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Question about subs and dB's... (1 Viewer)

Peter Johnson

Stunt Coordinator
I was always under the impression that a doubling of power = 3dB, so why do some people (such as Tom N and Tom V) say adding say another identical sub = a 6dB boost?

Patrick Sun

Senior HTF Member

Glen_L

Stunt Coordinator
If you were to double the power to a single driver, you would gain the 3dB. Adding a second driver (with the same wattage) has the potential to add 6dB. This is one of the reasons you try to keep both subs in the same corner--to keep the subs "in phase" together, or phase correlated. If I recall correctly, two out of phase sounds of the same loudness result in only a 3dB increase.
edit: Here's a quotation from the second link that Mario provided above:
But wait – haven't we already said that "twice as loud" means an increase of 6 dB? There appears to be a contradiction here, but really there isn't. When we talked before about a 6 dB boost in a sound being twice as loud, we were in fact talking about a single sound being boosted from it's previous level. The above formula holds true only when the two sounds being compared are different. It's a subtle but crucial distinction. The formula is useful, because when we talk about sound levels combining in this manner, we're almost always talking about different sounds. The fact is that if the two sounds are similar enough (i.e., phase correlated) the actual increase will be higher than predicted by the formula—and if the two sounds are the same, the increase in level can in fact be up to 6 dB.
[Edited last by Glen_L on July 19, 2001 at 02:21 PM]

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