I posted before, then shut the computer down and got ready for work. On my drive in, I started thinking about the post and realized there's a problem with it.
The part about 1,3, and 10 decibels is correct and can easily be verified by anyone who cares to. However, the second part about 6db vs. 3db for doubling the distance doesn't seem to hold up. (I had read that somewhere, it seemed to make sense, and it wound up in my post.)
Doubling the distance and taking readings make sense. It also fits my experience when we compared a BA, SA & Shertler David with a SPL meter. But what happens if you double the distance again? And then double it again? It'd start to look something like this:
.........................Single Point..........Line Array
Distance in feet.......SPL in Db...........SPL in Db
3...............................100............... ....100
6.................................94.............. ......97
12...............................88............... .....94
24...............................82............... .....91
48...............................76............... .....88
96...............................70............... .....85
192.............................64................ ....82
384.............................58................ ....79
768.............................52................ ....76
1536...........................46................. ...73
3072...........................40................. ...70
6144...........................34................. ...67
It's hard to format the columns here, but hopefully you get the idea: starting with 100db at 3 feet and then progressively doubling the distance to a ridiculous point (over a mile away), while reducing the single point by 6db and the line array by 3 db at each interval.
When we ran our non-perfect "test", the single-source speakers (Schertler & SA) fell off about 8 db at distances of 3 to 30 feet, while the BA fell off about 6db at the same distance. According to the above, the difference between line array and non-line array should have been about 9db. The actual (non-scientific) results we got were about 2db.
Hopefully someone with a thorough understanding of line arrays will be able to better explain the difference. In the meantime, I think I'd change my answer to "Yes, there's a difference, but I don't have the know-how to tell you exactly what the difference would be."
|