Thanks Steve, not certain I follow the math, but very helpfull nevertheless.
The speaker's sensitivity is 91dB at 1 meter distance. Each 3dB increase requires a doubling of power.
94dB = 2W
97dB = 4W
100dB = 8W
103dB = 16W
106dB = 32W
109dB = 64W
112dB = 128W
113.4dB = 180W (The maxiumum output of the B100 amp @ 4 ohms to the 4 ohm Model T speaker)115dB = 256W
118dB = 512W
The 118dB/512W figure also seems to be pretty much inline with the Model T specs of 118dB maximum output and 500W maximum power handling.
These figures are at 1 meter from the speaker. Each doubling of distance decreases the dB output by ~ 6dB, so the maximum output at 10 feet would be decreased to ~ 104dB. This is for one speaker. Two speakers increases the output by ~ 3dB. Having the speakers closer to a wall than out in the middle of the room also increases the output from boundary reinforcement, hence the estimate of ~ 110dB.
If you listen to music at an average 85dB level, this would allow peaks of ~ 25dB. These are all estimates and presumes that the drivers and crossovers are perfectly linear, but it gets you in the ballpark.
There are a number of SPL calculators online that you can plug numbers into and get a decent estimate of what one might expect. Here is one of them:
SPL Calculator . You can also download an Excel spreadsheet version from the site if you want to easily compare a number of possibilities.
Edit: Even though the above link is correct and works from my bookmarks, for some reason it is being redirected to the host website when clicked here on the forum. You can Google it however: http://www.lmgtfy.com/?q=spl+calculator+collins+cinemaSteve