Multi-woofer design questions

Kensai · 15th May 2006, 04:05 PM

First off, what is the sensitivity gain when using multiple identical woofers? Is it +3 or +6 when going from 1 to 2? Beyond that, what is the rule for increased output with increasing # of drivers?

Second, when designing a crossover, what impedence are you looking out when creating the lowpass filter for multiple woofers that you intend to share the same branch of the crossover? Say I've got 2 8ohm woofers . . . am I designing an 8ohm crossover, or a 4ohm crossover?

Thanks,
Kensai

Curmudgeon · 15th May 2006, 08:35 PM

For the two woofers in parallel, the gain is +6 dB. E^2 is constant, so E^2/R goes to e^/.5R for double the power, and 3 dB gain. The two woofers at low frequencies are much smaller than one wavelength, and are operating in the region where coupling to the air is inefficient. Doubling the area by using two speakers is good for an additional 3dB.

With the speakers in parallel, a 4 ohm crossover, for that branch. Seriesing speakers gets a bit messy, especially if the resonant frequencies are not identical.

15th May 2006, 04:05 PM	#1
Kensai diyAudio Member Join Date: Jan 2004 Location: St. Louis	Multi-woofer design questions First off, what is the sensitivity gain when using multiple identical woofers? Is it +3 or +6 when going from 1 to 2? Beyond that, what is the rule for increased output with increasing # of drivers? Second, when designing a crossover, what impedence are you looking out when creating the lowpass filter for multiple woofers that you intend to share the same branch of the crossover? Say I've got 2 8ohm woofers . . . am I designing an 8ohm crossover, or a 4ohm crossover? Thanks, Kensai

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15th May 2006, 08:35 PM	#2
Curmudgeon diyAudio Member Join Date: Nov 2005	For the two woofers in parallel, the gain is +6 dB. E^2 is constant, so E^2/R goes to e^/.5R for double the power, and 3 dB gain. The two woofers at low frequencies are much smaller than one wavelength, and are operating in the region where coupling to the air is inefficient. Doubling the area by using two speakers is good for an additional 3dB. With the speakers in parallel, a 4 ohm crossover, for that branch. Seriesing speakers gets a bit messy, especially if the resonant frequencies are not identical.

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