[net.audio] Cross-over networks for sub-woofers?

wwb@ihuxn.UUCP (Walt Barnes) (10/05/85)

I would like to build a sub-woofer for my stereo system.  I know how
to make crossover networks for regular speakers, but I can`t figure
out how to make one work for a sub-woofer.  The catch is that I want
bass from both right and left channels to driver the sub-woofer. 
I can use caps to eliminate the low frequencies sent to my
regular speakers and chokes to eliminate the high frequencies for
the sub-woofer, but how do I combine the left and right low
frequency signals so they can be sent to one speaker? 

						Thanks,
						Walt Barnes
						...!ihuxn!wwb

schley@mmm.UUCP (Steve Schley) (10/10/85)

In article <1203@ihuxn.UUCP> wwb@ihuxn.UUCP (Walt Barnes) writes:
>I would like to build a sub-woofer for my stereo system.  I know how
>to make crossover networks for regular speakers, but I can`t figure
>out how to make one work for a sub-woofer.  The catch is that I want
>bass from both right and left channels to driver the sub-woofer. 
>I can use caps to eliminate the low frequencies sent to my
>regular speakers and chokes to eliminate the high frequencies for
>the sub-woofer, but how do I combine the left and right low
>frequency signals so they can be sent to one speaker? 
>
>						Thanks,
>						Walt Barnes
>						...!ihuxn!wwb

From your posting, I assume you are interested in a passive crossover,
rather than an active one.  If this is correct, the simplest way to do
it is to use a dual-voice-coil driver in the subwoofer.  Use a
two-channel low-pass filter between the driver and the two amplifier
outputs.  The two coils keep the signals separate, due to their
electrical isolation, and the cone sums their signals.

You shouldn't have any trouble finding one of these drivers, they're
fairly common.  Check the advertisers in Speaker Builder...

-- 
	Steve Schley

	ihnp4!mmm!schley

gvcormack@watmum.UUCP (Gordon V. Cormack) (10/15/85)

> I would like to build a sub-woofer for my stereo system.  I know how
> to make crossover networks for regular speakers, but I can`t figure
> out how to make one work for a sub-woofer.  The catch is that I want
> bass from both right and left channels to driver the sub-woofer. 

The easiest way is to put two drivers in the same box.  Connect one
channel to each driver.  Alternatively, buy a separate amplifier for
the sub-woofer.  Then implement a low-power filter and mixer.        
There is no efficient, passive way to mix the two channels together
electrically.