SPL of Loudspeakers: Whhhhaaaaat??

[MarcMTL]

Guys and gals,

Quick question.

Let's say a 3-Way loudspeaker, with all drivers able to push out 90dbs 1w/1m.

If all are playing at the same time, so 90db times the three of them....

What's heard by the user? I doubt you are hearing the sum of the three, 270 dbs, which would turn you into a pile a rubble. Are you only hearing 90db's??? How do we calc this?

Many thanks,

Marc

[just a guy]

If a speaker is rated at 90 db, it should play 90 db at all frequencies within the passband (if it's well designed) regardless of how many drivers are in the speaker

In 3 way speakers, the 3 drivers break up the passband and each handle their own part, but each of the speakers is still only 90 db, and they are designed such that as they overlap each other they all still add up to 90 db all the way from low frequencies to highs.

Also, db's add exponentially (or logarithically or something like that) not linearly, so for example, your 2 90 db stereo speakers will add up to 93 db total (with the same 1 watt input divided between them), not 180 db.

Further note that this question belongs in the loudspeaker forum, not the fullrange forum, although I personally don't care. (In other words it's easier to get specific help for multi way designs there, but don't think I'm angry with you for posting here.)

[adason]

Multiple Sources
Two equal sources produce a 3 dB increase in sound power level.
Two equal sources produce a 3 dB increase in sound pressure level, assuming no interference.
Two 80 dB sources add to produce an 83 dB SPL.

[adason]

just a guy, you beat me to it!

[just a guy]

only by a second or 2

[adason]