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In Reply to: RE: like already said Multiple drivers for each pass band. posted by Don Reid on April 24, 2017 at 10:52:25
Here is how I look at it.Doubling the number of drivers (in and of itself) increases the driver sensitivity by 3db.
Now take into account that when the drivers are wired in parallel then the impedance is halved.
With a transistor amplifier (at least in theory) the output power will double when the load impedance is halved.
So with twice an many drivers (wired in parallel) the total increase in system sensitivity is 6db.
To say all of that a different way,
When you double the number of drivers (from one to two) it increases the sensitivity by 6db (twice the power gives 3db and twice the cone area gives another 3db).
BUT if you only provide one watt the net increase is only 3db because each driver is only getting 1/2 watt (twice the cone area gives 3db but we're not providing twice the power so 3db is the net increase).
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 04/24/17 04/24/17Follow Ups:
Answers on line array sensitivity can be found in my Near Field Line Array white paper.
SPL calculations are on page 17-18.
Jim
"For example, two speakers connected in
parallel and mounted within a wavelength center-to-center spacing would yield up to a 6dB increase in SPL. 3dB from the increase in acoustical energy and 3 dB from the reduction in impedance."That's what I said and what Bill said.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 04/25/17
Well with two sources a half wl apart, you get +6dB over one on axis only.
Think about a polar plot, the diameter is level vs angle and the area within the polar circle summed is the total acoustic power.
Two sources that far apart produce a figure 8 pattern who's peak value is +6dB on axis but the area enclosed by the polar circle is only 3 dB more than each source individually.
Move those sources to less than 1/4 wl apart and now you have a circle who's diameter is +6dB and the total energy is now 6dB greater than one was.
acoustic power
1+1=2
or
1+1=4
depends on the spacing and location
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