speakers farther from the front of the audience, without greatly increasing the distance to the back of the audience.
When I walk into a SOS gig as a fast one off show I would place my speaker stands to define the stage or performance area, raise the speaker as high as I can (I use TS99 stands) and then aim the center of the coverage pattern at the center of the audience area, and then confirm that both the back and front of the audience area are within the coverage patterns. For a SOS gig, the combination of Balanced tilters and the 7.5 built into the K series gives me 19.5 degrees of tilt to play with, and at times I feel like I would like some more tilt.
If your were to start with the speaker flat, with the horn at 7 feet, a person with their ears at 5 feet would have to be 5 feet back from the speaker to be within the coverage angles (as if that was actually a hard and fast edge) and the sound would have to travel about 5.5 feet. A person in the back of the room with ears at 5 feet, 75 feet from the speakers, would still be under the center line of the horns coverage and the sound would travel just a fraction over 75 feet to their ears. In other words, you are using less than 1/2 of the horns coverage pattern for covering the audience.
Changing to a 20 degree down tilt, with the speaker still at the same height, still leaves the person in the back of the room in the coverage pattern with the sound traveling 75 feet. However, the person at the front of the audience is at the coverage pattern when they are 2 feet back from the speaker instead of 5. But that for that person the sound is only traveling just under 3 feet.
My preference would be to raise the speaker to a minimum of 9 feet. At 9 feet, a person standing 4 feet back from the speaker is still at the edge of the coverage, but the sound is traveling almost 6 feet. The same person that was standing 5 feet back from the flat fronted speaker at the edge of the pattern is now well within the pattern and the sound is traveling 6.5 feet.
None of these changes significantly change the coverage pattern or the distance the sound travels at the back of the room. In addition, each degree of down tilt moves the point at which the HF reflects from the ceiling back in the audience, which may seem to reduce the overall level in the rear of the audience, but definitely helps with clarity.
Or for anyone seeking quick and dirty logic, if you can cover the audience with the speaker flat fronted only using the bottom half of the horns coverage, why couldn't you cover even more using the whole of the horns coverage?
