Originally Posted by J-hop
The difference could simply be a matter of the distance you measured them at?
If sound the sound waves from 2 pairs constructively interfere the amplitude should double which means a 6dB increase.
What distance does hella say they measure them at?
its actually a little less than that. a doubling of source = 3db increase.
10 * log10 (2) = 3.01 dB, where 2 is the double in power (volume).
agreed on the distance though, as that perceived volume will change.